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Want a trip through a black hole without having to experience that pesky death? You're in luck. There's a special kind of black hole that's not just survivable, but might get you to another time, or another universe.

Black holes are, traditionally, the scariest things in the universe. Huge, mysterious, inescapable, they wander through the universe and eat everything that gets too close. "Too close" is defined by their event horizon. This is the point at which they go dark, because it requires so much energy to escape them that not even light can get away. Since not even a photon can cross the barrier, no event that happens inside the horizon can ever have an effect on people outside.

Unless, something very odd was going on in the center of the black hole. Most black holes spin - this is something that was discovered way back in the 1960s by physicist Roy Kerr. It wasn't exactly a shock, because most of the material that collapses into a black hole was already spinning. Sometimes, however, the spin on Kerr black holes goes a little above and beyond. Ever spun a glass of water, or soda bottle, so that the liquid inside swirls? Sometimes, if you spin it enough, the liquid actually parts, leaving a clear center and a spinning ring of water around it. The same kind of thing can happen in Kerr black holes. Instead of a singularity at the center, there's a ring. And you can go through the open portion of that ring without touching the gravitational crush.

What's on the other side? A lot of people have wondered. Some people think that these kind of black holes might be our key to time travel. They might be wormholes that let us hop between different points of the universe. Or they might be portals to different universes entirely. First we'll have to find a few, and then we'll need a few volunteers to go through. Preferably ones that haven't seen Event Horizon.

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Time Zone X: Computer History - GameUp - BrainPOP.

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In this timeline skills game, students show their knowledge of computer history by following context clues to order events and win artifacts.

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I) Introduction

Before 1905 there wasn't much to say about time. In the 17th century Newton defined time as something that continues, no matter what, without any link with reality and according to its own nature. Everybody believed that time had its influence on the environment, but if you believed that the environment had its influence on time, you really had to be mad! That changed in 1905 with Einstein's special relativity theory, in which he showed that time can be influenced. But this doesn't mean time can be changed in such a way that you can travel to the future or the past. That's what it's all about on this pages: Is it possible to travel through time, and if possible, under which circumstances?
It will become very clear that the speed of light has got a major influence on the possibility of time travelling. An object should move faster than light speed to travel through time. Therefore we use the tunnel effect, an effect in the quantum mechanics. That means that a ray of light or a bundle of electrons that is sent through a certain barrier arrives sooner at the other side of the barrier than if there wasn't a barrier.
If time travelling is possible according to the relativity theory, there will be a lot of other problems. I'm not talking about the technical problems, 'cause that's not what this is about, but I mean the paradoxes. For these problems there is no such thing as a logical explanation, no matter how long you'll search.

II) Relativity

There are 2 sorts of physics: Newton's physics and Einstein's physics. When you use formulas from Newton and formulas from Einstein's physics to calculate a certain physical value, you'll become not the same value. In 'normal' situations these differences are extremely small. But in 'extreme' situations these differences will become very big. For example: someone who's in a train that moves with an incredible high speed (like 10 000 km/second) and who measures the distance between the sleepers of the train, will measure a smaller distance than someone who stands still beside the railway. According to the physics of Newton and our intuition we'd say the distance would remain the same. In 'normal' situations that's correct: measuring in a train that moves at hundreds, thousands or even ten thousands kilometers/hour would make the difference in distance immeasurably small. Newton's laws would certainly do in these situations. But when the speed of the train approaches the speed of light, the difference will become noticeable ('extreme' situations), and we would need Einstein's physics. According to the latest experiments, Einstein's formulas seem to be the right ones.

Einstein's special theory of relativity was finished in 1905. It's based on the constant speed of light and the fact that speed isn't absolute; when a helicopter lifts off you can also assume it's the chopper that stands still and the earth that moves. This theory describes the relation between observation of a certain phenomenon by observers that move with a constant speed related to each other.
The general theory of relativity was finished in 1912, but Einstein couldn't interpret his mathematical reasoning physically. He redeveloped the theory, not only based on mathematics but also on physics, and he ended up with the same result as 3 years earlier. Then he published it. This theory describes on one hand the relation between the observations of the observers that move with an accelerating speed related to each other. On the other hand it's about the influence of gravity on observations and the relation between observations that are done from places where gravity differs. Because a constant speed can be looked at as a speed with acceleration 0, the general theory of gravity includes the special one.

