My thought with regard to entropy was as follows: In a closed system entropy increases with time, 2nd law I believe. This coupled with the fact that entropy is nearly synonymous with the information a system carries implies that sending information backwards in time be it through photons or paper would result in a decreased system entropy. The problems with this argument are the same ones that conservation laws have, that the universe might not be closed....
Edit: Thinking about this further... it boils down the conservation laws ultimately...
My thought with regard to entropy was as follows: In a closed system entropy increases with time, 2nd law I believe. This coupled with the fact that entropy is nearly synonymous with the information a system carries implies that sending information backwards in time be it through photons or paper would result in a decreased system entropy. The problems with this argument are the same ones that conservation laws have, that the universe might not be closed....
Edit: Thinking about this further... it boils down the conservation laws ultimately...
In general, the higher the entropy, the less "organized" is the system, therefore it has less information contained. So if you send information backward, you lower the entropy of the past system but do pretty much nothing to the present one (no new information is received). But in my knowledge entropy does not include every single type of information. It relates to the thermodynamics state of the particles. I don't see a direct link how some human knowing the result of next week lottery through time travel really affects the thermodynamics state of any particles (except maybe a few of there braincells, but we don't even know how information is stored there. Never is entropy changed.
yeah... to update you... look up entropy and information on google. there are several good sites that discuss the current view point as entropy as information...
yeah... to update you... look up entropy and information on google. there are several good sites that discuss the current view point as entropy as information...
now that I think of it...
Google might be an interesting example of entropy as information in and of itself \
I don't see a direct link how some human knowing the result of next week lottery through time travel really affects the thermodynamics state of any particles (except maybe a few of there braincells, but we don't even know how information is stored there. Never is entropy changed.
It should be noted that the only "time travel" going on here in the form of FTL that we've been discussing is a deliberately very weak and abstract kind of time travel -- it's FTL with causality loops ruled out, which rules out knowing winning lottery numbers ahead of time.
Under normal rules of relativity, every point in spacetime is connected to a "past light cone" -- the set of spacetime points in the "absolute past" of a given point. The past light code includes every point in spacetime from which a light-speed or slower signal or other effect could possibly have been sent and have caught up with a given spacetime point.
There's also a "future light cone" which contains all spacetime points that can possibly be affected by a light-speed or slower effect originating at the given spacetime point. The rules of relativity keep the past and future light cones for any spacetime point completely distinct, without overlap. This being true for all points in spacetime preserves causality.
Then there's the "absolute elsewhere", spacetime points which are essentially completely cut off from a given point, neither affecting nor effected by anything which happens at that point. Spacetime points out in the "absolute elsewhere" can be said to be in the past or future of a given spacetime point, but two important facts apply:
(1) Unlike the absolute past and future of a given spacetime point, which is the same for all observers*, the relative past/future quality of points out in the absolute elsewhere is frame dependent, depending on the velocity of a particular observer.
(2) The past/future quality of a point out in the absolute elsewhere in many ways a very abstract concept, since under strict relativity no causal connection with those points is allowed. To highlight how abstract assigning "past" and "future" to points in the absolute elsewhere can be, simply imagine walking slowly back and forth in a small room, and also imagine a star exploding in a very distant galaxy.
The technical definition of "now" is tied to an observer's velocity. That "now" can be viewed as a set of spacetime points that, in a sense, "pivot" around an observer, sweeping out different three-dimensional slices of four-dimensional spacetime depending on the observer's velocity.
Major changes in velocity pivot that "now slice" quite a bit, but even small changes in velocity can be magnified greatly at great distances from an observer.
Back to that exploding star and the small room: Walk one way in the room, at the star won't explode for another few days. Turn around and walk the other way, and the star already exploded days ago. Yes, simply by walking around a room, you can change the chronology of a major event from past to future.
My point is not that we're all Lords of Space and Time, it's to point out how truly abstract, and nearly meaningless, it can be to worry about the past/future quality of points out in the absolute elsewhere.
What the FTL concepts we're playing with here do is allow you to bring more of the "absolute elsewhere" into causal contact with a given spacetime point. Each spacetime point can then have a "past FTL cone" and a "future FTL cone", which are inclusive of, but larger than, the past and future light cones. These new FTL cones, however, can be defined in such a way as to also insure that they are distinct and do not overlap, therefore also preserving causality. (Again, sorry, no lottery help here.)
I'd go on, but not only have I gone on pretty long already... I also need to clean snow off my car.
