Stephen Hawking: "Time Travel to the Future is Possible"
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July 18, 2010

Stephen Hawking: "Time Travel to the Future is Possible"


Eit_sl_1712"I do believe in time travel. Time travel to the future. Time flows like a river and it seems as if each of us is carried relentlessly along by time's current. But time is like a river in another way. It flows at different speeds in different places and that is the key to travelling into the future. This idea was first proposed by Albert Einstein over 100 years ago."

Stephen Hawking

Needed for assembly: "One wormhole, the Large Hadron Collider, or a rocket that goes really, really fast."

Stephen Hawking thinks for of the world's physicists are wrong believing that time travel is impossible: Hawking sides with Sir Arthur Clarke, author of Space Odyssey 2001 who famously stated that "when a distinguished scientist states that something is impossible, he is very probably wrong".  And a lot of distinguished scientists believe that just "Time travel is absolutely impossible".

Hawking says: "Although I cannot move and I have to speak through a computer, in my mind I am free. Free to explore the universe and ask the big questions, such as: is time travel possible? Can we open a portal to the past or find a shortcut to the future? Can we ultimately use the laws of nature to become masters of time itself?"

Several of the planet's leading scientists, including Charles Liu (author of "One Universe: At Home In The Cosmos"), Brian Greene (of "The Elegant Universe") and Michio Kaku ("Hyperspace") float a raft of objections to the concept of time travel. True to Clarke's statement, sometimes affectionately known as "Clarke's Law", each objection seems more like reason to expect time travel than rule it out. 

Professor Greene states that all time-travel theories operate at the very boundaries of known physics, and are therefore unlikely to work.  As opposed to, say, the boundaries of our understanding being where new discoveries are made.  As Sir Clarke said years ago: "The only way of discovering the limits of the possible is to venture a little way past them into the impossible".


3879394733_92091d29b0The other chief objection is the incomprehensible amounts of energy required to punch a hole in spacetime, or stabilize a wormhole, or engineer a double-cosmic-string-ring (yes, that's a real astrophysical concept) capable of bending space hard enough to let us pop back to the past.  One point eighty-one jigawatts just isn't going to cut it here, whatever "jigawatts" turn out to be, and most calculations show that powering a time machine with a lightning strike would be like powering a sixteen-wheeler with a bag of jelly babies.  (So it seems Marty won't be getting back to the future after all).  Of course, the idea of lighting up New York would have had you committed to a mental home in the early eighteenth century.  Pre-electricity, schemes were being suggested to transport the increasing numbers of people to the scant available heat and light in times of need.

Understand: the amount of energy we now take for granted was so vast, so utterly unimaginable to people in the past that they were preparing to restructure their whole society rather than even attempt to generate it.  Of course, this doesn't guarantee that we'll be able to pop back and tell them.  The false argument of past scientific ignorance, the "didn't scientists used to think the world was flat" gambit fails because we know so much more now.  The key to progress is our cumulative knowledge, developed and refined by generations of researchers into a vast, accurate body of knowledge.  We are far more likely to be able to find what's possible than at any point in history.  What we know so far is probably right, and allows us to make predictions about what might be possible.

But until we can explain absolutely everything, we should still steer clear of saying something is impossible. Here's what our beloved Professor Hawking says about time travel in his post in The Daily Mail:

"Time travel was once considered scientific heresy. I used to avoid talking about it for fear of being labeled a crank. But these days I'm not so cautious. In fact, I'm more like the people who built Stonehenge. I'm obsessed by time. If I had a time machine I'd visit Marilyn Monroe in her prime or drop in on Galileo as he turned his telescope to the heavens. Perhaps I'd even travel to the end of the universe to find out how our whole cosmic story ends.

"To see how this might be possible, we need to look at time as physicists do - at the fourth dimension. It's not as hard as it sounds. Every attentive schoolchild knows that all physical objects, even me in my chair, exist in three dimensions. Everything has a width and a height and a length.

"But there is another kind of length, a length in time. While a human may survive for 80 years, the stones at Stonehenge, for instance, have stood around for thousands of years. And the solar system will last for billions of years. Everything has a length in time as well as space. Travelling in time means travelling through this fourth dimension.

"To see what that means, let's imagine we're doing a bit of normal, everyday car travel. Drive in a straight line and you're travelling in one dimension. Turn right or left and you add the second dimension. Drive up or down a twisty mountain road and that adds height, so that's travelling in all three dimensions. But how on Earth do we travel in time? How do we find a path through the fourth dimension?

"Let's indulge in a little science fiction for a moment. Time travel movies often feature a vast, energy-hungry machine. The machine creates a path through the fourth dimension, a tunnel through time. A time traveller, a brave, perhaps foolhardy individual, prepared for who knows what, steps into the time tunnel and emerges who knows when. The concept may be far-fetched, and the reality may be very different from this, but the idea itself is not so crazy.

"Physicists have been thinking about tunnels in time too, but we come at it from a different angle. We wonder if portals to the past or the future could ever be possible within the laws of nature. As it turns out, we think they are. What's more, we've even given them a name: wormholes. The truth is that wormholes are all around us, only they're too small to see. Wormholes are very tiny. They occur in nooks and crannies in space and time. You might find it a tough concept, but stay with me. 