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Black hole (special object) editing
Black hole n. Black hole n.
Black hole is a modern general theory of relativity, the existence of an infinite space within the infinite volume infinitely small objects. The gravity of the black hole is so large that the escape velocity in the horizon is greater than the speed of light.
In 1916, Karl Schwarzschild (1873-1916), a German astronomer, calculated a vacuum solution of the Einstein's gravitational field equation. This solution shows that if a large amount of matter is concentrated in the space, Will produce a strange phenomenon, that is, there is a particle around the interface - "horizon" once into the interface, even if the light can not escape. This "incredible celestial body" by the American physicist John Archibald Wheeler (John Archibald Wheeler) named "black hole".
"The black hole is a space-time curvature big to light can not escape from its horizon." [1-3] (electromagnetic waves) also escape.
The black hole can not be directly observed, but it can be indirectly known by its existence and quality, and observed its impact on other things. The existence of a black hole can be obtained by the "edge information" of the gamma ray emitted by the object before being sucked in by the high heat. It is inferred that the existence of the black hole can be obtained by indirectly observing the detours of stars or interstellar clouds.
The latest research suggests that when a black hole dies, it may turn into a "white hole," unlike a black hole that engulfs all nearby material, but all the material that was captured before the black hole.
Scientists speculate that it may reach another space, or even space-time, through the black hole.
In fact, the black hole is not black

Black hole is a modern general theory of relativity, the existence of space within a very small volume of extremely small objects. The black hole is produced by the collapse of the gravitational collapse after a mass of massive enough stars in the nuclear fusion reaction fuel is exhausted and dies. Black hole gravity is great, even the light can not escape. In fact, the black hole is not "black", but can not be directly observed, but can indirectly by that its existence and quality, and observed its impact on other things.
Big Bang Cosmology more
The Big Bang Cosmology argues that the universe was formed by a densely packed singularity that swelled after the big bang of 13.7 billion years ago. It believed that the universe had a history of evolution from heat to cold. During this period, the universe system is constantly expanding, so that the density of matter from dense to rare evolution, as a large-scale explosion.
White hole is what? More
A special object predicted by general relativity in contrast to the black hole. White hole is still only a theoretical model, has not been confirmed by the observation. White holes also have a closed border. When the white hole inside the ultra-dense state of matter injected, it will be with the surrounding material violent collision, which released a huge energy.
Small walnut
Chinese name black hole foreign name Black Hole classification universe astronomer discoverer Karl Schwarzschild (Karl Schwarzschild) found time 1916 quality 3.2 times the mass of the sun ~ 10 ^ 10 times the average mass density of the sun infinite infinite diameter of the infinitely small surface temperature T = hc ^ 3 / 8πkGM escape velocity within the horizon beyond the light albedo 0 major explorers Hawking Einstein Schwartz

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5 strongest signs of aliens and alien life

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From time travellers caught on camera to messages from the year 2036. Top 10s presents the strongest signs of time travel and time travellers. If you could time travel where would you go?

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Proof of time travel can be found in many historical records and photographs. Lets starts our CIS investigation with the steam punk time traveller. (Above)

When: 1905 Who: a punk rocker. This guy was clearly a total amateur. He doesn't look anything like anyone else in the photo! He's got the Mohawk haircut (and whoever heard of Mohawks on white guys before 1970?), plus he's wearing a white short sleeved shirt and everyone else is in long sleeves and jackets and hats. Given the popularity of the haircut in the 1970s, actually, we'd argue that this time traveler probably traveled to 1905 from the 1970s. Who knew they had time travel back then? Personally, though, we're more concerned about that guy who is kind of in front of him and more in the foreground. He's wearing a hat but his hair looks like it's got a big vein in it, like he's got a giant head with huge veins that he is concealing with a hat. To us, he looks like a Talosian, those guys from the Star Trek episode The Menagerie/The Cage! That's right, it's a time traveling alien!

A Time Travelling hipster! This is the famous photograph that started the new craze for looking for time travelers in old photographs. This hipster's got totally cool wraparound glasses, is wearing a faded old silkscreened t-shirt of the sort not made until the 1970s (when Forrest Gump popularized them), has a pocket-size digital camera around his neck, and a modern haircut. He's also quite a bit taller than the people surrounding him, reflecting the greater height people have today. Who does he think he's fooling?

