74 réponses à ce sujet

[Boiny Bunny]

Hellbound555 wrote...

kglaser wrote...

Celrath wrote...

And this is where the parallel world theory comes in. Which is every time some one goes back in time they are creating an alternate reality leaving the original time you came from untouched and also making it impossible to get back

This I support.

Plus, tachyons.

so instead of time travel, we go to a parallel world thats main difference is that its in the past?

It's to avoid the creation of a paradox.  Suppose you invent a time machine, go back in time 60ish years, and kill your grandfather before he ever meets your grandmother.  What happens?  Because your grandfather never met your grandmother, you never existed, which means you never built the time machine, and never killed your grandfather.  If he was never killed, he met your grandmother, and you do exist, meaning you built the time machine, and went back to kill him, implying that you don't exist, and so on...

If you believe the 'alternate dimension' theory, if you go back in time, you wind up in an alternate dimension which is 100% identical to your dimension at the time you arrive, but is different from the point of your arrival onwards (your existance there changes it going forward).  Thus you can kill your grandfather in the alternate dimension, meaning you will never exist in the alternate dimension as you did in your native dimension - but you exist in some sense in the alternate dimension because you travelled there from your dimension.

That's a little bit simplified, but that's the general idea.  Paradox = bad

[Homebound]

Boiny Bunny wrote...

Hellbound555 wrote...

kglaser wrote...

Celrath wrote...

And this is where the parallel world theory comes in. Which is every time some one goes back in time they are creating an alternate reality leaving the original time you came from untouched and also making it impossible to get back

This I support.

Plus, tachyons.

so instead of time travel, we go to a parallel world thats main difference is that its in the past?

It's to avoid the creation of a paradox.  Suppose you invent a time machine, go back in time 60ish years, and kill your grandfather before he ever meets your grandmother.  What happens?  Because your grandfather never met your grandmother, you never existed, which means you never built the time machine, and never killed your grandfather.  If he was never killed, he met your grandmother, and you do exist, meaning you built the time machine, and went back to kill him, implying that you don't exist, and so on...

If you believe the 'alternate dimension' theory, if you go back in time, you wind up in an alternate dimension which is 100% identical to your dimension at the time you arrive, but is different from the point of your arrival onwards (your existance there changes it going forward).  Thus you can kill your grandfather in the alternate dimension, meaning you will never exist in the alternate dimension as you did in your native dimension - but you exist in some sense in the alternate dimension because you travelled there from your dimension.

That's a little bit simplified, but that's the general idea.  Paradox = bad

occams razor. Time travel is a horrible lie our parents tell us so we stay in bed.

[lobi]

Can anybody here create a single strand of Human DNA from a bunch of tachyons? No? Well how about the reverse then, DNA to Tachyon? No? Then why the F are you wasting valuable game time on this nonsense.
Time travel is a bus running on schedule. Alternate reality is schizophrenia and outer space is the back yard. Deal with it.

[pablodurando]

lobi wrote...
Time travel is a bus running on schedule. Alternate reality is schizophrenia and outer space is the back yard. Deal with it.

Time dilation shows that time travel forward is actually possible, backwards is still a mystery but several physicists claim to be on the trail to discovering it.  Quantum mechanics suggests that infinite alternate realities do exist since everything that can happen will happen.  Test have been made and the scientific fact that infinite universes exist is all but accepted by most quantum physicists.

In response to the OP, science is vulnerable to new innovation and change.  That's is what makes science so beautiful.  Half of the research collected by scientist in this modern day and age would have been deemed impossible just a century ago.  Science has shown that certain particles do travel at FTL speeds thus making Einstien's theory of relativity incomplete.  The consensus in the science community  now is that a new theory is needed, some even suggest a theory of everything.  What I'm getting at is even though it's considered impossible now do not discount it forever.

[AngryFrozenWater]

Boiny Bunny wrote...

Hellbound555 wrote...

kglaser wrote...

Celrath wrote...

And this is where the parallel world theory comes in. Which is every time some one goes back in time they are creating an alternate reality leaving the original time you came from untouched and also making it impossible to get back

This I support.

