future time travel speed

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:

share this!

May 14, 2020

Time travel into the future is totally possible

by Paul M. Sutter, Universe Today

Believe it or not, time travel is possible.

In fact, you're doing it right now. Every single second of every single day, you are advancing into your own future. You are literally moving through time, the same way you would move through space. It may seem pedantic, but it's a very important point. Movement through time is still movement, and you are reaching your own future (whether you like it or not).

And what's even cooler is that you can skip forward in time if you feel like it.

Well, let me be clear, you need to do a little bit of engineering first.

We know through the physics of Einstein's special theory of relativity that you can trade motion in space for motion in time. If you're standing perfectly still, you're moving through the dimension of time at a particular speed (the speed of light , for those of you who are curious). As soon as you start moving through space, however, you slow down your rate of moving through time.

In other words, the faster you move in space , the slower you move in time.

This means that moving objects, like a clock on a rocket, run a little bit slow. One second for someone in a moving spaceship lasts a little bit longer than a second for someone staying still.

The trick is that in order for this to have any sort of noticeable impact, you have to get close to the speed of light, which is really hard to do—to give you some perspective, astronauts that orbit the Earth at tens of thousands of miles per hour are off by only a microsecond or so from our clocks on the ground.

Our fastest human spacecraft don't even crack a tenth of a percent of the speed of light. But if you could somehow spend a good amount of time hugging close to that ultimate speed limit in the universe, the slower your clock will run. You will travel through time into the future. Nothing will feel different for you, but after a couple of years' journey you would return to the Earth to find our clocks advanced by thousands or even tens of thousands of years, depending on how fast you go.

So the future is yours, and you get to choose how quickly you reach it.

Source Universe Today

Explore further

Feedback to editors

New fossils provide evidence for an 'Age of Monotremes'

16 hours ago

TESS finds intriguing world sized between Earth and Venus

NASA launches ground-breaking climate change satellite

May 25, 2024

Dyson spheres: Astronomers report potential candidates for alien structures, and evidence against their existence

You leave a 'microbe fingerprint' on every piece of clothing you wear—and it could help forensic scientists solve crimes

Saturday Citations: The cheapness horizon of electric batteries; the battle-worthiness of ancient armor; scared animals

Cosmic leap: NASA Swift satellite and AI unravel the distance of the farthest gamma-ray bursts

Scientists discover CO₂ and CO ices in outskirts of solar system

Charge your laptop in a minute? Supercapacitors can help; new research offers clues

New study discovers tiny target on RNA to short-circuit inflammation

Relevant physicsforums posts, calculating vacuum -- these numbers do not make sense, replacing the measurement standards (si units).

May 24, 2024

What drives osmosis? (Statistics or Dynamics?)

May 20, 2024

Planck's Constant times the speed of light

May 17, 2024

How is a magnetic field formed in a space surrounded by one pole?

May 15, 2024

Why is My Homemade Cloud Chamber Not Working?

May 13, 2024

More from Other Physics Topics

Related Stories

Video: Can wormholes act like time machines?

Apr 30, 2020

What time is it in the universe?

Aug 29, 2014

Stephen Hawking's final book suggests time travel may one day be possible – here's what to make of it

Nov 9, 2018

How are galaxies moving away faster than light?

Oct 13, 2015

Does light experience time?

May 8, 2014

Testing the symmetry of space-time by means of atomic clocks

Mar 13, 2019

Recommended for you

Theory and experiment combine to shine a new light on proton spin

New method can create aquatic levitation at much lower temperature, has implications for cooling nuclear reactors

How a world record 'squeeze' could offer comfort for dark matter hunters

May 23, 2024

Atomic-resolution imaging shows why ice is so slippery

Nuclear physicists make first precision measurements of radium monofluoride

May 22, 2024

Researchers show how to use 'topological tweezers' to control active fluids

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

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: 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. 

Science and music festival Starmus VII is about to rock Bratislava with a stellar lineup

China's Chang'e 6 mission to collect samples of the far side of the moon enters lunar orbit (video)

How can we protect satellites in Earth-moon space? This new software could help

Most Popular

• 2 'The first time I read the script ... I sobbed.' 'Atlas' stars Jennifer Lopez and Sterling K. Brown on AI paranoia and their film's emotional core' (exclusive)
• 3 Asteroid-bound Psyche spacecraft fires up ion thrusters, starts cruising through space
• 4 We could float effortlessly in Pluto's subsurface ocean
• 5 International Space Development Conference 2024 beams up Star Trek's William Shatner and more in Los Angeles

April 26, 2023

Is Time Travel Possible?

The laws of physics allow time travel. So why haven’t people become chronological hoppers?

By Sarah Scoles

yuanyuan yan/Getty Images

In the movies, time travelers typically step inside a machine and—poof—disappear. They then reappear instantaneously among cowboys, knights or dinosaurs. What these films show is basically time teleportation .

Scientists don’t think this conception is likely in the real world, but they also don’t relegate time travel to the crackpot realm. In fact, the laws of physics might allow chronological hopping, but the devil is in the details.

Time traveling to the near future is easy: you’re doing it right now at a rate of one second per second, and physicists say that rate can change. According to Einstein’s special theory of relativity, time’s flow depends on how fast you’re moving. The quicker you travel, the slower seconds pass. And according to Einstein’s general theory of relativity , gravity also affects clocks: the more forceful the gravity nearby, the slower time goes.

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.

“Near massive bodies—near the surface of neutron stars or even at the surface of the Earth, although it’s a tiny effect—time runs slower than it does far away,” says Dave Goldberg, a cosmologist at Drexel University.

If a person were to hang out near the edge of a black hole , where gravity is prodigious, Goldberg says, only a few hours might pass for them while 1,000 years went by for someone on Earth. If the person who was near the black hole returned to this planet, they would have effectively traveled to the future. “That is a real effect,” he says. “That is completely uncontroversial.”

Going backward in time gets thorny, though (thornier than getting ripped to shreds inside a black hole). Scientists have come up with a few ways it might be possible, and they have been aware of time travel paradoxes in general relativity for decades. Fabio Costa, a physicist at the Nordic Institute for Theoretical Physics, notes that an early solution with time travel began with a scenario written in the 1920s. That idea involved massive long cylinder that spun fast in the manner of straw rolled between your palms and that twisted spacetime along with it. The understanding that this object could act as a time machine allowing one to travel to the past only happened in the 1970s, a few decades after scientists had discovered a phenomenon called “closed timelike curves.”

“A closed timelike curve describes the trajectory of a hypothetical observer that, while always traveling forward in time from their own perspective, at some point finds themselves at the same place and time where they started, creating a loop,” Costa says. “This is possible in a region of spacetime that, warped by gravity, loops into itself.”

“Einstein read [about closed timelike curves] and was very disturbed by this idea,” he adds. The phenomenon nevertheless spurred later research.

Science began to take time travel seriously in the 1980s. In 1990, for instance, Russian physicist Igor Novikov and American physicist Kip Thorne collaborated on a research paper about closed time-like curves. “They started to study not only how one could try to build a time machine but also how it would work,” Costa says.