Suffice to say for now that although these rules might "work" in a certain sense, there's certainly no evidence that any such FTL phenomena are real. These FTL ideas mess with relativity in ways that should not be lightly dismissed. What we're really discussing is how badly we would break known rules of physics by trying to fit certain FTL schemes like this into picture.
*I'm only talking here about the simple classification of a point as being in the past, or in the future. How far in the past or future a point in a past or future light cone might be said to be is also observer-dependent.
Read "The End of Time" by Julian Barbour. Although I personally don't like most of the conclusions and theories he comes up with, it was nonetheless refreshing and comforting that I'm not alone in thinking it might not exist at all.
Ignore for now that I use grammatical tenses! Even he doesn't mean time isn't useful or even unavoidable (in a "We are tempted to create it from nothing" kind of way). But it is a crutch and limited way of seeing things.
I can't summarize it and do it justice but flip through the book next time you're in a store. It's intriguing and not at all as cockamamie as it sounds at first.
Effects that seem like what time should be exist but perhaps not time itself.
To say time does not exist is like saying up and down don't exist. Sure, maybe, in some detached theoretical way, up and down don't exist, but as far as I, the observer, am concerned, up and down do exist. Even if the fundamental nature of reality is such that up and down, or time, does not actually exist (in so much as we can conceptualize "existence"), my observance of such is a reflection of some property of reality, which I call time.
At the speed of light, there is no distance, and no time, as I am sure you all know.
So, FTL, means that you would travel less than no distance, in less then no time. Thus is has zero actual meaning. Its really simple to understand isn't it.
Consider it in simple real terms.
scenario 1)You are aboard a spaceship. You are stationary, your destination planet is 10 light years away. Program into your computer that you wish to travel there at half the speed of light. Press go, and you're off, 20 earth years later you reach your target. Q. How much time has passed in your spaceship? Careful now.
scenario 2)You are aboard a spaceship. You are stationary, your destination planet is 10 light years away. Program into your computer that you wish to travel there at 99% speed of light. Press go, and you're off, 10.1 earth years later you reach your target. Q. How much time has passed in your spaceship? Very careful now.
scenario 3)You are aboard a spaceship. You are stationary, your destination planet is 10 light years away. Program into your computer that you wish to travel there at 100% speed of light. Press go, and you're off, it takes you 10 days to accelerate to the speed of light. The moment you hit 100% of light, what happens. The distance between you and your target is now 0. Thats not terrible good when approaching a 60billion kg mass at 186000 miles per second. Ok you knew that,look at it another way- lets suppose that you program your craft to accelerate to the speed of light, and then start to decellerate instantly. what happens, it takes you 10 days to accelerate to c. At the moment you hit c, there is no time, so not even a single clock tick of your 1000 GHZ G10 processor can pass to put the ship in decellerate before you hit the planet. The point here is that instantly, becomes infinitely forever.
Not only is there no definition of FTL, but there is no point. It isn't necessary.
Time and mass,distances and directions(axis) is just a consequence of travelling slower than c. Consider the universe from the point of view of a photon. How far is it from edge to edge, absolutely 0, how long does it take the photon to travel the expanse of the universe, absolutely gets there instantly.
From the photons POV. When did the universe start? It never did.
When did the universe end. It has already.
Here's my nobel prize winning theory---(C)MarcUK 2004
consider, that at the universe ages, it is currently expected that it will expand forever, the big freeze, as opposed to the big crunch. When all the matter has decayed back into pure radiation - How big will the universe be?
As there is only pure radiation, the only valid point of reference will be at the photon level. This means that all distances are 0. All time is 0. This means that every single energy in the universe will decay into the same position at the same time, regardless of how big that might seem to us earthlings at the moment. Eureka - big bang no2. it doesn't matter if the universe is open or closed, it will regenerate.
If common sense had anything to do with physics, there wouldn't be quantum mechanics.
Quote:
FTL by definition, has no definition. Heres Why.
At the speed of light, there is no distance, and no time, as I am sure you all know.
So, FTL, means that you would travel less than no distance, in less then no time. Thus is has zero actual meaning. Its really simple to understand isn't it.
You're making the mistake of thinking that you have to consider FTL from the imaginary viewpoint of an observer traveling at an FTL speed in order to define FTL. You don't.
First of all, plenty of things can go faster than light. Stand up, turn around, then sit down and take a rest, because you've just made the Sun whip around your body at well in excess of the speed of light*. It's perfectly valid to view yourself as not rotating, but rather everything else spinning around you, even if that results in assigning FTL radial velocities to other objects.
