Presidential Lunacy : Clark's 'Faith' Based On Time-Travel [Archive]

shetline

02-15-2004, 10:09 AM

Originally posted by SpcMs
I'm sure you're correct, but this Science articel from 1996 says differently:

The curved space and time of Einstein's theory of general relativity permits both time travel and travel at speeds faster than that of light. In his Perspective, Parsons describes recent theoretical studies that show how, in principle, a spacecraft in a bubble of warped space-time could travel faster than light. One consequence of this result is that such a spacecraft could also travel back in time.

http://www.sciencemag.org/cgi/content/summary/274/5285/202?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&titleabstract=time+travel&searchid=1076804567584_4568&stored_search=&FIRSTINDEX=0&fdate=10/1/1995&tdate=2/29/2004
The very fact that traveling faster than light means traveling backward in time (at least in some frames of reference) tends to make scientists believe that traveling faster than light is impossible, simply because it's hard to imagine a coherent universe where "shoot your own grandpa" paradoxes are possible.

On the other hand, there already are known faster-than-light interactions in quantum mechanics. You can act on one particle which is "entangled" with another particle, and instantaneously* affect the other particle, even over great distances.

The irony of this faster-than-light interaction is that it can't be used to transmit information -- you can only confirm the instantaneous connection of such particles by light-speed or slower means. It works sort of like this...

Imagine two scientists, one light hour (the distance traveled by light in one hour) apart, flipping "entangled" coins. They flip the coins and record the results, getting a random stream of heads and tails, HHTTHHHTHTTH..., etc. Let's say at first the entangled coins always land the same way. They can't send a message this way... there's nothing that can be done to force one coin to land a particular way, or even bias the coin towards landing one way. The only thing you can do is adjust the correlation of the entanglement, from full correlation (H/H, T/T) through no correlation (H/?, T/?), to full anti-correlation (H/T, T/H).

Since the stream of measurements is random data at either end, however, a change in correlation between the two coins can only be determined by comparing records of coin flips after-the-fact, using some light-speed or slower communication system.

Suppose the scientists decide to flip their coins at the top of every minute for one hour (they've synchronized their clocks, and, although far apart, are at rest relative to each other). During this hour, Scientist A is going to modify his coin somehow to change it from full correlation to full anti-correlation. Their results end up like this:

Scientist A: THHTHHTHHHHHTTTH...
Scientist B: THHTHHTTTTTTHHHT...

Scientist A decided to modify his coin just after the seventh flip. At the end of the experiment, each scientist radios his partner with his results -- messages which take an hour to arrive. They both can see that the modification of A's coin had a instantaneous effect across the light hour of distance between them -- but nothing in the data stands out that would have allowed either scientist to see the instantaneous effect until later, after an old-fashioned light-speed delay.

*I've read this use of the words "instantaneous" and "instantaneously" more than once, but something troubles me. Relativity tells us that time is relative to one's frame of reference, so the idea of two things happening "at the same time" is also relative. I have not yet heard it explained, when a quantum interaction is said to be "instantaneous", in which frame of reference the interaction is instantaneous.

drewprops

02-15-2004, 10:44 AM

Cool post Shetline...

jimmac

02-15-2004, 12:09 PM

Originally posted by drewprops
Here's the Link to the story (http://www.timetravelinstitute.com/article_tti.php?3442) at the 'Time Travel Institute'. I shall defer the honor of calling Mr. Clark an ASSHAT to others. Any takers?

Just a bit of the story:

Clark claims he has argued with physicists about the probability of time travel, but that despite opposition, he just has to "believe it," adding, "It's my only faith-based initiative," Wired reports.

Gary Melnick, a senior astrophysicist at the Harvard-Smithsonian Center for Astrophysics, told the newssite Clark's faith in the possibility of faster-than-light, or FTL, travel was "probably based more on his imagination than on physics."

Evidence suggests FTL travel is impossible, Melnick said.

"Even if Clark becomes president, I doubt it would be within his powers to repeal the powers of physics," Melnick told Wired.

darnit, misspelled 'Presidential'....could somebody fix that? Thanks!

Actually I was just reading the other day that scientists are now begining to entertain the possibility of FTL and even time travel in light of some of our more recent discoveries. Like new theories about wormholes or slowing light down ( which has always considered to be impossible but they've actually done it ) or watching particles reverse cause and effect ( coming back together, uncolliding, and going from point B to point A ). Also like in Shetline's time dilation example this theory has been measured already by fast moving aircraft and spacecraft. Since they weren't traveling at anywhere near the speed of light the effects weren't as apparent. but they did have sychronized clocks which did show a difference.

As for a time related paradox the most recent theories suggest that many different timelines exist. So if you go back and kill your grandfather when you go forward you find you never were born and yet there you are from another time line ( ala back to the future ). So no spacetime shattering paradox. Both timelines exist plus an infinite variety of other choices. We probably will not ever reach the speed of light but there may be a way around it.

As far our ability to actually do it I'm afraid the energy required and the gaps in our knowlege in this area put it's reality a long way off. Of course history has sometimes made accidental discoveries which speed things up. But if we are talking about a ship that could travel at these speeds a lot of other things need to be developed like material that could withstand the stress of this kind of travel etc. So it's probably a ways off. I'm sure there will always be a conservative scientist who will say this means nothing but progress is never made by the conservative elements is it?

