Here’s a proposed answer about time travel and why we haven’t seen people from the future.
Could it be that time travel into the future is potentially possible, as first stated, but the return trip is NOT possible???
If we are ever able to go into the future, maybe one should just buy a one-way ticket!
I’d rather have a bottle in front of me than a frontal lobotomy - Hawkeye 4077th
As an addendum to my comment above, let me clarify:
It was said that future travel may be possible at just below the speed of light (say 0.9c as a nominal value).
It was also said that the return trip would require a speed greater than the speed of light (say 1.1c as a nominal value).
So, maybe it is possible to go at 0.9c AND not possible to return at 1.1c…all we need is a guinea pig. Any volunteers to go?
A little knowledge is a dangerous thing
I’d rather have a bottle in front of me than a frontal lobotomy - Hawkeye 4077th
forget about the time machine, just take a nap-- ever have a dream come true? you were remembering the future. it may have been linear or spliced with other bits of your subconscious, but it was not just a deja vu brain fart.
YES! this happened to me back in college. Upon our waking to the alarm clock, my room mate asked me if i had good dreams. i replied that i had dreamt that the Mets had won 5-0. That day the Mets won 5-0. Did I perceive the future? I can perceive the past, why not the future? is not memory a kind of transchronic perception? Did i perceive an alternate universe? I don’t think time travel is possible for people’s bodies, but i do think we can communicate at faster than light speed-photons popping into and out of the quantum foam…this has been done in europe-2 years ago? Can information travel backwards in time…a pattern perceived through the foam? a ripple of an event expanding in all directions through time? the farther from the event, the weaker (more widely dispersed?) the ripple?..
I’d rather have a bottle in front of me than a frontal lobotomy - Hawkeye 4077th
In fact, Stephen Hawkings, in “History of Time” – or something like that – argues that time travel is not possible because of entrophy. He says that there are some “arrows” that can go back and forward, but the entrophy arrow only goes forward: Nature tends to caos. If we were to travel back in time, it would that the Second Law of Thermodynamics is violated. Thus, he concludes that time travel is not possible.
And also he puts forward an argument like the one yamo had: will we remember the future shall we travel back in time?
Ooops! Sorry for the double post:
The “arrows” he talks about are the dimensions of our Universe.
I should have written: Nature tends to Caos. If we were to travel back in time, it would MEAN that the Second Law of Thermodynamics is violated.
Now if you’ll just learn to spell “chaos”…
Here’s my question: why do people think that if the universe stops to collapse, time will suddenly run backwards? Is time’s arrow (entropy) tied to the expansion itself?
I would think that just because the universe stops expanding and starts contracting (assuming that happens) that time would still progress forward. I throw a ball up, it then falls down, but time still went forward even though the ball changed direction. Why would it be different with the expansion/contraction of the universe?
Starts to collapse! Starts to collapse! Ugh.
Hmm…there’s an interesting question proposed by Irishman. Even if the universe were to stop expanding and reach a static state (no collapse either), wouldn’t time also go on? If time were to stop, then would all motion stop, too? Afterall, motion is displacement over time! And if all motion were to stop, what about the law telling us to conserve all that momentum?
And, as expansion slows, is time expected to slow at some relation to the decreasing rate of expansion?
I’d rather have a bottle in front of me than a frontal lobotomy - Hawkeye 4077th
Ok, ok, sorry for the spelling of “chaos”… English is not my mother tongue, so sometimes I scramble it a little with my Spanish. =O
Anyway, the argument does not have to do with the Universe collapsing. It would only mean distances getting shorter but not anything else. The point is that if the time goes backward, the order in the Universe will increase (the Universe is getting more chaotic each time now) so the Second Law of Thermodynamics would be violated. Nothing to do with Universe expanding or collapsing.
Before I commit another mistake… does the Second Law of Thermodynamics the one about entropy?
The Zeroth Law: Can’t win
The First Law: Can’t break even
The Second Law: You’re bound to lose, anyway
The Third Law: Can’t kick manure in one end of a horse and get hay out the other.
(Film at 11pm)
Well, this was how it was taught to me in
AP Physics! yet, it doesn’t quite corrolate!
But seriously, the Second Law is entropy.
I’d rather have a bottle in front of me than a frontal lobotomy - Hawkeye 4077th
What with all this talk of expansion vs. collapse of the universe (depending on total mass)and entropy leads me to ask this: if, as some have suggested is possible, the universal expansion reverses and the universe collapses again into the primal particle, or whatever you want to call it, then bangs again (the so called yo-yo theory)to create a new universe, the new universe will have … well, recaptured, I guess, the state that the previous universe had. Thus in a sense at least entropy will have reversed, at least if we think of the two universes as being somehow connected by their source, and as long as the yo-yo keeps yo-ing forever (as long as the expansion-collapse-expansion cycle does not tend to damp out, as with some sort of pan-universal entropy).
Does the concept of entropy cover this?
woodja:
I think in “History of Time”, Hawkings also deals with that point. And Sagan has done so… Hmmm… I think I need to re-read those books so I can make some quotes. The idea is that if some information is passed to the new Universe after another Big Bang, “entropy would be reversed” as you say. So the most likely scenario is that nothing remains from Big Bang to Big Crunch to Big Bang, there is no “memory”. Anyway, I cannot imagine a way to do so (of course this is not proof of anything 
).
Some cosmologist have put forward that the new cosmos might have very different laws, different number of physical dimensions, etc.
Right. Also different ratios of particle to antiparticle (it’s just chance that what we call matter is dominant. In a new universe antimatter may win out), different quantum numbers and constants, etc.
So you are saying (I think) that entropy is limited to our current universe framework, and that a subsequent universe could be considered to be a part of ours (or connected, or within the same framework) if information is passed from the former to the latter. If no information is passed, the universes are distinct and the question of reversed entropy doesn’t apply, but if they are connected then entropy carries over into the new universe and if by some chance the new one is similar to ours it may seem as though entropy has been reversed.
The next question is, as I alluded to before, whether there is entropy across expansions and compression’s, like maybe each expansion has a little less steam than the last and the whole thing tends to peter out. This would allow the yo-yo thing to work, with the universes connected, while still not violating entropy. By extension, if it didn’t peter out and information was conserved entropy could be said to be violated.
This is all a bit ethereal, but I’m sure some theoretical physicist has taken a few hours off from inventing time machines to do the math.