It's the short description for the photograph shown at the virtual Bralorne Pioneer Museum, from British Columbia, Canada. The image can be seen above, among other items of the online exhibit. Did you notice anything out of place? Or perhaps, out of time?

The man with what appears to be very modern sunglasses seems to be wearing a stamped T-shirt with a nice sweater, all the while holding a portable compact camera!

Internet people reached to the obvious conclusion: it's a time traveller caught on camera on 1940! Finally, we have proof!

If the story seems straight out of a movie and the photo is in itself a great funny find, the most amusing thing i came up with while looking into this - as an Internet person, on the Internet - was the reply for a skeptical, or perhaps somewhat cynical comment on how spurious it would seem the idea that a time traveler would want to visit the reopening of a bridge in some small town in Canada.

Read this on Doc Brown's voice: "Of course, because we know nothing happened there right? But if we are considering time travel, how can we know if in some other timeline something historical happened right there?"

Indeed! Once you consider time travel, everything changes. But before writing Hollywood scripts, let's get back to reality and ask again: is the photo evidence of a time traveller?

In a behind the scenes footage, part of Charlie Chaplin's " The Circus" - A large woman dressed in black with a hat hiding most of her face, with what can only be described as a mobile phone device - talking as she walks alone. I have studied this film for over a year now - showing it to over 100 people and at a film festival, yet no-one can give any explanation as to what she is doing. My only theory many others - is simple... a time traveler on a mobile phone."

Here is the actual video for a better look at this unexplained mystery

Here is photo of what looks like an astronaut on a pillar at Salamanca Cathedral Church, which was started in the 1600's and finished in the 1800's. Wow, it looks like an astronaut to me. If it isn't an astronaut, what could it be that they carved into this pillar? What else might it represent?
Read: The Mystery of John Tito, time traveler
People have joined the discussion

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Proof of time travel can be found in many historical records and photographs. Lets starts our CIS investigation with the steam punk time traveller. (Above) When: 1905 Who: a punk rocker. This guy was clearly a total amateur. He doesn't look anything like anyone else in the photo!

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Minecraft: TIME MACHINE! - CHASING TIME - Custom Map [1]

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Today we are traveling through time! Jen's Channel http://youtube.com/gamingwithjen EPIC SHIRTS! Shirts! https://represent.com/store/popularmmos Don't forget to subscribe for epic Minecraft content! Facebook! https://www.facebook.com/pages/PopularMMOs/327498010669475 Twitter! https://twitter.com/popularmmos Download Map: http://www.minecraftmaps.com/adventure-maps/chasing-time In this Chasing Time 1.10 Custom Map: We are traveling through time to save the world!! Will be succeed?!

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A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—including particles andelectromagnetic radiation such as light—can escape from inside it.[1] The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.[2][3] The boundary of the region from which no escape is possible is called the event horizon. Although crossing the event horizon has enormous effect on the fate of the object crossing it, it appears to have no locally detectable features. In many ways a black hole acts like an ideal black body, as it reflects no light.[4][5] Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe.

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A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—including particles andelectromagnetic radiation such as light—can escape from inside it.[1] The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.[2][3] The boundary of the region from which no escape is possible is called the event horizon. Although crossing the event horizon has enormous effect on the fate of the object crossing it, it appears to have no locally detectable features. In many ways a black hole acts like an ideal black body, as it reflects no light.[4][5] Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe.

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A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing-not even particles and electromagnetic radiation such as light-can escape from inside it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.

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"Imagine you go out for six months and you turn around and you come back for six months."

While you are travelling at the speed of light, time stays slow relative to the people who are standing still back on Earth.

As a result, you would be going fast while your clock would still be going slow.

Prof Greene: "When you step out of your ship, you're one year older but Earth has gone through many, many years.

"It can have gone through 10,000, 100,000 or a million years depending on how close to the speed of light you traveled."

However, the only problem is that a machine travelling at such speed would require an "unimaginable" amount of energy, while the stress from the centrifugal force on the body would likely prove fatal.

But there is another feasible way to travel though time, and once again it involves going into outer space.

Einstein also theorised that if you were to situate yourself on the edge of a black hole, time would pass more slowly.

Prof Greene explains in his Big Think video: "You hang out [next to a black hole] for a while, you come back, get out of your ship and it will be any number of years into the future, whatever you want all depending on how close you got to the edge of the black hole and how long you hung out there.

"That is time travel to the future."

