time travel through light

Is Time Travel Possible?

We all travel in time! We travel one year in time between birthdays, for example. And we are all traveling in time at approximately the same speed: 1 second per second.

We typically experience time at one second per second. Credit: NASA/JPL-Caltech

NASA's space telescopes also give us a way to look back in time. Telescopes help us see stars and galaxies that are very far away . It takes a long time for the light from faraway galaxies to reach us. So, when we look into the sky with a telescope, we are seeing what those stars and galaxies looked like a very long time ago.

However, when we think of the phrase "time travel," we are usually thinking of traveling faster than 1 second per second. That kind of time travel sounds like something you'd only see in movies or science fiction books. Could it be real? Science says yes!

This image from the Hubble Space Telescope shows galaxies that are very far away as they existed a very long time ago. Credit: NASA, ESA and R. Thompson (Univ. Arizona)

How do we know that time travel is possible?

More than 100 years ago, a famous scientist named Albert Einstein came up with an idea about how time works. He called it relativity. This theory says that time and space are linked together. Einstein also said our universe has a speed limit: nothing can travel faster than the speed of light (186,000 miles per second).

Einstein's theory of relativity says that space and time are linked together. Credit: NASA/JPL-Caltech

What does this mean for time travel? Well, according to this theory, the faster you travel, the slower you experience time. Scientists have done some experiments to show that this is true.

For example, there was an experiment that used two clocks set to the exact same time. One clock stayed on Earth, while the other flew in an airplane (going in the same direction Earth rotates).

After the airplane flew around the world, scientists compared the two clocks. The clock on the fast-moving airplane was slightly behind the clock on the ground. So, the clock on the airplane was traveling slightly slower in time than 1 second per second.

Credit: NASA/JPL-Caltech

Can we use time travel in everyday life?

We can't use a time machine to travel hundreds of years into the past or future. That kind of time travel only happens in books and movies. But the math of time travel does affect the things we use every day.

For example, we use GPS satellites to help us figure out how to get to new places. (Check out our video about how GPS satellites work .) NASA scientists also use a high-accuracy version of GPS to keep track of where satellites are in space. But did you know that GPS relies on time-travel calculations to help you get around town?

GPS satellites orbit around Earth very quickly at about 8,700 miles (14,000 kilometers) per hour. This slows down GPS satellite clocks by a small fraction of a second (similar to the airplane example above).

GPS satellites orbit around Earth at about 8,700 miles (14,000 kilometers) per hour. Credit: GPS.gov

However, the satellites are also orbiting Earth about 12,550 miles (20,200 km) above the surface. This actually speeds up GPS satellite clocks by a slighter larger fraction of a second.

Here's how: Einstein's theory also says that gravity curves space and time, causing the passage of time to slow down. High up where the satellites orbit, Earth's gravity is much weaker. This causes the clocks on GPS satellites to run faster than clocks on the ground.

The combined result is that the clocks on GPS satellites experience time at a rate slightly faster than 1 second per second. Luckily, scientists can use math to correct these differences in time.

If scientists didn't correct the GPS clocks, there would be big problems. GPS satellites wouldn't be able to correctly calculate their position or yours. The errors would add up to a few miles each day, which is a big deal. GPS maps might think your home is nowhere near where it actually is!

In Summary:

Yes, time travel is indeed a real thing. But it's not quite what you've probably seen in the movies. Under certain conditions, it is possible to experience time passing at a different rate than 1 second per second. And there are important reasons why we need to understand this real-world form of time travel.

If you liked this, you may like:

A beginner's guide to time travel

Learn exactly how Einstein's theory of relativity works, and discover how there's nothing in science that says time travel is impossible.

Everyone can travel in time . You do it whether you want to or not, at a steady rate of one second per second. You may think there's no similarity to traveling in one of the three spatial dimensions at, say, one foot per second. But according to Einstein 's theory of relativity , we live in a four-dimensional continuum — space-time — in which space and time are interchangeable.

Einstein found that the faster you move through space, the slower you move through time — you age more slowly, in other words. One of the key ideas in relativity is that nothing can travel faster than the speed of light — about 186,000 miles per second (300,000 kilometers per second), or one light-year per year). But you can get very close to it. If a spaceship were to fly at 99% of the speed of light, you'd see it travel a light-year of distance in just over a year of time. 

That's obvious enough, but now comes the weird part. For astronauts onboard that spaceship, the journey would take a mere seven weeks. It's a consequence of relativity called time dilation , and in effect, it means the astronauts have jumped about 10 months into the future. 

Traveling at high speed isn't the only way to produce time dilation. Einstein showed that gravitational fields produce a similar effect — even the relatively weak field here on the surface of Earth . We don't notice it, because we spend all our lives here, but more than 12,400 miles (20,000 kilometers) higher up gravity is measurably weaker— and time passes more quickly, by about 45 microseconds per day. That's more significant than you might think, because it's the altitude at which GPS satellites orbit Earth, and their clocks need to be precisely synchronized with ground-based ones for the system to work properly. 

The satellites have to compensate for time dilation effects due both to their higher altitude and their faster speed. So whenever you use the GPS feature on your smartphone or your car's satnav, there's a tiny element of time travel involved. You and the satellites are traveling into the future at very slightly different rates.

But for more dramatic effects, we need to look at much stronger gravitational fields, such as those around black holes , which can distort space-time so much that it folds back on itself. The result is a so-called wormhole, a concept that's familiar from sci-fi movies, but actually originates in Einstein's theory of relativity. In effect, a wormhole is a shortcut from one point in space-time to another. You enter one black hole, and emerge from another one somewhere else. Unfortunately, it's not as practical a means of transport as Hollywood makes it look. That's because the black hole's gravity would tear you to pieces as you approached it, but it really is possible in theory. And because we're talking about space-time, not just space, the wormhole's exit could be at an earlier time than its entrance; that means you would end up in the past rather than the future.

Trajectories in space-time that loop back into the past are given the technical name "closed timelike curves." If you search through serious academic journals, you'll find plenty of references to them — far more than you'll find to "time travel." But in effect, that's exactly what closed timelike curves are all about — time travel

This article is brought to you by  How It Works .

How It Works is the action-packed magazine that's bursting with exciting information about the latest advances in science and technology, featuring everything you need to know about how the world around you — and the universe — works.

There's another way to produce a closed timelike curve that doesn't involve anything quite so exotic as a black hole or wormhole: You just need a simple rotating cylinder made of super-dense material. This so-called Tipler cylinder is the closest that real-world physics can get to an actual, genuine time machine. But it will likely never be built in the real world, so like a wormhole, it's more of an academic curiosity than a viable engineering design.

Yet as far-fetched as these things are in practical terms, there's no fundamental scientific reason — that we currently know of — that says they are impossible. That's a thought-provoking situation, because as the physicist Michio Kaku is fond of saying, "Everything not forbidden is compulsory" (borrowed from T.H. White's novel, "The Once And Future King"). He doesn't mean time travel has to happen everywhere all the time, but Kaku is suggesting that the universe is so vast it ought to happen somewhere at least occasionally. Maybe some super-advanced civilization in another galaxy knows how to build a working time machine, or perhaps closed timelike curves can even occur naturally under certain rare conditions.

This raises problems of a different kind — not in science or engineering, but in basic logic. If time travel is allowed by the laws of physics, then it's possible to envision a whole range of paradoxical scenarios . Some of these appear so illogical that it's difficult to imagine that they could ever occur. But if they can't, what's stopping them? 

Thoughts like these prompted Stephen Hawking , who was always skeptical about the idea of time travel into the past, to come up with his "chronology protection conjecture" — the notion that some as-yet-unknown law of physics prevents closed timelike curves from happening. But that conjecture is only an educated guess, and until it is supported by hard evidence, we can come to only one conclusion: Time travel is possible.

A party for time travelers 

Hawking was skeptical about the feasibility of time travel into the past, not because he had disproved it, but because he was bothered by the logical paradoxes it created. In his chronology protection conjecture, he surmised that physicists would eventually discover a flaw in the theory of closed timelike curves that made them impossible. 

In 2009, he came up with an amusing way to test this conjecture. Hawking held a champagne party (shown in his Discovery Channel program), but he only advertised it after it had happened. His reasoning was that, if time machines eventually become practical, someone in the future might read about the party and travel back to attend it. But no one did — Hawking sat through the whole evening on his own. This doesn't prove time travel is impossible, but it does suggest that it never becomes a commonplace occurrence here on Earth.

The arrow of time 

One of the distinctive things about time is that it has a direction — from past to future. A cup of hot coffee left at room temperature always cools down; it never heats up. Your cellphone loses battery charge when you use it; it never gains charge. These are examples of entropy , essentially a measure of the amount of "useless" as opposed to "useful" energy. The entropy of a closed system always increases, and it's the key factor determining the arrow of time.

It turns out that entropy is the only thing that makes a distinction between past and future. In other branches of physics, like relativity or quantum theory, time doesn't have a preferred direction. No one knows where time's arrow comes from. It may be that it only applies to large, complex systems, in which case subatomic particles may not experience the arrow of time.

Time travel paradox 

If it's possible to travel back into the past — even theoretically — it raises a number of brain-twisting paradoxes — such as the grandfather paradox — that even scientists and philosophers find extremely perplexing.

Killing Hitler

A time traveler might decide to go back and kill him in his infancy. If they succeeded, future history books wouldn't even mention Hitler — so what motivation would the time traveler have for going back in time and killing him?

Killing your grandfather

Instead of killing a young Hitler, you might, by accident, kill one of your own ancestors when they were very young. But then you would never be born, so you couldn't travel back in time to kill them, so you would be born after all, and so on … 

A closed loop

Suppose the plans for a time machine suddenly appear from thin air on your desk. You spend a few days building it, then use it to send the plans back to your earlier self. But where did those plans originate? Nowhere — they are just looping round and round in time.

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

How It Works has a special formula for making learning fun by answering questions on science, space, history, technology, transport and the environment with engaging articles, in-depth special features, global science news, and topical interviews. With impressive cutaway illustrations that show how things function, and mindblowing photography of the planet’s most inspiring spectacles, How It Works represents the pinnacle of engaging, factual fun for a mainstream audience keen to keep up with the latest tech and the most impressive phenomena on the planet and beyond. Written and presented in a style that makes even the most complex subjects interesting and easy to understand, How It Works is enjoyed by readers of all ages.

Get fantastic offers by subscribing to the digital and/or print edition now. Subscribers get 13 issues per year!

See the explosive 'devil comet' get its tail ripped off by a solar storm days before its close approach to the sun

Global 'time signals' subtly shifted as the total solar eclipse reshaped Earth's upper atmosphere, new data shows

Packs of dog-shaped robots could one day roam the moon — if they can find their footing on Earth first

Most Popular

• 2 James Webb telescope confirms there is something seriously wrong with our understanding of the universe
• 3 NASA spacecraft snaps mysterious 'surfboard' orbiting the moon. What is it?
• 4 'Exceptional' prosthesis of gold, silver and wool helped 18th-century man live with cleft palate
• 5 AI pinpoints where psychosis originates in the brain
• 2 Scientists are one step closer to knowing the mass of ghostly neutrinos — possibly paving the way to new physics
• 3 50-foot 'king of the serpents' may have been the biggest snake to ever live
• 4 Giant, 82-foot lizard fish discovered on UK beach could be largest marine reptile ever found
• 5 NASA's downed Ingenuity helicopter has a 'last gift' for humanity — but we'll have to go to Mars to get it

Is time travel possible? Why one scientist says we 'cannot ignore the possibility.'

A common theme in science-fiction media , time travel is captivating. It’s defined by the late philosopher David Lewis in his essay “The Paradoxes of Time Travel” as “[involving] a discrepancy between time and space time. Any traveler departs and then arrives at his destination; the time elapsed from departure to arrival … is the duration of the journey.”

Time travel is usually understood by most as going back to a bygone era or jumping forward to a point far in the future . But how much of the idea is based in reality? Is it possible to travel through time? 

Is time travel possible?

According to NASA, time travel is possible , just not in the way you might expect. Albert Einstein’s theory of relativity says time and motion are relative to each other, and nothing can go faster than the speed of light , which is 186,000 miles per second. Time travel happens through what’s called “time dilation.”

Time dilation , according to Live Science, is how one’s perception of time is different to another's, depending on their motion or where they are. Hence, time being relative. 

Learn more: Best travel insurance

Dr. Ana Alonso-Serrano, a postdoctoral researcher at the Max Planck Institute for Gravitational Physics in Germany, explained the possibility of time travel and how researchers test theories. 

Space and time are not absolute values, Alonso-Serrano said. And what makes this all more complex is that you are able to carve space-time .

“In the moment that you carve the space-time, you can play with that curvature to make the time come in a circle and make a time machine,” Alonso-Serrano told USA TODAY. 

She explained how, theoretically, time travel is possible. The mathematics behind creating curvature of space-time are solid, but trying to re-create the strict physical conditions needed to prove these theories can be challenging. 

“The tricky point of that is if you can find a physical, realistic, way to do it,” she said. 

Alonso-Serrano said wormholes and warp drives are tools that are used to create this curvature. The matter needed to achieve curving space-time via a wormhole is exotic matter , which hasn’t been done successfully. Researchers don’t even know if this type of matter exists, she said.

“It's something that we work on because it's theoretically possible, and because it's a very nice way to test our theory, to look for possible paradoxes,” Alonso-Serrano added.

“I could not say that nothing is possible, but I cannot ignore the possibility,” she said. 

She also mentioned the anecdote of  Stephen Hawking’s Champagne party for time travelers . Hawking had a GPS-specific location for the party. He didn’t send out invites until the party had already happened, so only people who could travel to the past would be able to attend. No one showed up, and Hawking referred to this event as "experimental evidence" that time travel wasn't possible.

