time travel

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Posted by: stak
Posted on: 2006-10-12 19:45:02

it snowed today! now that i've gotten that announcement out of the way, on to the main topic: time travel.

at work today (or rather, during lunch at the mall) some of my co-workers and i were discussing the possibility of time travel. the main problem we ended up with was that of matter creation/destruction. time travel implies moving a bunch of matter from one time to another, which is effectively the same as destroying matter in one time and creating it in another. also, what happens to the matter in the place you appear? since (i assume) at most a single particle can occupy a given position at a given time, it's possible for you to travel to some other time and have your particles collide with other particles already there. swapping the volume (i.e. you go back in time 10 minutes, and the air that you replace moves to the present) also doesn't work because of density differences (it's a different mass, and so you end up creating/destroying matter).

in the end, we came to the hypothesis that the only way to pull it off would be to shrink the object in question down to a point of infinite density, and then swap it with another point of infinite density in another time. since black holes do shrink things down to points of infinite density (maybe), we postulated that black holes are really time portals created by some super-advanced species in order to travel through the fourth dimension.

looking back at this now, i guess it still doesn't solve the problem of matter creation/destruction. hmm. anyway, what do you think?

Posted by rohan at 2006-10-12 20:34:09

snow? in waterloo??? it hasn't even snowed here! why is it so cold over there?

time travel into the future is definitely possible... just travel at close to the speed of light. the matter problem is avoided because you don't dissappear and rematerialise, you stay where you are and just advance in time at a different rate from other stuff.

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Posted by stak at 2006-10-12 20:51:55

beats me. weathernetwork.ca claims the temperature will go back up next week, though.

hm.. interesting proposition. but it's not true time travel unless you can freely go backwards as well as forwards. although being able to travel only forward does take care of all of those pesky be-your-own-father paradoxes.

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Posted by Eric at 2006-10-12 22:07:56

Of course time travel isn't possible. Where are all the time travellers?

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Posted by Fai at 2006-10-18 16:37:47

You have to move matter from one place to another when you move in three dimensions also, yet we manage it. Instead of disappearing from one time and appearing in another, you just need to move through time with a non zero velocity and the particles you displace will take up the space you were at. This would presumably be air. if the air was a different mass, how would walking work?

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Posted by John at 2006-10-18 22:57:42

Oh come on, don't you remember the 11-dimensional representation of the universe? Where every possible start, end, and in-between is represented all "at once"? In that system, the only thing that defines what we see, and what's around us, is how we traverse all 11 dimensions. We perceive 3 spatial dimensions, and are constantly taking snapshots as we go through the 4th. The other dimensions take care of all of those other possibilities - the way I want to think about it is that if you travel back in time, one of those traversals will cease to have you in it, while another traversal will have two copies of you. So universally speaking, no matter is created or destroyed, just moved between potential universes.

My view has the additional time-travel-associated "problem" of when you travel "back to the future", the you in the past of your current timeline traversal still exists, and now he's your age and won't give you back your car.

Unless you travel forward back to your own previously traversed "timeline", at which point you will have done nothing to your current traversal, and only messed with someone else's timeline.

Heck, I might do that just for fun. Freak myself out, you know... for kicks... if we ever figure this time travel business out...

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Posted by Robb at 2006-10-19 18:36:15

Wow! I didn't expect that many no's! Remember that 500 years ago the earth was flat, and 100 years ago we had solved all the hard problems of science. We still haven't even left our solar system. And yet so many people are willing to state that they know enough to say Time Travel is Not Possible. A bold statement.

In other news, Kats, your billion-letter captcha verification may mean that getting a OpenID would be the path of least resistence.

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Posted by stak at 2006-10-19 23:10:38

The billion-letter captcha is really only 10 letters. I'm considering switching it to a simple math question (i.e. "enter 3 + 4 here" instead of "copy these letters here"), since captchas (specially mine) are easy to break or otherwise solve. but i'll probably be lazy and wait until the spammers get around to harassing me again. in which case, yes, you should get an OpenID. :)

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