By the way don't worry about spelling. There are a lot of poor typists and spellers here. Mine's always been bad and have to keep Word open to suppliment. A weakness of mine.

Existence

02-15-2004, 12:38 PM

Originally posted by shetline
The very fact that traveling faster than light means traveling backward in time (at least in some frames of reference) tends to make scientists believe that traveling faster than light is impossible, simply because it's hard to imagine a coherent universe where "shoot your own grandpa" paradoxes are possible.

On the other hand, there already are known faster-than-light interactions in quantum mechanics. You can act on one particle which is "entangled" with another particle, and instantaneously* affect the other particle, even over great distances.

The irony of this faster-than-light interaction is that it can't be used to transmit information -- you can only confirm the instantaneous connection of such particles by light-speed or slower means. It works sort of like this...

Imagine two scientists, one light hour (the distance traveled by light in one hour) apart, flipping "entangled" coins. They flip the coins and record the results, getting a random stream of heads and tails, HHTTHHHTHTTH..., etc. Let's say at first the entangled coins always land the same way. They can't send a message this way... there's nothing that can be done to force one coin to land a particular way, or even bias the coin towards landing one way. The only thing you can do is adjust the correlation of the entanglement, from full correlation (H/H, T/T) through no correlation (H/?, T/?), to full anti-correlation (H/T, T/H).

Since the stream of measurements is random data at either end, however, a change in correlation between the two coins can only be determined by comparing records of coin flips after-the-fact, using some light-speed or slower communication system.

Suppose the scientists decide to flip their coins at the top of every minute for one hour (they've synchronized their clocks, and, although far apart, are at rest relative to each other). During this hour, Scientist A is going to modify his coin somehow to change it from full correlation to full anti-correlation. Their results end up like this:

Scientist A: THHTHHTHHHHHTTTH...
Scientist B: THHTHHTTTTTTHHHT...

Scientist A decided to modify his coin just after the seventh flip. At the end of the experiment, each scientist radios his partner with his results -- messages which take an hour to arrive. They both can see that the modification of A's coin had a instantaneous effect across the light hour of distance between them -- but nothing in the data stands out that would have allowed either scientist to see the instantaneous effect until later, after an old-fashioned light-speed delay.

*I've read this use of the words "instantaneous" and "instantaneously" more than once, but something troubles me. Relativity tells us that time is relative to one's frame of reference, so the idea of two things happening "at the same time" is also relative. I have not yet heard it explained, when a quantum interaction is said to be "instantaneous", in which frame of reference the interaction is instantaneous.

Well, if they are at rest relative to each other, they occupy they same local inertial frame and simultaneity exists. Ie. one could imagine a third person in middle of the two scientists at rest relative to them. He would recieve both scientist's signals' of the interactions simultaneously.

BTW, I believe fater than light travel is possible (not for humans). We know Einstien is wrong because of quantum mechanics, ie. we have lack a grand unified theory. An example is the GZK paradox where is it thought that Einstien-lorentz invariance breaks.

jimmac

02-15-2004, 12:46 PM

Actually Einstein was right in a sense. He just didn't have all the pieces to the puzzle. Also since quantum mechanics flies in the face of our notions of common sense he didn't grasp it very well. It's always what you don't know......yet.

Argento

02-15-2004, 01:06 PM

Time travel is possible. People have already done it. Granted they've only travled backwards in time by about .005 of a second but people who are orbiting the earth in space have technically gone back in time. I'd have to try to find the article somewhere but it was in an old Time magazine

Anders

02-15-2004, 01:48 PM

Originally posted by Argento
Time travel is possible. People have already done it. Granted they've only travled backwards in time by about .005 of a second but people who are orbiting the earth in space have technically gone back in time. I'd have to try to find the article somewhere but it was in an old Time magazine

No. They just don´t go as fast forward as the rest of us. Or we go a bit faster than they do, depending of the POV.

shetline

02-15-2004, 01:57 PM

Originally posted by Existence
BTW, I believe fater than light travel is possible. We know Einstien is wrong because of quamtum mechanics, ie. we have no idea what happens at high energies or small scales. An example is the GZK paradox where is it thought that Einstien-Lorentz invariance breaks.
Wrong is a very harsh word that you should use carefully when it comes to something as well-tested as Einstein's relativity.

In a sense, Einstein proved that Newton was "wrong", but that doesn't change the fact that Newton was "right enough" that we can use Newtonian mechanics quite successfully for the vast majority of engineering tasks. Newton being "wrong" didn't mean that all of a sudden apples started falling upward into trees instead of falling down out of them.

Einstein is "right enough" that his relativity isn't going to be totally overturned no matter what happens at high energies and small scales. Einstein is "right enough" that, regardless of what breakdowns in his theory might happen in extreme circumstances, very real and troubling issues of temporal paradoxes, e.g. "shoot your own grandpa", would remain if faster-than-light (FTL) communication or travel were possible.

I can conceive of a way for FTL phenomena to occur without temporal paradoxes, but this is my own private crackpot thinking, so it should be taken with a very large grain of salt. This is something that I came up with several years ago while designing some software for teaching Einstein's Special Relativity...

