Time travel implications

Factual Questions
21

It’s something to do with light cones in Minkowskian space-time that makes the communication meaningless, like Bell’s thing SingleDad just discussed. You can send a signal, but not communication. I’ll flip through “Emperor’s New Mind” tonight and reply if this thread hasn’t died by tomorrow.

Claiming that undetectable things don’t exist sounds more like Great Debate fodder, eh? :wink:

22

Bell’s theorem has profound implications for philosophy. SingleDad has touched on what it is really about. I have seen it misapplied to validate all manner of silliness, including but not limited to holistic universe and (my favorite) telepathy. Essentially, Bell shows that if you assume 1) Quantum Mechanics, 2) local causality, and 3) objective reality, then you reach a contradiction. This means that (at least) one of your assumptions is invalid. 1) QM and GR are the two most accurate theories science has ever produced. We are not willing to deny QM. We really don’t want to lose 2) local causality or 3) objective reality, but one must go. One of them is an illusion. It is objective reality that is sacrificed. Something does not have a (defined) value until it is measured.

Signal, but not communication. I don’t understand that.

I claim that undetectable things don’t exist by Occam’s razor.

Virtually yours,

DrMatrix
If I’ve told you once, I’ve told you 0.99999999… times.

23

Hey folks,

Thanks to all who have replied, I seem to have started a debate here which is getting a bit off course of what I intended to discuss (my fault here).

My fault for not being more specific about it in my original post, but the crux of my post was intended to be centered around this (cut and paste from my original post):

BEGIN CUT AND PASTE********

  1. Here’s the kicker…suppose for a minute that fore and aft time travel were possible. Not only possible, but even commonplace amongst humans. Yeah, people could walk up to high tech “phone booths” and, with the swipe of an ATM card, be whisked away instantly to any year of their choosing. Consider that this technology is available to all persons, world-wide.
    Now, you’ve got millions of people zipping in and out of time at their choosing. Sooner or later, someone would raise the question:
    “Hey, what is today’s real date, anyway?”
    There could be no answer!
    Not to mention the cessation of all sports on Earth, as well as gambling, prison sentences, warranties on purchased goods, etc., ect., let your mind run loose on the possibilities…
    The day AFT time travel is possible would be the end of humanity. You’d better hope like hell it NEVER happens!

********** END OF CUT AND PASTE**********

I was hoping to focus more on the “what if” as opposed to the “how”. I apologize for raising issues in my original post without specifying which of the issues was in fact the crux.

Again, in summary, SUPPOSE fore and aft time travel were commonplace…would you agree or disagree that it would effectively be the end of humanity via global chaos (as touched upon in the C&P above)??

Also, consider this…if time travel were possible, wouldn’t it have happened already (ala the “That’s impossible, we haven’t reached that year yet.”) argument which would be argued by anyone at any time (even now) when confronted by someone who claims to be from the “future”? (sorry for the run on)

It seems to me that these scenarios in and of themselves “disprove” aft time travel…if for no other reason than the associated paradoxes (sp?) themselves.

I also see sense in Vandal’s reply about time travel breaking the Law of Conservation of Energy.

Sure, this is all purely theoretical, but does that make it any less valid? Hope not, otherwise all of us electronics repair people would be theoretically out of our theoretical jobs! :slight_smile:

Bottom line, would aft time travel ultimately (if not rapidly) dispose of humanity as we know it??

Thanks again for all the replies…I’ve ordered some books on the subject thanks to a couple of posters… :slight_smile:

JJ Richard
(JJRichard@mindspring.com)

24

Man, there have been so many theories about time travel over the years… and, seemingly, each one has been made into a movie.

I just want to point out a couple things about “how”…

According to the theories I’ve seen, any sort of time travel would be A: extremely limited (traveling into the past, for example, would allow one to travel back only until the point that the time travel device was created), and B: probably not worth it, and C: not Time Travel in the classic “The Time Machine” sense of the word (a lot of it is just messing around with making something move really, really fast, or screwing with wormholes or gravitational effects).

However, IF scientists discover a new particle called… say… the chronolochon or whatever… that allowed for the manipulation of the time stream, we’d see it regulated by the government in a heart beat. This technology would take the place of the atomic (and hydrogen) bombs, with countries threatening to go back in time and annihilate their enemies. So time travel is really just the Nuke of the Next Generation (hey, I like that slogan… when I develop time travel, I think I’ll use it… I mean… uh… whoops).

But just something interesting I noticed about most time-travel theories… all the ones I know about (wormholes and such) require the manipulation of gravity fields. If humanity were to develop repulsorlifts (or similar gravity-manipulating devices), do y’all think time-travel could become more than just science fiction?