Point a laser pointer at the Moon. Swipe the beam across the Moon's face. You can easily make a point of light travel across the face of the Moon faster than the speed of light (although you'd need a really, really good laser to have much hope of creating a truly visible point of light).
If a rocket were traveling away from you at 0.9c (90% of the speed of light) on your left, and another rocket were traveling away from you at 0.9c on your right, it's quite alright to say that, in your frame of reference, the relative speed of the two rockets is 1.8c -- this is a perfectly valid, and quite meaningful, velocity in excess of the speed of light.
If something (and this something doesn't have to be a physical object) starts at point x = A at time t_A, and is later at point x = B at time t_B, and |(B - A) / (t_B - t_A)| > c, that's all the meaning "FTL" has to have.
The real question is not whether FTL phenomena exist, or if FTL has any meaning (it has a simple, clear meaning), it's only whether hypothetical information bearing or causal FTL phenomena can be reconciled with our understanding of physics.
It's definitely possible, and meaningful, to consider these issues without worrying about the POV of some imaginary observer traveling along with a hypothetical FTL effect.
Quote:
NO applause necessary.
How about a golf clap for effort?
*Okay, if the Sun happens to be almost directly over your head, or below your feet, at this particular moment, you'll have to try again later to work this amazing bit of FTL magic.
I get your point, but you're only proving a different context of FTL than I was trying to prove. Could you prove something can move FTL in the direction of its magnitute? (does that even make sense?)
A golf clap is the best response to a theory I've formulated so far. Thanks. Id have a smilie here, but I cant be bothered to enable javascript!
there is something intrinsically wrong with MarcUK's theory but its ok. You need anti-matter to make every single bit of matter into photons. Not only that but photons do have discreet positions determinable as far as the heisenburg uncertainty principle takes it...
there is something intrinsically wrong with MarcUK's theory but its ok. You need anti-matter to make every single bit of matter into photons. Not only that but photons do have discreet positions determinable as far as the heisenburg uncertainty principle takes it...
yeah, but ask the photon where it is at any given time, impossible!
Not only that but photons do have discreet positions determinable as far as the heisenburg uncertainty principle takes it...
Not only that, but the 'audiopollution uncertainty principle' is seriously affecting my ability to comprehend any of this.
I should have taken fewer business courses, and more sciences.
I'm still waiting to see the answers to the 'how much time has passed' questions. I know that perception of time/actual time is affected by theoretical light speed trvael. Just not how much.
This is all very interesting, and a bit overwhelming.
Comments
Originally posted by GardenOfEarthlyDelights
So explain to me again how the spherical cow is able to travel faster than light...
Are spherical cows composed of moo mesons?
Edit: Thinking about this further... it boils down the conservation laws ultimately...
Originally posted by billybobsky
My thought with regard to entropy was as follows: In a closed system entropy increases with time, 2nd law I believe. This coupled with the fact that entropy is nearly synonymous with the information a system carries implies that sending information backwards in time be it through photons or paper would result in a decreased system entropy. The problems with this argument are the same ones that conservation laws have, that the universe might not be closed....
Edit: Thinking about this further... it boils down the conservation laws ultimately...
In general, the higher the entropy, the less "organized" is the system, therefore it has less information contained. So if you send information backward, you lower the entropy of the past system but do pretty much nothing to the present one (no new information is received). But in my knowledge entropy does not include every single type of information. It relates to the thermodynamics state of the particles. I don't see a direct link how some human knowing the result of next week lottery through time travel really affects the thermodynamics state of any particles (except maybe a few of there braincells, but we don't even know how information is stored there. Never is entropy changed.
I might be totally wrong though...
Originally posted by billybobsky
yeah... to update you... look up entropy and information on google. there are several good sites that discuss the current view point as entropy as information...
now that I think of it...
Google might be an interesting example of entropy as information in and of itself
Originally posted by Matlock
I don't see a direct link how some human knowing the result of next week lottery through time travel really affects the thermodynamics state of any particles (except maybe a few of there braincells, but we don't even know how information is stored there. Never is entropy changed.
It should be noted that the only "time travel" going on here in the form of FTL that we've been discussing is a deliberately very weak and abstract kind of time travel -- it's FTL with causality loops ruled out, which rules out knowing winning lottery numbers ahead of time.
Under normal rules of relativity, every point in spacetime is connected to a "past light cone" -- the set of spacetime points in the "absolute past" of a given point. The past light code includes every point in spacetime from which a light-speed or slower signal or other effect could possibly have been sent and have caught up with a given spacetime point.