What did Albert Einstein invent?: Discoveries that changed the world

Just Curious for more? We've got you covered

USA TODAY is exploring the questions you and others ask every day. From "How to watch the Marvel movies in order" to "Why is Pluto not a planet?" to "What to do if your dog eats weed?" – we're striving to find answers to the most common questions you ask every day. Head to our Just Curious section to see what else we can answer for you. 

Time Travel: Observing Cosmic History

By observing light from faraway cosmic objects, the Hubble Space Telescope is like a time machine. Light takes time to reach Hubble, because it travels great distances. That means images captured by Hubble today, show what the objects looked like years ago!

The Hubble Space Telescope is many things. It’s an observatory, a satellite, and an icon of cultural and scientific significance – but perhaps most interestingly, Hubble is also a time machine.

Hubble isn’t that far away, locked in a low-Earth orbit just a few hundred miles up that takes about 90 minutes to complete. But with its position just above Earth’s murky atmosphere, Hubble’s transformative view of our universe literally lets us witness our universe’s past.  It allows us to effectively travel back in time.

How does that work? After all, Hubble doesn’t travel beyond our solar system, or even our home planet’s gravity. It certainly doesn’t have any sci-fi elements you might find in Doctor Who or Back to the Future.

Light Travel

The answer is simply light.

The term “light-year” shows up a lot in astronomy. This is a measure of distance that means exactly what it says – the distance that light travels in one year. Given that the speed of light is 186,000 miles (299,000 kilometers) per second, light can cover some serious ground over the course of 365 days. To be precise, almost 6 trillion miles (9.5 trillion kilometers)!

Traveling Back in Time: 8 minutes

Hubble works by gathering light from objects in our universe – some as close as our Moon, and some as distant as galaxy clusters that are billions of light-years away. All that light takes time to reach the telescope, just as it takes time for light to travel from its source to our eyes. For example, our Sun is located about 93 million miles (150 million kilometers) from Earth. That means that it takes roughly eight minutes for its light to reach us here on our planet, so when we look at the Sun (though directly is never recommended!) we see it exactly as it was eight minutes in the past.

Cosmically speaking, the 93 million miles between us and the Sun are nothing. We orbit around just one of billions of stars in the Milky Way Galaxy, which is one of countless trillions of galaxies in the universe.

With that in mind, time travel gets more intense when Hubble observes objects beyond our star system.

Traveling Back in Time: 4 years

Aside from our Sun, the next closest star to us is named Proxima Centauri. It’s about four light-years away, which makes it a close neighbor on a universal scale. But even with Hubble’s sharp, powerful vision, Proxima Centauri remains a point-like object – demonstrating our universe’s unfathomably large size.

Traveling Back in Time: 700 years

Another stellar target of Hubble’s is named Betelgeuse, which is about 700 light-years from Earth. Again, this means that when Hubble looks at Betelgeuse, the star appears exactly as it was 700 years ago. As one of the brightest stars in our sky, astronomers believe it’s likely that even the earliest humans knew of it, as this star appears in stories from several cultures.

This red supergiant star began to dim significantly in the fall of 2019, losing about 60% of its brightness within months. But by April 2020, its regular brightness returned. Hubble studied Betelgeuse and found out that the star “blew its top” – it went through a surface mass ejection, in which the star spewed out a large amount of its surface material into space. When that material in space cooled down, it became a dust cloud that temporarily blocked some of the star’s light.

Hubble’s unique ability to observe in ultraviolet light helped reveal the details of this dimming event and its aftermath. In this range of light, Hubble can better observe the hot layers of atmosphere above a star’s surface.

The telescope continues to be the go-to observatory for scientists who study Betelgeuse. Because it’s taken this long for the light from Betelgeuse to reach us, only in very recent history have we witnessed a cosmic event unfolding that really occurred about 700 years ago!

Scientists also believe that Betelgeuse is on the verge of going supernova – dying in an explosive event. In fact, it may have already done so, but the light from the explosion still hasn’t reached us. There’s a good chance that Betelgeuse no longer exists, though we can still see it today from Earth.

Traveling Back in Time: 6,500 years

Nebulae are clouds of gas and dust where stars are birthed, or the remnants of a dead or dying star itself. These beautiful, ethereal cosmic objects are the subject of some of Hubble’s most iconic images, but they can also teach us more about how our universe behaves and evolves.

For example, a favorite target for Hubble is the Crab Nebula, located about 6,500 light-years away. There are records from 1054 CE written by Chinese astronomers noting the new presence of a shockingly bright “guest” star in the sky, visible even during the daytime. Turns out, they actually saw a supernova – a star’s explosive death – which became the Crab Nebula, made up by the remnants of this violent event. Of course, those Chinese astronomers witnessed a supernova explosion that occurred about 5446 BCE, but it took the light from the explosion 6,500 years to reach Earth in the year 1054.

Traveling Back in Time: 2.5 million years

When Hubble looks beyond our own galaxy, we can watch cosmic history unfold over eons.

The Andromeda Galaxy is a whopping 2.5 million light-years away, but that’s just the closest major galaxy to us here in the Milky Way. Observing Andromeda is like staring into a vision from 2.5 million years ago – back during the Paleolithic period on Earth, when very early humans existed.

And if Andromeda is the closest major galaxy to us, it’s difficult to comprehend just how far the light from the most distant observed galaxies has traveled.

Traveling Back in Time: 12.9 billion years

Another Hubble record is for observing the most distant individual star ever detected, named Earendel. This faraway star emitted its light within the first billion years of the universe, which is about 13.8 billion years old, so it took quite a while to reach Hubble! In fact, that observation was only made possible by nature’s magnifying glass – an astronomical phenomenon known as gravitational lensing. When a massive cosmic object has enough gravity, its gravitational field can magnify and bend light coming from objects located behind it. The gravity of a galaxy cluster located between Hubble and Earendel magnified the star’s light, making it detectable.  The type of star that Earendel seems to be typically have brief lives, only surviving about half a billion years. That means Earendel has ceased to exist for over 12 billion years, yet we are able to look back in time and watch Earendel during its short life.

Traveling Back in Time: 13.4 billion years

Perhaps some of Hubble’s most legendary observations are its deep field images, which collect light from thousands of galaxies that are billions of light-years away.

With this type of imagery, we can better understand how our universe changes over time by puzzling out how galaxies evolve. The farther back we look with Hubble, the closer we get to the the big bang, when the universe began – so the most distant galaxies observed by Hubble often appear to us as the “youngest” ones – giving us a sneak peek at the universe in its infancy. Because these galaxies emitted their light when they were young, we get to witness them in their early stages. These early galaxies often appear simpler and smaller than the grandiose spiral galaxies and merged galaxies we see closer to us in distance, and therefore in time. These young galaxies are actually old galaxies now as they have evolved over the time this light has taken to reach us.

Hubble’s farthest observation is of a galaxy named GN-z11, observed as it was 13.4 billion years in the past! This places it within just 400 million years of the big bang itself.

Watching Our Universe Over Time

Observations of the most distant objects, like GN-z11 and Earendel, give astronomers exciting insight into the environment of our early universe. The light we see literally traveled from all the way back then!

Our universe remains mysterious, mind-bendingly large, and ever-expanding, but by gathering light from near and far – from the recent past to the dawn of the universe itself – Hubble helps answer questions about where we are and how the universe works.

At its core, astronomy is really just archaeology. Cosmic objects give off light, letting us learn more about their lives. It can take a long, long time for light to reach Hubble – just one telescope orbiting just one planet in just one solar system in just one galaxy. Scientists use Hubble like the time machine that it is to piece together the history and mystery of the cosmos, giving us all a glimpse right up to the edge of the universe – and time itself.

Explore More Hubble

The Lost Universe

NASA's Hubble Space Telescope has vanished from Earth’s timeline. Only an ambitious crew of adventurers can uncover what was lost. Are you up to the challenge?

Hubble Science Highlights

Hubble has affected every area of astronomy. Its most notable scientific discoveries reflect the broad range of research and the breakthroughs it has achieved.

Hubble's Cultural Impact

Even if you don't know anything about the Hubble Space Telescope, its pictures have been a part of your life.

What is Hubble Observing?

See the area of sky Hubble is currently investigating or explore its upcoming and past targets.

Hubble E-books

Investigate the mysteries of the universe with Hubble. Learn Hubble's history and dive deeper into its discoveries by downloading our e-books.

Time travel: Is it possible?

Science says time travel is possible, but probably not in the way you're thinking.

Albert Einstein's theory

• General relativity and GPS
• Wormhole travel
• Alternate theories

Science fiction

Is time travel possible? Short answer: Yes, and you're doing it right now — hurtling into the future at the impressive rate of one second per second. 

You're pretty much always moving through time at the same speed, whether you're watching paint dry or wishing you had more hours to visit with a friend from out of town. 

But this isn't the kind of time travel that's captivated countless science fiction writers, or spurred a genre so extensive that Wikipedia lists over 400 titles in the category "Movies about Time Travel." In franchises like " Doctor Who ," " Star Trek ," and "Back to the Future" characters climb into some wild vehicle to blast into the past or spin into the future. Once the characters have traveled through time, they grapple with what happens if you change the past or present based on information from the future (which is where time travel stories intersect with the idea of parallel universes or alternate timelines). 

Related: The best sci-fi time machines ever

Although many people are fascinated by the idea of changing the past or seeing the future before it's due, no person has ever demonstrated the kind of back-and-forth time travel seen in science fiction or proposed a method of sending a person through significant periods of time that wouldn't destroy them on the way. And, as physicist Stephen Hawking pointed out in his book " Black Holes and Baby Universes" (Bantam, 1994), "The best evidence we have that time travel is not possible, and never will be, is that we have not been invaded by hordes of tourists from the future."

Science does support some amount of time-bending, though. For example, physicist Albert Einstein 's theory of special relativity proposes that time is an illusion that moves relative to an observer. An observer traveling near the speed of light will experience time, with all its aftereffects (boredom, aging, etc.) much more slowly than an observer at rest. That's why astronaut Scott Kelly aged ever so slightly less over the course of a year in orbit than his twin brother who stayed here on Earth. 

Related: Controversially, physicist argues that time is real

There are other scientific theories about time travel, including some weird physics that arise around wormholes , black holes and string theory . For the most part, though, time travel remains the domain of an ever-growing array of science fiction books, movies, television shows, comics, video games and more. 

Einstein developed his theory of special relativity in 1905. Along with his later expansion, the theory of general relativity , it has become one of the foundational tenets of modern physics. Special relativity describes the relationship between space and time for objects moving at constant speeds in a straight line. 

The short version of the theory is deceptively simple. First, all things are measured in relation to something else — that is to say, there is no "absolute" frame of reference. Second, the speed of light is constant. It stays the same no matter what, and no matter where it's measured from. And third, nothing can go faster than the speed of light.

From those simple tenets unfolds actual, real-life time travel. An observer traveling at high velocity will experience time at a slower rate than an observer who isn't speeding through space. 

While we don't accelerate humans to near-light-speed, we do send them swinging around the planet at 17,500 mph (28,160 km/h) aboard the International Space Station . Astronaut Scott Kelly was born after his twin brother, and fellow astronaut, Mark Kelly . Scott Kelly spent 520 days in orbit, while Mark logged 54 days in space. The difference in the speed at which they experienced time over the course of their lifetimes has actually widened the age gap between the two men.

"So, where[as] I used to be just 6 minutes older, now I am 6 minutes and 5 milliseconds older," Mark Kelly said in a panel discussion on July 12, 2020, Space.com previously reported . "Now I've got that over his head."

General relativity and GPS time travel

The difference that low earth orbit makes in an astronaut's life span may be negligible — better suited for jokes among siblings than actual life extension or visiting the distant future — but the dilation in time between people on Earth and GPS satellites flying through space does make a difference. 

Read more: Can we stop time?

The Global Positioning System , or GPS, helps us know exactly where we are by communicating with a network of a few dozen satellites positioned in a high Earth orbit. The satellites circle the planet from 12,500 miles (20,100 kilometers) away, moving at 8,700 mph (14,000 km/h). 

According to special relativity, the faster an object moves relative to another object, the slower that first object experiences time. For GPS satellites with atomic clocks, this effect cuts 7 microseconds, or 7 millionths of a second, off each day, according to the American Physical Society publication Physics Central .  

Read more: Could Star Trek's faster-than-light warp drive actually work?

Then, according to general relativity, clocks closer to the center of a large gravitational mass like Earth tick more slowly than those farther away. So, because the GPS satellites are much farther from the center of Earth compared to clocks on the surface, Physics Central added, that adds another 45 microseconds onto the GPS satellite clocks each day. Combined with the negative 7 microseconds from the special relativity calculation, the net result is an added 38 microseconds. 

This means that in order to maintain the accuracy needed to pinpoint your car or phone — or, since the system is run by the U.S. Department of Defense, a military drone — engineers must account for an extra 38 microseconds in each satellite's day. The atomic clocks onboard don’t tick over to the next day until they have run 38 microseconds longer than comparable clocks on Earth.

Given those numbers, it would take more than seven years for the atomic clock in a GPS satellite to un-sync itself from an Earth clock by more than a blink of an eye. (We did the math: If you estimate a blink to last at least 100,000 microseconds, as the Harvard Database of Useful Biological Numbers does, it would take thousands of days for those 38 microsecond shifts to add up.) 

This kind of time travel may seem as negligible as the Kelly brothers' age gap, but given the hyper-accuracy of modern GPS technology, it actually does matter. If it can communicate with the satellites whizzing overhead, your phone can nail down your location in space and time with incredible accuracy. 

Can wormholes take us back in time?

General relativity might also provide scenarios that could allow travelers to go back in time, according to NASA . But the physical reality of those time-travel methods is no piece of cake. 

Wormholes are theoretical "tunnels" through the fabric of space-time that could connect different moments or locations in reality to others. Also known as Einstein-Rosen bridges or white holes, as opposed to black holes, speculation about wormholes abounds. But despite taking up a lot of space (or space-time) in science fiction, no wormholes of any kind have been identified in real life. 