What's needed is something that goes against the spirit of relativity, but that nevertheless could be possible if its effects are confined to a realm beyond things we've tried to test, or have been able to test experimentally -- admittedly shaky ground. That thing is a preferred frame of reference, like the old idea of the "aether".

I'm of the opinion that anything that would lead to temporal paradoxes is likely to be physically impossible. But merely going backwards in time does not, in and of itself, lead to such paradoxes. What causes such paradoxes are "causality loops", where an effect can loop back on itself to affect its own cause.

If FTL phenomena are mediated by a universal fixed frame of reference, and within that frame of reference nothing ever goes backwards in time, then no causality loops will occur. What goes against the grain of relativity is this: There would be a privileged frame of reference, and it would be possible to talk about "absolute speed" and "absolute time". If for no other reason, most physicists' appreciation for the beauty of relativity would cause them consider a fixed frame of reference to be too ugly to be true.

Ugly as the FTL fixed-frame concept might be for physicists, the practical benefits would be great if such a thing really existed. Suppose that nearly instantaneous one-way communication across this new kind of "aether" were possible. Two-way communication would also be nearly instantaneous, without paradox, but the results would work out with these odd relativistic consequences:

If you are at rest with respect to the aether, then you will measure all FTL messages you send as arriving essentially at the same time they were sent. If you start moving with respect to the aether, then messages you send backward with respect to your motion will seem to arrive more slowly, later than the sending time. Here's where it gets wierd -- messages sent in the forward direction will actually go backward in time, arriving before you sent them.

No paradox results, however, because the distance backward in time would always less than the light-speed distance between you and the recipient. A normal light-speed-limited message wouldn't be able to get back to you before you sent the original message, nor would an FTL message, since on the return trip, the message would be "swimming upstream" against the aether.

Here's something I'd really like to see done -- a sort of modern-day Michelson-Morley experiment (http://galileoandeinstein.physics.virginia.edu/lectures/michelson.html): My earlier example of "entangled" coins was a fanciful analogy for paired photons, a real phenomenon. I'd love to see an actual paired-photon experiment that attempts to measure the frame of reference for instantaneous quantum interactions. I have a secret hope that such an experiment might uncover a preferred frame of reference. If such a frame of reference were found, my guess is our speed relative to the preferred frame of reference would turn out to be the same as our apparent speed relative to the cosmic background radiation (which, if I recall correctly, is about 300 km/sec).

billybobsky

02-15-2004, 02:36 PM

Originally posted by jimmac
Actually Einstein was right in a sense. He just didn't have all the pieces to the puzzle. Also since quantum mechanics flies in the face of our notions of common sense he didn't grasp it very well. It's always what you don't know......yet.

quantum mechanics is common sense.

billybobsky

02-15-2004, 02:40 PM

Originally posted by shetline
Here's something I'd really like to see done -- a sort of modern-day Michelson-Morley experiment (http://galileoandeinstein.physics.virginia.edu/lectures/michelson.html): My earlier example of "entangled" coins was a fanciful analogy for paired photons, a real phenomenon. I'd love to see an actual paired-photon experiment that attempts to measure the frame of reference for instantaneous quantum interactions. I have a secret hope that such an experiment might uncover a preferred frame of reference. If such a frame of reference were found, my guess is our speed relative to the preferred frame of reference would turn out to be the same as our apparent speed relative to the cosmic background radiation (which, if I recall correctly, is about 300 km/sec).

Dude there is no ether. No preferred frame of reference. Einstein tried that I believe and it turns out regardless of whether he did or not (quantum is intuitive :)), that all of his frame of reference comparisons break down when one "real" frame is thrown in.

jimmac

02-15-2004, 03:04 PM

Originally posted by billybobsky
quantum mechanics is common sense.

Well yes today it is. But the notion that you can never really know the exact position or value of a particle at any given time is the type of thing that perplexed him. In his view everything should be provable and exact. Which would be more in line with our notions of common sense. Which like many things just isn't the way things really are.

shetline

02-15-2004, 04:13 PM

Originally posted by billybobsky
Dude there is no ether. No preferred frame of reference. Einstein tried that I believe and it turns out regardless of whether he did or not (quantum is intuitive :)), that all of his frame of reference comparisons break down when one "real" frame is thrown in.
Actually, all Einstein proved was that a preferred frame of reference wasn't necessary to explain anything about known phenomena, not that it didn't or couldn't exist. He applied Occam's Razor... if the aether doesn't help explain anything, then it's a needless multiplication of entities to suppose that it exists.

I'm not saying that I think there's an aether myself. What I am saying is that if FTL communication and travel are possible, then the idea might again have merit, because the aether concept, or something like it, allows for FTL without temporal paradoxes.

I'm also troubled, as I mentioned before, by the use of the word "instantaneous" in quantum mechanics. From what I understand of the current state of things between relativity and QM (please correct me if I'm wrong -- I could easily be way off base with what's current), one difficulty in reconciliation between the two theories is that computations in QM are usually done using a simple Newtonian concept of time. There is something very interesting that needs to be resolved there, whether a preferred frame of reference helps that resolution or not.

billybobsky

02-15-2004, 04:18 PM

Actually people apply relativity and quantum freely. For instance mercury is a liquid because of relativistic contraction of its outer shell electrons. The two theories are reconcilable. The problem with setting an intertial frame such as setting up an aether is that the math doesnt work out when you compare frames.