-SPOOFE

25

Superluminal signal without communication:

I’m led to believe there’s a similar limitation to tachyon communication. The ability to manipulate and detect them doesn’t translate into the ability to talk FTL.

Got no problem with Occam – if they’re undetectable they may as well be non-existent.

Doesn’t the Law of Conservation of Energy (or Massergy, I guess) only hold for the Universe as a whole? Massergy disappearing from one point in space-time and reappearing elsewhere/elsewhen leaves everything fine, no?

“The arrow of time moves in the direction of increasing entropy” also holds true for the universe as a whole. Localized entropy reversal (e.g., water freezing to ice) is ok as long as the overall entropy of the universe increases. Could this allow time travel only from certain space/times to other specific space/times (e.g., Julian May’s Guderian device)? We may have “forward” time travel possible in some cases, “backward” in others.

The end of human civialization as a result of time tampering strikes me as a decent increase in entropy.

26

a couple of things:

  1. we measure the time by our eyes in terms of light.
  2. time is a hypothetical thing, thus movement in time is possible. movement in space is quite another thing.
  3. moving faster than the speed of light within given space, moves you “backwards in time”(given space is the sun and the earth: the light takes approx 8 min. to travel from the sun to the earth, so the light eminating from the sun now is accually 8 min. before our time(earth time)).
  4. you can travel faster than the speed of light, the speed of light has been slowed down do approx. 60 km/hour. so if the speed of light can be slowed down, other matter is able to accelerate above it(if you are in a train traveling at 100 km/hour are YOU traveling at 100 km/hour?). also note that a light particle(debatable name) has been “teleported” a small distance.
  5. physical movement within the SAME TIME and SPACE is not possible, with the exeption of instantanious movement, which is normal movement…eh.
  6. you can VIEW the past. in fact you do it all the time. when you look up to the sky you are seeing “old” light. perhaps that lightsource has died in its own space, but its light takes time to travel to our space. note that this means you can not view the past of your own space, you must travel to another space to do so, and light remains essential when viewing the past, thus the deeper you want to view the past, the “older” light you must seek.

when traveling faster than the speed of light you propably become invisible(because light can not shine on your physical being). unless light is coming from more directions than one. but that would only be true if light is indeed particles, not waves(i hope that is the correct word, you know like “radio waves”).

anyway, i hope it helps a bit.

bj0rn - chickens for sale…!

(You know, I find it helps to copy it to WordPad and then fix all the punctuation errors, etc., so they’re not so distracting. Then I usually light some incense, sacrifice a chicken to the spirit of Kate Turabian, and get really drunk. Then it actually starts to make sense.) - notthemama

27

“Foreward” and “backward” are not functional concepts in time travel discussion. And logic also does not apply. One can only hope in the ultimate isness that sanity resides. Trying to reason around time travel is much like trying to define god. The more is said the less real it seems. Time is an imaginary invention of dimension, arbitrarily applied, much like latitude and longitude. Spatial and temporal constructs are factors of order. There are no such real critters. There is only order or lack of order.

28

“Foreward” and “backward” are not functional concepts in time travel discussion. And logic also does not apply. One can only hope in the ultimate isness that sanity resides. Trying to reason around time travel is much like trying to define god. The more is said the less real it seems. Time is an imaginary invention of dimension, arbitrarily applied, much like latitude and longitude. Spatial and temporal constructs are factors of order. There are no such real critters. There is only order or lack of order.

29

Today, my astronomy teacher told us to imagine the universe as the surface of a balloon: it is expanding, but it is not really expanding into anything. It is itself, and it is just getting larger. It is hard to think of the universe as both 2d (balloon surface), 3d with curved space, and somehow relate it to time as well. After reading bits of the Flatland story, I understand how it may be impossible for the less-than-genius to visualize higher dimensions. Is there anywhere on the internet that has pretty pictures at which I can look?

30

Oral,

I don’t know about on the net, but check out Brian Green’s book, “The Elegant Universe”. He has some pretty good graphics that may help you visualize more than three spacial dimensions… bearing in mind that these will actually be 2-D renderings…

31

Doh!.. That’s Brian Greene (not Green).

32

Virtually yours,

DrMatrix
If I’ve told you once, I’ve told you 0.99999999… times.

33

I don’t know what happed above. :confused:

What? Do you mean we use light to measure time?

Time is not hypothetical. It is real. We are always moving in time. Are you trying to say movement in space is not possible?

Which is it? Is the light eminating from the sun now or eight minutes ago?

No. The speed of light in a vacuum is constant. I’ve read about photon teleportation. This does not involve faster than light travel.

Are you saying instantanious movement is normal movement here?

Virtually yours,

DrMatrix
If I’ve told you once, I’ve told you 0.99999999… times.