Related: Best time travel movies

"The whole thing is very hypothetical at this point," Stephen Hsu, a professor of theoretical physics at the University of Oregon, told Space.com sister site Live Science . "No one thinks we're going to find a wormhole anytime soon."

Primordial wormholes are predicted to be just 10^-34 inches (10^-33 centimeters) at the tunnel's "mouth". Previously, they were expected to be too unstable for anything to be able to travel through them. However, a study claims that this is not the case, Live Science reported . 

The theory, which suggests that wormholes could work as viable space-time shortcuts, was described by physicist Pascal Koiran. As part of the study, Koiran used the Eddington-Finkelstein metric, as opposed to the Schwarzschild metric which has been used in the majority of previous analyses.

In the past, the path of a particle could not be traced through a hypothetical wormhole. However, using the Eddington-Finkelstein metric, the physicist was able to achieve just that.

Koiran's paper was described in October 2021, in the preprint database arXiv , before being published in the Journal of Modern Physics D.

Alternate time travel theories

While Einstein's theories appear to make time travel difficult, some researchers have proposed other solutions that could allow jumps back and forth in time. These alternate theories share one major flaw: As far as scientists can tell, there's no way a person could survive the kind of gravitational pulling and pushing that each solution requires.

Infinite cylinder theory

Astronomer Frank Tipler proposed a mechanism (sometimes known as a Tipler Cylinder ) where one could take matter that is 10 times the sun's mass, then roll it into a very long, but very dense cylinder. The Anderson Institute , a time travel research organization, described the cylinder as "a black hole that has passed through a spaghetti factory."

After spinning this black hole spaghetti a few billion revolutions per minute, a spaceship nearby — following a very precise spiral around the cylinder — could travel backward in time on a "closed, time-like curve," according to the Anderson Institute. 

The major problem is that in order for the Tipler Cylinder to become reality, the cylinder would need to be infinitely long or be made of some unknown kind of matter. At least for the foreseeable future, endless interstellar pasta is beyond our reach.

Time donuts

Theoretical physicist Amos Ori at the Technion-Israel Institute of Technology in Haifa, Israel, proposed a model for a time machine made out of curved space-time — a donut-shaped vacuum surrounded by a sphere of normal matter.

"The machine is space-time itself," Ori told Live Science . "If we were to create an area with a warp like this in space that would enable time lines to close on themselves, it might enable future generations to return to visit our time."

Amos Ori is a theoretical physicist at the Technion-Israel Institute of Technology in Haifa, Israel. His research interests and publications span the fields of general relativity, black holes, gravitational waves and closed time lines.

There are a few caveats to Ori's time machine. First, visitors to the past wouldn't be able to travel to times earlier than the invention and construction of the time donut. Second, and more importantly, the invention and construction of this machine would depend on our ability to manipulate gravitational fields at will — a feat that may be theoretically possible but is certainly beyond our immediate reach.

Time travel has long occupied a significant place in fiction. Since as early as the "Mahabharata," an ancient Sanskrit epic poem compiled around 400 B.C., humans have dreamed of warping time, Lisa Yaszek, a professor of science fiction studies at the Georgia Institute of Technology in Atlanta, told Live Science .  

Every work of time-travel fiction creates its own version of space-time, glossing over one or more scientific hurdles and paradoxes to achieve its plot requirements. 

Some make a nod to research and physics, like " Interstellar ," a 2014 film directed by Christopher Nolan. In the movie, a character played by Matthew McConaughey spends a few hours on a planet orbiting a supermassive black hole, but because of time dilation, observers on Earth experience those hours as a matter of decades. 

Others take a more whimsical approach, like the "Doctor Who" television series. The series features the Doctor, an extraterrestrial "Time Lord" who travels in a spaceship resembling a blue British police box. "People assume," the Doctor explained in the show, "that time is a strict progression from cause to effect, but actually from a non-linear, non-subjective viewpoint, it's more like a big ball of wibbly-wobbly, timey-wimey stuff." 

Long-standing franchises like the "Star Trek" movies and television series, as well as comic universes like DC and Marvel Comics, revisit the idea of time travel over and over. 

Related: Marvel movies in order: chronological & release order

Here is an incomplete (and deeply subjective) list of some influential or notable works of time travel fiction:

Books about time travel:

• Rip Van Winkle (Cornelius S. Van Winkle, 1819) by Washington Irving
• A Christmas Carol (Chapman & Hall, 1843) by Charles Dickens
• The Time Machine (William Heinemann, 1895) by H. G. Wells
• A Connecticut Yankee in King Arthur's Court (Charles L. Webster and Co., 1889) by Mark Twain
• The Restaurant at the End of the Universe (Pan Books, 1980) by Douglas Adams
• A Tale of Time City (Methuen, 1987) by Diana Wynn Jones
• The Outlander series (Delacorte Press, 1991-present) by Diana Gabaldon
• Harry Potter and the Prisoner of Azkaban (Bloomsbury/Scholastic, 1999) by J. K. Rowling
• Thief of Time (Doubleday, 2001) by Terry Pratchett
• The Time Traveler's Wife (MacAdam/Cage, 2003) by Audrey Niffenegger
• All You Need is Kill (Shueisha, 2004) by Hiroshi Sakurazaka

Movies about time travel:

• Planet of the Apes (1968)
• Superman (1978)
• Time Bandits (1981)
• The Terminator (1984)
• Back to the Future series (1985, 1989, 1990)
• Star Trek IV: The Voyage Home (1986)
• Bill & Ted's Excellent Adventure (1989)
• Groundhog Day (1993)
• Galaxy Quest (1999)
• The Butterfly Effect (2004)
• 13 Going on 30 (2004)
• The Lake House (2006)
• Meet the Robinsons (2007)
• Hot Tub Time Machine (2010)
• Midnight in Paris (2011)
• Looper (2012)
• X-Men: Days of Future Past (2014)
• Edge of Tomorrow (2014)
• Interstellar (2014)
• Doctor Strange (2016)
• A Wrinkle in Time (2018)
• The Last Sharknado: It's About Time (2018)
• Avengers: Endgame (2019)
• Tenet (2020)
• Palm Springs (2020)
• Zach Snyder's Justice League (2021)
• The Tomorrow War (2021)

Television about time travel:

• Doctor Who (1963-present)
• The Twilight Zone (1959-1964) (multiple episodes)
• Star Trek (multiple series, multiple episodes)
• Samurai Jack (2001-2004)
• Lost (2004-2010)
• Phil of the Future (2004-2006)
• Steins;Gate (2011)
• Outlander (2014-2023)
• Loki (2021-present)

Games about time travel:

• Chrono Trigger (1995)
• TimeSplitters (2000-2005)
• Kingdom Hearts (2002-2019)
• Prince of Persia: Sands of Time (2003)
• God of War II (2007)
• Ratchet and Clank Future: A Crack In Time (2009)
• Sly Cooper: Thieves in Time (2013)
• Dishonored 2 (2016)
• Titanfall 2 (2016)
• Outer Wilds (2019)

Additional resources

Explore physicist Peter Millington's thoughts about Stephen Hawking's time travel theories at The Conversation . Check out a kid-friendly explanation of real-world time travel from NASA's Space Place . For an overview of time travel in fiction and the collective consciousness, read " Time Travel: A History " (Pantheon, 2016) by James Gleik. 

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

Get the Space.com Newsletter

Breaking space news, the latest updates on rocket launches, skywatching events and more!

Ailsa is a staff writer for How It Works magazine, where she writes science, technology, space, history and environment features. Based in the U.K., she graduated from the University of Stirling with a BA (Hons) journalism degree. Previously, Ailsa has written for Cardiff Times magazine, Psychology Now and numerous science bookazines. 

Car-size asteroid gives Earth a super-close shave with flyby closer than some satellites

SpaceX launches advanced weather satellite for US Space Force (video)

Eclipse expert Jamie Carter wins media award for extensive solar eclipse coverage

Most Popular

• 2 'Devil Comet' 12P/Pons-Brooks reaches peak brightness tonight. Here's how to see it
• 3 Cosmonaut Muhammed Faris, first Syrian in space, dies at 72
• 4 This Week In Space podcast: Episode 107 — Mars Sample Return Blues
• 5 Lego Star Wars Millennium Falcon (2024) review

We have completed maintenance on Astronomy.com and action may be required on your account. Learn More

• Login/Register
• Solar System
• Exotic Objects
• Upcoming Events
• Deep-Sky Objects
• Observing Basics
• Telescopes and Equipment
• Astrophotography
• Space Exploration
• Human Spaceflight
• Robotic Spaceflight
• The Magazine

What is the speed of light? Here’s the history, discovery of the cosmic speed limit

On one hand, the speed of light is just a number: 299,792,458 meters per second. And on the other, it’s one of the most important constants that appears in nature and defines the relationship of causality itself.

As far as we can measure, it is a constant. It is the same speed for every observer in the entire universe. This constancy was first established in the late 1800’s with the experiments of Albert Michelson and Edward Morley at Case Western Reserve University . They attempted to measure changes in the speed of light as the Earth orbited around the Sun. They found no such variation, and no experiment ever since then has either.

Observations of the cosmic microwave background, the light released when the universe was 380,000 years old, show that the speed of light hasn’t measurably changed in over 13.8 billion years.

In fact, we now define the speed of light to be a constant, with a precise speed of 299,792,458 meters per second. While it remains a remote possibility in deeply theoretical physics that light may not be a constant, for all known purposes it is a constant, so it’s better to just define it and move on with life.

How was the speed of light first measured?

In 1676 the Danish astronomer Ole Christensen Romer made the first quantitative measurement of how fast light travels. He carefully observed the orbit of Io, the innermost moon of Jupiter. As the Earth circles the Sun in its own orbit, sometimes it approaches Jupiter and sometimes it recedes away from it. When the Earth is approaching Jupiter, the path that light has to travel from Io is shorter than when the Earth is receding away from Jupiter. By carefully measuring the changes to Io’s orbital period, Romer calculated a speed of light of around 220,000 kilometers per second.

Observations continued to improve until by the 19 th century astronomers and physicists had developed the sophistication to get very close to the modern value. In 1865, James Clerk Maxwell made a remarkable discovery. He was investigating the properties of electricity and magnetism, which for decades had remained mysterious in unconnected laboratory experiments around the world. Maxwell found that electricity and magnetism were really two sides of the same coin, both manifestations of a single electromagnetic force.

As Maxwell explored the consequences of his new theory, he found that changing magnetic fields can lead to changing electric fields, which then lead to a new round of changing magnetic fields. The fields leapfrog over each other and can even travel through empty space. When Maxwell went to calculate the speed of these electromagnetic waves, he was surprised to see the speed of light pop out – the first theoretical calculation of this important number.

What is the most precise measurement of the speed of light?

Because it is defined to be a constant, there’s no need to measure it further. The number we’ve defined is it, with no uncertainty, no error bars. It’s done. But the speed of light is just that – a speed. The number we choose to represent it depends on the units we use: kilometers versus miles, seconds versus hours, and so on. In fact, physicists commonly just set the speed of light to be 1 to make their calculations easier. So instead of trying to measure the speed light travels, physicists turn to more precisely measuring other units, like the length of the meter or the duration of the second. In other words, the defined value of the speed of light is used to establish the length of other units like the meter.

How does light slow down?

Yes, the speed of light is always a constant. But it slows down whenever it travels through a medium like air or water. How does this work? There are a few different ways to present an answer to this question, depending on whether you prefer a particle-like picture or a wave-like picture.

In a particle-like picture, light is made of tiny little bullets called photons. All those photons always travel at the speed of light, but as light passes through a medium those photons get all tangled up, bouncing around among all the molecules of the medium. This slows down the overall propagation of light, because it takes more time for the group of photons to make it through.

In a wave-like picture, light is made of electromagnetic waves. When these waves pass through a medium, they get all the charged particles in motion, which in turn generate new electromagnetic waves of their own. These interfere with the original light, forcing it to slow down as it passes through.

Either way, light always travels at the same speed, but matter can interfere with its travel, making it slow down.

Why is the speed of light important?

The speed of light is important because it’s about way more than, well, the speed of light. In the early 1900’s Einstein realized just how special this speed is. The old physics, dominated by the work of Isaac Newton, said that the universe had a fixed reference frame from which we could measure all motion. This is why Michelson and Morley went looking for changes in the speed, because it should change depending on our point of view. But their experiments showed that the speed was always constant, so what gives?

Einstein decided to take this experiment at face value. He assumed that the speed of light is a true, fundamental constant. No matter where you are, no matter how fast you’re moving, you’ll always see the same speed.

This is wild to think about. If you’re traveling at 99% the speed of light and turn on a flashlight, the beam will race ahead of you at…exactly the speed of light, no more, no less. If you’re coming from the opposite direction, you’ll still also measure the exact same speed.

This constancy forms the basis of Einstein’s special theory of relativity, which tells us that while all motion is relative – different observers won’t always agree on the length of measurements or the duration of events – some things are truly universal, like the speed of light.

Can you go faster than light speed?

Nope. Nothing can. Any particle with zero mass must travel at light speed. But anything with mass (which is most of the universe) cannot. The problem is relativity. The faster you go, the more energy you have. But we know from Einstein’s relativity that energy and mass are the same thing. So the more energy you have, the more mass you have, which makes it harder for you to go even faster. You can get as close as you want to the speed of light, but to actually crack that barrier takes an infinite amount of energy. So don’t even try.

How is the speed at which light travels related to causality?

If you think you can find a cheat to get around the limitations of light speed, then I need to tell you about its role in special relativity. You see, it’s not just about light. It just so happens that light travels at this special speed, and it was the first thing we discovered to travel at this speed. So it could have had another name. Indeed, a better name for this speed might be “the speed of time.”

