Register to reply

A topic for amusement... Debunking Time Travel

by Pattonias
Tags: debunking, human nature, paradox, time travel
Share this thread:
Mech_Engineer
#19
Sep23-09, 03:15 PM
Sci Advisor
PF Gold
Mech_Engineer's Avatar
P: 2,242
Quote Quote by Pattonias View Post
Ah, that is the source of my paradox...
The argument is that if it was possible, given enough time eventually someone would make it known to us here in our time. Of course, it is assumed that this person would make it known to us and have the means to prove it.
Simply stated, given enough time this would have to happen.

*And in answer to your tag Ivan I think the problem is that the extremists are primarily the only ones who bother to get involved with politics : ) *
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
#20
Sep23-09, 03:18 PM
Pattonias's Avatar
P: 378
Quote Quote by humanino View Post
If time travel were possible, you should go back in time and prevent yourself from posting this thread. However, if time travel is really impossible, at least outside the future cone of the invention, then this thread is worthy of keeping open. Therefore, time travel is impossible, at least in the intersection of the future cone of this discussion creation and the past cone of the invention of the time machine. What !?
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.

Quote Quote by Insanity View Post
  1. Experts have been wrong before, are likely wrong today, and will continue to be wrong in the future.
  2. Whatever the mind of a sentient being can conceive and believe, it can achieve.
  3. Any technology, no matter how primitive, is magic to those who don't understand it.

Although the means in which to achieve time travel are not currently understood, time travel is likely a possibility, though we may not recognize it as such even if observed.
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
#21
Sep23-09, 03:18 PM
Sci Advisor
HW Helper
Chi Meson's Avatar
P: 1,772
Quote Quote by kpax View Post

Second, the nature of time travel may prohibit you from traveling back in time further than the point at which the time machine was invented. So there's no going back to 1930 and killing Hitler, no killing your grandad or any of that. You couldn't travel back into history because there weren't any time machines back then.
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
#22
Sep23-09, 03:23 PM
Pattonias's Avatar
P: 378
Quote Quote by Mech_Engineer View Post
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-traveler 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 traveler's paradox: what happens when a time traveler 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.
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
#23
Sep23-09, 03:29 PM
humanino's Avatar
P: 2,828
Quote Quote by Chi Meson View Post
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.
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
#24
Sep23-09, 03:32 PM
Pattonias's Avatar
P: 378
Quote Quote by Chi Meson View Post
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)
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
#25
Sep23-09, 03:32 PM
Sci Advisor
HW Helper
Chi Meson's Avatar
P: 1,772
Quote Quote by humanino View Post
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...
Sounds risky. You first!
humanino
#26
Sep23-09, 04:19 PM
humanino's Avatar
P: 2,828
Quote Quote by Chi Meson View Post
Sounds risky. You first!
I'll be quick
Discover Interview The Man Who Imagined Wormholes and Schooled Hawking
General relativity says wormholes could exist. When we combine general relativity with quantum theory, we find moderately strong evidence that wormholes cannot exist after all—but we just don’t know for sure yet.
If any highly advanced civilization attempts to make a time machine for backward time travel, quantum effects will cause the time machine to begin to self-destruct explosively at the moment you activate it. We don’t know whether the explosion is strong enough to always destroy the time machine. We will have to have in our hands the full quantum theory of gravity [a combination of general relativity and quantum mechanics, yet to be understood] to find out the answer.
Huckleberry
#27
Sep23-09, 05:53 PM
P: 606
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
#28
Sep23-09, 06:02 PM
humanino's Avatar
P: 2,828
Quote Quote by Huckleberry View Post
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.
"Dr" Ronald Mallett seems to be unaware of Hawking's weak energy theorems ensuring chronology protection. Did not we talk about him already ?
Evo
#29
Sep23-09, 06:21 PM
Mentor
Evo's Avatar
P: 26,473
Sorry, this is too overly speculative and has links to banned topics.


Register to reply

Related Discussions
A question with masses and distance to travel, find the time to travel so far... Introductory Physics Homework 5
Calculating Gravitational Time Dilation in black hole/Future Time Travel Special & General Relativity 5
Calculating the travel time in relativistic travel Special & General Relativity 1