Plus, tachyons.

so instead of time travel, we go to a parallel world thats main difference is that its in the past?

It's to avoid the creation of a paradox.  Suppose you invent a time machine, go back in time 60ish years, and kill your grandfather before he ever meets your grandmother.  What happens?  Because your grandfather never met your grandmother, you never existed, which means you never built the time machine, and never killed your grandfather.  If he was never killed, he met your grandmother, and you do exist, meaning you built the time machine, and went back to kill him, implying that you don't exist, and so on...

If you believe the 'alternate dimension' theory, if you go back in time, you wind up in an alternate dimension which is 100% identical to your dimension at the time you arrive, but is different from the point of your arrival onwards (your existance there changes it going forward).  Thus you can kill your grandfather in the alternate dimension, meaning you will never exist in the alternate dimension as you did in your native dimension - but you exist in some sense in the alternate dimension because you travelled there from your dimension.

That's a little bit simplified, but that's the general idea.  Paradox = bad

It is maybe interesting to note that many of the popular paradoxes that are supposed to exist, may not apply even without a multiverse.

The Paradoxes of Time Travel by Ken Perszyk and Nicholas J.J. Smith.

Humans have long been fascinated by the idea of visiting the past and of seeing what thefuture will bring. Time travel has been one of the most popular themes of science fiction. Most people have seen the TV series ‘Dr Who’ or ‘Quantum Leap’ or ‘Star Trek’. You’ve probably seen one of the ‘Back to the Future’ or ‘Terminator’ movies, or ‘Twelve Monkeys’. Time travel narratives provide fascinating plots, which exercise our imaginations in ever so many ways. But is the idea of travelling forward and backward in time pure fantasy—or can it be done? To be sure, not all time travel scenarios are coherent. But we hope to persuade you that the most common objections to the very idea of time travel have no real force.

And...

Why Would Time Travelers Try to Kill Their Younger Selves? by Nicholas J.J. Smith.

In this note I raise a new problem for backwards time travel, and make some first suggestions as to how it might be solved. I call it the motivation problem. It is not a logical or a metaphysical problem, but a psychological one. It does not impact upon the possibility, or even the likelihood, of backwards time travel. Yet it is deeply puzzling, and we
will have no idea what time travel would actually be like until we explore it. Thus, where other problems for backward time travel assume that we know what time travel would be like, and argue that we cannot have it, this new problem gives us no reason to think that we cannot have time travel, but argues that we have much less idea than we usually suppose about what it would really be like to travel back in time.

I am not trying to derail the thread, so I won't go into it, but if you are interested in those topics then follow the above links.

Modifié par AngryFrozenWater, 26 juillet 2011 - 07:09 .

[Boiny Bunny]

Ta, Angry!  Always interesting reads!

[ipgd]

pablodurando wrote...

Test have been made and the scientific fact that infinite universes exist is all but accepted by most quantum physicists.

Not entirely so. The Many Worlds interpretation is popular, but not definitively conclusive. The Copenhagen interpretation has just as much if not more traction in the scientific community. Neighboring universes are a popular explanation for dark energy, but, again, not conclusive. And String theory is, well, very fascinating but ultimately untestable and essentially unsubstantiated BS at this point. The LHC may give some insight on upper dimensions or the theoretical existence of parallel universes, but as far as I know it hasn't produced anything noteworthy in that regard as yet.

What I'm getting at is even though it's considered impossible now do not discount it forever.

FTL travel is like nothing else before. Just because science has been wrong in the past does not mean that literally anything is possible. Even if it became technologically possible to reach the speed of light, it would, again, be totally impractical, because it is effectively time travel. You may be able to zip 500 light years from point A to B near instantaneously from your point of reference, but back home centuries will still have passed and more will pass by the time you return. And if you exceed the speed of light, congrats, you have broken cause and effect.

Modifié par ipgd, 26 juillet 2011 - 01:10 .