Related: Is time travel possible? An astrophysicist explains

We live in a universe of causes and effects. All effects are preceded by a cause, and all causes lead to effects. The speed of light limits how quickly causes can lead to effects. Because it’s a maximum speed limit for any motion or interaction, in a given amount of time there’s a limit to what I can influence. If I want to tap you on the shoulder and you’re right next to me, I can do it right away. But if you’re on the other side of the planet, I have to travel there first. The motion of me traveling to you is limited by the speed of light, so that sets how quickly I can tap you on the shoulder – the speed light travels dictates how quickly a single cause can create an effect.

The ability to go faster than light would allow effects to happen before their causes. In essence, time travel into the past would be possible with faster-than-light travel. Since we view time as the unbroken chain of causes and effects going from the past to the future, breaking the speed of light would break causality, which would seriously undermine our sense of the forward motion of time.

Why does light travel at this speed?

No clue. It appears to us as a fundamental constant of nature. We have no theory of physics that explains its existence or why it has the value that it does. We hope that a future understanding of nature will provide this explanation, but right now all investigations are purely theoretical. For now, we just have to take it as a given.

2024 Full Moon calendar: Dates, times, types, and names

Jupiter: Size, distance from the Sun, orbit

Jupiter’s moon Io has likely been active for our solar system’s entire history

While millions watched the eclipse, these Purdue University scientists listened

The best telescopes if you want to spend somewhere from $90 to $11,000

The search is on for extraterrestrial life on worlds like Enceladus

The clever prince Ulugh Beg built — and used — an ingenious observatory in the 15th century

The largest digital camera ever made for astronomy is done

NASA seeks faster, cheaper options to return Mars samples to Earth

• Newsletters

Time travel: five ways that we could do it

Cathal O’Connell

Cathal O'Connell is a science writer based in Melbourne.

In 2009 the British physicist Stephen Hawking held a party for time travellers – the twist was he sent out the invites a year later (No guests showed up). Time travel is probably impossible. Even if it were possible, Hawking and others have argued that you could never travel back before the moment your time machine was built.

But travel to the future? That’s a different story.

Of course, we are all time travellers as we are swept along in the current of time, from past to future, at a rate of one hour per hour.

But, as with a river, the current flows at different speeds in different places. Science as we know it allows for several methods to take the fast-track into the future. Here’s a rundown.

1. Time travel via speed

This is the easiest and most practical way to time travel into the far future – go really fast.

According to Einstein’s theory of special relativity, when you travel at speeds approaching the speed of light, time slows down for you relative to the outside world.

This is not a just a conjecture or thought experiment – it’s been measured. Using twin atomic clocks (one flown in a jet aircraft, the other stationary on Earth) physicists have shown that a flying clock ticks slower, because of its speed.

In the case of the aircraft, the effect is minuscule. But If you were in a spaceship travelling at 90% of the speed of light, you’d experience time passing about 2.6 times slower than it was back on Earth.

And the closer you get to the speed of light, the more extreme the time-travel.

Computer solves a major time travel problem

The highest speeds achieved through any human technology are probably the protons whizzing around the Large Hadron Collider at 99.9999991% of the speed of light. Using special relativity we can calculate one second for the proton is equivalent to 27,777,778 seconds, or about 11 months , for us.

Amazingly, particle physicists have to take this time dilation into account when they are dealing with particles that decay. In the lab, muon particles typically decay in 2.2 microseconds. But fast moving muons, such as those created when cosmic rays strike the upper atmosphere, take 10 times longer to disintegrate.

2. Time travel via gravity

The next method of time travel is also inspired by Einstein. According to his theory of general relativity, the stronger the gravity you feel, the slower time moves.

As you get closer to the centre of the Earth, for example, the strength of gravity increases. Time runs slower for your feet than your head.

Again, this effect has been measured. In 2010, physicists at the US National Institute of Standards and Technology (NIST) placed two atomic clocks on shelves, one 33 centimetres above the other, and measured the difference in their rate of ticking. The lower one ticked slower because it feels a slightly stronger gravity.

To travel to the far future, all we need is a region of extremely strong gravity, such as a black hole. The closer you get to the event horizon, the slower time moves – but it’s risky business, cross the boundary and you can never escape.

And anyway, the effect is not that strong so it’s probably not worth the trip.

Assuming you had the technology to travel the vast distances to reach a black hole (the nearest is about 3,000 light years away), the time dilation through travelling would be far greater than any time dilation through orbiting the black hole itself.

(The situation described in the movie Interstellar , where one hour on a planet near a black hole is the equivalent of seven years back on Earth, is so extreme as to be impossible in our Universe, according to Kip Thorne, the movie’s scientific advisor.)

The most mindblowing thing, perhaps, is that GPS systems have to account for time dilation effects (due to both the speed of the satellites and gravity they feel) in order to work. Without these corrections, your phones GPS capability wouldn’t be able to pinpoint your location on Earth to within even a few kilometres.

3. Time travel via suspended animation

Another way to time travel to the future may be to slow your perception of time by slowing down, or stopping, your bodily processes and then restarting them later.

Bacterial spores can live for millions of years in a state of suspended animation, until the right conditions of temperature, moisture, food kick start their metabolisms again. Some mammals, such as bears and squirrels, can slow down their metabolism during hibernation, dramatically reducing their cells’ requirement for food and oxygen.

Could humans ever do the same?

Though completely stopping your metabolism is probably far beyond our current technology, some scientists are working towards achieving inducing a short-term hibernation state lasting at least a few hours. This might be just enough time to get a person through a medical emergency, such as a cardiac arrest, before they can reach the hospital.

In 2005, American scientists demonstrated a way to slow the metabolism of mice (which do not hibernate) by exposing them to minute doses of hydrogen sulphide, which binds to the same cell receptors as oxygen. The core body temperature of the mice dropped to 13 °C and metabolism decreased 10-fold. After six hours the mice could be reanimated without ill effects.

Unfortunately, similar experiments on sheep and pigs were not successful, suggesting the method might not work for larger animals.

Another method, which induces a hypothermic hibernation by replacing the blood with a cold saline solution, has worked on pigs and is currently undergoing human clinical trials in Pittsburgh.

4. Time travel via wormholes

General relativity also allows for the possibility for shortcuts through spacetime, known as wormholes, which might be able to bridge distances of a billion light years or more, or different points in time.

Many physicists, including Stephen Hawking, believe wormholes are constantly popping in and out of existence at the quantum scale, far smaller than atoms. The trick would be to capture one, and inflate it to human scales – a feat that would require a huge amount of energy, but which might just be possible, in theory.

Attempts to prove this either way have failed, ultimately because of the incompatibility between general relativity and quantum mechanics.

5. Time travel using light

Another time travel idea, put forward by the American physicist Ron Mallet, is to use a rotating cylinder of light to twist spacetime. Anything dropped inside the swirling cylinder could theoretically be dragged around in space and in time, in a similar way to how a bubble runs around on top your coffee after you swirl it with a spoon.

According to Mallet, the right geometry could lead to time travel into either the past and the future.

Since publishing his theory in 2000, Mallet has been trying to raise the funds to pay for a proof of concept experiment, which involves dropping neutrons through a circular arrangement of spinning lasers.

His ideas have not grabbed the rest of the physics community however, with others arguing that one of the assumptions of his basic model is plagued by a singularity, which is physics-speak for “it’s impossible”.

The Royal Institution of Australia has an Education resource based on this article. You can access it here .

Related Reading: Computer solves a major time travel problem

Originally published by Cosmos as Time travel: five ways that we could do it

Please login to favourite this article.

December 5, 2023

Light Can Travel Backward in Time (Sort Of)

Light can be reflected not only in space but also in time—and researchers exploring such “time reflections” are finding a wealth of delightfully odd and useful effects

By Anna Demming

Ekrem EDALI/Alamy Stock Photo

Can we turn back time? Ask a savvy physicist, and the answer will be “it depends.”

Schemes for retrograde time travel abound but usually involve irreconcilable paradoxes and rely on outlandish theoretical constructs such as wormholes (which may not actually exist). Yet when it comes to simply turning back the clock—akin to stirring a scrambled raw egg and seeing the yolk and white reseparate—a rich and growing subfield of wave physics shows that such “time reversal” is possible.

Reversing time would seem to fundamentally clash with one of the most sacred tenets of physics, the second law of thermodynamics, which essentially states that disorder—more specifically “entropy”—is always increasing, as humbly demonstrated in the incessant work needed to keep things tidy. This inexorable slide toward mess and decay is what tends to make unscrambling eggs impossibly difficult—and what propels time’s arrow on a one-way trip through our day-to-day experiences. And although so far there’s no way to unscramble an egg, in certain carefully controlled scenarios within relatively simple systems, researchers have managed to turn back time.

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing . By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

The trick is to create a certain kind of reflection. First, imagine a regular spatial reflection, like one you see in a silver-backed glass mirror. Here reflection occurs because for a ray of light, silver is a very different transmission medium than air; the sudden change in optical properties causes the light to bounce back, like a Ping-Pong ball hitting a wall. Now imagine that instead of changing at particular points in space, the optical properties all along the ray’s path change sharply at a specific moment in time. Rather than recoiling in space, the light would recoil in time, precisely retracing its tracks, like the Ping-Pong ball returning to the player who last hit it. This is a “time reflection.”

Time reflections have fascinated theorists for decades but have proved devilishly tricky to pull off in practice because rapidly and sufficiently changing a material’s optical properties is no small task. Now, however, researchers at the City University of New York have demonstrated a breakthrough: the creation of light-based time reflections .

To do so, physicist Andrea Alù and his colleagues devised a “metamaterial” with adjustable optical properties that they could tweak within fractions of a nanosecond to halve or double how quickly light passes through. Metamaterials have properties determined by their structures; many are composed of arrays of microscopic rods or rings that can be tuned to interact with and manipulate light in ways that no natural material can. Bringing their power to bear on time reflections, Alù says, revealed some surprises. “Now we are realizing that [time reflections] can be much richer than we thought because of the way that we implement them,” he adds.

Such structural properties are also found in nature—for example, in the radiant iridescence of a butterfly’s wing. Picking up where nature left off, however, researchers studying metamaterials have engineered structures that can render objects invisible , and applications range from better antennas and earthquake protection to building light-based computers . Now scientists are trading in spatial dimensions of these structural features for temporal ones. “We design metamaterials to do unusual things, and this is one of those unusual things,” says Nader Engheta, a professor at the University of Pennsylvania and a pioneer in metamaterial-modulated wave physics.

Waves Gone Weird

The device Alù and his collaborators developed is essentially a waveguide that channels microwave-frequency light. A densely spaced array of switches along the waveguide connects it to capacitor circuits, which can dynamically add or remove material for the light to encounter. This can radically shift the waveguide’s effective properties, such as how easily it allows light to pass through. “We are not changing the material; we are adding or subtracting material,” Alù says. “That is why the process can be so fast.”

Time reflections come with a range of counterintuitive effects that have been theoretically predicted but never demonstrated with light. For instance, what is at the beginning of the original signal will be at the end of the reflected signal—a situation akin to looking at yourself in a mirror and seeing the back of your head. In addition, whereas a standard reflection alters how light traverses space, a time reflection alters light’s temporal components—that is, its frequencies. As a result, in a time-reflected view, the back of your head is also a different color. Alù and his colleagues observed both of these effects in the team’s device. Together they hold promise for fueling further advances in signal processing and communications—two domains that are vital for the function of, say, your smartphone, which relies on effects such as shifting frequencies.

Just a few months after developing the device, Alù and his colleagues observed more surprising behavior when they tried creating a time reflection in that waveguide while shooting two beams of light at each other inside it . Normally colliding beams of light behave as waves, producing interference patterns where their overlapping peaks and troughs add up or cancel out like ripples on water (in “constructive” or “destructive” interference, respectively). But light can, in fact, act as a pointlike projectile, a photon, as well as a wavelike oscillating field—that is, it has “ wave-particle duality .” Generally a particular scenario will distinctly elicit just one behavior or the other, however. For instance, colliding beams of light don’t bounce off each other like billiard balls! But according to Alù and his team’s experiments, when a time reflection occurs, it seems that they do.

The researchers achieved this curious effect by controlling whether the colliding waves were interfering constructively or destructively—whether they were adding or subtracting from each other—when the time reflection occurred. By controlling the specific instant when the time reflection took place, the scientists demonstrated that the two waves bounce off each other with the same wave amplitudes that they started with, like colliding billiard balls. Alternatively they could end up with less energy, like recoiling spongy balls, or even gain energy, as would be the case for balls at either end of a stretched spring. “We can make these interactions energy-conserving, energy-supplying or energy-suppressing,” Alù says, highlighting how time reflections could provide a new control knob for applications that involve energy conversion and pulse shaping, in which the shape of a wave is changed to optimize a pulse’s signal.

Unscrambling the Physics

Readers who are well versed in the laws of physics can be reassured that Alù’s device does not violate the tenets of thermodynamics. The waveguide does not, for instance, create or destroy energy but simply transforms it efficiently from one form to another—the energy gained or lost by the waves comes from that which is added or subtracted to change the metamaterial’s properties. But what about the inescapable increase of disorder—entropy—over time, as prescribed by thermodynamics? How is a light beam’s time reflection not the equivalent of unscrambling an egg?

As John Pendry, a metamaterial-focused physicist at Imperial College London, explains, however odd reversing a light beam may look, it’s wholly consistent with ironclad thermodynamic principles. The rise of entropy is really a matter of losing information, he says. For instance, line schoolchildren up in alphabetical order, and someone will know exactly where to find each child. But let them loose in the playground, and there’s a vast number of different ways the children could be arranged, which equates to an increase in entropy, and what information you had for locating each child is lost. “If [something is] time-reversible, it means you’re not generating entropy,” Pendry says, even if it looks like you are. Going back to the playground analogy, although the children still run off to play, they know what lines to form to return to class at the bell—so no entropy is generated. “You don’t lose the information,” he says.

