# Time Travel
**URL:** https://boards.straightdope.com/t/time-travel/3706
**Category:** Factual Questions
**Created:** [October 4, 1999, 4:24am UTC](https://boards.straightdope.com/t/time-travel/3706 "1999-10-04T04:24:00Z")
**Posts on this page:** 4
**Page:** 3
### Author:  [@AWB](https://boards.straightdope.com/u/AWB)
#### Post date: [November 30, 2000, 5:09pm UTC](https://boards.straightdope.com/t/time-travel/3706/41 "2000-11-30T17:09:37Z")
> [@](#):
>
> \*Originally posted by tanstaafl \*
> **AWB - _The Proteus Operation_ by James P Hogan.**
Yes, that was it! I’ll have to see if I can get a reprint. That was a great story.
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### Author:  [@davesink](https://boards.straightdope.com/u/davesink)
#### Post date: [November 30, 2000, 5:32pm UTC](https://boards.straightdope.com/t/time-travel/3706/42 "2000-11-30T17:32:44Z")
OK… I know this thread has been done to death, but one point I seldom heard mentioned re. feasavbility of time travel is the issue of creating something from nothing. When traveling back in time, wouldn’t that amount to creating matter, when faced with your old self. I thought matter could be neither created nor destroyed, only change form.
BTW since someone earlier mentioned Robert Heinlein, his excellent short story on the subject, “All you Zombies” can be found at the following link:
[http://www.geocities.com/CapeCanaveral/Launchpad/5505/all\_you.html](http://www.geocities.com/CapeCanaveral/Launchpad/5505/all_you.html)
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### Author:  [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)
#### Post date: [November 30, 2000, 5:56pm UTC](https://boards.straightdope.com/t/time-travel/3706/43 "2000-11-30T17:56:50Z")
> [@](#):
>
> When traveling back in time, wouldn’t that amount to creating matter, when faced with your old self.
Good point. perhaps you’d have to send as much matter an equal amount forward in time, or twice as much matter half as far forward. Or maybe spend some time in the future to balance how much you spend in the past.
Of course, all our conservation laws are only _known_ to hold when time travel is not occurring. Since we don’t know the physics of time travel, we can only _guess_ that some form of the conservation laws will hold.
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### Author:  [@Phobos](https://boards.straightdope.com/u/Phobos)
#### Post date: [November 30, 2000, 6:19pm UTC](https://boards.straightdope.com/t/time-travel/3706/44 "2000-11-30T18:19:15Z")
You can fake-time-travel to the future by travelling at relativistic speeds (a la Twins Paradox). But I assume that this is not what the OP is about.
Backward time travel seems to need a wormhole to work. But wormholes may not exist. IIRC, Kip Thorne and/or Stephen Hawking believe that backward time travel would still be impossible this way because there would be some kind of energy feedback through the wormhole that would destroy you & the wormhole. Unfortunately, I forget the details at the moment. (sorry! IIRC, I think I read about it in the book “Carl Sagan’s Universe”)
[hijack]
If forward-time-travel is possible, then do you think that would mean that the universe is predetermined?
[/hijack]
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