Just as importantly, though, they investigated the problems with time travel. What if, for instance, you tossed a billiard ball into a time machine, and it traveled to the past and then collided with its past self in a way that meant its present self could never enter the time machine? “That looks like a paradox,” Costa says.

Since the 1990s, he says, there’s been on-and-off interest in the topic yet no big breakthrough. The field isn’t very active today, in part because every proposed model of a time machine has problems. “It has some attractive features, possibly some potential, but then when one starts to sort of unravel the details, there ends up being some kind of a roadblock,” says Gaurav Khanna of the University of Rhode Island.

For instance, most time travel models require negative mass —and hence negative energy because, as Albert Einstein revealed when he discovered E = mc 2 , mass and energy are one and the same. In theory, at least, just as an electric charge can be positive or negative, so can mass—though no one’s ever found an example of negative mass. Why does time travel depend on such exotic matter? In many cases, it is needed to hold open a wormhole—a tunnel in spacetime predicted by general relativity that connects one point in the cosmos to another.

Without negative mass, gravity would cause this tunnel to collapse. “You can think of it as counteracting the positive mass or energy that wants to traverse the wormhole,” Goldberg says.

Khanna and Goldberg concur that it’s unlikely matter with negative mass even exists, although Khanna notes that some quantum phenomena show promise, for instance, for negative energy on very small scales. But that would be “nowhere close to the scale that would be needed” for a realistic time machine, he says.

These challenges explain why Khanna initially discouraged Caroline Mallary, then his graduate student at the University of Massachusetts Dartmouth, from doing a time travel project. Mallary and Khanna went forward anyway and came up with a theoretical time machine that didn’t require negative mass. In its simplistic form, Mallary’s idea involves two parallel cars, each made of regular matter. If you leave one parked and zoom the other with extreme acceleration, a closed timelike curve will form between them.

Easy, right? But while Mallary’s model gets rid of the need for negative matter, it adds another hurdle: it requires infinite density inside the cars for them to affect spacetime in a way that would be useful for time travel. Infinite density can be found inside a black hole, where gravity is so intense that it squishes matter into a mind-bogglingly small space called a singularity. In the model, each of the cars needs to contain such a singularity. “One of the reasons that there's not a lot of active research on this sort of thing is because of these constraints,” Mallary says.

Other researchers have created models of time travel that involve a wormhole, or a tunnel in spacetime from one point in the cosmos to another. “It's sort of a shortcut through the universe,” Goldberg says. Imagine accelerating one end of the wormhole to near the speed of light and then sending it back to where it came from. “Those two sides are no longer synced,” he says. “One is in the past; one is in the future.” Walk between them, and you’re time traveling.

You could accomplish something similar by moving one end of the wormhole near a big gravitational field—such as a black hole—while keeping the other end near a smaller gravitational force. In that way, time would slow down on the big gravity side, essentially allowing a particle or some other chunk of mass to reside in the past relative to the other side of the wormhole.

Making a wormhole requires pesky negative mass and energy, however. A wormhole created from normal mass would collapse because of gravity. “Most designs tend to have some similar sorts of issues,” Goldberg says. They’re theoretically possible, but there’s currently no feasible way to make them, kind of like a good-tasting pizza with no calories.

And maybe the problem is not just that we don’t know how to make time travel machines but also that it’s not possible to do so except on microscopic scales—a belief held by the late physicist Stephen Hawking. He proposed the chronology protection conjecture: The universe doesn’t allow time travel because it doesn’t allow alterations to the past. “It seems there is a chronology protection agency, which prevents the appearance of closed timelike curves and so makes the universe safe for historians,” Hawking wrote in a 1992 paper in Physical Review D .

Part of his reasoning involved the paradoxes time travel would create such as the aforementioned situation with a billiard ball and its more famous counterpart, the grandfather paradox : If you go back in time and kill your grandfather before he has children, you can’t be born, and therefore you can’t time travel, and therefore you couldn’t have killed your grandfather. And yet there you are.

Those complications are what interests Massachusetts Institute of Technology philosopher Agustin Rayo, however, because the paradoxes don’t just call causality and chronology into question. They also make free will seem suspect. If physics says you can go back in time, then why can’t you kill your grandfather? “What stops you?” he says. Are you not free?

Rayo suspects that time travel is consistent with free will, though. “What’s past is past,” he says. “So if, in fact, my grandfather survived long enough to have children, traveling back in time isn’t going to change that. Why will I fail if I try? I don’t know because I don’t have enough information about the past. What I do know is that I’ll fail somehow.”

If you went to kill your grandfather, in other words, you’d perhaps slip on a banana en route or miss the bus. “It's not like you would find some special force compelling you not to do it,” Costa says. “You would fail to do it for perfectly mundane reasons.”

In 2020 Costa worked with Germain Tobar, then his undergraduate student at the University of Queensland in Australia, on the math that would underlie a similar idea: that time travel is possible without paradoxes and with freedom of choice.

Goldberg agrees with them in a way. “I definitely fall into the category of [thinking that] if there is time travel, it will be constructed in such a way that it produces one self-consistent view of history,” he says. “Because that seems to be the way that all the rest of our physical laws are constructed.”

No one knows what the future of time travel to the past will hold. And so far, no time travelers have come to tell us about it.

• The Open University
• Guest user / Sign out
• Study with The Open University

My OpenLearn Profile

Personalise your OpenLearn profile, save your favourite content and get recognition for your learning

Back to the Future: Is time travel possible?

In the Back to the Future films, Marty McFly travels backwards and forwards in time with the help of Doc Emmett Brown and his souped up DeLorean car. But is time travel really possible?

The simple answer to this question is: Yes! In fact as you read this, you are travelling through time at a rate of one second per second. OK, that’s not quite the answer you were expecting, but it is time travel nonetheless – we can’t help but travel through time, because that’s the nature of time itself. It flows relentlessly from past to future, and the instant of ‘now’ is an infinitesimally short period of time that it’s impossible to remain in. However it turns out that the rate at which time flows forwards is not necessarily a fixed quantity.

So, what about travelling into the future or the past – is that sort of real time travel possible? Well, the first of these is certainly possible, but as far as we know, the other is impossible to achieve.

Time travel into the future is easy – in principle at least. Albert Einstein’s theory of special relativity, which he devised in 1905, shows that ‘moving clocks run slow’. This is an effect known as time dilation. Quite simply, if a clock moves at a constant speed with respect to a stationary observer, that observer would see the moving clock ticking more slowly than one at rest next to her. And the faster the clock moves, the more slowly it ticks. This isn’t just a trick either – all physical or biological process, or anything at all that you care to measure, would indeed happen more slowly when moving rapidly, as viewed from a stationary view point.

And this is what makes time travel into the future possible. Imagine that you boarded a spaceship to the star Tau Ceti, which is 12 light years away. Your spaceship can travel at 80% of the speed of light, which is about 240,000 kilometres per second. As soon as you get there, you turn round and come straight home. Back on Earth, 30 years have passed by the time you return, but on the spaceship, time has passed more slowly. To you on the spaceship, only 18 years would have passed. In effect, you would therefore have travelled 12 years into the future.

The faster you travel, the further into the future you can jump. For instance, in order to jump 1000 years into the future, but only have 1 year elapse on your spaceship, you would need to travel at 99.99995% of the speed of light.