Reflection is far from the only optical phenomenon to receive the time-domain treatment. In April Pendry and a team of researchers, including Riccardo Sapienza of Imperial College London, demonstrated a time-domain analogue of a classic experiment from centuries ago that ultimately played a key role in establishing light’s wave-particle duality. First performed by physicist Thomas Young in 1801, the “ double-slit experiment ” provided such irrefutable evidence of light’s wavelike nature that in the face of subsequent evidence for light acting as a particle, scientists could only conclude that both descriptions applied. Send a wave at a barrier with two slits, and waves fanning out from one slit will interfere with those emanating from the other. With light, this constructive and destructive interference shows up on a screen beyond the double slit as multiple bright stripes, or “fringes.” Sapienza, Pendry and their colleagues used indium tin oxide (ITO), a photoreactive substance that can rapidly change from transparent to opaque, to produce “time slits.” They showed that a beam of light interacting with double time slits would produce a corresponding interference pattern in frequency, which was used as a time analogue—that is, there were bright light fringes at different frequencies.

According to Engheta, what motivates experiments that swap time and space in optical effects are the “exciting and novel features we can find in the physics of light-matter interaction.” And there are plenty. Pendry describes with a chuckle how he and his colleagues’ temporal explorations with metamaterials have revealed “some very strange things,” including what he calls a “photonic compressor.” Pendry’s photonic compressor is a metamaterial that is striped with regions of different optical properties that affect the speed at which light propagates. The stripes are adjustable, forming a sort of “metagrating,” and when this metagrating moves through the metamaterial alongside light, it can act to trap and herd the photons together, effectively compressing them. Further investigation has also revealed that this kind of photonic compressor shares characteristics with black holes , potentially providing a more manageable lab-scale analogue for studying those extreme astronomical objects. Having unfurled a whole new time dimension to metamaterials, photon-compressing black hole analogues are just one avenue of curious phenomena to delve into, and the possibilities are legion.

“It’s really assembling a toolbox,” Pendry says, “and then showing this to the world and saying, ‘What can you do with it?’”

• April 11, 2024 | How Our Brains Work: Connecting Lab-Grown Brain Cells Yields New Insights
• April 11, 2024 | Double Trouble: Decoding the Pain-Depression Feedback Loop
• April 11, 2024 | Elemental Surprise: Physicists Discover a New Quantum State
• April 11, 2024 | A Real Life Eye of Sauron? New Technology To Detect Airborne Threats Instantly
• April 11, 2024 | This Math Problem Stumped Scientists for Almost a Century – Two Mathematicians Have Finally Solved It

A Quantum Leap Through Time: Famous Double-Slit Experiment Reimagined

By Monash University April 13, 2023

A team of international physicists led by Imperial College London has successfully recreated the double-slit experiment, demonstrating light’s dual nature as both a particle and a wave, but this time in the domain of time rather than space. The experiment relied on materials that change their optical properties in femtoseconds (quadrillionths of a second), which could potentially be used in new technologies or to explore fundamental questions in physics. The researchers used a thin film of indium-tin-oxide, a metamaterial, which had its reflectance changed by lasers on ultrafast timescales, creating the ‘slits’ for light. This groundbreaking experiment could lead to the development of ultrafast, parallelized optical switches and pave the way for future research in time crystals and metamaterials.

Physicists have recreated the double-slit experiment in time rather than space, using materials that change their optical properties in femtoseconds. This research could lead to ultrafast optical switches and advancements in time crystals and metamaterials .

A team of international physicists has recreated the famous double-slit experiment, which showed light behaving as particles and a wave, in time rather than space.

The experiment relies on materials that can change their optical properties in fractions of a second, which could be used in new technologies or to explore fundamental questions in physics.

The original double-slit experiment, performed in 1801 by Thomas Young at the Royal Institution, showed that light acts as a wave. Further experiments, however, showed that light actually behaves as both a wave and as particles – revealing its quantum nature.

These experiments had a profound impact on quantum physics, revealing the dual particle and wave nature of not just light, but other ‘particles’ including electrons, neutrons, and whole atoms.

The research team led by Imperial College London physicists performed the experiment using ‘slits’ in time rather than space. They achieved this by firing light through a material that changes its properties in femtoseconds (quadrillionths of a second), only allowing light to pass through at specific times in quick succession.

Monash University Head of the School of Physics and Astronomy, Professor Stefan Maier, was part of the team involved with this exciting experiment and a co-author on the study published in the scientific journal Nature Physics .

“The concept of time crystals has the potential to lead to ultrafast, parallelized optical switches,” Professor Maier said.

“It is additionally a beautiful demonstration of wave physics and how we can transfer concepts such as interference from the domain of space to the domain of time.”

Lead researcher Professor Riccardo Sapienza, from the Department of Physics at Imperial College London , said: “Our experiment reveals more about the fundamental nature of light while serving as a stepping-stone to creating the ultimate materials that can minutely control light in both space and time.”

The original double slit setup involved directing light at an opaque screen with two thin parallel slits in it. Behind the screen was a detector for the light that passed through.

To travel through the slits as a wave, light splits into two waves that go through each slit. When these waves cross over again on the other side, they ‘interfere’ with each other. Where peaks of the wave meet, they enhance each other, but where a peak and a trough meet, they cancel each other out. This creates a striped pattern on the detector of regions of more light and less light.

Light can also be parcelled up into ‘particles’ called photons, which can be recorded hitting the detector one at a time, gradually building up the striped interference pattern. Even when researchers fired just one photon at a time, the interference pattern still emerged, as if the photon split in two and travelled through both slits.

In the classic version of the experiment, light emerging from the physical slits changes its direction, so the interference pattern is written in the angular profile of the light. Instead, the time slits in the new experiment change the frequency of the light, which alters its colour. This created colours of light that interfere with each other, enhancing and cancelling out certain colours to produce an interference-type pattern.

The material the team used was a thin film of indium-tin-oxide, which forms most mobile phone screens. The material had its reflectance changed by lasers on ultrafast timescales, creating the ‘slits’ for light. The material responded much quicker than the team expected to the laser control, varying its reflectivity in a few femtoseconds.

The material is a metamaterial – one that is engineered to have properties not found in nature. Such fine control of light is one of the promises of metamaterials, and when coupled with spatial control, could create new technologies and even analogues for studying fundamental physics phenomena like black holes .

Co-author Professor Sir John Pendry from Imperial College said: “The double time slits experiment opens the door to a whole new spectroscopy capable of resolving the temporal structure of a light pulse on the scale of one period of the radiation.”

The team next want to explore the phenomenon in a ‘time crystal’, which is analogous to an atomic crystal, but where the optical properties vary in time.

For more on this experiment, see Physicists Reveal Quantum Nature of Light in a New Dimension .

Reference: “Double-slit time diffraction at optical frequencies” by Romain Tirole, Stefano Vezzoli, Emanuele Galiffi, Iain Robertson, Dries Maurice, Benjamin Tilmann, Stefan A. Maier, John B. Pendry and Riccardo Sapienza, 3 April 2023, Nature Physics . DOI: 10.1038/s41567-023-01993-w

More on SciTechDaily

Time-Bending Experiment: Physicists Reveal Quantum Nature of Light in a New Dimension

Playing Games With Quantum Interference to Solve a Mysterious Physics Puzzle

In Einstein’s Footsteps and Beyond: New Insights Into the Foundations of Quantum Mechanics

Quantum Interference Shown Experimentally in Larger Molecules

Science , Technology

Kirigami Inspires Better Bandages for Deformable Regions of the Body

Underground Neutrino Experiment Searches for Neutrinoless Double Beta Decay

Snapshots of ultrafast switching in quantum electronics could lead to faster computing devices.

Scientists Reveal Quantum Behavior in Fluid Dynamics

6 comments on "a quantum leap through time: famous double-slit experiment reimagined".

A netizen once left a statement in the comment. Science is not concerned with where an idea comes from. The sole test of the validity of an idea is experiment. The man who wrote that on the blackboard was Richard Feynman. Experiments can indeed promote the progress of theory. However, the limitations of experiments make it inevitable that many theories cannot be tested through experiments. The reason why humans are great is because they have powerful theories based on logic and mathematics. Any experiment cannot do without correct and scientific theories. Just like the famous Double-Slit Experiment was reimagined, what is the foundation and basis for designing a scientific experiment? Objective conditions? Subjective thinking? What can humans do?

a bit too overexcited about an on/off switch that yielded the expected results.

First, the general result was predicted but not yet tested. The test and its method was a first, and the material response time was unexpected.

Second, this – experiment, rapid response – yielded a method that “could create new technologies and even analogues for studying fundamental physics phenomena like black holes.”

Where is the overexcitement!?

This is very exciting stuff! So easy to have it slip by. Things are happening super fast!

Light is a wave, not a particle. One error is in thinking they fired one “photon” at a time. You can’t fire a single photon when light is a wave, which is why the interference pattern still builds up. This is another monster error in physics (along with Red Shift vs Light Dimming) leading to the inability to describe gravity, which is a form of space deformation that can be simulated using EM wave generators in a standing wave-like pattern (the same way we can build images with lasers). Just because a laser is a narrow directed wave, that doesn’t mean it’s a particle stream either, but rather a single directional wave (instead of two dimensional). Until science begins to recognize such basic fundamental thinking errors, we will never move into the age of warping space to get around the speed of light, which itself is the CPU clock speed of the computer simulation we call the “universe” (Sorry, but we’re actually inside a computer simulation).

Wave-particle duality?

Leave a comment Cancel reply

Email address is optional. If provided, your email will not be published or shared.

Save my name, email, and website in this browser for the next time I comment.

Why does time change when traveling close to the speed of light? A physicist explains

Assistant Professor of Physics and Astronomy, Rochester Institute of Technology

Disclosure statement

Michael Lam does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Rochester Institute of Technology provides funding as a member of The Conversation US.

View all partners

• Bahasa Indonesia

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to [email protected] .

Why does time change when traveling close to the speed of light? – Timothy, age 11, Shoreview, Minnesota

Imagine you’re in a car driving across the country watching the landscape. A tree in the distance gets closer to your car, passes right by you, then moves off again in the distance behind you.

Of course, you know that tree isn’t actually getting up and walking toward or away from you. It’s you in the car who’s moving toward the tree. The tree is moving only in comparison, or relative, to you – that’s what we physicists call relativity . If you had a friend standing by the tree, they would see you moving toward them at the same speed that you see them moving toward you.

In his 1632 book “ Dialogue Concerning the Two Chief World Systems ,” the astronomer Galileo Galilei first described the principle of relativity – the idea that the universe should behave the same way at all times, even if two people experience an event differently because one is moving in respect to the other.

If you are in a car and toss a ball up in the air, the physical laws acting on it, such as the force of gravity, should be the same as the ones acting on an observer watching from the side of the road. However, while you see the ball as moving up and back down, someone on the side of the road will see it moving toward or away from them as well as up and down.

Special relativity and the speed of light

Albert Einstein much later proposed the idea of what’s now known as special relativity to explain some confusing observations that didn’t have an intuitive explanation at the time. Einstein used the work of many physicists and astronomers in the late 1800s to put together his theory in 1905, starting with two key ingredients: the principle of relativity and the strange observation that the speed of light is the same for every observer and nothing can move faster. Everyone measuring the speed of light will get the same result, no matter where they are or how fast they are moving.

Let’s say you’re in the car driving at 60 miles per hour and your friend is standing by the tree. When they throw a ball toward you at a speed of what they perceive to be 60 miles per hour, you might logically think that you would observe your friend and the tree moving toward you at 60 miles per hour and the ball moving toward you at 120 miles per hour. While that’s really close to the correct value, it’s actually slightly wrong.

This discrepancy between what you might expect by adding the two numbers and the true answer grows as one or both of you move closer to the speed of light. If you were traveling in a rocket moving at 75% of the speed of light and your friend throws the ball at the same speed, you would not see the ball moving toward you at 150% of the speed of light. This is because nothing can move faster than light – the ball would still appear to be moving toward you at less than the speed of light. While this all may seem very strange, there is lots of experimental evidence to back up these observations.

Time dilation and the twin paradox

Speed is not the only factor that changes relative to who is making the observation. Another consequence of relativity is the concept of time dilation , whereby people measure different amounts of time passing depending on how fast they move relative to one another.

Each person experiences time normally relative to themselves. But the person moving faster experiences less time passing for them than the person moving slower. It’s only when they reconnect and compare their watches that they realize that one watch says less time has passed while the other says more.

This leads to one of the strangest results of relativity – the twin paradox , which says that if one of a pair of twins makes a trip into space on a high-speed rocket, they will return to Earth to find their twin has aged faster than they have. It’s important to note that time behaves “normally” as perceived by each twin (exactly as you are experiencing time now), even if their measurements disagree.

You might be wondering: If each twin sees themselves as stationary and the other as moving toward them, wouldn’t they each measure the other as aging faster? The answer is no, because they can’t both be older relative to the other twin.

The twin on the spaceship is not only moving at a particular speed where the frame of references stay the same but also accelerating compared with the twin on Earth. Unlike speeds that are relative to the observer, accelerations are absolute. If you step on a scale, the weight you are measuring is actually your acceleration due to gravity. This measurement stays the same regardless of the speed at which the Earth is moving through the solar system, or the solar system is moving through the galaxy or the galaxy through the universe.

Neither twin experiences any strangeness with their watches as one moves closer to the speed of light – they both experience time as normally as you or I do. It’s only when they meet up and compare their observations that they will see a difference – one that is perfectly defined by the mathematics of relativity.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to [email protected] . Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

• General Relativity
• Special Relativity
• Time dilation
• Speed of light
• Albert Einstein
• Curious Kids
• Theory of relativity
• Curious Kids US

Sydney Horizon Educators (Identified)

Senior Disability Services Advisor

Deputy Social Media Producer

Associate Professor, Occupational Therapy

GRAINS RESEARCH AND DEVELOPMENT CORPORATION CHAIRPERSON

share this!