Edit: I should say that they often choose not to because the effects are minor up to a point (mercury).

shetline

02-15-2004, 04:55 PM

Originally posted by billybobsky
Actually people apply relativity and quantum freely. The two theories are reconcilable.
This kind of thing is done in a piecemeal way, however. A little QM in this safe little box over here, a little relativity in its own box over there. A lot of useful work gets done this way, but it's not the same thing as a reconciliation.
The problem with setting an intertial frame such as setting up an aether is that the math doesnt work out when you compare frames.
How so? The whole point of Special Relativity (which I know reasonably well, and for which I have done calculations) is to be able to translate measurements across inertial frames, replacing the old Newtonian invariants of distance and time with the relativistic invariants of "interval" and the speed of light.

General Relativity extends this invariance to accelerated frames of reference. I have a half-decent layman's understanding of GR, but no mathematical rigor to back it up. At any rate, GR extends, it does not overthrow or replace, what Special Relativity has to say about inertial frames of reference.

You could pick a random rock floating in space and say "we shall call this our standard reference inertial frame". How's that going to cause any problems? If pointing out that rock doesn't cause a problem, a fixed aether doesn't cause a problem either. It's just another inertial frame of reference like any other.

A hypothetical aether is simply arbitrary and superfluous to relativity -- which is crime enough -- but it is not contradictory to relativity.

When I wrote the software for RelLab (http://webassign.net/pasnew/rellab/rellab.html), one of the physicists I worked with even suggested using a "hidden" preferred frame of reference within my software, as a way to stave of cumulative round-off errors. I never did this (we just decided to live with the small errors that were nearly always masked by the precision that users were allowed to see), but a hidden preferred inertial frame of reference would not only have been quite doable, it would actually have solved some calculational problems.

billybobsky

02-15-2004, 05:05 PM

The theories are not opposed to each other (relativity and QM, they cover different concepts).

If there is a basis inertial frame (in the sense of an aether) you can convert to and from it fine, but the numbers do not work out if you try to convert from one frame to another without going to the basis frame.

shetline

02-15-2004, 05:42 PM

Originally posted by billybobsky
The theories are not opposed to each other (relativity and QM, they cover different concepts).
I never said they are opposed, but any physicist I've heard speak about the matter has said the two are not fully reconciled. Regardless of whether the two theories are typically applied to different problem spaces, there's something fishy about basic QM equations treating time as if relativity did not exist and Newton were still king.

If there is a basis inertial frame (in the sense of an aether) you can convert to and from it fine, but the numbers do not work out if you try to convert from one frame to another without going to the basis frame.
The number works out fine. Trust me, I've done it. My software had to do it all of time.

Discounting small effects from general relativity, here are three inertial frames of reference: Rocket A flying away from Earth at 1/2 the speed of light, the Earth itself, and another rocket, B, flying away from Earth at 3/4 the speed of light in the opposite direction.

There is no problem at all translating between any of these frames of reference. From the Earth frame, the speeds of the rockets are as stated above. From the Earth perspective, it can also be said that the relative speed of the two rockets is 1.25c -- and that's not a contradiction to relativity.

From Rocket A's frame, A itself is not moving, the Earth is moving away at 0.5c, and Rocket B is moving at about 0.909c.

From Rocket B's frame, B itself is not moving, the Earth is moving away at 0.75c, and Rocket A is moving at about 0.909c.

No problems whatsoever. Rename the Earth frame of reference the aether frame of reference, and no problems suddenly appear either.

billybobsky

02-15-2004, 09:43 PM

So what do you mean exactly by a preferred reference frame? I was taking it to mean an actual aether, that logically the speed of light in one direction with the reference frame was different than the speed of light in the opposite direction. If this is not what you meant then I am sorry, but there still is a problem no amount of experimental evidence is ever going to prove that one frame is preferred unless Einstein was wrong -- special relativity in the simplest description and the most valid says that all frames are equal, this parity breaks if one is preferred and down comes the theory.

I looked around on the internet for the break between quantum and relativity. The problem exists with GR and not SR at this point. And it is a problem not with the treatment of time but with the fact that a concept of energy in quantum mechanics is inherently linear -- add a quanta of energy and the system is perturbed by that much -- whereas is GR if you "add more gravity" the system perturbation is non-linear -- space bends like a rubber sheet; the hole doesn't merely get deeper. I think the problem is with GR not quantum -- GR doesn't have a way to treat light as far as I know and that is the quintessential quanta (the deepest I have delved into the math of GR is with blackholes and it was a crippled introduction -- Einstein's field equations were not shown or really discussed except to point out that he basically just wrote them down based upon advanced topics of geometry at the time and the guy who obtained the first solution was dead within a month because of WWI.)

shetline

02-15-2004, 10:39 PM

Originally posted by billybobsky
So what do you mean exactly by a preferred reference frame? I was taking it to mean an actual aether, that logically the speed of light in one direction with the reference frame was different than the speed of light in the opposite direction.
Please remember that I said I was talking about something like the old idea of the aether, but not the same... something would that mediate or limit hypothetical faster than light interactions, not something that would have an effect on the measured speed of light.