But time travel has already happened.

Serial ISS resident Sergei Krikalev holds the record for the longest amount of time spent in space with 803 days, 9 hours, 39 minutes under his belt.

The ISS travels at around 7.66 km/s when orbiting around Earth, and due to the high speed and length of time which he spent in space, the cosmonaut actually arrived back in Earth 0.02 seconds in the future thanks to a process known as time dilation.

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Russian Cosmonaut already lives in FUTURE - proving time travel IS possible

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"Imagine you go out for six months and you turn around and you come back for six months." While you are travelling at the speed of light, time stays slow relative to the people who are standing still back on Earth. As a result, you would be going fast while your clock would still be going slow.

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Arrival HD BBC Documentary Animals & Nature

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Planet Earth 100 Million Years In The Future- BBC documentary- Life on Mars-New Science documentary

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WELCOME to documentary channel ! SUBSCRIBE NOW With great new content coming out regularly subscribing will help you keep up to date! If you love documentaries about wildlife, space, cars, knowledge, history and much more, this is the channel for you! Like and Comment to share your experience with all our viewers!

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The Future of Space Travel and Prospects of Discovering Alien Life │ Full Documentary │

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2013 This video documentary and the other documentaries that you can see on this channel are very informative, interesting, and even fun. You will see docume. the three rocketeers and the future of space travel (documentary). thanks for watching history life discovery science technology tech learning education nati.

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How to make time move into the Future. Tutorial at the end of the video ● Download from Planetminecraft http://www.planetminecraft.com/member/actennisac/ I made the Video for fun to show what you can do.

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Extraordinary Time Travel Stories & Mysterious Time Slip Experiences

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How to Build a Real Working Time Machine

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This instructional video will show you how to make a time machine with household items. Follow these easy steps and you'll be time traveling in no time!

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Full Documentary 2016 - The World's First Real Time Travel Machine - Discovery Channel Documentaries

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Full Documentary 2016 - The World's First Real Time Travel Machine - Discovery Channel Documentaries ,Documentary ,Documentaries ,Full Documentary ,Full Documentaries ,Documentary 2016 ,Documentaries 2016 ,Discovery Channel ,Discovery Channel Documentaries ,Discovery Channel Documentary ,Time Travel Machine Documentary ,Time Travel Documentary ,Real Time Travel Machine Documentary ,First Time Travel Machine Documentary https://youtu.be/UUo7mm0lnMw

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Stephen Hawking - Train Ride to the Future

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Professor Stephen Hawking explains how by traveling at near light speeds, we can travel into the future. Into The Future With Stephen Hawking - Time Travel This video Belongs to Discovery Communications and is being used for educational purposes only.

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From people captured with technological devices centuries before being made, or famous celebrities pictured before they were even born - these images are just some of the best examples.

But recent research has cast doubt on their reliability in certain cases and even raised questions as to whether some may even have been hoaxed.

But what do YOU think?
1. Swiss watch found in ancient Chinese tomb
Chinese archaeologists were allegged to have found a small, but perfectly formed metal watch when they opened a previously undisturbed giant coffin in the 400-year-old Si Qing tomb in Shangsi County, China in December 2008.

They were reportedly shocked to find the object with its time frozen at 10:06 and ³Swiss² engraved on the back.

Suggestions were made at the time that the only plausible explanation was a time traveller had gone back from the future with the watch, and somehow, who over's tomb it was had at some point obtained the futuristic timepiece from the time traveller.

However, it is now widely accepted the watch was a clever and original digitally-edited addition.

Despite, this the picture still makes it onto several sites as "proof of time travel".
2. Time-travelling trendy
At first glance, nothing seems to odd about this old black and white photo which turned up on the Virtual Museum of Canada website.

It was said to be of the early 1940s reopening of South Fork Bridge in Gold Bridge, British Colombia.

On closer inspection, one of the crowd appears to be out of place with modern urban clothing, complete with shades and logo-emblazoned top.

It was also billed as being proof of time travel, as surely no one from that era would have been dressed like that.

But further research concluded his appearance may not have been so unusual for the time.

It was established that the style of sunglasses had been available from the 1920s - so 20 years earlier.The "modern printed T-shirt" was also found to probably be a sweater with a sewn-on emblem, and of the type worn by sports teams of the period.