May 8, 2014

Does light experience time?

by Fraser Cain, Universe Today

Have you ever noticed that time flies when you're having fun? Well, not for light. In fact, photons don't experience any time at all. Here's a mind-bending concept that should shatter your brain into pieces.

As you might know, I co-host Astronomy Cast, and get to pick the brain of the brilliant astrophysicist Dr. Pamela Gay every week about whatever crazy thing I think of in the shower. We were talking about photons one week and she dropped a bombshell on my brain. Photons do not experience time . [SNARK: Are you worried they might get bored?]

Just think about that idea. From the perspective of a photon, there is no such thing as time. It's emitted, and might exist for hundreds of trillions of years, but for the photon, there's zero time elapsed between when it's emitted and when it's absorbed again. It doesn't experience distance either. [SNARK: Clearly, it didn't need to borrow my copy of GQ for the trip.]

Since photons can't think, we don't have to worry too much about their existential horror of experiencing neither time nor distance, but it tells us so much about how they're linked together. Through his Theory of Relativity, Einstein helped us understand how time and distance are connected.

Let's do a quick review. If we want to travel to some distant point in space, and we travel faster and faster, approaching the speed of light our clocks slow down relative to an observer back on Earth. And yet, we reach our destination more quickly than we would expect. Sure, our mass goes up and there are enormous amounts of energy required, but for this example, we'll just ignore all that.

If you could travel at a constant acceleration of 1 g, you could cross billions of light years in a single human generation. Of course, your friends back home would have experienced billions of years in your absence, but much like the mass increase and energy required, we won't worry about them.

The closer you get to light speed , the less time you experience and the shorter a distance you experience. You may recall that these numbers begin to approach zero. According to relativity, mass can never move through the Universe at light speed. Mass will increase to infinity, and the amount of energy required to move it any faster will also be infinite. But for light itself, which is already moving at light speed… You guessed it, the photons reach zero distance and zero time.

Photons can take hundreds of thousands of years to travel from the core of the Sun until they reach the surface and fly off into space. And yet, that final journey, that could take it billions of light years across space, was no different from jumping from atom to atom.

Source: Universe Today

Explore further

Feedback to editors

Crucial building blocks of life on Earth can more easily form in outer space, says new research

Saturday Citations: Irrationality modeled; genetic basis for PTSD; Tasmanian devils still endangered

Apr 20, 2024

Lemur's lament: When one vulnerable species stalks another

Study uncovers neural mechanisms underlying foraging behavior in freely moving animals

Scientists assess paths toward maintaining BC caribou until habitat recovers

European XFEL elicits secrets from an important nanogel

Apr 19, 2024

Chemists introduce new copper-catalyzed C-H activation strategy

Scientists discover new way to extract cosmological information from galaxy surveys

Compact quantum light processing: New findings lead to advances in optical quantum computing

Some plant-based steaks and cold cuts are lacking in protein, researchers find

Relevant physicsforums posts, how to avoid breaking physics with your “what if” question.

Apr 18, 2024

NASA is seeking a faster, cheaper way to bring Mars samples to Earth

Apr 17, 2024

Could you use the moon to reflect sunlight onto a solar sail?

Apr 14, 2024

Biot Savart law gives us magnetic field strength or magnetic flux density?

Why charge density of moving dipole is dependent on time.

Apr 5, 2024

I have a question about energy & ignoring friction losses

Apr 3, 2024

More from Other Physics Topics

Related Stories

How long does it take sunlight to reach the Earth?

Apr 15, 2013

Can light orbit a black hole?

Mar 25, 2014

Mass is energy

Nov 21, 2011

A photon’s point of view

Aug 8, 2011

The first model for capturing and condensing light under realistic conditions

Mar 24, 2014

Light speed

Oct 10, 2011

Recommended for you

Ghost particle on the scales: Research offers more precise determination of neutrino mass

Smoother surfaces make for better accelerators

Vibrations of granular materials: Theoretical physicists shed light on an everyday scientific mystery

Physicists explain, and eliminate, unknown force dragging against water droplets on superhydrophobic surfaces

Apr 16, 2024

CMS collaboration releases Higgs boson discovery data to the public

Study uses thermodynamics to describe expansion of the universe

Apr 15, 2024

Let us know if there is a problem with our content

Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form . For general feedback, use the public comments section below (please adhere to guidelines ).

Please select the most appropriate category to facilitate processing of your request

Thank you for taking time to provide your feedback to the editors.

Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.

E-mail the story

Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient's address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Phys.org in any form.

Newsletter sign up

Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we'll never share your details to third parties.

More information Privacy policy

Donate and enjoy an ad-free experience

We keep our content available to everyone. Consider supporting Science X's mission by getting a premium account.

E-mail newsletter

• The Magazine
• Stay Curious
• The Sciences
• Environment
• Planet Earth

Could A Telescope Ever See The Beginning Of Time?

The James Webb Space Telescope, or JWST for short, is one of the most advanced telescopes ever built . Planning for JWST began over 25 years ago, and construction efforts spanned over a decade. It was launched into space on Dec. 25, 2021, and within a month arrived at its final destination: 930,000 miles away from Earth. Its location in space allows it a relatively unobstructed view of the universe .

The telescope design was a global effort , led by NASA, and intended to push the boundaries of astronomical observation with revolutionary engineering. Its mirror is massive – about 21 feet (6.5 meters) in diameter. That’s nearly three times the size of the Hubble Space Telescope, which launched in 1990 and is still working today.

It’s a telescope’s mirror that allows it to collect light. JWST’s is so big that it can “see” the faintest and farthest galaxies and stars in the universe. Its state-of-the-art instruments can reveal information about the composition, temperature and motion of these distant cosmic objects.

As an astrophysicist , I’m continually looking back in time to see what stars, galaxies and supermassive black holes looked like when their light began its journey toward Earth, and I’m using that information to better understand their growth and evolution. For me, and for thousands of space scientists, the James Webb Space Telescope is a window to that unknown universe.

Just how far back can JWST peer into the cosmos and into the past? About 13.5 billion years.

Time Travel

A telescope does not show stars, galaxies and exoplanets as they are right now. Instead, astronomers are catching a glimpse of how they were in the past . It takes time for light to travel across space and reach our telescopes. In essence, that means a look into space is also a trip back in time.

This is even true for objects that are quite close to us. The light you see from the Sun left it about 8 minutes, 20 seconds earlier. That’s how long it takes for the Sun’s light to travel to Earth .

You can easily do the math on this. All light – whether sunlight, a flashlight or a light bulb in your house – travels at 186,000 miles (almost 300,000 kilometers) per second . That’s just over 11 million miles (about 18 million kilometers) per minute. The Sun is about 93 million miles (150 million kilometers) from Earth. That comes out to about 8 minutes, 20 seconds.

But the farther away something is, the longer its light takes to reach us. That’s why the light we see from Proxima Centauri , the closest star to us aside from our Sun, is 4 years old; that is, it’s about 25 trillion miles (approximately 40 trillion kilometers) away from Earth, so that light takes just over four years to reach us. Or, as scientists like to say, four light years .

Most recently, JWST observed Earendel, one of the farthest stars ever detected . The light that JWST sees from Earendel is about 12.9 billion years old.

The James Webb Space Telescope is looking much farther back in time than previously possible with other telescopes, such as the Hubble Space Telescope . For example, although Hubble can see objects 60,000 times fainter than the human eye is able, the JWST can see objects almost nine times fainter than even Hubble can .

The Big Bang

But is it possible to see back to the beginning of time?

The Big Bang is a term used to define the beginning of our universe as we know it. Scientists believe it occurred about 13.8 billion years ago . It is the most widely accepted theory among physicists to explain the history of our universe.

The name is a bit misleading, however, because it suggests that some sort of explosion, like fireworks, created the universe. The Big Bang more closely represents the appearance of rapidly expanding space everywhere in the universe. The environment immediately after the Big Bang was similar to a cosmic fog that covered the universe, making it hard for light to travel beyond it. Eventually, galaxies, stars and planets started to grow.

That’s why this era in the universe is called the “cosmic dark ages.” As the universe continued to expand, the cosmic fog began to rise , and light was eventually able to travel freely through space. In fact, a few satellites have observed the light left by the Big Bang, about 380,000 years after it occurred. These telescopes were built to detect the splotchy leftover glow from the Big Bang , whose light can be tracked in the microwave band.

However, even 380,000 years after the Big Bang, there were no stars and galaxies. The universe was still a very dark place. The cosmic dark ages wouldn’t end until a few hundred million years later, when the first stars and galaxies began to form.

The James Webb Space Telescope was not designed to observe as far back as the Big Bang, but instead to see the period when the first objects in the universe began to form and emit light. Before this time period, there is little light for the James Webb Space Telescope to observe, given the conditions of the early universe and the lack of galaxies and stars.

Peering back to the time period close to the Big Bang is not simply a matter of having a larger mirror – astronomers have already done it using other satellites that observe microwave emission from very soon after the Big Bang . So, the James Webb Space Telescope observing the universe a few hundred million years after the Big Bang isn’t a limitation of the telescope. Rather, that’s actually the telescope’s mission. It’s a reflection of where in the universe we expect the first light from stars and galaxies to emerge.

By studying ancient galaxies, scientists hope to understand the unique conditions of the early universe and gain insight into the processes that helped them flourish. That includes the evolution of supermassive black holes, the life cycle of stars, and what exoplanets – worlds beyond our solar system – are made of.

Adi Foord is an Assistant Professor of Astronomy and Astrophysics at the University of Maryland, Baltimore County. This article is republished from The Conversation under a Creative Commons license . Read the original article .

• spaceflight
• space exploration

Already a subscriber?

Register or Log In

Keep reading for as low as $1.99!

Sign up for our weekly science updates.

Save up to 40% off the cover price when you subscribe to Discover magazine.

Astrophysicist says he has cracked the code for time travel

C an you imagine going back in time to visit a lost loved one? This heartwrenching desire is what propelled astrophysicist Professor Ron Mallett on a lifelong quest to build a time machine. After years of research, Professor Mallett claims to have finally developed the revolutionary equation for time travel.

The idea of bending time to our will – revisiting the past, altering history, or glimpsing into the future – has been a staple of science fiction for over a century. But could it move from fantasy to reality?

The inspiration: A father's love and a classic novel

Professor Mallett's obsession with time travel and its equation has its roots in a shattering childhood experience. When he was just ten years old, his father, a television repairman who fostered his son's love of science, tragically passed away from a heart attack.

Devastated, the young Mallett sought solace in books. It was H.G. Wells' The Time Machine that sparked a lifelong fascination.

Wells' opening lines became his mantra: "Scientific people know very well that Time is only a kind of Space. And why cannot we move in Time as we move about in the other dimensions of Space?"

This profound question ignited Mallett's scientific journey. He dedicated himself to understanding the nature of time, determined to find a way to revisit the past and see his beloved father once more.

Time travel equation in the hospital

Decades of research into black holes and Einstein's theories of relativity led to the time travel equation.

While hospitalized for a heart condition, Mallett had a revelation. "It turns out that black holes can create a gravitational field that could lead to the creation of time loops that could allow us to go back in time," he explained.

Imagine the fabric of spacetime as a river. While time usually flows in one direction, Mallett theorizes that the immense gravity of a spinning black hole can create whirlpools, where time twists back on itself.

The time machine blueprint

Mallett's vision for a time machine centers on what he calls "an intense and continuous rotating beam of light" to manipulate gravity. His device would use a ring of lasers to mimic the spacetime-distorting effects of a black hole.

"Let's say you have a cup of coffee in front of you. Start stirring the coffee with the spoon. It started to spin, right? That's what a spinning black hole does," explained Mallett.

"In Einstein's theory, space and time are related to each other. That's why it's called space-time. So when the black hole spins, it will actually cause time to shift."

"Eventually, a rotating beam of laser lights can be used as a kind of time machine and cause a time warp that will allow us to go back to the past," said Mallett. Perhaps, what began as a son's wish to see his father one last time might one day transform our understanding of time itself.

Challenges and limitations

The obstacles on the path from time travel equation to machine are immense. Mallett acknowledges the "galactic amounts of energy" needed to power such a device – energy levels far beyond our current capabilities.

The sheer size of a theoretical time machine is also unknown. While Mallett optimistically states, "I figured out how to do it. In theory, it is possible," the reality is that he may not live to see the machine built.

Furthermore, Mallett's theory comes with a significant constraint. "You can send information back, but you can only send it back to the point where you started operating the device."

In this sense, the time machine is like a one-way message service to the past. You can't travel to a point before the machine existed.

Mallet's lifetime of dedication to time travel

Despite the daunting challenges, Mallett's remarkable journey is a testament to the human spirit. Alongside his time travel research, he's led a distinguished academic career, teaching physics at the University of Connecticut .

Now in his seventies, his work has been propelled by an unwavering belief in the possibility of the seemingly impossible.

Equation vs. reality of time travel

Whether Mallett's time machine will ever transcend the realm of theory is uncertain. Skeptics point to the vast technological hurdles and potential paradoxes raised by tampering with time.

Yet, the mere possibility that science might one day unlock the secrets of temporal travel is enough to ignite the imagination. Could we rewrite our regrets, learn from past mistakes, or witness historical events firsthand?

Perhaps Professor Mallett's greatest legacy won't be a time travel equation itself, but the inspiration he provides – a reminder that audacious dreams and unrelenting curiosity have the power to push the boundaries of what we believe is possible.

Read more about Professor Mallett's work here .

More about space-time

As discussed above, space-time, a concept that feels as vast and complex as the universe itself, forms the backbone of our cosmic understanding.

At its core, it blends the dimensions of space and time into a single four-dimensional continuum, challenging our perceptions of reality. This intertwined nature of space and time underpins everything from the motion of planets to the flow of time itself.