"A wormhole is a theoretical 'tunnel' or shortcut, predicted by Einstein's theory of relativity, that links two places in space-time - visualised above as the contours of a 3-D map, where negative energy pulls space and time into the mouth of a tunnel, emerging in another universe. They remain only hypothetical, as obviously nobody has ever seen one, but have been used in films as conduits for time travel - in Stargate (1994), for example, involving gated tunnels between universes, and in Time Bandits (1981), where their locations are shown on a celestial map

"Nothing is flat or solid. If you look closely enough at anything you'll find holes and wrinkles in it. It's a basic physical principle, and it even applies to time. Even something as smooth as a pool ball has tiny crevices, wrinkles and voids. Now it's easy to show that this is true in the first three dimensions. But trust me, it's also true of the fourth dimension. There are tiny crevices, wrinkles and voids in time. Down at the smallest of scales, smaller even than molecules, smaller than atoms, we get to a place called the quantum foam. This is where wormholes exist. Tiny tunnels or shortcuts through space and time constantly form, disappear, and reform within this quantum world. And they actually link two separate places and two different times.

"Unfortunately, these real-life time tunnels are just a billion-trillion-trillionths of a centimetre across. Way too small for a human to pass through - but here's where the notion of wormhole time machines is leading. Some scientists think it may be possible to capture a wormhole and enlarge it many trillions of times to make it big enough for a human or even a spaceship to enter.

"Given enough power and advanced technology, perhaps a giant wormhole could even be constructed in space. I'm not saying it can be done, but if it could be, it would be a truly remarkable device. One end could be here near Earth, and the other far, far away, near some distant planet.

"Theoretically, a time tunnel or wormhole could do even more than take us to other planets. If both ends were in the same place, and separated by time instead of distance, a ship could fly in and come out still near Earth, but in the distant past. Maybe dinosaurs would witness the ship coming in for a landing. 

"The fastest manned vehicle in history was Apollo 10. It reached 25,000mph. But to travel in time we'll have to go more than 2,000 times faster

"Now, I realise that thinking in four dimensions is not easy, and that wormholes are a tricky concept to wrap your head around, but hang in there. I've thought up a simple experiment that could reveal if human time travel through a wormhole is possible now, or even in the future. I like simple experiments, and champagne. 

"So I've combined two of my favourite things to see if time travel from the future to the past is possible.

"Let's imagine I'm throwing a party, a welcome reception for future time travellers. But there's a twist. I'm not letting anyone know about it until after the party has happened. I've drawn up an invitation giving the exact coordinates in time and space. I am hoping copies of it, in one form or another, will be around for many thousands of years. Maybe one day someone living in the future will find the information on the invitation and use a wormhole time machine to come back to my party, proving that time travel will, one day, be possible.

"In the meantime, my time traveller guests should be arriving any moment now. Five, four, three, two, one. But as I say this, no one has arrived. What a shame. I was hoping at least a future Miss Universe was going to step through the door. So why didn't the experiment work? One of the reasons might be because of a well-known problem with time travel to the past, the problem of what we call paradoxes.

"Paradoxes are fun to think about. The most famous one is usually called the Grandfather paradox. I have a new, simpler version I call the Mad Scientist paradox.

"I don't like the way scientists in movies are often described as mad, but in this case, it's true. This chap is determined to create a paradox, even if it costs him his life. Imagine, somehow, he's built a wormhole, a time tunnel that stretches just one minute into the past.

"Through the wormhole, the scientist can see himself as he was one minute ago. But what if our scientist uses the wormhole to shoot his earlier self? He's now dead. So who fired the shot? It's a paradox. It just doesn't make sense. It's the sort of situation that gives cosmologists nightmares.

"This kind of time machine would violate a fundamental rule that governs the entire universe - that causes happen before effects, and never the other way around. I believe things can't make themselves impossible. If they could then there'd be nothing to stop the whole universe from descending into chaos. So I think something will always happen that prevents the paradox. Somehow there must be a reason why our scientist will never find himself in a situation where he could shoot himself. And in this case, I'm sorry to say, the wormhole itself is the problem.

"In the end, I think a wormhole like this one can't exist. And the reason for that is feedback. If you've ever been to a rock gig, you'll probably recognise this screeching noise. It's feedback. What causes it is simple. Sound enters the microphone. It's transmitted along the wires, made louder by the amplifier, and comes out at the speakers. But if too much of the sound from the speakers goes back into the mic it goes around and around in a loop getting louder each time. If no one stops it, feedback can destroy the sound system.

"The same thing will happen with a wormhole, only with radiation instead of sound. As soon as the wormhole expands, natural radiation will enter it, and end up in a loop. The feedback will become so strong it destroys the wormhole. So although tiny wormholes do exist, and it may be possible to inflate one some day, it won't last long enough to be of use as a time machine. That's the real reason no one could come back in time to my party.

"Any kind of time travel to the past through wormholes or any other method is probably impossible, otherwise paradoxes would occur. So sadly, it looks like time travel to the past is never going to happen. A disappointment for dinosaur hunters and a relief for historians.

"But the story's not over yet. This doesn't make all time travel impossible. I do believe in time travel. Time travel to the future. Time flows like a river and it seems as if each of us is carried relentlessly along by time's current. But time is like a river in another way. It flows at different speeds in different places and that is the key to travelling into the future. This idea was first proposed by Albert Einstein over 100 years ago. He realised that there should be places where time slows down, and others where time speeds up. He was absolutely right. And the proof is right above our heads. Up in space.

"This is the Global Positioning System, or GPS. A network of satellites is in orbit around Earth. The satellites make satellite navigation possible. But they also reveal that time runs faster in space than it does down on Earth. Inside each spacecraft is a very precise clock. But despite being so accurate, they all gain around a third of a billionth of a second every day. The system has to correct for the drift, otherwise that tiny difference would upset the whole system, causing every GPS device on Earth to go out by about six miles a day. You can just imagine the mayhem that that would cause.