It was even found to be similar to one used by the Montreal Maroons, an ice hockey team of the day.
3. Woman on mobile phone in 1928
In October 2010 a YouTube film claiming to prove time travel went viral and led to many TV news and newspaper reports.

George Clarke from Northern Ireland uploaded the clip entitled "Chaplin's Time Traveler".

It was made from a new DVD release of the Charlie Chaplin film The Circusbonus, inclusing previously unreleased footage.

This included recordings taken at the film's Los Angeles premiere at Grauman's Chinese Theatre in 1928.

During these scenes, a woman walks by, holding an object to her ear.

Mr Clarke concluded she was speaking into a modern mobile phone, so could possibly be a time traveller caught on camera.

But Nicholas Jackson, associate editor for The Atlantic, later decided it was probably a portable hearing aid, as the technology, including rectangular-shaped ear trumpets, was just being developed back then.

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PICTURED: The STAGGERING photos thought to 'PROVE time travel EXISTS'

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From people captured with technological devices centuries before being made, or famous celebrities pictured before they were even born - these images are just some of the best examples. But recent research has cast doubt on their reliability in certain cases and even raised questions as to whether some may even have been hoaxed.

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What does it look like inside of a black hole

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What Does The Inside Of A Black Hole Look Like?

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Time travel is the concept of movement (such as by a human) between certain points in time, to movement between different points in space, typically using a hypothetical device known as a time machine, in the form of a vehicle or of a portal connecting distant points in time. Time travel is a recognized concept in philosophy and fiction, but traveling to an arbitrary point in time has a very limited support in theoretical physics, and usually only in conjunction with quantum mechanics or Einstein–Rosen bridges. In a more narrow sense, one-way time travel into the future via time dilation is a proven phenomenon in relativistic physics, but traveling any significant "distance" requires motion at speeds close to the speed of light, which is not feasible for human travel with current technology.[1] The concept was touched upon in various earlier works of fiction, but was popularized by H. G. Wells' 1895 novel The Time Machine, which moved the concept of time travel into the public imagination, and it remains a popular subject in science fiction.

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https://en.wikipedia.org/wiki/Time_travel

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Things that prove time travalling is real

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Things that prove time travalling is real

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'If time travel is possible, where are the tourists from the future?' Stephen Hawking asked in A Brief History Of Time.

Hawking also famously staged a party for time travelers, complete with champagne and a banner saying, 'Welcome time travelers'.

None showed up, in case you were wondering.

But there ARE certain unsettling signs which seem to suggest that time travelers are in our midst - from a woman on a mobile in a Charlie Chaplin film, to a Greek statue using a laptop.

Here are five things which 'prove' time travel exists - at least according to people on the internet.
Vladimir Putin, the immortal

Is Vladimir Putin a time traveler - or a magical, ageless being who has defended his native Russia through the ages?

UFO site Disclose.tv says, 'On social networks are circulating pictures from 1920. and in 1941. for which some people claim that they are pictures of Russian President Vladimir Putin.

'In fact, supporters of the thesis that Putin is almighty and immortal, have launched a story that their president is a mythical creature that resides on our planet for hundreds, if not thousands of years.'

But, like previous 'sightings' of celebrities such as Jay-Z 'in the past', this is just a case of hoaxers finding similar faces in old photos.
The Greek statue with the laptop

Hang on, is this an ancient Greek woman actually using a laptop - complete with USB ports?

That's what conspiracy theorists would have you believe.

The statue, 'Grave Naiskos of an Enthroned Woman with an Attendant' is in The J. Paul Getty Museum in Malibu, California.

YouTuber StillSpeakingOut says it, 'depicts an astonishing object which bears a striking resemblance with a modern laptop or some hand-held device.'

The gallery's own description is much more modest, describing it as a 'shallow chest'.
The woman using a mobile in a Charlie Chaplin film
A woman is clearly seen talking into what appears to be a mobile phone in a DVD extra of Charlie Chaplin's film The Circus - in 1928.

The clip was unearthed by film-maker George Clarke, and was the subject of TV news slots around the world.

But while the clip is still touted as evidence for time travel, more sober analysis by experts at Washington University in St Louis suggests that she is actually using an ear trumpet.

Other experts have pointed out that the first portable hearing aids were being developed around this time.
The time-traveling hipster

Debate still rages about the man seen here in seemingly modern clothes - in a photo dated from 1941.