Einstein's groundbreaking contribution

Albert Einstein, with his theory of relativity, revolutionized our understanding of space-time. He posited that space and time are not separate entities but are connected in a dynamic relationship affected by mass and energy.

This relationship implies that the presence of a massive object, like a planet or a star, can warp the fabric of space-time around it. It's a concept that turns the notion of a flat, unchanging universe on its head, suggesting that the very structure of the cosmos is malleable.

The warp and weft of the cosmos

Imagine space-time as a vast sheet of fabric. When a heavy object sits on this fabric, it creates a dip or curve. This curvature is what we perceive as gravity.

Planets orbit stars not because they are being "pulled" in a straight line towards them, but because they are following the curved space-time geometry that these massive objects create.

This curvature of space-time is not just a theoretical concept; it's observable and measurable, especially in the presence of extremely massive and dense objects, like black holes.

Gravitational waves: Echoes of cosmic events

One of the most compelling pieces of evidence for the theory of relativity and the dynamic nature of space-time comes from the detection of gravitational waves.

These waves are ripples in the fabric of space-time, generated by some of the most violent and energetic processes in the universe, such as colliding black holes.

Their discovery not only confirmed Einstein's predictions but also opened a new window into observing cosmic events that were previously invisible to us.

Practical impact of space-time

While these concepts might seem distant from daily life, they have real-world applications, particularly in technology. The Global Positioning System (GPS), a technology integral to modern navigation, relies on an understanding of space-time.

Satellites orbiting Earth need to account for the effects of gravitational time dilation -- a consequence of the curvature of space-time -- to provide accurate location data to users on the ground.

In summary, space-time is a framework that shapes our understanding of the universe. From guiding the planets in their orbits to enabling precise navigation on Earth, its effects are both profoundly cosmic and surprisingly practical.

As we continue to explore and understand the intricacies of space-time, we edge closer to unraveling the mysteries of the cosmos, one gravitational wave at a time.

How black holes are linked to time travel

Playing a major role in Dr. Mallett's time machine, black holes exert a gravitational pull so immense that not even light can escape their grasp. This intense gravity fundamentally alters the fabric of space-time around the black hole.

The stronger the gravity, the more pronounced these effects become, leading to what scientists call gravitational time dilation -- a phenomenon where time itself warps, slowing down relative to an observer far from the gravitational pull.

Time dilation explained

At the heart of this phenomenon lies Albert Einstein's theory of General Relativity, which posits that gravity is the result of masses warping the space-time around them.

In the vicinity of a black hole, this warping becomes so extreme that it significantly affects the flow of time.

An observer standing at a safe distance would perceive time to pass much slower for someone closer to the black hole.

This effect intensifies as one approaches the event horizon, the point of no return beyond which the gravitational pull becomes inescapable.

Boundary between time zones

The event horizon of a black hole marks a stark boundary in the universe, where time as we understand it undergoes a dramatic transformation.

To an external observer, objects approaching the event horizon appear to slow down and almost freeze in time, never quite crossing the threshold.

This illusion results from the light from those objects taking longer and longer to reach the observer as the objects move closer to the event horizon, due to the extreme gravitational pull affecting the light's path.

Theoretical implications and observations

This warping of time around black holes is not just a theoretical curiosity. As Dr. Mallett explained previously in this article, it has practical implications for our understanding of the universe. For instance, it plays a crucial role in the behavior of binary systems where one star orbits a black hole.

Moreover, advancements in technology, such as precise atomic clocks and observations from space telescopes, have allowed scientists to measure these effects, further confirming the predictions of General Relativity.

In summary, black holes serve as natural laboratories for testing the limits of our understanding of physics, offering insights into the complex interplay between gravity and the fabric of space-time.

The phenomenon of time dilation near these cosmic behemoths challenges our notions of time and space, inviting us to explore beyond the boundaries of our current knowledge.

As we continue to observe and study these fascinating objects, we inch closer to unraveling the mysteries of the universe.

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap , a free app brought to you by Eric Ralls and Earth.com.

Protect Your Trip »

How to see the northern lights in alaska in 2024.

If seeing the northern lights in Alaska is on your bucket list, this is the year to do it.

How to See the Northern Lights in Alaska

Chris McLennan | Courtesy of State of Alaska

The National Oceanic and Atmospheric Administration says solar activity is intensifying and will peak (at a higher level than previously thought) in 2024. This means travelers will have more opportunities to see the northern lights around the world .

If you're considering a trip to Alaska to witness this atmospheric phenomenon, read on to discover the best months to visit as well as a variety of viewing options.

The best time to see the northern lights in Alaska

Where to see the northern lights in alaska, northern lights alaska cruises.

• Alaska northern lights tours

Courtesy of Travel Alaska

According to the Alaska Travel Industry Association, the best time to see the northern lights is typically from Aug. 21 to April 21 , also known as the Aurora Season. While the aurora can appear at any time of night, 10 p.m. to 2 a.m. are the prime viewing hours.

The winter solstice – which is the shortest day of the year, typically falling between Dec. 20 and 23 – is a particularly good time to be in Alaska for the northern lights. This day affords less daylight and more time to spot the aurora. In parts of Alaska, the amount of daylight during the winter solstice can range from around six hours in Anchorage to less than four further north in Fairbanks. Up in remote Utqiagvik (formerly called Barrow), about 320 miles north of the Arctic Circle, there are roughly 67 days of darkness from Nov. 18 to Jan. 23, resulting in even more opportunities to spot the northern lights.

Of course, 2024 is expected to be a little different. Scientists say solar activity will reach its peak from January to October, expanding the typical time frame for spotting the aurora. Ahead of and during your visit, experts recommend utilizing these forecasting resources:

• Aurora Tracker: Whether you're a beginner or an experienced aurora chaser, you'll appreciate Explore Fairbanks' real-time Aurora Tracker . This online reference shows up-to-the-minute information on the temperature, weather and likelihood of catching the northern lights in Fairbanks. Much of the data comes from one of the world's foremost aurora research centers, the Geophysical Institute at the University of Alaska–Fairbanks . To further assist in your search, you can also download the My Aurora Forecast & Alerts app on your smartphone.
• Aurora Forecast: For other parts of the state, the Geophysical Institute website's Aurora Forecast has daily forecasts of geomagnetic activity up to three days in advance and taken at three-hour intervals. There's also a summation on the webpage of whether the aurora will be active – or not – and where you'll find the best visibility in Alaska.

Courtesy of Aurora Villa

Below are the top destinations to consider when deciding where to see the northern lights in Alaska.

Fairbanks, known as the Golden Heart of Alaska, sits at 65 degrees north latitude, making it an excellent choice for aurora hunters, especially first-timers. It's easily accessible and offers plenty of accommodations , restaurants and other unique attractions . You can also be outside of Fairbanks within minutes to find excellent northern lights viewing locales.

Your chances of seeing the aurora display are excellent as the city sits where the activity of the polar lights is concentrated – under the ring-shaped zone known as the auroral oval. Local experts say that on clear evenings when the sky is very dark, you should be able to witness the skies light up on an average of four out of five nights in Fairbanks.

Where to stay:

• Aurora Villa : Located on the outskirts of Fairbanks, Aurora Villa offers luxurious guest rooms with floor-to-ceiling windows for viewing the northern lights in a cozy private space. The modern wooden cabin sits on 10 acres surrounded by forested hills, yet it's close enough to the city (less than 15 miles northeast) to explore all that Fairbanks has to offer.
• Pike's Waterfront Lodge : Located along the Chena River in Fairbanks, just minutes from Fairbanks International Airport, this property offers 180 rooms and 28 cabins for aurora-hunting adventurers. As a guest of the lodge, you can request that the front desk alert you when the northern lights appear – no matter the time of day or night. Pike's Waterfront Lodge also offers amenities to keep guests warm while viewing the light show outdoors.

Talkeetna sits about 115 miles north of Anchorage in south-central Alaska, at the base of Denali, the tallest mountain peak in North America. With its old clapboard buildings, log cabins and roadhouse dating back to 1917, this historic town offers a lot of outdoor fun beyond chasing the aurora. Main Street is filled with galleries, shops, restaurants and a brewery. The quirky village, once a former mining town, was the inspiration for the imaginary borough of Cicely in the TV show "Northern Exposure."

If you visit in December, check out the festivities at the monthlong Winterfest. This event features a parade of lights, a tree lighting ceremony and the Taste of Talkeetna food festival, plus entertaining events like the Bachelor Auction and the Wilderness Woman Competition.

When it's time to look up in the sky for the lights, local aurora hunters recommend heading out of town to Christiansen Lake or past the airport on Beaver Road. If you prefer to stay close by, look north into the sky toward Denali from Talkeetna Riverfront Park.

• Talkeetna Alaskan Lodge : Book a Mountain View room for views of Denali and the Alaskan Range. The cozy lodge offers multiple dining venues, including the award-winning Foraker Restaurant.
• Talkeetna Lakeside Cabins : These cabins provide peace and quiet on a private lake just 12 miles from Talkeetna.

Denali National Park

Denali National Park is another spectacular place to view the northern lights in Alaska – not to mention one of the top tourist attractions in the U.S. The National Park Service says almost everywhere within the park is free from city light pollution, so if the conditions are right (meaning that's it's clear and dark enough), you should be able to see the aurora borealis, especially when looking toward the northern horizon.

However, when wintertime rolls around – from September or October through April – it's more difficult to access parts of the park, even though it's open year-round. Keep in mind, too, that the lodges closest to the park are typically closed from mid-September to mid-May.

Where to stay: Located less than 15 miles from the Denali National Park entrance, the Aurora Denali Lodge offers year-round accommodations equipped with queen-sized beds, smart TVs and private bathrooms. Rates at the lodge include a continental breakfast, free Wi-Fi, free parking and complimentary hot drinks. What's more, the property says visitors can expect plenty of wildlife sightings, such as bears, moose, lynxes, owls and snowshoe hares, just outside your door.

Coldfoot Camp

Coldfoot Camp is situated above the Arctic Circle in the Brooks Mountain Range, near the Gates of the Arctic National Park and Preserve and the Arctic National Wildlife Refuge. The remote wilderness destination is ideal for aurora viewing since it sits directly under the auroral oval. It's also the perfect locale for backcountry snowshoeing, wildlife viewing and dog mushing.

Where to stay: The Inn at Coldfoot Camp offers rustic accommodations located in trailers that once housed Alaskan pipeline workers. The rooms include two twin beds and a private bathroom and shower. Guests can dine at the on-site Trucker's Cafe, which offers breakfast and dinner buffets in the summer months and all-day a la carte dining in the winter. When you're ready for a cold one at the end of the day, check out the Frozen Foot Saloon and order an Alaska-brewed beer.

If you prefer camping and have your own gear , you can camp free of charge on the property during the summer months. Coldfoot Camp also hosts a selection of year-round Arctic adventures and excursions, including a trip to the nearby village of Wiseman for aurora viewing.

This remote wilderness retreat has just 13 full-time residents. Wiseman is located in Alaska's Brooks Range, about 15 miles north of Coldfoot Camp, 60 miles north of the Arctic Circle and 270 miles from Fairbanks. The community sits directly under the auroral oval, making it one of the best places in Alaska to view the northern lights. You can expect to see the spectacle in the sky in Wiseman about 250 nights a year, especially between late August and mid-April.

• Arctic Hive : Arctic Hive has the distinction of being the northernmost yoga studio in the U.S. A common fiberglass lodge allows guests to gather for cooking and meals, and meditation, educational gatherings and other activities are hosted in a geodesic dome. Arctic Hive also offers retreats that include northern lights viewing opportunities in February and March.
• Arctic Getaway : This bed-and-breakfast sits between the middle fork of the Koyukuk River and Wiseman Creek, offering three cabins. While here, you can learn what it's like to homestead in Alaska above the Arctic Circle and enjoy outdoor activities like dog sled rides across the vast wilderness, cross-country skiing , pack rafting and flightseeing by bush plane.
• Boreal Lodging : Reachable by vehicle, Boreal Lodging has several rental options, ranging from lodge rooms to larger cabins with living areas and kitchens.

Located in western Alaska overlooking the Norton Sound of the Bering Sea, Nome is the ending point for the more than 1,000-mile, 51-year-old Iditarod Trail Dog Sled Race in March. Once the most populated city in Alaska, Nome had almost 20,000 residents and an average of 1,000 new people arriving daily during the height of the gold rush in 1899. Nome is a little quieter now, with a population of less than 4,000 residents.

Where to stay: Some of the best spots for viewing the aurora are at the end of town, where the 52-room Aurora Inn & Suites is located. The hotel conveniently offers car rentals on-site.

Tips on Trips and Expert Picks Newsletter

Travel tips, vacation ideas and more to make your next vacation stellar.

Sign up to receive the latest updates from U.S News & World Report and our trusted partners and sponsors. By clicking submit, you are agreeing to our Terms and Conditions & Privacy Policy .

Situated on the banks of the Arctic Ocean, Utqiagvik is the northernmost city in the U.S. The town, formerly known as Barrow, changed its name in 2016 back to Utqiagvik, its traditional Inupiaq name. Utqiagvik is only accessible by plane: Alaska Airlines and other regional carriers offer service from both Anchorage and Fairbanks.

Where to stay: For accommodations, make reservations at a hotel named for its location – the Top of the World Hotel . The property's comfortable rooms offer views of the Arctic Ocean, and the on-site restaurant, Niggivikput (meaning "our place to eat"), serves traditional local dishes like reindeer soup. While you may be there for aurora hunting, don't miss the excellent wildlife-viewing opportunities: You may see polar bears, caribou, foxes, bearded seals, whales, walruses, migratory birds and the great snowy owl on the tundra.