So much for time travel into the future – but why is time travel into the past so difficult? This all comes down to what’s known as causality and is perhaps best summed up by the Grandfather paradox. If time travel into the past were possible, then you could (if you really wanted to) travel into the past to a time before your parents were born and kill your Grandfather. Then your parent would never be born, so neither would you, so you couldn’t travel into the past to kill your Grandfather after all… Because paradoxes like this simply don’t occur in the Universe (as far as we know), time travel into the past cannot be possible.

My favourite exploration of this time travel paradox is in a short story by Robert A. Heinlein from 1958 called “All you zombies”. The plot concerns a character who is eventually revealed (by a series of time travel experiences) to be both his own father and mother. Thankfully, such paradoxes seem not to occur in the real world or, if they do – like Marty McFly when he ensures his parents really did get together in 1955 – people just make sure things happen in the past the way they were meant to!

Learn more about time travel

60 Second Adventures in Astronomy: Special relativity

Who had more fun in life, Albert Einstein or Richard Feynman? Whichever one of them was travelling faster

Level: 1 Introductory

BBC Inside Science: Back to the Future special

BBC Inside Science explores the theme of time travel along with the Film programme as part of their Back to the Future special.

External link

60 second adventures in thought - The Grandfather Paradox

A well known story that questions the logic of time travel. Part of a series of fast-paced animations explaining six famous thought experiments.

This article came Back to the Future from 2013 when it was originally written to celebrate the 50th anniversary of Doctor Who -  discover more perspectives on science fiction and time travel.

Become an OU student

Ratings & comments, share this free course, copyright information, publication details.

• Originally published: Monday, 19 October 2015
• Body text - Creative-Commons : The Open University
• Image 'An angled close-up of a large outdoor clock face that has golden numbers of Roman numerals on it and shows the numbers twelve to three within in the image. The clock-face is a grey and green coloured metal. ' - Marko [ CC BY-ND-NC 2.0 ] via Flickr Creative Commons under Creative-Commons license
• Image 'Save the Clock tower leaflet, Back to the Future' - Alex Headrick [ CC BY-NC-ND 2.0 ] via Flickr Creative Commons under Creative-Commons license
• Image '100 years of General Relativity' - Wally Gobetz [ CC BY-NC-ND 2.0 ] via Flickr Creative Commons under Creative-Commons license
• Image '60 Second Adventures in Astronomy: Special relativity' - under Creative-Commons license

Rate and Review

Rate this article, review this article.

Log into OpenLearn to leave reviews and join in the conversation.

Article reviews

For further information, take a look at our frequently asked questions which may give you the support you need.

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!

Space photo of the week: NASA sees a 'Platypus' move on Jupiter's moon Europa

James Webb telescope sees 'birth' of 3 of the universe's earliest galaxies in world-1st observations

NASA detects Earth-size planet just 40 light-years away that's 'not a bad place' to hunt for life

Most Popular

• 2 James Webb telescope confirms there is something seriously wrong with our understanding of the universe
• 3 Scientists grow diamonds from scratch in 15 minutes thanks to groundbreaking new process
• 4 Scientists just discovered an enormous lithium reservoir under Pennsylvania
• 5 Ancient Mycenaean armor is so good, it protected users in an 11-hour battle simulation inspired by the Trojan War
• 2 Man Coughs Up a Giant Blood Clot in the Shape of His Lung
• 3 10 surprising things that are made from petroleum
• 4 Alaska's rivers are turning bright orange and as acidic as vinegar as toxic metal escapes from melting permafrost
• 5 What's the highest place on Earth that humans live?

Create a free profile to get unlimited access to exclusive videos, sweepstakes, and more!

What we think we know about time travel

Credit: Universal Pictures

It's strange living in a post- Back to the Future world. Not only have we surpassed the date of the future portrayed in Back to the Future Part II , we're also 30 years removed from the release of the third and final film , which premiered in theaters on May 25, 1990.

Over the course of three movies, we saw Marty McFly and Doc Brown travel throughout recent human history and the near future, going as far back as the Wild West and as far forward as the unimaginably distant 2015. The Back to the Future films are fanciful science fiction comedies, not meant to be taken seriously. The science is accurate only insofar as it serves to tell a good story.

Still, is it possible to go forward and see our mistakes before they happen? Is it possible to go back and fix things that are already in our past? Here's what we know — or think we know — about time travel.

WHAT IS TIME?

Time: the great equalizer. Time doesn't care about you at all. You can't gain more of it, and you can't give it away. Irrespective of any other thing about you, each of us lives through the same 24 hours every day. Right?

Not exactly.

Time is mushy. It's variable. Some have called it wibbly-wobbly. And it turns out, you can manipulate it if you try hard enough, thanks to Einstein.

We evolved in a sort of medium environment. Human beings are medium-sized objects, somewhere between the very small (quarks, electrons, atoms, and the like) and the very large (planets, stars, and supermassive black holes). And we operate at medium speeds, faster than the slow movements of tectonic plates, but slower than the speed of light.

Physics operates in pretty predictable ways in the world we inhabit. Gravity impacts objects in ways we can accurately measure; comets orbit and return at regular intervals. We know when solar eclipses will happen because the cosmic dance of the sun and moon follows along a known path. Time ticks onward in one direction and at a consistent rate. All is as it should be, all is according to plan.

Outside of our medium-sized world, however, things can get weird.

Physics breaks down when you get too small, or too massive. Gravity does things we can't quite work out, quantum effects find their way in. Things cease to play by the rules as we know them. Likewise, the faster we accelerate beyond our medium speed, the weirder time gets.

Special relativity concluded that the speed of light is consistent for all observers. Photons moving through a vacuum travel at a staggering 186,282 miles per second.

That speed is impressive all on its own. It's fast enough that the time delay between when light hits an object, bounces off, and enters our eyes is so short as to not be noticed. Which is good, especially for our ancient ancestors. It would have been difficult to evade predators if we were already half-swallowed by the time we noticed them.

The speed of light, though, becomes even more impressive and bizarre, because of the way it remains constant no matter the position or speed of the observer. Let's break down what that means. The actual speed of any given object is a combination of its personal speed, combined with the speed of any other objects acting upon it.

For instance, let's suppose you're reading this while sitting down. Your personal speed is zero. You aren't moving at all, relative to any objects you're in contact with. Easy enough. But maybe you're on a train on your way to work, and that train is traveling at 75 miles per hour.

Your speed then becomes the combined speed of you and the speed of the train. Let's go further. The train is traveling at 75 miles per hour relative to the Earth, but the Earth is traveling at 67,000 miles per hour around the Sun. Furthermore, the Sun is traveling at 514,000 miles per hour around the center of our galaxy.

Assuming the train, the Earth, and the Sun are all traveling in the same direction, your total speed is actually 581,075 miles per hour.

That doesn't even take into account the speed of the galaxy through space, but you get the point. To someone sitting on the train with you, our speed is zero. Your speed is different to an observer standing on the ground outside the train, it's different to someone observing from the Sun, or from the center of the galaxy. The position of the observer matters, it changes the outcome.

Speeds compound, that's the way things work in the Medium world. Not so with light.