Here's the thought experiment that led me to what I've been trying to describe: Imagine a long, essentially infinite, line of clocks and meter sticks -- lines or gridworks like this are things I've heard used in relativity illustrations before. All of the clocks are at relative rest to each other, and within that inertial frame, all of the clocks have been synchronized to the same time.

Now augment that traditional image like this: Imagine that you can use any clock to instantaneously send a message to any other clock along the line. A message goes into one clock at a given time, and at that same instant (plus some arbitrarily short delay), the message is received at another clock.

This assumption does produce some odd relativistic consequences, including that for anyone traveling in the direction in which a message is sent, the message will appear to go backward in time. But that oddness does not lead to any temporal paradoxes, if you make one very big assumption -- that the FTL messaging system is unique, that no other such device exists anywhere else in the universe, or at least that if another such device exists, that it is at rest* to the original FTL device.

While it's a bit silly to imagine a universe that would impose such restrictions on particular technological artifacts, it's at least a little less absurd to postulate a kind of "FTL aether" that would mediate hypothetical FTL communication or travel.

*I'm not sure multiple devices would have to be completely at relative rest in order to avoid paradoxes. I think they could all be moving away from each other without problems, for instance. Extending this idea to the FTL aether, I imagine the aether could be an expanding medium, maybe even have other internal relative motions between areas that are locally synchronous, without introducing temporal paradoxes.

billybobsky

02-16-2004, 09:30 AM

so the clocks in the SR framework are syncronized by light meaning two clocks separated by a meter are set to the same time when a light pulse leaving the first one is detected at the second one. There is no instantaneous signaling or signaling faster than light because that is the cosmological speed limit -- it just is. A signal moving faster than the speed of light would appear to go back in time wrt the lattice; however, if that was the case you could just set the lattice to that signal thus creating a new cosmological constant. Unfortunately, all evidence points to the speed of light as the true speed limit of the universe. So called spooky action at a distance probably moves at the speed of light, just like gravity...

shetline

02-16-2004, 10:26 AM

Originally posted by billybobsky
so the clocks in the SR framework are syncronized by light meaning two clocks separated by a meter are set to the same time when a light pulse leaving the first one is detected at the second one. There is no instantaneous signaling or signaling faster than light because that is the cosmological speed limit -- it just is.
This is a hypothetical game... FTL is being taken as a given, even if it isn't real. The idea of the game is to see if you can come up with something that works under the proposition of FTL without falling apart with things like temporal paradoxes.
A signal moving faster than the speed of light would appear to go back in time wrt the lattice; however, if that was the case you could just set the lattice to that signal thus creating a new cosmological constant.
I'm presuming the lattice to be synchronized by normal light-speed means, even if the lattice is also given the hypothetical capability of FTL transmission, because the idea is to start with a relativistic definition of time and simultaneity, and move from there.

WRT the lattice, the proposed FTL signals don't go backward in time, because, by definition, a signal sent at time t from one clock arrives at another clock at time t + epsilon, where epsilon is an arbitrarily small, but positive, transmission delay. Such signal will appear to go backwards in time, but only wrt some frames of reference in motion relative to the lattice.
Unfortunately, all evidence points to the speed of light as the true speed limit of the universe. So called spooky action at a distance probably moves at the speed of light, just like gravity...
I suggest you look into Bell's Theorem (http://en.wikipedia.org/wiki/Bell%27s_theorem). There is some argument over this, but many conclude that QM actually requires non-local effects to be consistent. Unlike the the hypothetical FTL premise that I'm playing with, however, this "spooky action at a distance" in QM can't be exploited as an information transmission system.

Argento

02-16-2004, 10:30 AM

Originally posted by Anders
No. They just don´t go as fast forward as the rest of us. Or we go a bit faster than they do, depending of the POV.

Which by definition is time travel, it's just not all that science fiction has hyped itself up to be.

shetline

02-16-2004, 10:44 AM

Originally posted by Argento
Which by definition is time travel, it's just not all that science fiction has hyped itself up to be.
If you're satisfied with time travel that simply takes the form of rushing into the future faster than everyone else, with no return trip to possible, that limited kind of time travel is certainly possible.

Just fly away from the Earth at high speed for a long time, turn around and come back, and more time will have passed on the Earth than has passed for you while you were gone. The rate at which you travel into the Earth's future, in Earth years per traveller year, is limited only by the amount of energy you have available to expend and the degree of acceleration you can withstand.

Personally, I think perfecting cryogenics would be an easier and cheaper way to take a one-way trip into the future, however. :D

billybobsky

02-16-2004, 11:55 AM

Shetline,
The clock in the lattice will not read t+epsilon if your signal travels faster than light for the signal maintaining the lattice time structure is traveling at light speed hence your signal will arrive at the next lattice point at t-epsilon hence going back in time which is why none of the faster than light travel makes sense in an unbent lattice because it is always possible to set the clocks up according to the fastest signal -- and right now the fastest signal and all related calculations suggest the speed of light is the speed limit of the universe.