Borealis Basecamp

One of the best glamping destinations in the U.S. , Borealis Basecamp is a remote 100-acre property that sits within a boreal forest 25 miles north of Fairbanks. The property features 20 individual igloos, resembling those you'd find at Arctic research stations and on polar expeditions, as well as five glass cubes. All accommodations allow guests to gaze up at the aurora and the starry night sky while snuggled up in bed. You'll also enjoy many amenities you'd find in a hotel, including full bathrooms with toiletries and a selection of coffee, hot cocoa and tea.

Choose from a variety of packages that include accommodations and activities like dog-sledding, UTV tours, helicopter sightseeing experiences and more.

Getty Images

One of the best times to cruise to Alaska is during the aurora season. Aurora season sailings to Alaska are available with the following cruise lines this year.

If you're interested in excursions for aurora viewing, look for a line that offers cruisetours, such as Holland America. These tours offer the best of both worlds, giving you time on land and at sea to view the dancing night sky. Holland America's cruisetours range from overnight stays just 2 miles from Denali National Park at the McKinley Chalet Resort to a domed luxury train ride through Alaska's backcountry on the McKinley Explorer. On a Tundra Wilderness Tour in Denali, look for Alaska's "Big Five": grizzly bears, moose, caribou, Dall sheep and wolves. Just keep in mind that none of the above cruise lines can guarantee you'll see the northern lights during your journey.

The best northern lights tours in Alaska

Jody Overstreet | Courtesy of State of Alaska

If you want to experience the aurora borealis by joining a tour group, you'll find a variety of options led by expert guides and granting you easier access to many of the state's remote destinations, often with other activities included. (Just be aware that, on any tour or excursion, there's no way to guarantee that the aurora will be visible.) These are some of the best northern lights tours in Alaska:

Arctic Dog Adventure Co.: Aurora Overnight Tour

Dog-sledding is one of the top winter activities in Alaska, and you can choose to do it by day or night. If you want to experience an Alaska dog-sledding adventure while chasing the aurora, book a once-in-a-lifetime experience with Arctic Dog's Aurora Overnight Tour. Highlights of this two-day, one-night excursion – which starts in Fairbanks – are dog mushing your own sled team and glamping in a heated tent under an aurora-filled sky. Other features of the tour include cold weather gear, a photography lesson and Alaska-inspired meals.

Alaska Wildlife Guide: Northern Lights & Murphy Dome Tour

Located around 20 miles northwest of the city, Murphy Dome is regarded as one of the best places to watch the northern lights in Fairbanks at nearly 3,000 feet above sea level. This location, once home to Murphy Dome Air Force Station with as many as 250 personnel stationed at the base, now houses a long-range radar station that detects military air threats from overseas.

Alaska Wildlife Guide leads 5.5-hour northern lights tours to Murphy Dome, typically from late August to early April – you can check with the company for day-to-day tour availability. Excursion prices include round-trip transportation from Fairbanks, 360-degree views of the north-facing sky, hot beverages and bottled water – in addition to (hopefully) hours of memorable aurora viewing.

Alaska Wildlife Guide: Northern Lights & Arctic Circle Tour

This full-day (14-hour) excursion, also offered by Alaska Wildlife Guide, begins in Fairbanks and crosses the Arctic Circle into Alaska's vast and remote wilderness. The tour includes a drive along the more than 800-mile Trans-Alaskan Pipeline and a half-mile walk along the loop at Finger Mountain with views overlooking the Kanuti Flats (depending on the season). Your guide will also stop along the riverbank after crossing the Yukon River Bridge.

During the tour, you'll learn about the history of the pipeline and hear narratives around the other included stops. A snack and warm beverage are included; then, if conditions are just right, you'll have the chance to see the brilliant light show dance across the dark, clear skies before you arrive back in Fairbanks at dawn.

Alaska Journey Tours: Northern Lights (Aurora) Chasing Tour

Get picked up at your Fairbanks hotel (or meet at the Hyatt Place Fairbanks) for this three-hour northern lights tour in a heated SUV. Guides take photos of tourgoers as well as their own photos of the night sky, which are later shared with the group. Recent travelers praise this tour, and appreciate that the guides are always determined to give them the best northern lights viewing experience.

Alaska Tours: Bettles Lodge Winter Adventure

Hosted by Alaska Tours, the Bettles Lodge Winter Adventure is available January to March and August to December. This excursion includes two, three or four nights at this wilderness lodge about 35 miles north of the Arctic Circle. During the winter days, enjoy outdoor Arctic sports such as snowshoeing and cross-country skiing or stay warm indoors chatting with other guests at the Aurora Lodge. In the evenings, you can bundle up and head outside at one of the best places in Alaska to see the spectacle in the sky.

Prices include round-trip airfare between Fairbanks and Bettles, accommodations at the lodge, meals, a village tour and complimentary use of the Arctic gear (in season).

Alaska Photo Treks: Anchorage Aurora Quest

Alaska Photo Treks offers one of the best ways to see the northern lights in Anchorage – and you'll even learn how best to photograph the aurora, which can be a challenge to capture digitally or on film. This experience, the Anchorage Aurora Quest, is available nightly (when conditions are right), typically from mid-August to mid-April. The approximately six-hour guided tour with a professional photographer explains the science behind the northern lights and provides photo tips for budding aurora photographers in a small-group format. Tourgoers are picked up from their hotel by the guide at about 10 p.m. and return around 4 a.m., though that time can vary based on the aurora forecast.

On the Alaska Photo Treks website, you'll find a list of recommended camera equipment to bring. If you're using a smartphone, the tour group suggests downloading an aurora app and bringing a tripod. The company also advises that you'll be outdoors for about two hours, so you need to dress appropriately for the weather. For the best aurora viewing, the guides usually travel between one to three locations within a 70-mile radius of Anchorage. If you're in town for an extended stay, Alaska Photo Treks also offers a four-day pass for even more nocturnal viewing of the auroral activity.

Alaska Tours: Chena Hot Springs and Northern Lights

Chena Hot Springs Resort is known for its therapeutic waters and aurora-viewing opportunities. If you prefer to head out with a guide rather than on your own, book the Chena Hot Springs and Northern Lights tour with Alaska Tours. This package includes a four- to five-hour Aurora Expedition tour, four nights of accommodations, and access to resort amenities including cross-country skiing and snow machine tours.

Alaska Wildlife Guide: Northern Lights and Chena Hot Springs

Day trips are also an option for those who'd like to enjoy the resort amenities and a chance at seeing the northern lights from Chena Hot Springs. This tour offered by Alaska Wildlife Guide includes admission to the hot springs and Aurora Ice Museum as well as pickup from local hotels. Recent travelers say the tour guides are top-notch.

John Hall's Alaska: Alaska's Winter Wonders

For an extended land tour to chase the aurora – and experience Alaska's magical winter wonderland – book this bucket list eight-day adventure with John Hall's Alaska. The company's Alaska's Winter Wonders tour is offered in February and March; it features up to seven nights of northern lights viewing, as well as adventure-filled days with skiing, snowmobiling and snowshoeing. You'll also take an awe-inspiring flightseeing bush plane ride over Denali National Park, which includes a fly-by of the Foraker, Silverthorne, Hunter and Moose's Tooth peaks before landing on the Great Gorge of Ruth Glacier – the deepest in the world.

If that's not enough adventure, test your skills at dog mushing and curling or take an aerial tram ride. Travelers can also check out the local breweries or just sit back, relax and enjoy the spectacular views. Additional highlights include spending two evenings under the dancing night sky in one of the domed igloos at Borealis Basecamp, as well as aurora borealis photography lessons.

All-inclusive pricing covers accommodations, meals, luxury land and small plane transportation, fully guided service, gratuities, and baggage handling – plus a black subzero jacket to keep you warm during your Alaska adventure.

Why Trust U.S. News Travel

Gwen Pratesi is an avid travel adventurer who fell in love with Alaska on her first visit to the state many years ago. She's returned several times on land trips and by ship for year-round outdoor adventure and to chase the northern lights in one of the best places on the planet to view them. She writes about the travel and culinary industries for a variety of major publications.

You might also be interested in:

• The Top Packable Jackets
• The Top Things to Do in Alaska
• How to See the Northern Lights in Iceland
• The Best Travel Insurance Companies

Tags: Travel , Alaska Vacations , Vacation Ideas

World's Best Places To Visit

• # 1 South Island, New Zealand
• # 4 Bora Bora

If you make a purchase from our site, we may earn a commission. This does not affect the quality or independence of our editorial content.

You May Also Like

The best east coast beaches.

April 19, 2024

The Best Luggage Brands

Rachael Hood April 17, 2024

The Best Hard-sided Luggage Picks

Erin Evans , Rachael Hood , Catriona Kendall , Amanda Norcross and Leilani Osmundson April 17, 2024

The Best Carry-on Luggage

The Best Yellowstone National Park Tours

John Rodwan April 17, 2024

The Best Rome Colosseum Tours

Laura Itzkowitz April 17, 2024

Best Alaska Tours

Lyn Mettler April 16, 2024

The Best Fredericksburg Wine Tours

The Best Personal Item Bags

Rachael Hood April 16, 2024

The 17 Best Costa Rica Tours

Lyn Mettler April 12, 2024

Mindfulness

How time perspective affects travel, do you live in the past, present, or future.

Posted April 15, 2024 | Reviewed by Michelle Quirk

• What Is Mindfulness?
• Find a mindfulness-based counsellor
• Understanding your own time perspective can enhance your life experience.
• Our characteristic types are neither good nor bad, just different from one another.
• Children are present-oriented, while adults favor the future. Seniors tend to preserve the past.

As an enjoyable vacation winds down, some of us become impatient to get home and move on to the next thing. Maybe that’s you. But, instead, you might be someone who tries to preserve, or even expand, every remaining moment. In either case, you’ll attempt to lock these precious flashes into your memory bank with mental snapshots. But without any effort, and all too quickly, the present quickly fades into the past. How we experience time is relevant to travel. Understanding your own time perspective can enhance your experience.

Stanford University Professor Emeritus Phil Zimbardo, author of The Time Paradox , notes that we are all oriented to time in one of the following characteristic ways—past, present, or future. According to his profile, I am future-oriented. What might your style be? Let’s see.

Those of us in the future category are goal-driven, focused on the future consequences of our actions, and forward-looking in general. Then there are the present-hedonic folks, the pleasure seekers who enjoy things in real-time, with less concern about tomorrow. Folks who live in the present tend to be open to experiences they didn’t necessarily plan, and they don’t need to check it off their bucket list. If this style fits, you’re probably most content with the moment-to-moment flow of your travel.

Past-oriented people make up the remaining category. This might be you if you compare current experiences with memories of past events or situations. Past-oriented folks determine the value of travel, according to Zimbardo, by assigning a pleasure quotient to the comparison—better or worse and by how much? This style is more analytic and rational, and based less on emotional factors than is true for present-focused folks. Does this sound like you?

Our characteristic types are neither good nor bad—just different from one another. Future- and past-oriented travelers provide a logical, systematic understanding of where travel fits into human experience. These styles have great evolutionary value. Our distant ancestors, who chronicled the past and predicted the future, tended to be the shaman and storytellers of the tribe. Reviewing the past and predicting the future was critical to human survival.

Present-oriented people tend to have more fun in the moment, and every society needs this type of person to keep things from getting too serious. Savoring the present is an acquired skill and is worth the effort to cultivate! Also, by expanding the present-pleasant and then reviewing a trip in the past-positive, you can have both good feelings and pleasurable memories. Since, as Zimbardo’s research indicates, we have characteristic ways of perceiving time, maintaining a present focus may require some work—if this isn’t naturally how you see the world.

Zimbardo points to another dimension of time—one that is age-related. In general, children are present-oriented while adults favor the future. Seniors tend to preserve the past. As a future-focused senior, I'm aware of the need to put my foot on the brake and try to prolong the present—particularly the pleasing moments while vacationing. This takes some work.

Regardless of the type that best explains you, here are some strategies to expand your time orientation:

• If you’re naturally drawn to the past or future , notice these tendencies and gently nudge yourself toward the present moment. When you catch yourself reminiscing about the last time you were in Paris, as you sit at an outdoor café savoring your steaming latte and munching on a croissant, remind yourself that the people you see strolling by are there right now—not last time or next time. The weather is uniquely now, not needing a contrast with a warmer or sunnier last visit. The present can be pleasant without any backward reference—or simply less.
• Future- oriented travelers tend to spend their present moments imagining future trips, which makes sense in planning life but can steal from the here and now. Recently, on a river cruise through Austria, I was struck by how much conversation I overheard about planning the next trip. Busily sharing these thoughts with fellow travelers, these vacationers sat by a large picture window as the ship sailed into a new city—totally missing the present moment, unnoticed outside of the window.
• Again, if future is your natural mode, keep that in mind as you travel. Learn to prolong the only moment that truly exists—this one that you anticipated for months or maybe years. The first step involves gently guiding your awareness back to the present. Practicing meditation even a few minutes a day will make this process easier.

This article is based on a chapter from my book: Inward Traveler: 51 Ways to Explore the World Mindfully, 2018.

Stanford University professor emeritus, Phil Zimbardo, authored The Time Paradox, Free Press, N.Y., 2008.

Francine Toder, Ph.D. , is an emeritus faculty member of California State University, Sacramento and is a clinical psychologist retired from private practice.

• Find a Therapist
• Find a Treatment Center
• Find a Support Group
• International
• New Zealand
• South Africa
• Switzerland
• Asperger's
• Bipolar Disorder
• Chronic Pain
• Eating Disorders
• Passive Aggression
• Personality
• Goal Setting
• Positive Psychology
• Stopping Smoking
• Low Sexual Desire
• Relationships
• Child Development
• Therapy Center NEW
• Diagnosis Dictionary
• Types of Therapy

Understanding what emotional intelligence looks like and the steps needed to improve it could light a path to a more emotionally adept world.

• Coronavirus Disease 2019
• Affective Forecasting
• Neuroscience