A topic for amusement... Debunking Time Travel

Insanity

Correct.

Mech_Engineer

You made the "rule" to start with that we have only one single thread of existence, and that may be the source of the problem for a time traveler changing the past...

Ivan asked the question how would we know that history had been changed, and the answer is that with a single thread we cannot know. If a time-traveller goes back in time and changes something, the change will continue through the thread to his time and he will be unaware of the change; he won't even have the thought to travel back in time and change whatever it is he went back to change in the first place, because in changing the past he will have also changed himself (this goes back to the single-string time traveller's paradox: what happens when a time traveller kills his father?).

It seems that someone could come back and predict something that was not due to human interaction such as a volcanic eruption, or asteroid strike. The fact that no one has done this means either that time travel through this model is not possible, or that there is nothing worth predicting to us right now.

Pattonias

lol, this is really a good point... We should try to keep the thread open lest I forget to go tell myself to eat my own words.

True if a sufficient regulatory force existed to keep people from taking advantage of the ability to time travel existed perhaps we are already being interfered with on a daily basis.

Perhaps "miracles" are a result of the influence of future beings who felt a need to make a change.

Is someone in the future deciding what needs to be changed and what doesn't? Is someone in the future permitted to make these very important decisions.

Chi Meson

As far as I recall from my studies long ago...

Kip Thorne created a plausible model for "time travel" through the quantum foam. It is essentially approaching the realm of "impossible" to accomplish due to the enormous quantity of negative energy density required to expand a "foam bubble" large enough to fit through.

Even then, the "portal" would be fixed at that point in time. Its not so much the invention of the time machine itself, but the point in space-time that the opening was created. The "tube," of sorts, could be stretched from that point allowing transit between the future and the initial point.

That's from a very old memory. Sounded iffy 15 or 20 years ago, and it looks more suspect even now, but hey, it's Kip! I'm not gonna argue. (I don't really understand it, honestly)

Pattonias

Good point, if a time traveler goes back and changes something he would essentially remove his need to go and thus have never left... Another paradox.

It could also be argued that the human race is wiped out before time travel is ever invented/discovered...quantumthere'dededupon-at

humanino

My memory of Kip et al conclusions

• you need an exotic form of matter, whose pressure exceed its own energy content, to ensure the stability of the wormhole. We have not the faintest idea whether such an exotic form of matter is possible even in principle
• even if you come up with your exotic matter, the wormhole is still unstable : spontaneous quantum fluctuations will amplify themselves, blowing up your wormhole in less than a Planck time, as measured by the observer attempting to go through the wormhole...

Pattonias

It should be very possible to travel into the future from the perspective of the traveler certaintly. "Simply" traveling at the speed of light away from the earth for a time and coming back should provide a certain form of forward time travel. A way to see what your
great(x10^6)grand kids are doing with themselves. This is assuming Einstein was totally right.

Chi Meson

Sounds risky. You first!

humanino

I'll be quick
Discover Interview The Man Who Imagined Wormholes and Schooled Hawking

Huckleberry

A person doesn't need to be sent back in time to influence history. If there is an energy cost/unit of mass then that method would be ineffecient for most purposes. Sending information back could be enough.

Dr. Ronald Mallett, professor of physics at the University of Connecticut, wants to build a time machine that will send subatomic particles into the past that can be interpreted as information in our present. It only functions from the point that the machine is constructed.
http://www.youtube.com/watch?v=GHC8z6ULs18

edit- whether it works or fails the results of his experiments could be informative.

humanino

"Dr" Ronald Mallett seems to be unaware of Hawking's weak energy theorems ensuring chronology protection. Did not we talk about him already ?

Evo

Sorry, this is too overly speculative and has links to banned topics.