The image comes from the Bralorne Pioneer Museum, and shows the re-opening of the South Fork Bridge in Gold Bridge, British Columbia.

Many suggest that the style of sunglasses and clothes worn by the man suggest he is not from 1941.

But after the story went viral in 2011, many internet users pointed out that the style of sunglasses worn by the man actually appeared in the 1920s - and that while it looks like he is wearing a T-shirt, he is probably wearing an ice hockey sweater with a sewn-on emblem.
Henry Fonda checking his iPhone, 1948
Conspiracy sites touted footage of Henry Fonda 'checking an iPhone' in the 1948 film Fort Apache as proof that time travel is real.

But others suggest that it is simply a notepad - and that internet users have forgotten how we used to use these in the days before iPhones existed.

Nigel Watson, paranormal expert and author of the UFO Investigations Manual, 'Would time travelers from the future really be using mobile phones? Wouldn't they use something more sophisticated and less visible? Then again Dr Who still uses a sonic screwdriver and that is so 20th Century...'

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5 Pictures And Videos Which 'Prove' Time Travel Exists

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'If time travel is possible, where are the tourists from the future?' Stephen Hawking asked in A Brief History Of Time. Hawking also famously staged a party for time travelers, complete with champagne and a banner saying, 'Welcome time travelers'. None showed up, in case you were wondering.

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Send Your Name to Jupiter's Moon Europa

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The International Space Station advances scientific knowledge in Earth, space, physical, and biological sciences, for the benefit of all.

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Globular Cluster Omega Centauri Looks Radiant in Infrared

A cluster brimming with millions of stars glistens like an iridescent opal in this image from NASA's Spitzer Space Telescope. Called Omega Centauri, the sparkling orb of stars is like a miniature galaxy. It is the biggest and brightest of the 150 or so similar objects, called globular clusters, that orbit around the outside of our Milky Way galaxy. Stargazers at southern latitudes can spot the stellar gem with the naked eye in the constellation Centaurus. Globular clusters are some of the oldest objects in our universe. Their stars are over 12 billion years old, and, in most cases, formed all at once when the universe was just a toddler. Omega Centauri is unusual in that its stars are of different ages and possess varying levels of metals, or elements heavier than boron. Astronomers say this points to a different origin for Omega Centauri than other globular clusters: they think it might be the core of a dwarf galaxy that was ripped apart and absorbed by our Milky Way long ago. In this new view of Omega Centauri, Spitzer's infrared observations have been combined with visible-light data from the National Science Foundation's Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile. Visible-light data with a wavelength of .55 microns is colored blue, 3.6-micron infrared light captured by Spitzer's infrared array camera is colored green and 24-micron infrared light taken by Spitzer's multiband imaging photometer is colored red. Where green and red overlap, the color yellow appears. Thus, the yellow and red dots are stars revealed by Spitzer. These stars, called red giants, are more evolved, larger and dustier. The stars that appear blue were spotted in both visible and 3.6-micron-, or near-, infrared light. They are less evolved, like our own sun. Some of the red spots in the picture are distant galaxies beyond our own.

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10 Real incidents that proves time travelers exist

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Time travel - moving between different points in time - has been a popular topic for science fiction for decades. Franchises ranging from "Doctor Who" to "Star Trek" to "Back to the Future" have seen humans get in a vehicle of some sort and arrive in the past or future, ready to take on new adventures. Each come with their own time travel theories.

The reality, however, is more muddled. Not all scientists believe that time travel is possible. Some even say that an attempt would be fatal to any human who chooses to undertake it.

Understanding time

What is time? While most people think of time as a constant, physicist Albert Einstein showed that time is an illusion; it is relative - it can vary for different observers depending on your speed through space. To Einstein, time is the "fourth dimension." Space is described as a three-dimensional arena, which provides a traveler with coordinates - such as length, width and height -showing location. Time provides another coordinate - direction - although conventionally, it only moves forward. (Conversely, a new theory asserts that time is "real.")

Einstein's theory of special relativity says that time slows down or speeds up depending on how fast you move relative to something else. Approaching the speed of light, a person inside a spaceship would age much slower than his twin at home. Also, under Einstein's theory of general relativity, gravity can bend time.

Picture a four-dimensional fabric called space-time. When anything that has mass sits on that piece of fabric, it causes a dimple or a bending of space-time. The bending of space-time causes objects to move on a curved path and that curvature of space is what we know as gravity.