That is a long sentance.
This post is done.

pfflam

02-16-2004, 12:01 PM

Come on . . . every school boy knows about Bell's theorem and the experiment that showed us non-local causality!!

but what alludes us all is why no school boy yet has a real explanation . .

could it be that we just are not absolutely certain about everything that we will and won't be able to do?!?!?!

after all, we can now sail a boat around the globe without falling off of the edge of the world
(at least, so I am told)

Anders

02-16-2004, 12:46 PM

Originally posted by Argento
Which by definition is time travel, it's just not all that science fiction has hyped itself up to be.

But you were arguing that you would go back in time. You wouldn´t. You just went ahead in time a bit slower. If we both walk on the sidewalk and I walk 0.05% faster than you you would not go backwards.

shetline

02-16-2004, 12:49 PM

Originally posted by billybobsky
The clock in the lattice will not read t+epsilon if your signal travels faster than light for the signal maintaining the lattice time structure is traveling at light speed hence your signal will arrive at the next lattice point at t-epsilon hence going back in time which is why none of the faster than light travel makes sense in an unbent lattice because it is always possible to set the clocks up according to the fastest signal -- and right now the fastest signal and all related calculations suggest the speed of light is the speed limit of the universe.
I'm beginning to feel like it's as if I'm saying "Suppose the Earth were flat, then...", and rather than go along with the idea, just to see what interesting things that might come out of supposing that the Earth were flat, instead you'd rather argue why the Earth isn't flat.

Let me go step by step through what I'm trying to establish here:

1) The clocks in the lattice are assumed to have been synchronized using light-speed signals. I care not one whit that if something faster than light were available, that that method would be used instead. I'm saying light has been used so as to establish the usual relativistic sense of time, and of simultaneity within an inertial frame of reference.

2) I'm not trying to work from within the moving frame of reference of an FTL message itself. I don't care about that frame of reference. The assumption is that some how, some way, you send a message at time t, and it arrives at any given destination at t + epsilon, where epsilon is an arbitrarily small positive value. If the message arrives later than you sent the message in the lattice's frame of reference, the message didn't go backwards in time in the lattice's frame of reference. Later equals forward in time... I don't know how I can make that more clear.

3) I think light speed is probably the ultimate speed limit too, but the whole point is to see what, if anything, breaks if you assume something can go faster, and what rules, fanciful or not, would keep temporal paradoxes in an FTL world at bay.

billybobsky

02-16-2004, 01:34 PM

WRONG!
Oh my god. I failed to understand the confusion until now. By definition if something arrives at a lattice clock at t +epsilon it is traveling slower than the speed of light if it left another lattice point at t. By definition. Otherwise you would need to go back in time arriving at a point t-epsilon when you left at t.

Now that we have gotten to the point that traveling faster than light does (in the rest frame) indicate that you go back in time what is your point?

shetline

02-16-2004, 01:43 PM

Originally posted by billybobsky
WRONG!
Oh my god. I failed to understand the confusion until now. By definition if something arrives at a lattice clock at t +epsilon it is traveling slower than the speed of light if it left another lattice point at t. By definition. Otherwise you would need to go back in time arriving at a point t-epsilon when you left at t.

Now that we have gotten to the point that traveling faster than light does (in the rest frame) indicate that you go back in time what is your point?
There's confusion here, but I think the confusion is over what is meant by "synchronized".

Are you assuming that when I say "synchronized by a light speed signal" that I'm saying that each clock sets itself to the same time when the light speed signal arrives?

No, no, no...

What's typically meant by synchronizing clocks in relativity is that you compensate for light travel time. If one clock sets itself to 0:00:00 when a synchronization signal passes by, a clock that's one light second away from that clock sets itself to 0:00:01 when the signal arrives.

sammi jo

02-16-2004, 02:26 PM

Bear in mind that people in the present always feel that the "state of the art" of science represents the absolute truth about reality. Ptolemy's model of the universe was a horrible "kludge", but it did explain astronomical phenomena remarkably well until science moved a step further and brought that whole deck of cards crashing down. Perhaps in a couple hundred years (or maybe much less)...we will look back at early 21st Century science as having been decidely primitive. It's all relative.

As we rant about Clark's imagination and "presidential "lunacy"...does anyone recall that infamous poll taken in 2002, in which 44% (!!!!!!!!!!) of the American public (+/- 2%) believed that the Earth was created ex nihil, less than 10,000 years ago!!!!! I just thought I should add this extraordinary (and sad) statistic, re. the state of awareness of one of the most basic facts about the Earth and/or Universe.

:wow: :wow: :wow: :wow: :wow: :wow:

shetline

02-16-2004, 03:59 PM

Originally posted by sammi jo
Bear in mind that people in the present always feel that the "state of the art" of science represents the absolute truth about reality.
A good scientist knows that "absolute truth" is something we lack, and probably always will. Even if he isn't astute enough to know that, he or she is probably smart enough to avoid phrases like "absolute truth", because saying something like that would make all of the other scientists point and laugh. :D

Of course, scientists are human, and get rather strongly attached to their ideas, perhaps too attached at times to adapt as quickly as they should to new ideas and new evidence.

Ptolemy's model of the universe was a horrible "kludge", but it did explain astronomical phenomena remarkably well until science moved a step further and brought that whole deck of cards crashing down. Perhaps in a couple hundred years (or maybe much less)...we will look back at early 21st Century science as having been decidely primitive. It's all relative.
Newton's Principia Mathematica is over 300 years old, and it's hardly looked at as primitive today. His work holds up so well that his equations are still used routinely today... not Absolute Truth™ for sure, but close enough to reality to get the job done.