There's also a "future light cone" which contains all spacetime points that can possibly be affected by a light-speed or slower effect originating at the given spacetime point. The rules of relativity keep the past and future light cones for any spacetime point completely distinct, without overlap. This being true for all points in spacetime preserves causality.
Then there's the "absolute elsewhere", spacetime points which are essentially completely cut off from a given point, neither affecting nor effected by anything which happens at that point. Spacetime points out in the "absolute elsewhere" can be said to be in the past or future of a given spacetime point, but two important facts apply:
(1) Unlike the absolute past and future of a given spacetime point, which is the same for all observers*, the relative past/future quality of points out in the absolute elsewhere is frame dependent, depending on the velocity of a particular observer.
(2) The past/future quality of a point out in the absolute elsewhere in many ways a very abstract concept, since under strict relativity no causal connection with those points is allowed. To highlight how abstract assigning "past" and "future" to points in the absolute elsewhere can be, simply imagine walking slowly back and forth in a small room, and also imagine a star exploding in a very distant galaxy.
The technical definition of "now" is tied to an observer's velocity. That "now" can be viewed as a set of spacetime points that, in a sense, "pivot" around an observer, sweeping out different three-dimensional slices of four-dimensional spacetime depending on the observer's velocity.
Major changes in velocity pivot that "now slice" quite a bit, but even small changes in velocity can be magnified greatly at great distances from an observer.
Back to that exploding star and the small room: Walk one way in the room, at the star won't explode for another few days. Turn around and walk the other way, and the star already exploded days ago. Yes, simply by walking around a room, you can change the chronology of a major event from past to future.
My point is not that we're all Lords of Space and Time, it's to point out how truly abstract, and nearly meaningless, it can be to worry about the past/future quality of points out in the absolute elsewhere.
What the FTL concepts we're playing with here do is allow you to bring more of the "absolute elsewhere" into causal contact with a given spacetime point. Each spacetime point can then have a "past FTL cone" and a "future FTL cone", which are inclusive of, but larger than, the past and future light cones. These new FTL cones, however, can be defined in such a way as to also insure that they are distinct and do not overlap, therefore also preserving causality. (Again, sorry, no lottery help here.)
I'd go on, but not only have I gone on pretty long already... I also need to clean snow off my car.
Suffice to say for now that although these rules might "work" in a certain sense, there's certainly no evidence that any such FTL phenomena are real. These FTL ideas mess with relativity in ways that should not be lightly dismissed. What we're really discussing is how badly we would break known rules of physics by trying to fit certain FTL schemes like this into picture.
*I'm only talking here about the simple classification of a point as being in the past, or in the future. How far in the past or future a point in a past or future light cone might be said to be is also observer-dependent.
Surely time doesn't actually exist?
Originally posted by johnq
Surely time doesn't actually exist?
Only if events change...if everything were to suddenly become stagnant (read electrons would stop in their orbits) then there would be no time
Originally posted by Ganondorf
Of course time exists.
Don't be so sure.
Read "The End of Time" by Julian Barbour. Although I personally don't like most of the conclusions and theories he comes up with, it was nonetheless refreshing and comforting that I'm not alone in thinking it might not exist at all.
Ignore for now that I use grammatical tenses!
I can't summarize it and do it justice but flip through the book next time you're in a store. It's intriguing and not at all as cockamamie as it sounds at first.
Effects that seem like what time should be exist but perhaps not time itself.
But, hey, I'm a pragmatist.
FTL by definition, has no definition. Heres Why.
At the speed of light, there is no distance, and no time, as I am sure you all know.
So, FTL, means that you would travel less than no distance, in less then no time. Thus is has zero actual meaning. Its really simple to understand isn't it.
Consider it in simple real terms.
scenario 1)You are aboard a spaceship. You are stationary, your destination planet is 10 light years away. Program into your computer that you wish to travel there at half the speed of light. Press go, and you're off, 20 earth years later you reach your target. Q. How much time has passed in your spaceship? Careful now.
scenario 2)You are aboard a spaceship. You are stationary, your destination planet is 10 light years away. Program into your computer that you wish to travel there at 99% speed of light. Press go, and you're off, 10.1 earth years later you reach your target. Q. How much time has passed in your spaceship? Very careful now.
scenario 3)You are aboard a spaceship. You are stationary, your destination planet is 10 light years away. Program into your computer that you wish to travel there at 100% speed of light. Press go, and you're off, it takes you 10 days to accelerate to the speed of light. The moment you hit 100% of light, what happens. The distance between you and your target is now 0. Thats not terrible good when approaching a 60billion kg mass at 186000 miles per second. Ok you knew that,look at it another way- lets suppose that you program your craft to accelerate to the speed of light, and then start to decellerate instantly. what happens, it takes you 10 days to accelerate to c. At the moment you hit c, there is no time, so not even a single clock tick of your 1000 GHZ G10 processor can pass to put the ship in decellerate before you hit the planet. The point here is that instantly, becomes infinitely forever.