Both the general and special relativity theories have been proven with GPS satellite technology that has very accurate timepieces on board. The effects of gravity, as well as the satellites' increased speed above the Earth relative to observers on the ground, make the unadjusted clocks gain 38 microseconds a day. (Engineers make calibrations to account for the difference.)

In a sense, this effect, called time dilation, means astronauts are time travelers, as they return to Earth very, very slightly younger than their identical twins that remain on the planet.

Through the wormhole

General relativity also provides scenarios that could allow travelers to go back in time, according to NASA. The equations, however, might be difficult to physically achieve.

One possibility could be to go faster than light, which travels at 186,282 miles per second (299,792 kilometers per second) in a vacuum. Einstein's equations, though, show that an object at the speed of light would have both infinite mass and a length of 0. This appears to be physically impossible, although some scientists have extended his equations and said it might be done.

A linked possibility, NASA stated, would be to create "wormholes" between points in space-time. While Einstein's equations provide for them, they would collapse very quickly and would only be suitable for very small particles. Also, scientists haven't actually observed these wormholes yet. Also, the technology needed to create a wormhole is far beyond anything we have today.

Alternate time travel theories

While Einstein's theories appear to make time travel difficult, some groups have proposed alternate solutions to jump back and forth in time.
Infinite cylinder
Astronomer Frank Tipler proposed a mechanism (sometimes known as a Tipler Cylinder) where one would take matter that is 10 times the sun's mass, then roll it into very long but very dense cylinder.

After spinning this up a few billion revolutions per minute, a spaceship nearby - following a very precise spiral around this cylinder - could get itself on a "closed, time-like curve", according to the Anderson Institute. There are limitations with this method, however, including the fact that the cylinder needs to be infinitely long for this to work.

(Image: © NASA/JPL-Caltech)

Black holes
Another possibility would be to move a ship rapidly around a black hole, or to artificially create that condition with a huge, rotating structure.

"Around and around they'd go, experiencing just half the time of everyone far away from the black hole. The ship and its crew would be traveling through time," physicist Stephen Hawking wrote in the Daily Mail in 2010.

"Imagine they circled the black hole for five of their years. Ten years would pass elsewhere. When they got home, everyone on Earth would have aged five years more than they had."

However, he added, the crew would need to travel around the speed of light for this to work. Physicist Amos Iron at the Technion-Israel Institute of Technology in Haifa, Israel pointed out another limitation if one used a machine: it might fall apart before being able to rotate that quickly.
Cosmic strings
Another theory for potential time travelers involves something called cosmic strings - narrow tubes of energy stretched across the entire length of the ever-expanding universe. These thin regions, left over from the early cosmos, are predicted to contain huge amounts of mass and therefore could warp the space-time around them.

Cosmic strings are either infinite or they're in loops, with no ends, scientists say. The approach of two such strings parallel to each other would bend space-time so vigorously and in such a particular configuration that might make time travel possible, in theory.

Time machines

It is generally understood that traveling forward or back in time would require a device - a time machine - to take you there. Time machine research often involves bending space-time so far that time lines turn back on themselves to form a loop, technically known as a "closed time-like curve."

To accomplish this, time machines often are thought to need an exotic form of matter with so-called "negative energy density." Such exotic matter has bizarre properties, including moving in the opposite direction of normal matter when pushed. Such matter could theoretically exist, but if it did, it might be present only in quantities too small for the construction of a time machine.

However, time-travel research suggests time machines are possible without exotic matter. The work begins with a doughnut-shaped hole enveloped within a sphere of normal matter. Inside this doughnut-shaped vacuum, space-time could get bent upon itself using focused gravitational fields to form a closed time-like curve. To go back in time, a traveler would race around inside the doughnut, going further back into the past with each lap. This theory has a number of obstacles, however. The gravitational fields required to make such a closed time-like curve would have to be very strong, and manipulating them would have to be very precise. [ Related: Warp Speed, Scotty? Star Trek's FTL Drive May Actually Work]

Grandfather paradox

Besides the physics problems, time travel may also come with some unique situations. A classic example is the grandfather paradox, in which a time traveler goes back and kills his parents or his grandfather - the major plot line in the "Terminator" movies - or otherwise interferes in their relationship - think "Back to the Future" - so that he is never born or his life is forever altered.