I do not foresee Relativity or Quantum Mechanics as appearing quaint or primitive in the foreseeable future. They may not be, and probably aren't, the last word, but they work so well over such large practical domains that they will likely remain useful even when superseded by something else.

While it's important to understand that science changes over time, some people make the mistake of going a bit too far with that notion, acting dismissively towards today's science as if it were ephemeral, just a bit of fashionable intellectual fluff waiting to be blown away by the next thing that comes along.

Such is not typically the case. I believe we've set down some solid foundations in many areas of science that are more likely to be built upon and enhanced, rather than swept aside and utterly replaced.

pfflam

02-16-2004, 04:08 PM

That's SO trendy~

billybobsky

02-16-2004, 04:43 PM

Originally posted by shetline
What's typically meant by synchronizing clocks in relativity is that you compensate for light travel time. If one clock sets itself to 0:00:00 when a synchronization signal passes by, a clock that's one light second away from that clock sets itself to 0:00:01 when the signal arrives.

Nope thats not what is meant in the conventional sense. Think about traveling with that light wave if you took into account how fast the signal was moving then it would appear to you that time is passing, but it is not since you are moving at the speed of light. :)

I am sorry for calling you on this but without these basic concepts SR thought experiments have no uniformity.

shetline

02-16-2004, 05:39 PM

Originally posted by billybobsky
Nope thats not what is meant in the conventional sense.
Of course that's what's typically meant by synchronizing clocks... think about a basic two dimensional space-time diagram (http://www.physics.nyu.edu/courses/V85.0020/node39.html), with position x being the horizontal axis, and time t being the vertical axis.

A horizontal line across such a diagram represents simultaneity in the frame of reference of any body with zero motion along the x axis. Light obviously can't travel straight across such a diagram (it's typically shown at a 45 degree angle, with each axis in like units, such as seconds and light seconds), yet despite the fact that light can't cut straight across, all of those points in a straight horizontal line are said to represent simultaneous events in the rest frame of the diagram.

A row of clocks set to the same time would be plotted horizontally across a space-time diagram, not arbitrarily along a left-leaning or right-leaning light line. If you think clocks are synchronized along a light line, how would you choose which one?

billybobsky

02-16-2004, 06:23 PM

You are wrong, the clocks are synchronized at the reception of a light signal sent out from any clock it doesnt matter which -- think about it, if you had one clock on which all were based you would have to know the distance you are from all clocks, in einstein's construction all clocks are equivalent and measure a signal of light passing by at the same time.

shetline

02-16-2004, 06:53 PM

Originally posted by billybobsky
You are wrong, the clocks are synchronized at the reception of a light signal sent out from any clock it doesnt matter which -- think about it, if you had one clock on which all were based you would have to know the distance you are from all clocks, in einstein's construction all clocks are equivalent and measure a signal of light passing by at the same time.
My iChat is shetline@mac.com if you want to hash this out... it's getting hard to do with posts back and forth.

When you synchronize clocks, you're supposed to know the distance between them. Yes, you can't synchronize until a light-speed signal arrives, but once it does, you compensate for light-travel time.
From Special Relativity: Synchronizing Clocks -- Michael Fowler (http://galileoandeinstein.physics.virginia.edu/lectures/synchronizing.html):
Suppose we want to synchronize two clocks that are some distance apart.

We could stand beside one of them and look at the other through a telescope, but we'd have to remember in that case that we are seeing the clock as it was when the light left it, and correct accordingly.
We can't get anywhere unless we agree on the very basics of what it means to synchronize clocks.

I hate to make this sort of appeal, but at least consider this: I was the sole software developer for an award-winning piece of software for teaching Special Relativity. The software won two awards in the 1992 EDUCOM national educational software competition: one for Best Natural Science Software (Physics), the other for Best Design.

The software would have utterly failed if I did not understand the concept of clock synchronization. My math would have utterly failed. The clock synchronization demo written using the software would have failed. I could not have slipped such gross errors past either the reviewers or the physicists I worked with as advisors to the project.

At least give me a little benefit of the doubt, and look a little harder for what you might be misunderstanding that I'm saying.

billybobsky

02-16-2004, 08:33 PM

D'oh. Two different constructions. Ah well.

Shetline. You have my apologies...

shetline

02-16-2004, 09:36 PM

Originally posted by billybobsky
I cant say whether what you did in your program matters really because presumably you only used the lattice of clocks as a teaching tool and the math from there on out had been worked out.
The software was a free-from thought experiment constructor. When you start up the program, a blank document consists of a single default object at rest at 0, 0 in an x/y coordinate system.

You are allowed to add objects at any point in space, assign those objects velocities, assign actions which occur at given moments of time, such as sending out pulses of light or changing speed and direction.

You can select any object in the simulation and switch into that object's frame of reference. On the fly, all space and time coordinates are updated using the appropriate relativistic transforms.

If you'd been thinking the software was just a dumb playback tool showing canned scenarios that were pre-computed for me by someone else, you'd have the wrong picture. The simulations had to be based on a proper understanding of special relativity, including how time is defined, or the simulations would fail.