"The problem doesn't lie with the clocks. They run fast because time itself runs faster in space than it does down below. And the reason for this extraordinary effect is the mass of the Earth. Einstein realised that matter drags on time and slows it down like the slow part of a river. The heavier the object, the more it drags on time. And this startling reality is what opens the door to the possibility of time travel to the future.

"Right in the centre of the Milky Way, 26,000 light years from us, lies the heaviest object in the galaxy. It is a supermassive black hole containing the mass of four million suns crushed down into a single point by its own gravity. The closer you get to the black hole, the stronger the gravity. Get really close and not even light can escape. A black hole like this one has a dramatic effect on time, slowing it down far more than anything else in the galaxy. That makes it a natural time machine.

"I like to imagine how a spaceship might be able to take advantage of this phenomenon, by orbiting it. If a space agency were controlling the mission from Earth they'd observe that each full orbit took 16 minutes. But for the brave people on board, close to this massive object, time would be slowed down. And here the effect would be far more extreme than the gravitational pull of Earth. The crew's time would be slowed down by half. For every 16-minute orbit, they'd only experience eight minutes of time.

"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 travelling through time. 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.

"So a supermassive black hole is a time machine. But of course, it's not exactly practical. It has advantages over wormholes in that it doesn't provoke paradoxes. Plus it won't destroy itself in a flash of feedback. But it's pretty dangerous. It's a long way away and it doesn't even take us very far into the future. Fortunately there is another way to travel in time. And this represents our last and best hope of building a real time machine.

"You just have to travel very, very fast. Much faster even than the speed required to avoid being sucked into a black hole. This is due to another strange fact about the universe. There's a cosmic speed limit, 186,000 miles per second, also known as the speed of light. Nothing can exceed that speed. It's one of the best established principles in science. Believe it or not, travelling at near the speed of light transports you to the future.

"To explain why, let's dream up a science-fiction transportation system. Imagine a track that goes right around Earth, a track for a superfast train. We're going to use this imaginary train to get as close as possible to the speed of light and see how it becomes a time machine. On board are passengers with a one-way ticket to the future. The train begins to accelerate, faster and faster. Soon it's circling the Earth over and over again.

"To approach the speed of light means circling the Earth pretty fast. Seven times a second. But no matter how much power the train has, it can never quite reach the speed of light, since the laws of physics forbid it. Instead, let's say it gets close, just shy of that ultimate speed. Now something extraordinary happens. Time starts flowing slowly on board relative to the rest of the world, just like near the black hole, only more so. Everything on the train is in slow motion.

"This happens to protect the speed limit, and it's not hard to see why. Imagine a child running forwards up the train. Her forward speed is added to the speed of the train, so couldn't she break the speed limit simply by accident? The answer is no. The laws of nature prevent the possibility by slowing down time onboard.

"Now she can't run fast enough to break the limit. Time will always slow down just enough to protect the speed limit. And from that fact comes the possibility of travelling many years into the future.

"Imagine that the train left the station on January 1, 2050. It circles Earth over and over again for 100 years before finally coming to a halt on New Year's Day, 2150. The passengers will have only lived one week because time is slowed down that much inside the train. When they got out they'd find a very different world from the one they'd left. In one week they'd have travelled 100 years into the future. Of course, building a train that could reach such a speed is quite impossible. But we have built something very like the train at the world's largest particle accelerator at CERN in Geneva, Switzerland.

"Deep underground, in a circular tunnel 16 miles long, is a stream of trillions of tiny particles. When the power is turned on they accelerate from zero to 60,000mph in a fraction of a second. Increase the power and the particles go faster and faster, until they're whizzing around the tunnel 11,000 times a second, which is almost the speed of light. But just like the train, they never quite reach that ultimate speed. They can only get to 99.99 per cent of the limit. When that happens, they too start to travel in time. We know this because of some extremely short-lived particles, called pi-mesons. Ordinarily, they disintegrate after just 25 billionths of a second. But when they are accelerated to near-light speed they last 30 times longer.

"It really is that simple. If we want to travel into the future, we just need to go fast. Really fast. And I think the only way we're ever likely to do that is by going into space. The fastest manned vehicle in history was Apollo 10. It reached 25,000mph. But to travel in time we'll have to go more than 2,000 times faster. And to do that we'd need a much bigger ship, a truly enormous machine. The ship would have to be big enough to carry a huge amount of fuel, enough to accelerate it to nearly the speed of light. Getting to just beneath the cosmic speed limit would require six whole years at full power.

"The initial acceleration would be gentle because the ship would be so big and heavy. But gradually it would pick up speed and soon would be covering massive distances. In one week it would have reached the outer planets. After two years it would reach half-light speed and be far outside our solar system. Two years later it would be travelling at 90 per cent of the speed of light. Around 30 trillion miles away from Earth, and four years after launch, the ship would begin to travel in time. For every hour of time on the ship, two would pass on Earth. A similar situation to the spaceship that orbited the massive black hole.

After another two years of full thrust the ship would reach its top speed, 99 per cent of the speed of light. "At this speed, a single day on board is a whole year of Earth time. Our ship would be truly flying into the future. 

"The slowing of time has another benefit. It means we could, in theory, travel extraordinary distances within one lifetime. A trip to the edge of the galaxy would take just 80 years. But the real wonder of our journey is that it reveals just how strange the universe is. It's a universe where time runs at different rates in different places. Where tiny wormholes exist all around us. And where, ultimately, we might use our understanding of physics to become true voyagers through the fourth dimension."