If that were to happen, some physicists say, you would be not be born in one parallel universe but still born in another. Others say that the photons that make up light prefer self-consistency in timelines, which would interfere with your evil, suicidal plan.

Some scientists disagree with the options mentioned above and say time travel is impossible no matter what your method. The faster-than-light one in particular drew derision from American Museum of Natural History astrophysicist Charles Lu.

That "simply, mathematically, doesn't work," he said in a past interview with sister site LiveScience.

Also, humans may not be able to withstand time travel at all. Traveling nearly the speed of light would only take a centrifuge, but that would be lethal, said Jeff Tollaksen, a professor of physics at Chapman University, in 2012.

Using gravity would also be deadly. To experience time dilation, one could stand on a neutron star, but the forces a person would experience would rip you apart first.

Time travel in fiction

Two 2015 articles by Space.com described different ways in which time travel works in fiction, and the best time-travel machines ever. Some methods used in fiction include:

One-way travel to the future: The traveler leaves home, but the people he or she left behind might age or be dead by the time the traveler returns. Examples: "Interstellar" (2014), "Ikarie XB-1" (1963)

Time travel by moving through higher dimensions: In "Interstellar" (2014), there are "tesseracts" available in which astronauts can travel because the vessel represents time as a dimension of space. A similar concept is expressed in Madeleine L'Engle's "A Wrinkle In Time" (2018, based on the book series that started in 1963), where time is folded by means of a tesseract. The book, however, uses supernatural beings to make the travel possible.

Travelling the space-time vortex: The famous "Doctor Who" (1963-present) TARDIS ("Time And Relative Dimension In Space") uses an extra-dimensional vortex to go through time, while the travelers inside feel time passing normally.

Instantaneous time jumping: Examples include "The Girl Who Leapt Through Time" (2006), the DeLorean from "Back To The Future" (1985), and the Mr. Peabody's WABAC machine from "The Rocky and Bullwinkle Show" (1959-64).

Time travelling while standing still: Both the "Time Machine" (1895 book) and Hermione Granger's Time-Turner from "Harry Potter" keep the traveler still while they move through time.

Slow time travel: In "Primer" (2004), a traveler stays in a box while time traveling. For each minute they want to go back in time, they need to stay in the box for a minute. If they want to go back a day in time, they have to stay there for 24 hours.

Traveling faster than light: In "Superman: The Movie" (1979), Superman flies faster than light to go back in time and rescue Lois Lane before she is killed. The concept was also used in the 1980 novel "Timescape" by Gregory Benford, in which the protagonist sends (hypothetical) faster-than-light tachyon particles back to Earth in 1962 to warn of disaster. In several "Star Trek" episodes and movies, the Enterprise travels through time by going faster than light. In the comic book and TV series "The Flash," the super-speedster uses a cosmic treadmill to travel through time.

Difficult methods to categorize: There's a rocket sled in "Timecop" (1994) that pops in and out of view when it's being used, which has led to much speculation about what's going on. There's also the Time Displacement Equipment in "The Terminator" movie series, which shows off how to fight a war in four dimensions (including time).

So is time travel possible?

While time travel does not appear possible - at least, possible in the sense that the humans would survive it - with the physics that we use today, the field is constantly changing. Advances in quantum theories could perhaps provide some understanding of how to overcome time travel paradoxes.

One possibility, although it would not necessarily lead to time travel, is solving the mystery of how certain particles can communicate instantaneously with each other faster than the speed of light.

In the meantime, however, interested time travelers can at least experience it vicariously through movies, television and books.

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Time Travel: Theories, Paradoxes & Possibilities

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Time travel - moving between different points in time - has been a popular topic for science fiction for decades. Franchises ranging from "Doctor Who" to "Star Trek" to "Back to the Future" have seen humans get in a vehicle of some sort and arrive in the past or future, ready to take on new adventures.

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how to time travel by black holes

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Since 1995 I have received over 4000 questions and previously posted the answers to all of them at The Astronomy Café. Here are Top-100 most popular questions I have encountered over the years! I will be updating these FAQs over the next few weeks as the interest level for this resource increases.
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Since 1995 I have received over 4000 questions and previously posted the answers to all of them at The Astronomy Café. Here are Top-100 most popular questions I have encountered over the years! I will be updating these FAQs over the next few weeks as the interest level for this resource increases.

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what is a black hol

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A black hole is a place in space where gravity pulls so much that even light cannot get out.

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