Replace the train traveler with light and everything we expect about compounding speeds goes out the window. The apparent speed of light remains the same, 186,282 miles per second, regardless of the position or relative speed of the observer. Light gets no faster and no slower.

Special Relativity suggests an elegant, if counterintuitive, solution to this problem. As objects increase in speed, time moves more slowly. Changing the length of each tick of the clock allows the speed of light to remain consistent no matter how fast you're traveling in respect to it.

When Special Relativity was published, these ideas were just numbers on a page, but they've been confirmed by observation and experimentation. In fact, engineers have to account for time dilation when designing satellites.

Because they are orbiting at speeds much faster than we're accustomed to on the ground, a satellite's internal clocks will run more slowly. The difference is very small, but can stack up over time. Since satellites often need to have accurate timekeeping, this time dilation has to be accounted and corrected for.

It gets even more complicated because of gravity.

Gravity bends spacetime and, since GPS satellites orbit so far away from the surface of the Earth, they feel the effects of gravity less than we do, which has the opposite effect of causing the clocks to tick more quickly. All told, GPS satellites in orbit would drift 38 microseconds into the future every day if we didn't account for relativity.

It's a small amount, it would take about 72 years for their clocks to drift ahead of ours by one second, but it's enough to wreak havoc with GPS services, pretty quickly.

Besides, the synchronicity of our clocks isn't the important bit. What's important is the reality that those satellites are actually time-traveling at a rate of one second every 72 years. The effect is slow, but that's only because the fraction of the speed of light at which their traveling is small.

Time isn't static. It's personal. We aren't all experiencing the passage of time in the same way or at the same rate. Every time you get in a car, a train, or a plane, every time you go for a jog or even stagger to the bathroom in the middle of the night, you're altering the way you travel through time.

GRAVITY AND SPEED

Now that we know we can alter our relationship to time, by altering our speed or by manipulating gravity, how can we use that to our advantage and travel to distant temporal locales?

Speed is probably our best bet right now.

Considering the timescale of human existence, we've made incredible strides in increasing our maximum speed over the last several decades. It was once believed we would never break the sound barrier; that was accomplished by Chuck Yeager in 1947, a little more than 70 years ago.

That was the first time a human being traveled faster than 343 meters per second. That's about ten-thousandth of a percent of the speed of light. Pretty fast by human standards — very slow on the cosmic scale.

A little more than a decade later, Neil Armstrong, Buzz Aldrin, and Michael Collins blasted off in a rocket, headed for the Moon. Their top speed was 25,000 miles per hour, more than 32 times faster than Yeager. Still, the crew of Apollo 11 was traveling at only 6.94 miles per second, roughly 0.0037 percent of the speed of light.

Getting closer, some of those zeroes are falling off. Still, it's a long way away.

That's about where we top off, for now. At least for crewed vehicles. We have created faster spacecraft.

The Parker Solar Probe, launched in 2018, was sent on a mission to study the Sun's corona. It approached to within 18.7 million kilometers, granting it the honor of closest approach of any artificial object.

At its fastest, it was traveling 430,000 miles per hour, or, 119.4 miles per second. That gets us to 0.064 of the speed of light.

We'd have to get moving more than 15 times faster than the fastest craft we've ever built to hit one percent the speed of light.

Even at those speeds, we'd notice a difference in relative time of about 26 minutes over the course of a year.

If you really want to time-travel in a significant way, you have to get much faster.

At 90 percent of the speed of light (167,653.8 miles per second), a craft traveling for 10 years according to their own clock would arrive back on Earth to discover that nearly 23 years had passed.

At 99.99 percent of the speed of light, a craft traveling for one year would come back to a world that had aged more than 70 years in their absence.

At 99.99999 percent of the speed of light, for a year, more than 2000 years would pass on Earth.

The point is, the closer you get to the speed of light, the more time dilation is experienced.

Achieving those speeds, however, is incredibly unlikely and probably impossible. Physics conspires against us in this regard. Any object with mass increases in mass as it approaches the speed of light . In effect, it gets heavier, which requires more fuel to continue to accelerate. Eventually, you reach an infinite mass and infinite energy requirement. It's like pushing a stone up a continuously inclining hill. It gets harder the closer you get to the top.

Which is too bad, because nearing the speed of light would allow us to travel forward in time, with minimal investment of personal time. And, if we could break the light speed barrier, all bets are off. The math suggests that it might allow us to violate causality and travel back.

If speed isn't the answer, then what about gravity?

Since we know space and time are intimately tied together, and that gravity impacts both (see GPS satellites, above) sufficiently warping space-time would create closed time loops. At least according to research by theoretical physicist Amos Ori at the Technion-Israel Institute of Technology in Haifa.

Ori suggests using focused gravitational fields to bend spacetime into a donut-shaped vacuum.

There is one speed bump: A traveler would only be able to go to time-destinations that occurred after the creation of the donut. No going back to see the dinosaurs or save your mom from marrying the wrong person. No preventing things that have already happened before the creation of the machine. Additionally, the gravitational fields required are on the order of those created by black holes, far beyond what we're capable of creating or controlling.

For now, time travel is outside of our capability, at least as it's portrayed in movies. If you really want to evade the ticking of the clock, your best bet is to run as fast as you can.

• Back To The Future
• Science Behind The Fiction
• Time Travel

Related Stories

Remembering Dwayne “The Rock” Johnson in The Rundown

Knock at the Cabin's Abby Quinn on Getting Killed by Shyamalan

Vin Diesel Righted the Science Fiction Ship with Riddick

Are Tornadoes Getting Worse? "Historic" 2024 Tornado Season Explained

Wonder Woman: DC’s Most Complete Movie Since Batman

'Pitch Black' and the Science of Enhanced Vision

How We'll Avoid the Dystopian Eco-Nightmare of Mad Max

Chris Pratt Mourns Jurassic World Stunt Double

Abigail Star Reveals Alternate Ending for Vampire Flick

Spy Kids is Still a Benchmark For Latinx Representation in Blockbusters

What Ate the Boat Crew at the Beginning of Jurassic Park III?

Hot Take: The Rock and Karl Urban's 2005 Doom Movie Doesn’t Suck

Recommended for you.

Linda Hamilton on Resident Alien Role: "I'm Not the Funny Girl, I'm the Straight Man"

The Classic Twilight Zone Episode That Inspired Jordan Peele's Us

Resident Alien's Alan Tudyk on Harry's New Love Interest, Edi Patterson's Blue Avian

Time Travel: Dream or Possible Reality?

• An Introduction to Astronomy
• Important Astronomers
• Solar System
• Stars, Planets, and Galaxies
• Space Exploration
• Weather & Climate
• Ph.D., Physics and Astronomy, Purdue University
• B.S., Physics, Purdue University

Time travel is a favorite plot device in science fiction stories and movies. Perhaps the most famous recent series is Dr. Who , with its traveling Time Lords who whisk throughout time as if traveling by jet. In other stories, the time travel is due to unexplainable circumstances such as a too-close approach to a very massive object like a black hole. In Star Trek: The Voyage Home , the plot device was a trip around the Sun that hurled Kirk and Spock back to 20th century Earth. In the popular movie series Back to the Future , the characters traveled both backward and forward in time. However it is described in stories, traveling through time seems to pique people's interest and ignite their imaginations. But, is such a thing possible? 