Casey Kazan with Luke McKinney via The Daily Mail


Links:

Livescience: Time Travel Forbidden

'Stephen Hawking's Universe' begins on May 9 on Discovery Channel (HD) at 9pm


Image credit: Manic Mind
http://www.flickr.com/photos/sonnymarciano/

Comments

The reason no one showed up to his party is because everyone moves at the same speed in time.

Time travel to the past doesn't work because as Stephen said, time travels like a river, but it takes matter with it.

We're all on this rollercoaster together.

I mean that literally.

Example:

If you and a bunch of your friends are on a rollercoaster, and you just stood up and jumped off the rollercoaster onto the track.. You would be the only person on the track, while your friends ride off on the rest of the rollercoaster ride.

It's very similar to the way the earth spins. If one were to go really high up, close to orbit, and come back down a few hours later, they'd be on the other side of the planet.

Because matter moves with time.

That is the answer to the mad scientist paradox.

The mad scientist creates a wormhole to look at himself in the past and ultimately shoot himself.

The wormhole would show him one of three things.

1. Absolutely nothing at all, because matter moves with time. And he can't shoot himself in the past because he, everything in the room, and even the whole planet is already there in the present trying to shoot himself.

2. It would show an alternate reality. Another universe that is identical to ours, except that in that universe he dies by the bullet of his alternate self.

3. It would show himself in that present time. If somehow the wormhole was controlled and calculated to find himself anywhere in the past, present or future.. It would show himself right then and there, because he doesn't exist anywhere but where he already is.

For this reason, I do not give in to the idea of time travel to our past.

I do agree with Stephen about the future.

We're trying too hard though. I think nature already did it for us.

The universe is so vast that if you go far enough, you'll find anything and everything you're looking for.

There is a part of the universe where there are wormholes already made, calculated to every second and every co-ordinate in time you want.

It's different realities in time though.. And nothing will ever be exactly the same.. But you can meet yourself in the past. Just not your past.

We just have to find a way to look into the sky far enough.

And find a way to reach them.

Of course if you travel close to the speed of light, you'll go into the future. But where exactly? And for what purpose?

You're trillions of light years from Earth, and 400 billion years into the future... Now what?

Your body still has till it reaches 100 years at best.

I think the whole point to life is that no matter how far you go, or where you go, you have what you need right here. You need human contact. You need people who love you. That's the bottom line, and that's the only matter that time can not move.

lol @ Jeffrey

Like many Americans, I also look forward into time, where this Great Free Society recovers lost freedoms and traditions, instead of accepting illegal invaders´impositions and where the now N ameless, colored minority recovers its racial conscience, identity and freedom to be seen as they were been born...

Freedom of Thought shall be a must in the future...

There is no three dimensions. No time. And beyond counting tomatoes, numbers aren't very good when actually applied. I could go on.

Great article!

I published this published two weeks ago, also on time travel:

'So is our dream of time machines just that, a dream? I think the main thing to understand here is that our experience of the universe is not objective. We cannot get out of ourselves and study time because we are time perceiving animals. And we can’t physically travel back to the past or forward to the future because our vehicles, which are made up of a certain kind of matter, are not designed to withstand the laws that dictate time travel. We would have to connect our perception to an entirely different level of matter.'

To see the rest of the article go to: http://tiltyourhead.wordpress.com/2010/07/04/time-travel/to:

Stephen , you use the word Impossible, no no use improbable.
NOTHING IS IMPOSSIBLE !!!
some things are improbable but that's is where humans are...
And there are things which go faster than light, `NEUTRINOS`are 1 name another?
P.S there is a way to fix your body, but you like all others cannot see the forest, the trees are in the way, we ghave been told how for a very long amount of time.

Hawking states that in his mind he is free to travel about the universe. This means that we all can too, in the quantum realm of black holes. A tiny white hole is an entangled photon of information like the dual slit experiment. The paradox of shooting oneself in the past is resolved by realizing that a tiny quanta of information traveling thru a wormhole appears like traveling into another parallel dimension. Maybe the new traveler would get shot instead of the past self, and besides changing clothers, nothing much would be changed. No doubt to travel into the past annihilates your body essentially killling you, except the quantum information that you have about yourself. Nobody but you would know that you were the real traveler from the future.

I can understand how a fifth grader might be confused by the difference between speed and time travel, but a top physicist? He must really be loosing his grip.

Honestly, it's this simple: If something was moving at .99C (99/100 of the speed of light) it's nucleus (the relatively stationary part at the center of an atom) would have to be moving at 99C, and the electrons (which orbited the atom) would have to move at somewhere between .99C and .999C to pass up the speeding nucleus and make it's orbit. This naturally would slow down the orbit time of the atom involved, and would as a result slow down the motion of the matter which the atoms comprise. It would slow down the speed of a human body, slow down the fall of a dropped object, and slow down the ticking of an atomic clock. It would also slow down the passage of bio-electrical impulses through a person's nervous system (affecting reaction time and thought processes accordingly) so that everything appeared normal. Time would still pass naturally, but it would seem to speed up for everything moving at that speed. It's not time travel so much as a form of stasis.

If you where sitting completely still, the amount of kinetic energy present would be 0, and the amount of potential energy to be harnessed would be MC^2 (we have Einstein to thank for this). If you suddenly accelerated to .99C, the potential energy left to be harnessed would decrease to 1/99 of MC^2, and that would be all the energy that was left over for other things (for example, kinetic energy and electrical energy). This in mind, a person in a spaceship moving at .99C would only be able to move their bodies at 1 percent of the speed in which they would normally be able to move them, hence time would appear to speed up and they would appear to be moving much faster than the speed of light. This, of course, is an illusion created by your' own slowed reflexes and thought processes. by the time you processed the information that you had reached a distance marker, you would have moved 99 'thoughts' ahead of it, and be striving to catch up with what was going on around you.