[Swordfishtrombone]

ipgd wrote...
FTL travel is like nothing else before. Just because science has been wrong in the past does not mean that literally anything is possible. Even if it became technologically possible to reach the speed of light, it would, again, be totally impractical, because it is effectively time travel. You may be able to zip 500 light years from point A to B near instantaneously from your point of reference, but back home centuries will still have passed and more will pass by the time you return. And if you exceed the speed of light, congrats, you have broken cause and effect.

QFT.

Also, what makes FTL travel impossible is not only time dillation, but the fact that your mass increases with speed. Thus, to accelarate further, you need relatively more energy than you had to expend to accelarate the same amount before. As you approach the speed of light, your mass approaches infinity, and also the energy you would need to employ to achieve that speed aproaches infinity.

Scientists saying that FTL travel is impossible isn't comparable to some scientists in the past saying, for example, that humans would never fly, or that we could never achieve the speed of sound; comparing the latter situations to the former is comparing apples and oranges.

The basis for saying that FLT travel is impossible is much, much better than the bases for any of those false statements before - there's nothing in physics that would absolutely prevent faster than sound travel, nor could the people who claimed that humans would never fly point to any directly observed physical law that would prevent such a thing.

The effects of relativity, like time dillation, HAVE been directly observed, and the theory's predictions have been consistently borne out by experiment. Thus we DO know that as you accelarate, and approach the speed of light, time inside your space ship slows down relative to the rest of the universe, and mass increases - since we know that you need more energy to accelerate heavier objects than you do light ones, we know that as the mass increases, to accelerate further you need increasingly greater amounts of energy.

The math clearly shows that reaching the speed of light would lead to absurdities, like infinite mass, zero length along the axis of the direction you are travelling, and stopped time.

All the energy contained in all the atoms and dark matter, and dark energy in the universe would not suffice to accelerate a space ship made to hold one miniature giant space hamster to the speed of light. It would not suffice to accelarate an ATOM to the speed of light.

Thus if there is a way to get from place to place faster than it would take to travel that distance at less than light speed, it has to come from some sort of a "wormhole" scenario.

And all those scenarios that I am aware of are highly hypothetical, AND even in the most optimistic of the scenarios that are at least losely based on realistic physics, would require such vast energies that if it's not impossible, it might as well be, for our purposes.

[AlanC9]

Swordfishtrombone wrote...
And all those scenarios that I am aware of are highly hypothetical, AND even in the most optimistic of the scenarios that are at least losely based on realistic physics, would require such vast energies that if it's not impossible, it might as well be, for our purposes.

Well, there's always vacuum energy.....

[TheMufflon]

AlanC9 wrote...

Well, there's always vacuum energy.....

That's all well and good when I'm cleaning my apartment, but how's it gonna help me with interstellar travel?

[Kaiser Arian XVII]

For a long time since 1950s every scientist has condemned 18th/19th century German philosophers for saying unempirical nonsense. I'm happy that the variety of sayings and theories among current scientists is not so much better than them.
- GB the Freelance Thinker

[pablodurando]

ipgd wrote...

pablodurando wrote...

Test have been made and the scientific fact that infinite universes exist is all but accepted by most quantum physicists.

Not entirely so. The Many Worlds interpretation is popular, but not definitively conclusive. The Copenhagen interpretation has just as much if not more traction in the scientific community. Neighboring universes are a popular explanation for dark energy, but, again, not conclusive. And String theory is, well, very fascinating but ultimately untestable and essentially unsubstantiated BS at this point. The LHC may give some insight on upper dimensions or the theoretical existence of parallel universes, but as far as I know it hasn't produced anything noteworthy in that regard as yet.

I don't agree with you here.  String theory has been tested extensively through conceptual expirements and had above average success.  To call it BS is just ignorant since many geniuses are involved in the activity and see it as the best explanation for the universe.  

igpd wrote...
FTL travel is like nothing else before. Just because science has been wrong in the past does not mean that literally anything is possible. Even if it became technologically possible to reach the speed of light, it would, again, be totally impractical, because it is effectively time travel. You may be able to zip 500 light years from point A to B near instantaneously from your point of reference, but back home centuries will still have passed and more will pass by the time you return. And if you exceed the speed of light, congrats, you have broken cause and effect.