The Nature of Time

It's important to remember that we are always traveling into the future. That's the nature of space-time. This is why we remember the past (instead of "remembering" the future). The future is largely unpredictable because it hasn't happened yet, but everyone is headed into it all the time.

To speed up the process, to peer further into the future, to experience events more quickly than those around us, what would or could anyone do to make it happen? It's a good question without a definitive answer. Right now, no one has built a working time machine to travel temporally.

Traveling into the Future

While it's not possible (yet) to travel to the future fast than the rate at which we're doing it now, it is possible to speed up the passage of time. But, it only happens in small increments of time. And, it has only happened (so far) to very few people who have traveled off Earth's surface. For them, time moves at an infinitesimally different rate. Could it happen over longer time spans? 

It might, theoretically. According to Einstein's theory of special relativity , the passage of time is relative to an object's speed. The more quickly an object moves through space, the more slowly time passes for it compared to an observer traveling at a slower pace. 

The classic example of traveling into the future is the twin paradox . It works like this: take a pair of twins, each 20 years old. They live on Earth. One takes off on a spaceship on a five-year journey traveling at nearly the speed of light . The traveling twin ages five years while on the journey and returns to Earth at the age of 25. However, the twin who stayed behind is 95 years old! The twin on the ship experienced only five years of time passing, but returns to an Earth that is much farther into the future.

Using Gravity as a Means of Time Travel

In much the same way that traveling at speeds close to the speed of light can slow down perceived time, intense gravitational fields can have the same effect.

Gravity only affects the movement of space, but also the flow of time. Time passes more slowly for an observer inside a massive object's gravitational well. The stronger the gravity, the more it affects the flow of time. 

Astronauts on the  International Space Station experience a combination of these effects, though on a much smaller scale. Since they are traveling quite quickly and orbiting around Earth (a massive body with significant gravity), time slows down for them compared to people on Earth. The difference is much less than a second over the course of their time in space. But, it is measurable.

Could We Ever Travel into the Future?

Until we can figure out a way to approach the speed of light (and warp drive doesn't count , not that we know how to do that at this point, either), or travel near black holes (or travel to black holes for that matter) without falling in, we won't be able to do time travel any significant way into the future. 

Travel into the Past

Moving into the past is also impossible given our current technology. If it were possible, some peculiar effects could occur. These include the famous "go back in time and kill your grandfather" paradox. If you did do it, you couldn't do it, because you already killed him, so therefore you don't exist and can't go back in time to do the dastardly deed. Confusing, isn't it? 

Key Takeaways

• Time travel is a science fiction trope that may possibly be technically possible. But, no one has achieved it.
• We do travel into the future all our lives, at a second per second. To do it faster requires technology we don't have.
• Travel to the past is also impossible at the present time.
• Is Time Travel Possible?| Explore , www.physics.org/article-questions.asp?id=131.
• NASA , NASA, spaceplace.nasa.gov/review/dr-marc-space/time-travel.html.
• “Time Travel.”  TV Tropes , tvtropes.org/pmwiki/pmwiki.php/Main/TimeTravel.

Edited by Carolyn Collins Petersen .

• Can We Travel Through Time to the Past?
• Is Time Travel Possible?
• What Is Time? A Simple Explanation
• Wormholes: What Are They and Can We Use Them?
• What Is the Twin Paradox? Real Time Travel
• Learn About the True Speed of Light and How It's Used
• Is Warp Drive From 'Star Trek' Possible?
• An Introduction to Black Holes
• Closed Timelike Curve
• Amazing Astronomy Facts
• The Science of Star Trek
• Cosmic Rays
• An Introduction to Gravitational Lensing
• Cosmos Episode 4 Viewing Worksheet
• Einstein's Theory of Relativity
• Learn about the Doppler Effect

Screen Rant

Back to the future: why the delorean had to go 88mph to time travel.

Your changes have been saved

Email Is sent

Please verify your email address.

You’ve reached your account maximum for followed topics.

Dune Shouldn't Have A Part 3 – But A Sequel Still Needs To Happen

Steven spielberg's new movie will revive a career-defining trend after 10 years away & it's very exciting, why george lucas took his name off thriller directed by empire strikes back writer with 96% rt score.

Doc Brown’s souped-up DeLorean from Back to the Future   must reach exactly 88mph to travel through time, but what’s the significance of this number? Some simple math can provide a perfectly plausible scientific explanation for how Doc arrives at the number forever emblazoned in the minds of sci-fi fans everywhere. On top of that, there’s also an explanation, requiring no math whatsoever, for how the producers of Back to the Future  arrived at this number.

Back to the Future  helped popularize the concept of time travel back in 1985 by using a formula that encapsulates the head-scratching physics theory into a digestible, wildly entertaining movie that still has fans talking nearly 40-years later. The sci-fi classic centers on a teenager, Marty McFly, who inadvertently travels back to 1955 and must enlist the help of eccentric scientist Doctor Emmett “Doc” Brown in order to travel back to the future. To accomplish this, Doc Brown invents the flux capacitor and attaches it to a DeLorean, along with a plethora of other bells and whistles, thus creating a practical yet effective time machine.

Related:  Back To The Future: All 8 Timelines In The Movies Explained

Although traveling forward in time is an accepted scientific possibility, traveling backwards in time is far more theoretical, but the DeLorean may be able to achieve such a feat thanks to the flux capacitor. A common theory of backwards time travel involves sending an object, like a DeLorean, through a traversable wormhole. Doc Brown’s flux capacitor, which he describes as making time travel possible, may open such a wormhole for a limited amount of time when the car reaches a certain speed. Therefore, Doc Brown could have mathematically arrived at the 88mph speed by calculating how fast the DeLorean needs to travel in relation to how long the wormhole stays open.

A calculation of the DeLorean’s speed relative to the wormhole’s stability, or time it remains open, needs to also account for the length of the DeLorean, which is 4.216 meters. Doc needs to know how long it would take the DeLorean to travel its own length. Assuming the wormhole remains open for .1072 seconds, and that Doc knew this fact, he could divide the length of the car by 107.2, arriving at 39.33 meters per second or 88mph. Setting the flux capacitor to open the wormhole at a slower or faster speed could result in the wormhole collapsing on the car and effectively cutting it in half or missing the wormhole all together.

One theory suggests that the .1072 second interval was chosen by Doc so that after the DeLorean travels through time it arrives at its destination at the same physical space from which it departed. This requires math best left to a physicist, along with a few leaps of faith, which is why it’s more plausible to assume that the interval was a technological limitation of the flux capacitor. Another, less scientific, explanation is that Doc chose the double 8s because the number is the infinity sign rotated 90 degrees.

The bigger takeaway here is that none of the science behind Doc’s time machine really matters because Back to the Future   is so entertaining. A lesser movie that tackles such a complex subject may leave fans scratching their heads as to how the science works, but Back to the Future is packed with so many memorable characters and moments that the science behind it all quickly fades away. At the end of day, in-universe explanations for the 88mph number are fun to dissect, but there's another more practical reason why the number was chosen. In an interview with ComicBook , Back to the Future producer and co-writer Bob Gale reveals, “First of all we wanted it to be a speed that somebody wouldn’t accidentally drive at. The other thing is, it’s easy to remember.” It would be hard to accidentally reach speeds over 80mph, so that makes sense. As for the second reason, well, fans are still talking about it.