Yes, I know that the orbit of the electrons should even itself out. If it looses time trying to catch up with the nucleus, it should gain time as it falls behind on the second half of it's orbit. I don't have an explanation for this, but all i can say is that those bums have been telling us that classical physics doesn't apply to electrons for years, and now i'm rubbing it in their faces! Prove it doesn't work! I dare you! just like I can't prove that time travel is impossible, why don't you scientists try to prove that electron orbits don't loose time as they accelerate, causing the preservation of matter at high speeds! Prove it!!!!!!!!!! can't can you? Ha! Little thing called the Uncertainty Principle standing in the way of proving me wrong!!!

I can understand how a fifth grader might be confused by the difference between speed and time travel, but a top physicist? He must really be loosing his grip.

Honestly, it's this simple: If something was moving at .99C (99/100 of the speed of light) it's nucleus (the relatively stationary part at the center of an atom) would have to be moving at 99C, and the electrons (which orbited the atom) would have to move at somewhere between .99C and .999C to pass up the speeding nucleus and make it's orbit. This naturally would slow down the orbit time of the atom involved, and would as a result slow down the motion of the matter which the atoms comprise. It would slow down the speed of a human body, slow down the fall of a dropped object, and slow down the ticking of an atomic clock. It would also slow down the passage of bio-electrical impulses through a person's nervous system (affecting reaction time and thought processes accordingly) so that everything appeared normal. Time would still pass naturally, but it would seem to speed up for everything moving at that speed. It's not time travel so much as a form of stasis.

If you where sitting completely still, the amount of kinetic energy present would be 0, and the amount of potential energy to be harnessed would be MC^2 (we have Einstein to thank for this). If you suddenly accelerated to .99C, the potential energy left to be harnessed would decrease to 1/99 of MC^2, and that would be all the energy that was left over for other things (for example, kinetic energy and electrical energy). This in mind, a person in a spaceship moving at .99C would only be able to move their bodies at 1 percent of the speed in which they would normally be able to move them, hence time would appear to speed up and they would appear to be moving much faster than the speed of light. This, of course, is an illusion created by your' own slowed reflexes and thought processes. by the time you processed the information that you had reached a distance marker, you would have moved 99 'thoughts' ahead of it, and be striving to catch up with what was going on around you.

Yes, I know that the orbit of the electrons should even itself out. If it looses time trying to catch up with the nucleus, it should gain time as it falls behind on the second half of it's orbit. I don't have an explanation for this, but all i can say is that those bums have been telling us that classical physics doesn't apply to electrons for years, and now i'm rubbing it in their faces! Prove it doesn't work! I dare you! just like I can't prove that time travel is impossible, why don't you scientists try to prove that electron orbits don't loose time as they accelerate, causing the preservation of matter at high speeds! Prove it!!!!!!!!!! can't can you? Ha! Little thing called the Uncertainty Principle standing in the way of proving me wrong!!!

I, too, am writing several articles like William Page, but more along the lines of what I just posted. (though maybe not so enthusiastic...) I intend to post them all on my site at Webs.com over the next month or so, as I make final corrections, and then i'll try to post a link to it on a related article. My writing ranges from time travel, to faulty ideas in science fiction, to my novice understanding of quantum mechanics and a road map to the future possibilities of interstellar exploration. If there is any such thing as conservative scientific speculation, I am an expert in the field. (The Daily Galaxy could take a lesson from me in toning down these ridiculous theories they regularly come up with...)

Light` is the space modulus to measure the Time` being metaphorically depicted with a flowing water in the entire length of a given river.

Indeed, the metaphorical simile does recall my innate essence to extend an axiom ...

"All` is Progeny` of Fluid`... Time is cosmic-fluid, Light is stellar-fluid and Water is Global-fluid"

Greetings...

ok? well , i believe you can travel back in "time" .... say the river is time and we are the salmon traveling in that river ......salmon swim upstream against the current ...therefore we can move the opposite direction in time ....i also dont believe it should be considered time travel ....its just momentary place and location travel because everything is really happening all at once ..time is just an illusion

ok? well , i believe you can travel back in "time" .... say the river is time and we are the salmon traveling in that river ......salmon swim upstream against the current ...therefore we can move the opposite direction in time ....i also dont believe it should be considered time travel ....its just momentary place and location travel because everything is really happening all at once ..time is just an illusion

When a person travels back into the past, and (consciously)modifies some undesirable details of his life; can this mental action be considered as time travel? Physical transportation to points in the past... is a different matter, raising the question about the quantic/wave/particle composition of the human body. How would one see fellow travelers with quantic sight?

I find it funny that so many people here actually think they know what they're talking about... And not only that, they talk about it as irrefutable facts.

Vigas I openly admit that I don't have a clue what I'm talking about, but my idea makes millions of times more sense than this article. Some of my theory is derived from my high school education, and some from the books of Isaac Asimov, but mostly it's common sense. Things just don't work out that way in real life. There is no such thing time travel: only a perspective of doing so. If there was actual 'time travel' forward, then it stands to reason that it should exist backwards, and thus that paradoxes are possible (which they're not.)

I've written an article on the many forms of theoretical time travel and time dilation, which I intend to post on my Webs.com site soon. In the article I use common sense and basic science to rule out many of the commonly upheld delusions pertaining to time travel (Including the one mentioned in this article.)