Not only is there no definition of FTL, but there is no point. It isn't necessary.
Time and mass,distances and directions(axis) is just a consequence of travelling slower than c. Consider the universe from the point of view of a photon. How far is it from edge to edge, absolutely 0, how long does it take the photon to travel the expanse of the universe, absolutely gets there instantly.
From the photons POV. When did the universe start? It never did.
When did the universe end. It has already.
Here's my nobel prize winning theory---(C)MarcUK 2004
consider, that at the universe ages, it is currently expected that it will expand forever, the big freeze, as opposed to the big crunch. When all the matter has decayed back into pure radiation - How big will the universe be?
As there is only pure radiation, the only valid point of reference will be at the photon level. This means that all distances are 0. All time is 0. This means that every single energy in the universe will decay into the same position at the same time, regardless of how big that might seem to us earthlings at the moment. Eureka - big bang no2. it doesn't matter if the universe is open or closed, it will regenerate.
NO applause necessary.
Originally posted by MarcUK
Right, I am the authority of common sense.
If common sense had anything to do with physics, there wouldn't be quantum mechanics.
FTL by definition, has no definition. Heres Why.
At the speed of light, there is no distance, and no time, as I am sure you all know.
So, FTL, means that you would travel less than no distance, in less then no time. Thus is has zero actual meaning. Its really simple to understand isn't it.
You're making the mistake of thinking that you have to consider FTL from the imaginary viewpoint of an observer traveling at an FTL speed in order to define FTL. You don't.
First of all, plenty of things can go faster than light. Stand up, turn around, then sit down and take a rest, because you've just made the Sun whip around your body at well in excess of the speed of light*. It's perfectly valid to view yourself as not rotating, but rather everything else spinning around you, even if that results in assigning FTL radial velocities to other objects.
Point a laser pointer at the Moon. Swipe the beam across the Moon's face. You can easily make a point of light travel across the face of the Moon faster than the speed of light (although you'd need a really, really good laser to have much hope of creating a truly visible point of light).
If a rocket were traveling away from you at 0.9c (90% of the speed of light) on your left, and another rocket were traveling away from you at 0.9c on your right, it's quite alright to say that, in your frame of reference, the relative speed of the two rockets is 1.8c -- this is a perfectly valid, and quite meaningful, velocity in excess of the speed of light.
If something (and this something doesn't have to be a physical object) starts at point x = A at time t_A, and is later at point x = B at time t_B, and |(B - A) / (t_B - t_A)| > c, that's all the meaning "FTL" has to have.
The real question is not whether FTL phenomena exist, or if FTL has any meaning (it has a simple, clear meaning), it's only whether hypothetical information bearing or causal FTL phenomena can be reconciled with our understanding of physics.
It's definitely possible, and meaningful, to consider these issues without worrying about the POV of some imaginary observer traveling along with a hypothetical FTL effect.
NO applause necessary.
How about a golf clap for effort?
*Okay, if the Sun happens to be almost directly over your head, or below your feet, at this particular moment, you'll have to try again later to work this amazing bit of FTL magic.
A golf clap is the best response to a theory I've formulated so far. Thanks. Id have a smilie here, but I cant be bothered to enable javascript!
Originally posted by billybobsky
there is something intrinsically wrong with MarcUK's theory but its ok. You need anti-matter to make every single bit of matter into photons. Not only that but photons do have discreet positions determinable as far as the heisenburg uncertainty principle takes it...
yeah, but ask the photon where it is at any given time, impossible!
Originally posted by billybobsky
Not only that but photons do have discreet positions determinable as far as the heisenburg uncertainty principle takes it...
Not only that, but the 'audiopollution uncertainty principle' is seriously affecting my ability to comprehend any of this.
I should have taken fewer business courses, and more sciences.
I'm still waiting to see the answers to the 'how much time has passed' questions. I know that perception of time/actual time is affected by theoretical light speed trvael. Just not how much.
This is all very interesting, and a bit overwhelming.