Thread: Is it Physically Possible to Travel BACKWARDS in Time?

1. Is it Physically Possible to Travel BACKWARDS in Time?

We all know it's possible to time travel into the future relative to everyone else. For example, say you went 75% the speed of light for an hour. The world around you relative to you would have aged thousands of years just from going at that speed for an hour.

The tricky situation is that once you travel into the future, there is no going back. You're stuck in the present and all your friends and family have already died.

Source for Relative "Time Traveling" into the future: (before crying about wiki, check the sources listed on the site) http://en.wikipedia.org/wiki/Time_dilation

Now the big question: How do you Travel BACKWARDS in time? Is it even possible?

Everything we know about physics so far points to no. There seems to be a system that protects itself from traveling backwards in time. We may just be looking in the wrong places or formulas. Now if you COULD travel backwards in time.....There are a few problems.

-Grand Father Paradox: If you traveled backwards in time and killed your grandfather, would it make you disappear from reality?

- What would happen if you ran into your past self?

Personally, I think if you travelled backwards in time, you would create simply another parallel universe in our already infinite amount of universes.(assuming string theory is true)

Fun Fact: If you travelled the speed of light, you would become infinitely massive and time would stop relative to you. I bet that would be fun.

2. fly at the speed of light around the word backwards until the earth rotates the other direction like in Superman returns. DUH!

3. No.

Originally Posted by golds
We all know it's possible to travel in to the future relative to everyone else.
While you can call that "time travel", this is completely different to the traveling back in time. With time dilation, all you are doing is make time slow down for you relative to everyone else. You are not traveling through time.

4. Right it's not time traveling in a sense of skipping actual time. But it is possible to age slower relative to the earth at accelerated speeds.

Either way, the Earth would have aged 5000 years (given the right speed) and you'd have basically the same result as time travel...... minus the doppleganger obviously.

But is there an opposite side of that?

5. Originally Posted by golds
Right it's not time traveling in a sense of skipping actual time. But it is possible to age slower relative to the earth at accelerated speeds.

Either way, the Earth would have aged 5000 years (given the right speed) and you'd have basically the same result as time travel...... minus the doppleganger obviously.

But is there an opposite side of that?
Not without the existence of some sort of wormhole that transcends time and space.

6. There's a theory that once a time machine has been invented then backwards time travel will be possible but only back as far as the time machine was first turned on, and I think it has to remain on as well so if it was made 100 years ago but got turned off and on again 40 years ago you could only go back 40 years, or something along those lines.

That's barely even a theory though, so as far as we know it's not possible.

7. Despite what Doctor Who fans would like to believe, our understanding of time is that it's linear and unidirectional. Translation: you can only go in one direction. Time-travel, and dilation, and all that, is all about accelerating the passing of time... still in that one direction.

Also, flying west doesn't count.

8. M-theory suggests there are universes where time travels backwards. Also, near a blackhole time is significantly distorted and it's theoretically postulated that time reverses as you approach the singularity.

9. Originally Posted by golds
But is there an opposite side of that?
Currently, no. Velocity is can only be zero or greater. You can't really go slower than zero (a negative velocity or positive velocity only indicates direction of travel, i.e. going -60 mph west is really just going 60 mph east). There's no way to trigger "time contraction" like you can with dilation.

Originally Posted by Kaeleena
Also, near a blackhole time is significantly distorted and it's theoretically postulated that time reverses as you approach the singularity.
Not entirely accurate. Take Ann and Bob. Bob is driving towards a black hole while Ann is watching from far away. As Bob approaches the black hole's event horizon, he doesn't really notice ever crossing it as he spirals down towards the center of the black hole (we're going to ignore the beyond deadly radiation and crushing forces he would encounter). However, due to gravity's warping of spacetime near the event horizon, Ann watches as Bob's progress slows more and more as he gets closer to the black hole. From Ann's perspective, Bob slows so much that he never appears to reach the EH even though Bob does in fact make it without so much as a speed bump.

There's still no "backwards" progression of time, only slowly approaching zero from Ann's view.

10. Originally Posted by golds
Right it's not time traveling in a sense of skipping actual time. But it is possible to age slower relative to the earth at accelerated speeds.

Either way, the Earth would have aged 5000 years (given the right speed) and you'd have basically the same result as time travel...... minus the doppleganger obviously.

