# Is time travel possible?

If time travel to the past was possible then somebody would have done it. Though, it is known to be impossible now but if 20,000 years in the future somebody figures out how to do it, then our current now would already be altered.

Traveling to the future in the sense of faster then 1 second at a time is indeed possible.

Because it is impossible to go faster then the speed of light, once your velocity approaches it, time in for you would slow down.

yes but nothing is definite.... some how or some day we can

think about it... spacecraft is impossible back hundreds years ago.. people wont even think about it ..

long time ago.. people would think that travel faster than sound is impossible

but they all came possible

so dont be too precise

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Einstein said the faster you move, the slower time passes for you and the smaller you'd become.
At the speed of light, your length would decrease to zero and time would stop for you.
Now go at twice the speed of light and your length would become negative, or lets say opposite, and you would be going back in time as fast as you are moving forward at the moment.
Now wouldnt that be sweet?

One of my favorite quotes in reference to time travel asks,
"Since we've never seen a time traveler, does that mean it is never invented, or that we just live in a very boring time?"

Does absolute zero have anything to do with it?

Because i understand time as a measurement of events (or should i say moments?) and temperature as a measure of atomic/sub-atomic vibration (or something like that) and if absolute zero were to be reached the atomic/sub-atomic bits and bobs at that temperature would be completely still (apparently) as in no events passing by in that area.

So if someone were able to make something reach absolute zero could they then not go a little lower and cause events to reverse (time going backwards effectively)?

To further extend this idea to cause full time travel everything would freeze (as in really cold) and we would all perish as a result.

I reckon my logic is a little off somewhere, but i dunno where.

There is a much more possible way of time travel. Before i say anything else, see time travel won't be that cool thing. Your clock will be ticking at the same rate every thing will be normal to you, but when compared to the time of earth. Relatively, yours will be faster. So time travel works when compared.

Next thing, There is a something called Gravitational Time Dilation. In a nutshell, which says(and it is also measurable with great precision and accuracy) That time runs slower in the basement and faster on the roof. The basic idea behind is the closer you are to the center of a massive body, the slower is the time for you. As i said the roof-basement thing is when compared to the time in middle floors.

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Also, you see the past when you look up to the black sky in night. Every celestial body you are seeing, you are seeing how they looked, sometimes hours or years or million-billion years back. Since, light has a speed it had to take some time from the light to come to us. There can be at present infinite stars you see which don't exist in reality as they are dead now. While looking through and at those mesmerizing photos from Hubble space telescope, we actually are seeing the past, the past so old sometimes that nor earth nor sun existed.

Mute
Homework Helper
Does absolute zero have anything to do with it?

Because i understand time as a measurement of events (or should i say moments?) and temperature as a measure of atomic/sub-atomic vibration (or something like that) and if absolute zero were to be reached the atomic/sub-atomic bits and bobs at that temperature would be completely still (apparently) as in no events passing by in that area.
No. Due to the uncertainty principle of quantum mechanics (you can only decrease your uncertainty about an object's position by increasing your uncertainty of its momentum, and vice versa), even at absolute zero objects still possess motion, otherwise the uncertainty principle would be violated.

yes but nothing is definite.... some how or some day we can

think about it... spacecraft is impossible back hundreds years ago.. people wont even think about it ..

long time ago.. people would think that travel faster than sound is impossible

but they all came possible

so dont be too precise
I agree, information and aspiration leads to inventions. Just in last century, what we humans have achieved is far more than all our discoveries added up. We still think our theories about universe are not entirely correct, there is still a vacant position for the universal theory of everything.

I agree, information and aspiration leads to inventions. Just in last century, what we humans have achieved is far more than all our discoveries added up. We still think our theories about universe are not entirely correct, there is still a vacant position for the universal theory of everything.
yes which means that we are still not there yet... its a umimaginable long way to go even though we have someone times times better than Einstein

sophiecentaur
Gold Member

is time travel possible?

If yes, how is it possible to travel through time?