Vigas I openly admit that I don't have a clue what I'm talking about, but my idea makes millions of times more sense than this article. Some of my theory is derived from my high school education, and some from the books of Isaac Asimov, but mostly it's common sense. Things just don't work out that way in real life. There is no such thing time travel: only a perspective of doing so. If there was actual 'time travel' forward, then it stands to reason that it should exist backwards, and thus that paradoxes are possible (which they're not.)

I've written an article on the many forms of theoretical time travel and time dilation, which I intend to post on my Webs.com site soon. In the article I use common sense and basic science to rule out many of the commonly upheld delusions pertaining to time travel (Including the one mentioned in this article.)


"Time" as we know it now is only a concept. Actually, TIME is not moving like a stream, it's the other way round.

Time is standing still - in the NOW or PRESENT - and we are moving in time like a stream. There is no FUTURE or PAST where we can enter and socialize with the people of that period, teach them or learn from them something new. There is only NOW, period.

Quote: "Through the wormhole, the scientist can see himself as he was one minute ago. But what if our scientist uses the wormhole to shoot his earlier self? He's now dead. So who fired the shot? It's a paradox."

This is not a paradox, but a fallacy. If we accept that time-travel is possible, and we are able to travel
to the past, we need also to accept that we cannot change what has already occurred.

I know how to build a simple telescope; so for instance, can I travel to - say - the year 1600 and make a telescope to observe the heavens much before Galileo did? And announce that Jupiter has some 63 moons? I would be changing history! Or if I carry a copy of "A Brief History of Time" to the year 1980 and get a publisher to publish it in my name? Sorry, Stephen!

Agreed, the passengers in your super-fast train of the year 2050 succeed in slowing down time and land themselves in 2150, what have they achieved? [I will not ask silly questions like where will the train stop? Will they still have railways in 2150?]

This is like Rip Van Winkle who slept for twenty years and returned home to find no-one recognized him and everything had changed!

[Right here on our planet, anyone can go back in time by crossing the date-line!]

However, if the super-fast train-passengers could collect as much information and hi-tech knowledge as they can and RETURN to 2050 (one week later, of course) now, THAT WOULD BE SOMETHING!!

Does light really move at 186,000 miles per second? or is it possible that as observers we are merely moving faster through time so it only appears to be moving at 186,000 miles per second but in actuallity is moving much faster? In professor Hawkings example he mentions that a time traveller merely needs enough speed to travel to the future and that one week travelling at 99.9 percent the speed of light would land one 100 years in the future. to the observers on the train only one week has passed. to the observers on the platform 100 years have passed lets think of this another way there is a star 100 light years from earth and a photon is emitted from that star on a trajectory to hit the earth in 100 years to the observers on earth it takes that photon 100 years to get from that star to earth but for the photon it takes less than a week. So from one perspective it moves 100light years while from another perspective it moves only one light week and yet the distance is the same, or is it?

1st law of time travel that which has happened must happen or paradoxes are not allowed by the universe.

professor Hawkings mad scientist paradox has only one result he has created a worm whole to the past but this wormhole is not one way so in effect he has also created a worm hole to the future from the mad scientists perspective. So which mad scientist actully fires the gun and how does the scientist know which side of the worm hole he is actually on? the answer is obvious the past self kills the future self and then is killed shortly thereafter by his past self as events unfold.

If one were to find a way to instantly travel to the past which I do believe is allowed by the laws of physics as we know them today, one must take in to acount where one would be in space as one enters the past. for instance one goes one day into the past then one will necessarily be one day away from the earth in space at the speed the earth travels through space. Now you might think well then I will take a space ship back with me so I can land safely on the earth in less time than it takes for the planet to catch up with me and here is the kicker that makes paradoxes impossible. One day away from earth as the earth moves through space may seem like a very short distance untill one takes into acount all the motion of the universe. Not just the earth moving around the sun or the sun moving around the galaxy but also the galaxy moving through the local group and the local groups expansion into the void this coupled with the fact that you will enter the past with all the momentum of those movements so that in one day you will be no closer to the earth than you were when you entered the past and your ship will need more fuel than is easily calculated in order to slow that momentum and allow the earth to catch up with you which will take more than a day. In the end we will find time travel to be more usefull for traveling or communicating over great distances than we will ever find it to be a way to alter the past.

2nd law of time travel the future can have an affect on the past or the observer affects the observed.

This law is taken directly from the uncertainty principle. we observe the past constantly and we thereby affect it. By having an affect on the past Im not saying you can violate the 1st law of time travel. Nothing you can do can cause a paradox. However, we can observe very distant things and have an affect on them that will in no way change what is happening now but may have a bearing on our own future.

3rd law of time travel travel traveling to the future is not only possible but required or time is personal. You can not stop time you will always be moving toward your personal future and nothing you can do not even dying will stop you from entering the future. Even when traveling to the past one will still be moving toward ones own personal future. The time each person has is finite and no amount of time traveling will change this.

4th law of time travel Time is not segmented it is an unbroken whole.
we can easily see a very short distance into the future and a very long distance into the past. There is not an independant me in the past that is seperate from the me that exists now or the me that will exist in the future we are all one entity. The same is true for time the past is not independant from the now or the future it is all one unbroken whole.

In closing I want everyone who reads this to think very long and hard on why they would want to travel to the future at a rate faster than they are already traveling there or want to travel to the past. If your reason for traveling to the past is because you want to make some change that will change the present in some significant or insignificant way then perhaps you should consider making changes in the present so that the future will be more to your liking and then remember the past since you were/ are there right now. If you want to see the future but are just impatient then read a good sci fi novel chances are like with jules verne and many other good writers that what they are thinking of will eventually come to pass. but if you want to observe the past your already doing it and if you want to be in the future think back to when you were a little kid and how far away todays date seemed then and you will find you are already there.