More:  Back To The Future: All Three Movies, Ranked Worst To Best

• SR Originals
• Back to the Future (1985)

• Red Light, Green Light
• Engineering Healthy Silence: Using Noise-Cancelling Headphones to Block Harmful Sound
• Crushing the Sound Barrier
• The Powers of Melanin
• E-Ink Technology: the Secret Behind Kindle

USC Viterbi School of Engineering

The Science of Time Travel

About the Author: Mark Villanueva

At the time of publication, Mark Villanueva was a student at the University of Southern California in his third year towards his BS in Computer Science. Back to the Future is one of his favorite movies.

Introduction

Definition of time travel.

Traversing in the fourth dimension is vastly different than moving in the previously mentioned three. We simply cannot will ourselves to move forward five minutes or back ten days. In other words, time only moves forward, and we are stuck moving in that direction like corks bobbing helplessly in a river [1]. Thus, the end goal of time travel is to enable us to control where we go in this fourth dimension. Much like moving back and forth, time travel involves moving to either the past or the future. However, our actions in the fourth dimension are cause for concern. What we do now in the present affects our future. In the same manner, our actions in the past should have affected our present lives. Changing the outcomes of past events leads to what physicists and philosophers refer to as the “Grandfather Paradox,” an issue that needs to be addressed in any serious discussion of time travel.

The Grandfather Paradox

“building” a time machine.

Unfortunately​, no black hole has yet been positively identified. Black holes, if they exist, could come in an extreme range of sizes. The English physicist Stephen Hawking has speculated that tiny black holes with masses no larger than that of a large mountain are possible. Such black holes, in the size range of elementary particles, would have been formed only under the extreme conditions that cosmology theories indicate existed in the very first moments of the universe. On the other hand, gigantic black holes may lie at the center of galaxies [7]. Einstein envisioned a situation in which the ends of two different black holes could be connected. This is known as a wormhole.

The wormhole is one basis for time travel into the past. Physicists liken wormholes to quick paths through the universe, much like the hole a worm burrows through an apple [8]. Instead of apples, these wormholes are theoretical tunnel shortcuts through space (Fig. 3).The trick in this case would be flying a spaceship into the one mouth of the wormhole and coming out the other side in a different time and place [9]. This involves moving one end of the wormhole close to the speed light and keeping the other end stationary near earth in outer space. Like the example with the spaceship traveling near the speed of light in space, the moving end of the wormhole in space will “age” slower than the stationary one; the “younger” end is a quick shortcut that connects to an earlier time on the fixed end [1], so the moving end of the wormhole will bring the traveler back to the past. The time travel process will probably involve a team of advanced scientists that can create wormholes and move them while the time traveler goes through the wormhole in outer space via a spaceship.

The Reality of Time Travel

• [1] J. R. Gott. “Will We Travel Back (Or Forward) In Time?”  Time , Apr. 10, 2000: pp. 68.
• [2] M. Kaku.  Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the Tenth Dimension. New York: Anchor Books, 1994.
• [3] P. J. Riggs. “The Principal Paradox of Time Travel.”  Ratio X , Apr. 1, 1997: pp. 49-64.
• [4] S. Mowbray. “Let’s do the time warp again.”  Popular Science]/i], Mar. 2002: pp. 46-51.
• [5] “How to murder your grandfather and still get born.”  The Economist , Jan. 20, 1996: pp. 81.
• [6] J. M. Zavisa. “How Special Relativity Works” Internet: http://www.howstuffw​orks.com, May 2, 2003. [Oct. 18, 2002].
• [7] L. Smarr. “Black Hole”.  The New Grolier Multimedia Encyclopedia . CD-ROM. 1993 Grolier Electronic Publishing, Inc.
• [8] A. Ramirez. “Clockwork: time travel isn’t what it used to be.”  The New York Times  Jul. 28 2002, natl. ed.: pp. WK3.
• [9] S. W. Hawking. “Protecting the Past: Is Time Travel Possible?”  Astronomy , Apr. 2002: pp. 46.
• [10] M. Moyer. “The Physics of Time Travel.”  Popular Science , Mar. 2002: pp. 52-53.
• [11] C. J. Wheeler. “Of wormholes, time machines and paradoxes.”  Astronomy , Feb 1996: pp. 52-58.
• ← The Quest for the Perfect Racket: Advances in Tennis Racket Design
• Improving the Bicycle →

Similar Posts

The Beauty of Science: New Technologies in Art Restoration

To Boldly Go Where No Man Has Gone Before: Faster-than-Light Travel in the 21st Century

Another atomic age, leave a reply cancel reply.

Your email address will not be published. Required fields are marked *

Faster-than-light ‘warp speed’ interstellar travel now thought to be possible

I n another example of how truth is often stranger than fiction, scientists have taken a significant step towards turning the sci-fi concept of "warp drives" into a feasible reality.

According to Einstein's theory of relativity , going faster than the speed of light is off-limits in the real world. For this reason, warp drives, like the one powering spaceships in Star Wars and other science fiction movies, have always been firmly in the realm of imagination -- until now.

New research, led by Dr. Jared Fuchs from Applied Physics and published in the prestigious Classical and Quantum Gravity journal, presents a new solution to one of the long-standing challenges in realizing warp drive technology.

Traditional warp drive concept

The traditional sci-fi concept of a warp drive involves distorting spacetime in a very specific way: compressing it in front of the ship and expanding it behind.

In theory, this would allow the ship to effectively travel faster-than-light without actually exceeding the speed limit locally.

However, previous studies of this idea suggested that it would require exotic forms of matter with "negative energy density."

Understanding negative energy density

In our everyday experience, energy is always positive. Even in a vacuum, there is a small amount of positive energy called the " vacuum energy " or "zero-point energy."

This is a consequence of the Heisenberg uncertainty principle in quantum mechanics , which states that there are always fluctuations in the energy of a system, even at the lowest possible energy state.

The existence of negative energy density is highly speculative and problematic within the framework of known physics. The laws of thermodynamics and the energy conditions in general relativity seem to prohibit the existence of large amounts of negative energy density.

Some theories, such as the Casimir effect and certain quantum field theories, do predict the existence of small amounts of negative energy density under specific conditions. However, these effects are typically very small and confined to microscopic scales.

New approach to warp drive technology

This is where the new study comes in. Applied Physics researchers identified a new way in which warp technology might one day be possible. The team introduced the concept of a "constant-velocity subluminal warp drive" aligned with the principles of relativity.

The new model eliminates the need for exotic energy, using instead a sophisticated blend of traditional and novel gravitational techniques to create a warp bubble that can transport objects at high speeds within the bounds of known physics.

"This study changes the conversation about warp drives," said lead author Dr. Fuchs. "By demonstrating a first-of-its-kind model, we've shown that warp drives might not be relegated to science fiction."

Warp factory: Enabling warp drive spacetimes

The team's theoretical model for a new type of warp bubble uses traditional and innovative gravitational techniques, made possible with their publicly-available tool Warp Factory .