Can we travel in the future?

Can we travel back in the past?
Hawking believes that we may travel to future when entering wormhole,but it seems impossible to go back.Because there is no anyone come from future as yet.

But Einstein said that we can't travel to the future but we can travel to the past though.

And I can say that's it true because by me time passes along with us and creates itself along its way and we can't go into a different moment of time that does not exist.

But I still have a doubt if we are moving along with time or not or if we have some replications of ourselves in the future.

the way a wormhole works is that you fix one end at the present time and make the other end travel at near the speed of light so that it experiences time dilation. As a result of this, future people can enter the time dilated end and go back to the past where the past end is located. But you can only go back as far as when the worm hole was created.. not before that. Since we have not created a worm hole yet then no one from the future can come back in time to visit us.
I'm very surprised that someone of Hawking's stature in the physics world would lend himself to a TV program so full of errors as the one that aired on the Discovery channel.. or was it the History channel? I don't watch them.

But Einstein said that we can't travel to the future but we can travel to the past though.

And I can say that's it true because by me time passes along with us and creates itself along its way and we can't go into a different moment of time that does not exist.

But I still have a doubt if we are moving along with time or not or if we have some replications of ourselves in the future.
Einstein never said that. go google time dilation and learn something

I read that in a book but wasn't sure of it though.

I read that in a book but wasn't sure of it though.
You should provide the name and author of that book. It seems to be an mistake.

Time travel to the future is "relatively" simple to prove mathematically with Einstein's own postulates, and it has been demonstrated experimentally with subatomic particles.

Time travel to the past has no experimental support.

In a few centuries, or a few thousand years hence, the earth will have revolved around the sun a commensurate number of times. The sun will have consumed billions of tons of hydrogen, having converted it into energy and radiated it into space.

To pretend that with some magic time machine, one can speed up all these processes everywhere in the universe simultaneously is the height of folly.

Going back in time would require restoring what once was. Can pre-World War II Berlin be rebuilt with this imaginary time machine?
Can Hitler's body be reconstructed from the very same atoms that once composed it, and are now spread out around the earth? But not only Hitler's, but everyone who was alive at that time.

This is almost as preposterous as the Multiverse Cockamamey.

Seen some interesting connections here.

Now here are some possibilities that were not considered here. First clarify 2 things:
1. Time has direction - from "now" to "future"
2. Time has speed - 1 sec/sec for you at rest

What would be the implications(i.e. what paradoxes arise) of the following:
1. A speed of >1 sec/sec for you relative to the universe.
2. Reversing the direction time progression: not as in your general idea, like lets go from 2010 to 1939 and shoot Hitler, so WWII never happens without any time in between.
But rather in that state, for every second you age, everybody gets a second younger(and the other way around also).

DaveC426913
Gold Member
To pretend that with some magic time machine, one can speed up all these processes everywhere in the universe simultaneously is the height of folly.
Yes that would be folly. Luckily no one has suggested that except you.

Can Hitler's body be reconstructed from the very same atoms that once composed it, and are now spread out around the earth? But not only Hitler's, but everyone who was alive at that time.

This is almost as preposterous as the Multiverse Cockamamey.
Yes that is preposterous. Luckily no one has suggested that except you. (Not to mention completely misunderstanding the entire concept of 'backwards in time'.)

The lesson here is to debate what people are in fact saying, not your own fallacious ideas of the topic. These are both red herring fallacies.

Going back in time would require restoring what once was. Can pre-World War II Berlin be rebuilt with this imaginary time machine?
Can Hitler's body be reconstructed from the very same atoms that once composed it, and are now spread out around the earth? But not only Hitler's, but everyone who was alive at that time.
So would this mean that everything in the current time would need to be destroyed? Or would it still exist?

There is experimental evidence (such as the delayed choice quantum eraser) of reverse causality. If reverse causality can be proven and then used as a means of transmitting information backwards in time that in itself would be a certain form if time travel.

Redbelly98
Staff Emeritus