Does light really move at 186,000 miles per second? or is it possible that as observers we are merely moving faster through time so it only appears to be moving at 186,000 miles per second but in actuallity is moving much faster? In professor Hawkings example he mentions that a time traveller merely needs enough speed to travel to the future and that one week travelling at 99.9 percent the speed of light would land one 100 years in the future. to the observers on the train only one week has passed. to the observers on the platform 100 years have passed lets think of this another way there is a star 100 light years from earth and a photon is emitted from that star on a trajectory to hit the earth in 100 years to the observers on earth it takes that photon 100 years to get from that star to earth but for the photon it takes less than a week. So from one perspective it moves 100light years while from another perspective it moves only one light week and yet the distance is the same, or is it?

1st law of time travel that which has happened must happen or paradoxes are not allowed by the universe.

professor Hawkings mad scientist paradox has only one result he has created a worm whole to the past but this wormhole is not one way so in effect he has also created a worm hole to the future from the mad scientists perspective. So which mad scientist actully fires the gun and how does the scientist know which side of the worm hole he is actually on? the answer is obvious the past self kills the future self and then is killed shortly thereafter by his past self as events unfold.

If one were to find a way to instantly travel to the past which I do believe is allowed by the laws of physics as we know them today, one must take in to acount where one would be in space as one enters the past. for instance one goes one day into the past then one will necessarily be one day away from the earth in space at the speed the earth travels through space. Now you might think well then I will take a space ship back with me so I can land safely on the earth in less time than it takes for the planet to catch up with me and here is the kicker that makes paradoxes impossible. One day away from earth as the earth moves through space may seem like a very short distance untill one takes into acount all the motion of the universe. Not just the earth moving around the sun or the sun moving around the galaxy but also the galaxy moving through the local group and the local groups expansion into the void this coupled with the fact that you will enter the past with all the momentum of those movements so that in one day you will be no closer to the earth than you were when you entered the past and your ship will need more fuel than is easily calculated in order to slow that momentum and allow the earth to catch up with you which will take more than a day. In the end we will find time travel to be more usefull for traveling or communicating over great distances than we will ever find it to be a way to alter the past.

2nd law of time travel the future can have an affect on the past or the observer affects the observed.

This law is taken directly from the uncertainty principle. we observe the past constantly and we thereby affect it. By having an affect on the past Im not saying you can violate the 1st law of time travel. Nothing you can do can cause a paradox. However, we can observe very distant things and have an affect on them that will in no way change what is happening now but may have a bearing on our own future.

3rd law of time travel travel traveling to the future is not only possible but required or time is personal. You can not stop time you will always be moving toward your personal future and nothing you can do not even dying will stop you from entering the future. Even when traveling to the past one will still be moving toward ones own personal future. The time each person has is finite and no amount of time traveling will change this.

4th law of time travel Time is not segmented it is an unbroken whole.
we can easily see a very short distance into the future and a very long distance into the past. There is not an independant me in the past that is seperate from the me that exists now or the me that will exist in the future we are all one entity. The same is true for time the past is not independant from the now or the future it is all one unbroken whole.

In closing I want everyone who reads this to think very long and hard on why they would want to travel to the future at a rate faster than they are already traveling there or want to travel to the past. If your reason for traveling to the past is because you want to make some change that will change the present in some significant or insignificant way then perhaps you should consider making changes in the present so that the future will be more to your liking and then remember the past since you were/ are there right now. If you want to see the future but are just impatient then read a good sci fi novel chances are like with jules verne and many other good writers that what they are thinking of will eventually come to pass. but if you want to observe the past your already doing it and if you want to be in the future think back to when you were a little kid and how far away todays date seemed then and you will find you are already there.

Does light really move at 186,000 miles per second? or is it possible that as observers we are merely moving faster through time so it only appears to be moving at 186,000 miles per second but in actuallity is moving much faster? In professor Hawkings example he mentions that a time traveller merely needs enough speed to travel to the future and that one week travelling at 99.9 percent the speed of light would land one 100 years in the future. to the observers on the train only one week has passed. to the observers on the platform 100 years have passed lets think of this another way there is a star 100 light years from earth and a photon is emitted from that star on a trajectory to hit the earth in 100 years to the observers on earth it takes that photon 100 years to get from that star to earth but for the photon it takes less than a week. So from one perspective it moves 100light years while from another perspective it moves only one light week and yet the distance is the same, or is it?

1st law of time travel that which has happened must happen or paradoxes are not allowed by the universe.

professor Hawkings mad scientist paradox has only one result he has created a worm whole to the past but this wormhole is not one way so in effect he has also created a worm hole to the future from the mad scientists perspective. So which mad scientist actully fires the gun and how does the scientist know which side of the worm hole he is actually on? the answer is obvious the past self kills the future self and then is killed shortly thereafter by his past self as events unfold.