This solution enables the transportation of objects at high but subluminal speeds without the need for exotic energy sources. This can be achieved by engineering warp drive spacetimes to gravitate like ordinary matter, which is a first-of-its-kind solution.

"Although such a design would still require a considerable amount of energy, it demonstrates that warp effects can be achieved without exotic forms of matter ," added Dr. Christopher Helmerich, co-author of the study. "These findings pave the way for future reductions in warp drive energy requirements."

No g-forces for passengers

Unlike in planes or rockets, passengers in a warp craft experience no g-forces. This is a stark contrast to some sci-fi fantasies. The team's research shows how we might construct such a craft using regular matter.

"While we're not yet packing for interstellar voyages, this achievement heralds a new era of possibilities," explained Gianni Martire, CEO of Applied Physics. "We're continuing to make steady progress as humanity embarks on the Warp Age."

Dawn of faster-than-light travel?

The team at Applied Physics is now focused on addressing these challenges as they continue to refine their models and collaborate across disciplines and institutions to turn this once-fantastical dream into reality.

As we stand on the threshold of a new era in space exploration, the prospect of warp drives becoming a reality tantalizes us more than ever. With each new discovery and breakthrough, we inch closer to the stars and the boundless possibilities that await us in the vast expanse of the cosmos.

As humanity begins the chase for faster-than-light travel, perhaps using warp drives, we can only imagine the incredible adventures and revelations that the universe has in store for us.

The full study was published in the journal Classical and Quantum Gravity .

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.

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

Research Fellow

Senior Research Fellow - Women's Health Services

Lecturer / Senior Lecturer - Marketing

Assistant Editor - 1 year cadetship

Executive Dean, Faculty of Health

Unleashing The Speed: Experiencing The Thrill Of Traveling At Mach 5

• Last updated May 26, 2024
• Difficulty Advanced

• Category Travel

Imagine being able to travel at speeds faster than the speed of sound - whizzing through the sky at a mind-blowing Mach 5. Unleashing the Speed: Experiencing the Thrill of Traveling at Mach 5 takes you on a thrilling journey into the world of hypersonic travel. Strap in for an adrenaline-pumping adventure as we explore the cutting-edge technology, the breathtaking speeds, and the endless possibilities that come with traveling at Mach 5. Get ready to have your mind blown as we uncover the secrets behind this incredible feat of engineering and take you along for the ride of a lifetime. Are you prepared to unleash the speed? Let the adventure begin!

What You'll Learn

Introduction to mach 5 travel, advantages of traveling at mach 5, challenges and risks of mach 5 travel, future implications of mach 5 travel.

Traveling at Mach 5 is a thrilling and exhilarating experience that pushes the boundaries of what is possible. Mach 5, also known as hypersonic speed, is five times the speed of sound, which equates to approximately 3,800 miles per hour or 6,174 kilometers per hour. At this incredible speed, the world becomes a blur and the sensation of speed is unimaginable. In this article, we will explore what it is like to travel at Mach 5 and delve into the unique aspects that make this type of travel so extraordinary.

One of the key features of Mach 5 travel is the use of advanced aerospace technology, such as hypersonic vehicles or supersonic aircraft. These vehicles are specifically designed to withstand the extreme conditions and forces that come with traveling at such high speeds. They are equipped with cutting-edge materials and engineering techniques to ensure the safety and stability of the vehicle and its passengers.

One of the most notable aspects of traveling at Mach 5 is the reduced travel time. The speed at which the vehicle travels allows for significantly shorter travel durations compared to conventional modes of transportation. For instance, a journey that would normally take several hours or even days can be completed in a matter of minutes or hours. This opens up a whole new realm of possibilities for travel, making it feasible to explore destinations that were once considered unreachable due to time constraints.

The sensation of traveling at Mach 5 is akin to being inside a high-speed roller coaster. The sheer acceleration and velocity experienced during takeoff and throughout the journey is truly breathtaking. As the vehicle reaches Mach 5, the surrounding landscape stretches into a blur, with only fleeting glimpses of the ground below. The intense acceleration forces create a feeling of weightlessness, similar to what astronauts experience in space. It is both thrilling and awe-inspiring to witness the world passing by at such a rapid pace.

However, it is not only the speed that makes Mach 5 travel remarkable - it is also the potential for global connectivity it brings. With the ability to traverse vast distances within a short time frame, Mach 5 travel opens up new possibilities for trade, commerce, and tourism. It allows for faster delivery of goods, rapid response to emergencies, and seamless international collaboration. The world becomes more interconnected, with previously distant locations feeling just a stone's throw away.

Traveling at Mach 5 is undoubtedly an incredible feat of human ingenuity and engineering. It pushes the boundaries of what is considered possible, taking us into a world where time and distance are no longer constraints. However, it is important to note that achieving Mach 5 travel on a commercial scale is still a work in progress. The development of the necessary technology and infrastructure is ongoing, and there are many challenges to overcome before it becomes a widespread reality.

In conclusion, traveling at Mach 5 is a thrilling and awe-inspiring experience that propels humanity into a new era of transportation. It offers reduced travel times, incredible sensations of speed, and the potential for global connectivity. While still in its early stages of development, Mach 5 travel holds great promise for the future, pushing the boundaries of what is possible and opening up a world of opportunities.

Exploring the Rich Cultures: Traveling to Japan or China

You may want to see also

Traveling at Mach 5, or five times the speed of sound, may seem like a concept out of science fiction. However, with advancements in technology, this high-speed travel is becoming a reality. Here are some of the advantages of traveling at Mach 5:

• Reduced Travel Time: One of the most significant advantages of traveling at Mach 5 is the reduced travel time. At this speed, it would be possible to travel across the globe in a matter of hours rather than days. For example, a flight from London to Sydney would take less than three hours, compared to the current average of over 20 hours. This would revolutionize long-distance travel and make the world feel smaller and more accessible.
• Increased Efficiency: Traveling at Mach 5 would also be more efficient compared to current transportation methods. With faster speeds, the overall energy consumption per passenger would decrease. This could be achieved through the use of advanced propulsion systems and streamlined aerodynamics. More efficient travel would not only conserve energy but also reduce the environmental impact of long-distance travel.
• Enhanced Connectivity: High-speed travel at Mach 5 would lead to improved connectivity between different parts of the world. Currently, long travel times limit the ability to visit distant locations. However, with the increased speed, people from different continents could meet and connect more frequently. This could foster cultural exchange, business opportunities, and collaboration between nations. It would encourage people to explore more, whether for leisure or work, and create a more interconnected global community.
• Economic Growth: The advent of high-speed travel would also have significant economic implications. It would open up new markets, facilitate trade, and boost tourism. Businesses would be able to expand their operations internationally, with executives easily traveling between different locations. Additionally, the increased accessibility of remote areas would bring economic development to regions previously considered hard to reach. Traveling at Mach 5 would create new opportunities for growth and propel global economies forward.
• Scientific and Technological Advancements: The development of high-speed travel technology would require significant advancements in various scientific disciplines. This would drive innovation and push the boundaries of aerospace engineering, materials science, propulsion systems, and more. The knowledge gained from developing and implementing such technology could have far-reaching implications beyond transportation, leading to breakthroughs in other fields. It would be a catalyst for further scientific and technological advancements, benefiting society as a whole.