But is there an opposite side of that?
As someone already alluded to, although it's tempting to consider this time travel, it's really just experiencing different amounts of time. It is possible that everyone on the Earth could move faster relative to yourself, and thus experience less time than you. However, both you and the Earth will never reach the speed of light so you'll both be traveling positively through time. You basically cannot re-experience an event that has already occurred.

11. Originally Posted by golds
But is there an opposite side of that?
An opposite of it would be for time to go faster for you relative to everyone else. That is, you will age and die "faster".

That's why it's not really time travel. You aren't traveling through time, you are just controlling the rate of time's passage. The opposite of it is still NOT going backwards.

12. Originally Posted by semaphore
No.

If it wasn't so late ta night right now and I wasn't just about to go to bed, I'd pull up the article in Time magazine from...March? last year where it showed particles at the massive particle accelerator near the alps (I think...it's so late here right now lol) arriving something like 12 billionths of a second before the calculated speed of light. At first, all ~200 scientists involved in the project believed it to be an error, but after a whole bunch more trials, and after new scientists joined the operation, the results remained the same. A large number of the scientists involved in the study refused to sign the research because of fear of backlash from the scientific community.

This was one of the biggest stories (you never heard about?) last year because if it is indeed true, this is the most major reakthrough in physics in a century. It makes Einstein's theory of relativity obsoloete and will cause a total overhaul in the realm of physics.

So, time travel hasn't been *proven* but there is evidence that shows that the idea cannot be completely dismissed.

EDIT:

I feel it's a story everyone should read about as it will likely blow your mind, so here it is http://www.time.com/time/health/arti...094665,00.html

13. I yea, that sounds familiar, Anakso.

I believe Steven Hawking said something of the sort of "The Greatest evidence backwards time travel is not possible is that we have not encountered any travelers yet."

Sort of the Human version of a Fermi Paradox....... Thought the comparison is still a little apples and oranges

14. Traveling back in time is impossible because it creates paradoxes. (ie, you go back in time and kill yourself -- how did you then get to the future to travel back in time to kill yourself?)

15. Originally Posted by Dkitty
Traveling back in time is impossible because it creates paradoxes. (ie, you go back in time and kill yourself -- how did you then get to the future to travel back in time to kill yourself?)
Multiple universes. When you travel back in time you're creating/traveling to a universe where you exist twice.

16. Originally Posted by Dkitty
Traveling back in time is impossible because it creates paradoxes. (ie, you go back in time and kill yourself -- how did you then get to the future to travel back in time to kill yourself?)
What evidence supports this theory outside pure speculation? This is not a fact, it is an opinion that (likely) cannot be proven.

17. Originally Posted by Annapolis
As someone already alluded to, although it's tempting to consider this time travel, it's really just experiencing different amounts of time. It is possible that everyone on the Earth could move faster relative to yourself, and thus experience less time than you. However, both you and the Earth will never reach the speed of light so you'll both be traveling positively through time. You basically cannot re-experience an event that has already occurred.

Dilating thousands of years into the future(relative to you) is close enough imo. :P

18. Originally Posted by Xombo
If it wasn't so late ta night right now and I wasn't just about to go to bed, I'd pull up the article in Time magazine from...March? last year where it showed particles at the massive particle accelerator near the alps (I think...it's so late here right now lol) arriving something like 12 billionths of a second before the calculated speed of light. At first, all ~200 scientists involved in the project believed it to be an error, but after a whole bunch more trials, and after new scientists joined the operation, the results remained the same. A large number of the scientists involved in the study refused to sign the research because of fear of backlash from the scientific community.

This was one of the biggest stories (you never heard about?) last year because if it is indeed true, this is the most major reakthrough in physics in a century. It makes Einstein's theory of relativity obsoloete and will cause a total overhaul in the realm of physics.
It is indeed not true. They found that it was a loosened cable throwing the readings.

19. Time is a dimension. Your perception of time is simply a perception of your orientation in the fourth dimension.

20. Originally Posted by Dkitty
Traveling back in time is impossible because it creates paradoxes. (ie, you go back in time and kill yourself -- how did you then get to the future to travel back in time to kill yourself?)
What about just creating a different parallel universes, like String theory suggests? (infinite universes)

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