 FTL travel is not that insane when you think of what science has found to date.  Structure of black holes, existence of quarks, extensive medicinial innovation, these are all deemed as impossible a couple of decades ago as FTL is today.

We honestly don't know enough on this field to predict if it's impractical or not.

[Homebound]

isnt time itself just a perception?

[pablodurando]

Hellbound555 wrote...

isnt time itself just a perception?

That in fact is up for debate.  Is time the 11th dimension, or does it exist completely independent of all other dimensions in the universe, that is quality question to consider.

[dubsaves]

I refer you to Arthur C. Clarke: "Any sufficiently advanced technology is indistinguishable from magic."

[Nizzemancer]

I'd love it if we got an alien visitor one day, they'd talk to our prime scientists and then they'd laugh their asses off, tell us "you guys are so dumb, you'll never get out of your solar system" then they'd fly back to their own galaxy in time for dinner.

[naughty99]

dubsaves wrote...

I refer you to Arthur C. Clarke: "Any sufficiently advanced technology is indistinguishable from magic."

bòn móts!

[Swordfishtrombone]

pablodurando wrote...

I don't agree with you here.  String theory has been tested extensively through conceptual expirements and had above average success.  To call it BS is just ignorant since many geniuses are involved in the activity and see it as the best explanation for the universe.  

I wouldn't call it BS either, but it IS, as it currently stands, practically untestable. Conceptual experiments aren't the sorts of tests science requires - a test would be a unique prediction (as it something not predicted by the standard model), of a phenomena or particle, or something that exists in the Universe, or can be brought to existence in experiment. If that experiment or observation were then to confirm the prediction, THAT is when string theory would earn it's stripes.

As it stands, string theory is internally consistent, sure, and intriguing, sure, consistent with observation, sure, but nobody has come up with any novel predictions it makes, that the already thoroughly tested standard model does not make.

String theory has advantages, and may indeed be true, and I suspect that some version of it is true, but it's central problem is that it is ultimately untested, and not testable with any experiment we can realistically produce. I hope someone comes up with a test of string theory that we CAN use, but until then, String theory is a hypothesis that's on the edges of what can be called science.

[Swordfishtrombone]

dubsaves wrote...

I refer you to Arthur C. Clarke: "Any sufficiently advanced technology is indistinguishable from magic."

I'll call your Clarke, and trump you an Asimov!

Asimov wrote an outstanding essay in response to the notion that because scientists were wrong in the past, they are likey to be as wrong today, and nothing in science should be believed. I know it isn't exactly the argument anyone here is promoting, but the early thread argumentation does get close enough, that I think this essay is something everyone should read:

Isaac Asimov - The Relativity of Wrong

We don't know everything of physics, but what we DO know, and have experimentally verified, tells us that FLT travel is impossible. I can't even imagine what a theory that would allow FLT travel, and still be consistent with everything we've observed, would look like. Does that mean that we KNOW with absolute certainty, that no future discovery can lead to a finding that FLT travel is possible after all? No - but it makes the likelyhood of such a finding akin to finding that the Earth was flat all along.

[dubsaves]

Modifié par dubsaves, 28 juillet 2011 - 02:18 .

[dubsaves]

Its sort of like if we misundestood fundamentally how space works, that under a given set of circumstances the distance between two points could be shortened, folding space time. Obviously the energy req for ftl is impossible, but what if mass is reduced to zero? A field where the laws of physics become weird ...then the energy required would be less. Energy beyond say fusion. I'd be interested to see the scifi answer for how space travel in ME works

[pablodurando]

I think the key to FTL travel is not in transferring mass, but by figuring out the dimensions of the universe. If humans could comprehend even the 7th dimension then scientific accomplishment will be accelerated by unimaginable speeds. I have enough faith in string theory that we will find the secrets of the universe.

[Homebound]

science changes. For now its considered impossible. So lets go with that until someone proves otherwise. You gotta be flexible with these things.