If one were to find a way to instantly travel to the past which I do believe is allowed by the laws of physics as we know them today, one must take in to acount where one would be in space as one enters the past. for instance one goes one day into the past then one will necessarily be one day away from the earth in space at the speed the earth travels through space. Now you might think well then I will take a space ship back with me so I can land safely on the earth in less time than it takes for the planet to catch up with me and here is the kicker that makes paradoxes impossible. One day away from earth as the earth moves through space may seem like a very short distance untill one takes into acount all the motion of the universe. Not just the earth moving around the sun or the sun moving around the galaxy but also the galaxy moving through the local group and the local groups expansion into the void this coupled with the fact that you will enter the past with all the momentum of those movements so that in one day you will be no closer to the earth than you were when you entered the past and your ship will need more fuel than is easily calculated in order to slow that momentum and allow the earth to catch up with you which will take more than a day. In the end we will find time travel to be more usefull for traveling or communicating over great distances than we will ever find it to be a way to alter the past.

2nd law of time travel the future can have an affect on the past or the observer affects the observed.

This law is taken directly from the uncertainty principle. we observe the past constantly and we thereby affect it. By having an affect on the past Im not saying you can violate the 1st law of time travel. Nothing you can do can cause a paradox. However, we can observe very distant things and have an affect on them that will in no way change what is happening now but may have a bearing on our own future.

3rd law of time travel travel traveling to the future is not only possible but required or time is personal. You can not stop time you will always be moving toward your personal future and nothing you can do not even dying will stop you from entering the future. Even when traveling to the past one will still be moving toward ones own personal future. The time each person has is finite and no amount of time traveling will change this.

4th law of time travel Time is not segmented it is an unbroken whole.
we can easily see a very short distance into the future and a very long distance into the past. There is not an independant me in the past that is seperate from the me that exists now or the me that will exist in the future we are all one entity. The same is true for time the past is not independant from the now or the future it is all one unbroken whole.

In closing I want everyone who reads this to think very long and hard on why they would want to travel to the future at a rate faster than they are already traveling there or want to travel to the past. If your reason for traveling to the past is because you want to make some change that will change the present in some significant or insignificant way then perhaps you should consider making changes in the present so that the future will be more to your liking and then remember the past since you were/ are there right now. If you want to see the future but are just impatient then read a good sci fi novel chances are like with jules verne and many other good writers that what they are thinking of will eventually come to pass. but if you want to observe the past your already doing it and if you want to be in the future think back to when you were a little kid and how far away todays date seemed then and you will find you are already there.


Shawn:

You said "So from one perspective it moves 100 light years while from another perspective it moves only one light week and yet the distance is the same, or is it?"

We need to remember that "Time" as we know it, is only relevant to our planet - and in particular, humans on our planets. And yes, the light arriving from 100 light years may have spent just one week of "our time" moving at 186,000 miles per second.. or it may be an "instant" on some other timescale, but 100 years for us on Earth.

Our concept of time is related to our movement in space - "Not just the earth moving around the sun or the sun moving around the galaxy but also the galaxy moving through the local group and the local groups expansion into the void" - as you have pointed out. If our planet's rotational speed was even one hour more (or less) or if the orbital speed was a few days longer (or shorter) our "time" would have been quite different.

Science says time stays constant at the speed of light. So what happens? Does everything come to a standstill? Let's imagine, at the edge of the observable universe there is a star with a planetary system, all moving at 99.99% of light-speed (the law says it cannot reach the speed of light) and if any or all the planets harbor life, what kind of timescale would they be in?? Kind of suspended animation?

From the various points raised in this thread, one would imagine that the history of our planet is like a roll of movie film and each frame is "out there" for us to view by traveling in time.

If, for instance I "travel" to say - April 10th of 1896 to Athens - Greece, I would be able to witness part of the first ever modern Olympic Games. This means, any time traveler visiting Athens - Greece on 10th April would be able to witness the Olympic Games. In other words, the Games will be in progress forever. I can narrow it further. Say I witness the 100m dash for a few minutes at 10 AM, any other time-traveler from the year 2011 or later visiting the same location at the same time would be able to witness the 100m dash - which then, from my perspective, is going on forever and ever!! Like one frame of a movie film.

Another important point that no-one has touched so far is the complexities of time-travel. Obviously, a "spaceship" is not used for time-travel, but a "Time-ship" if you please. I need to set the exact time I wish to go to (not just the year and month)
and the exact location. Here is the hitch. I cannot navigate in a time-ship. Therefore, wherever the time-ship is located is the location I will arrive on the preset date. (H.G.Wells's Time Machine) What happens if I arrive at the bottom of a lake or inside a huge tree that might have existed in that location in that period?

I am sure future generations will sort all this out!

In a few years, virtual time-travel may be possible - to a selected few locations, but physically going back in time seems
unlikely. And going to the future is a one-way ride!

The last para of your post is very profound.

Asking "is time travel possible" is like asking "can objects disappear" or "can I have a square circle", etc.

That is, a failure to make real sense makes goals such as time-travel appear "possible". This "possibility" is of course grounded on grammatical and conceptual incoherence, and not on practical matters.

The idea of time-travel is taken from old black and white comedy film tricks (Charlie Chaplin, etc) where playing the comedy scene with stop/start/faster or backwards, etc, makes us think that we could do it in real time.

Theoretically (I hate this theory) time travel is possible by way of multiple universes. I don't know the name of this theory (or if it even has a name) but I do understand the basics of it

The idea is to have an infinite number of identical universes existing at infinitely (or infinitesimally) different points in time. One could theoretically find a way to 'hop' from one universe to another, and emerge at what, by their perspective, is another point in time.

The problem with this is that we are not where we where when you started reading this sentence. in the time it took me to get this message across, we have moved millions of miles through space. If you traveled back in time even one second (without accounting for motion), you would probably pop up in the vacuum of space. It's impossible with our level of technology to know where we are and how fast we're moving in relation to what might be called "real space," and so it is impossible to calculate where one will materialize if one where to travel to a different point in time.


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