Traveling at Mach 5 would revolutionize the way we explore the world, bringing people closer together and expanding horizons. With reduced travel times, increased efficiency, enhanced connectivity, and economic growth, the advantages of high-speed travel are undeniable. While this technology is still in its early stages, the possibilities it holds are exciting. As we continue to push the boundaries of what is possible, the dream of traveling at Mach 5 may soon become a reality.

Knowing When to Switch Travel Teams: Signs It's Time for a Change

Traveling at Mach 5, which is five times the speed of sound, is an exhilarating experience that comes with a set of challenges and risks. While it may seem like a glamorous and futuristic mode of transportation, there are certain factors that need to be carefully considered before embarking on such a journey. Let's explore some of the main challenges and risks associated with Mach 5 travel.

One of the greatest challenges of traveling at such high speeds is the immense amount of heat generated. When an aircraft reaches Mach 5, it experiences a tremendous increase in air friction, causing the temperature to soar to extreme levels. This can pose a risk to both the aircraft and its passengers. To counteract this, special materials with high heat resistance need to be used for the construction of the aircraft. Additionally, advanced cooling systems are necessary to dissipate the heat and prevent any damage to the aircraft and its internal components.

Another major challenge is the control and stability of the aircraft. At Mach 5 speeds, even the slightest deviation from the intended flight path can have disastrous consequences. The aerodynamics of the aircraft need to be meticulously designed to ensure stability and control. This includes the shape and design of the wings, control surfaces, and other flight control systems. Advanced computer algorithms and control systems need to be employed to maintain the aircraft's stability and make precise adjustments to keep it on course.

Furthermore, traveling at Mach 5 requires extensive planning and coordination. The aircraft needs to follow a carefully calculated flight path that takes into account factors such as air traffic, weather conditions, and restricted airspace. Advanced communication systems and coordination with air traffic control are crucial to ensure the safety and efficiency of the journey. Additionally, emergency response plans need to be in place to address any unforeseen events or emergencies that may occur during the flight.

One of the main risks associated with Mach 5 travel is the potential for structural failure. The immense forces exerted on the aircraft at such high speeds can put tremendous stress on its structure. Fatigue, vibration, and other factors need to be carefully analyzed and accounted for during the design and testing phase of the aircraft. Rigorous testing, including high-speed wind tunnel simulations and computer modeling, is necessary to ensure the structural integrity of the aircraft and mitigate the risk of failure.

Furthermore, the speed of air travel at Mach 5 can have significant implications for the environment. The emissions produced by an aircraft traveling at such high speeds can have a substantial impact on the atmosphere. It is essential to develop and utilize greener technologies, such as sustainable fuels and advanced propulsion systems, to minimize both the carbon footprint and the ecological impact of Mach 5 travel.

In conclusion, traveling at Mach 5 is an exciting prospect, but it comes with its fair share of challenges and risks. From dealing with extreme temperatures and ensuring control and stability to extensive planning and coordination, this mode of transportation requires meticulous attention to detail and advanced technological solutions. By addressing these challenges and risks, we can pave the way for a future where high-speed travel becomes a reality without compromising safety, efficiency, and environmental sustainability.

The Ultimate Guide to Traveling from London to the Isle of Wight

Mach 5 travel, also known as hypersonic travel, is a highly anticipated technology that has the potential to revolutionize the way we travel. With speeds five times the speed of sound, traveling at Mach 5 would allow us to reach our destinations in a fraction of the time it currently takes.

One of the most immediate implications of Mach 5 travel is the significant reduction in travel time. For example, a trip from New York to London, which currently takes around 7 hours, could be completed in just over an hour at Mach 5 speeds. This would not only save travelers time but would also open up opportunities for more frequent travel, both for business and leisure.

Another important aspect of Mach 5 travel is the potential for increased connectivity and globalization. With the ability to travel at such high speeds, it would be possible to reach remote and isolated areas of the world in record time. This could have a profound impact on various industries, such as tourism and trade, as destinations that were once considered inaccessible become easily reachable.

Furthermore, Mach 5 travel could also have a positive impact on the environment. Although the technology required for hypersonic travel is still in its early stages, there are indications that it could be more fuel-efficient compared to traditional air travel. This is because hypersonic aircraft fly at much higher altitudes where the air is thinner, resulting in lower drag and reduced fuel consumption. If this proves to be true, Mach 5 travel could contribute to reducing greenhouse gas emissions and mitigating the effects of climate change.

However, it's important to note that there are also challenges and considerations associated with Mach 5 travel. One of the main challenges is the development of suitable infrastructure, including airports and runways capable of accommodating hypersonic aircraft. Additionally, there are also technical hurdles to overcome, such as the need for advanced materials that can withstand the extreme temperatures generated by traveling at such high speeds.

Moreover, the cost of Mach 5 travel is likely to be initially prohibitive for the average traveler. The development and operation of hypersonic aircraft require significant investments, and it may take some time for the technology to become affordable and accessible to a wider audience.

In conclusion, the future implications of Mach 5 travel are vast and exciting. From reducing travel time and increasing connectivity to potentially benefiting the environment, the possibilities are immense. While there are challenges to overcome, it's clear that Mach 5 travel has the potential to transform the way we explore and interact with our world.

Sharing Your Life Story: Traveling to China - What You Need to Know

Frequently asked questions.

Traveling at Mach 5 is incredibly fast and exhilarating. It is approximately 3,836 miles per hour, or about five times the speed of sound. The experience is characterized by intense speed and acceleration, with the surroundings blurring by in a blur of motion.

Traveling at Mach 5 can be a thrilling yet intense experience. The forces of acceleration and deceleration are significantly higher compared to conventional speeds, causing extreme g-forces on the body. This can lead to intense pressure and strain, making it a physically demanding experience. However, the sheer speed and the feeling of breaking through the sound barrier can also provide an adrenaline rush like no other.

Traveling at Mach 5 presents numerous challenges. The first and foremost is the development of technology capable of withstanding the immense heat generated by such high speeds. The aerodynamics of the vehicle also play a crucial role in maintaining stability and maneuverability. Furthermore, ensuring the safety and well-being of passengers and crew in such extreme conditions is a significant challenge that must be addressed. Overall, the engineering, technical, and safety considerations make traveling at Mach 5 a complex and demanding endeavor.

• Merve Nussman Author Reviewer Traveller

• Pop Panupong Author Reviewer Traveller

It is awesome. Thank you for your feedback!

We are sorry. Plesae let us know what went wrong?

We will update our content. Thank you for your feedback!

Leave a comment

Travel photos, related posts.

Traveling to the US with a Tourist Visa: Everything You Need to Know

• Mar 22, 2024

The Adventurous Nature of Virgos: How Traveling is Enjoyed by this Astrological Sign

• May 26, 2024

The Ultimate Guide on Getting from Phuket Airport to Your Hotel

• May 18, 2024

The Ultimate Guide to Traveling from London to Disneyland Paris

• May 09, 2024

The Pros and Cons of Travel in Intramural Sports Teams

• May 10, 2024

How to Properly Check Military Travel Pay

• May 11, 2024