4 ms·

It's official: Time machines won't work

11 points by uladzislau 15y ago

__rkaup__ 15y ago
I've always wondered: isn't travelling to the past the same thing as making matter from nothing? That is, since then there would be two copies of you.
- Udo 15y ago
  Kind of, I always saw it as leaving this universe irreversibly and entering an earlier version of it from out of nowhere. But since atoms don't have unique IDs, it's no problem to have two (almost) identical people beside each other. Also, contrary to popular fiction, the past isn't changed only because a blundering human is transported into it, it is already altered by the mere introduction of additional matter into a system that would have evolved differently without it. So, if you want to change the past, transport a single proton back 2 million years into some swamp. Of course, that would be pointless because nobody would ever know what changed... The real conundrum is what actually happens to the "old" universe at the instant of traveling back into the past. Is everything that happened between those two points in time erased? Or does the old universe continue as if nothing happened and a new parallel one branches out that is of no consequence at all? In the infinite universes theory, time travel would merely amount to "jumping" into the "right" neighboring universe (however, personally this whole business with infinite branching parallel universes always seemed like a wasteful and inelegant model to me). All these theories have one thing in common though: things change only for the time travelers themselves. So for meaningful time travel, you would have to be able to transport whole beings across a doorway in spacetime. Twice. In the right direction. Given the known conditions near theoretically surmised holes in spacetime, that's not an easy task. Atoms: maybe. Huge fragile collections of unstable molecules: probably not.
- glimcat 15y ago
  Well, does the past currently exist?
glimcat 15y ago
There was some real science done. Then the media took it and ran with it. Spoilers: the real science did not in any way involve time travel.
hamner 15y ago
Please link to more reputable sources for scientific articles. For an example, the university press release is intended for a general audience and more factual: http://www.ust.hk/eng/news/press_20110719-893.html http://www.ust.hk/eng/news/press_20110719-893.html, and the peer-reviewed publication is here: http://www.phys.ust.hk/dusw/Publication/PhysRevLett_106_243602.pdf http://www.phys.ust.hk/dusw/Publication/PhysRevLett_106_2436...
nohat 15y ago
The research determined that single photons could not move faster than the speed of light (sounds obvious, but quantum scale objects don't necessarily behave). This does not disprove time travel, just one hypothetical phenomena that could have led to time travel.
beej71 15y ago
Dup and ancient. I read this back in 2067.

11 points by uladzislau 15y ago

I've always wondered: isn't travelling to the past the same thing as making matter from nothing? That is, since then there would be two copies of you.

Udo 15y ago
Kind of, I always saw it as leaving this universe irreversibly and entering an earlier version of it from out of nowhere. But since atoms don't have unique IDs, it's no problem to have two (almost) identical people beside each other. Also, contrary to popular fiction, the past isn't changed only because a blundering human is transported into it, it is already altered by the mere introduction of additional matter into a system that would have evolved differently without it. So, if you want to change the past, transport a single proton back 2 million years into some swamp. Of course, that would be pointless because nobody would ever know what changed... The real conundrum is what actually happens to the "old" universe at the instant of traveling back into the past. Is everything that happened between those two points in time erased? Or does the old universe continue as if nothing happened and a new parallel one branches out that is of no consequence at all? In the infinite universes theory, time travel would merely amount to "jumping" into the "right" neighboring universe (however, personally this whole business with infinite branching parallel universes always seemed like a wasteful and inelegant model to me). All these theories have one thing in common though: things change only for the time travelers themselves. So for meaningful time travel, you would have to be able to transport whole beings across a doorway in spacetime. Twice. In the right direction. Given the known conditions near theoretically surmised holes in spacetime, that's not an easy task. Atoms: maybe. Huge fragile collections of unstable molecules: probably not.
glimcat 15y ago
Well, does the past currently exist?

glimcat 15y ago

There was some real science done. Then the media took it and ran with it. Spoilers: the real science did not in any way involve time travel.

hamner 15y ago

Please link to more reputable sources for scientific articles. For an example, the university press release is intended for a general audience and more factual: http://www.ust.hk/eng/news/press_20110719-893.html http://www.ust.hk/eng/news/press_20110719-893.html, and the peer-reviewed publication is here: http://www.phys.ust.hk/dusw/Publication/PhysRevLett_106_243602.pdf http://www.phys.ust.hk/dusw/Publication/PhysRevLett_106_2436...

nohat 15y ago

The research determined that single photons could not move faster than the speed of light (sounds obvious, but quantum scale objects don't necessarily behave). This does not disprove time travel, just one hypothetical phenomena that could have led to time travel.

beej71 15y ago

Dup and ancient. I read this back in 2067.