My simulation worked so well, I even rediscovered a phenomenon that the physicists I was working with hadn't known about themselves ahead of time.

Rather than putting all motion in a straight line, as is typical in many discussions of SR and related thought experiments, I decided to give the user a playing field with two spacial dimensions. I set up a square course to travel around at high speed... starting at rest wrt to the square, moving around the square, then returning to rest wrt to the square.

When I came to rest at the end of the course, the square course was rotated slightly, tipped on its side. I thought I had a bug in my software. My physicist colleagues were intrigued -- they thought maybe it was a bug too, but worth looking into. One of them came up with the answer after a little research: I'd rediscovered something called "Wigner rotation".

If the software was good enough to rediscover phenomena that we, the writers of the software, didn't even explicitly put into the code, I'd say that's a pretty good sign the math I was using and my understanding of SR that I applied to the code was solid.

We agree that if you are traveling at the speed of light that time does not change according to you in some inertial frame (any inertial frame in fact).
Actually, I don't think we can agree on this, because it's a mistake to talk about an observer traveling at the speed of light. Near c is okay -- at c is verboten.

The procedure of synchronizing clocks has nothing to do with trying to put yourself into the frame of reference of photons flying between one clock and the next. You start by assuming the clocks you wish to synchronize are at rest with one another (in the same inertial frame), that you know the distance between the clocks, and that you know the speed of light.
That means that the clocks you see in the inertial frame (lets say in this case a lattice of clocks) always seem to read the same time when you pass them.
If you were truly at the speed of light, the universe would be crunched down to zero length in your direction of travel... or, to be more mathematically precise about something you can't really do, length l would approach 0 as velocity v approached c.

Let's see if there is something else we can find to agree on, and work from there...

I think we can both agree that it makes no sense to try to synchronize clocks that are in motion relative to each other, that we are talking about synchronization of clocks within a shared inertial reference frame.

Now, can you agree to this: If two clocks are very accurate, then after an initial synchronization, later synchronization should simply confirm the initial synchronization, altering it very little, if at all. Can you agree to that?

Can you also agree that once two clocks are synchronized, it shouldn't matter which clock you choose to use for a later confirmation of synchronization?

Now consider this: Two clocks at rest wrt to each other, exactly one light second (aproximately 300,000 km) apart.

Your clock is not yet set. The distant clock has been set, and you can read what that clock says through a very powerful telescope. What do you do when you see the distant clock strike midnight?

Unless I'm totally misreading you, what I'm getting out of what you're saying is that the moment you see midnight on the distant clock, you set your own clock to midnight too.

What I'm saying is that as soon as you see midnight on the distant clock, you should set your own clock to one second after midnight.

Before I go on, do you agree with what I've said so far, and my evaluation of what you are saying?

billybobsky

02-16-2004, 09:47 PM

You are fine shetline -- i was using a construction that i had forgotten to forget...

shetline

02-16-2004, 10:10 PM

Originally posted by billybobsky
You are fine shetline -- i was using a construction that i had forgotten to forget...
Well, shall we take things back to the hypothetical "hyper-aether" and FTL, now that this other horse has been beaten to death? :)

billybobsky

02-16-2004, 10:19 PM

sure...

You want to ignore the real/imaginary space transition made at v=c?

shetline

02-16-2004, 11:01 PM

Originally posted by billybobsky
sure...

You want to ignore the real/imaginary space transition made at v=c?
Yes... because the exercise simply starts with the assumption that FTL messages can get from one place to another with a preferred reference frame with an arbitrarily small, positive delay. The way the message system would work -- tachyons, quantum gnomes, wishful thinking -- is immaterial.

One thing than can be said... these FTL messages would never travel at the speed of light. Like tachyons, their timelines would also lie outside of the light cone, and no transformation to any inertial frame would change that.

Although I don't know exactly how to bring full mathematical rigor to bear on this, I think I can go this far in explaining what a preferred frame of reference buys you for FTL...

By definition, all of my FTL cause-and-effect relationships will move forward in time within the preferred FTL frame -- a cause at t, an effect at t + epsilon. Since this direction is always forward, a chain of causality linked to these messages will always be forward.

Add normal, light-speed or slower interactions to the mix, and still, everything must move forward in time, because all normal cause-and-effect time lines, in any frame of reference, occur within the light cone, and move forward in time in all frames of reference, including the preferred FTL frame.

I think it's fair to say that if your timeline always moves forward, you can't have a loop, a troubling paradox where an effect turns back on it's own chain of causality.

Now, when you observe a causality timeline that has both FTL and normal components from any other frame of reference, it is possible that some of the steps in that timeline will go backward in time. However, geometrically speaking, such transformations are simple matters of skew and rotation -- they can't put a loop into something that doesn't start with a loop.

As artificial as this construction might be, I feel fairly confident that it allows for FTL without causality paradoxes.

The moment you introduce another inertial frame in which messages can be sent at arbitrarily fast FTL speeds, however, you're in trouble. Some of those timelines will be seen to go backward in time in the orginal FTL frame, and suddenly, you now have a way to make a closed loop out of a chain of events, and thus possibly create a violation of causality.

billybobsky

02-17-2004, 08:31 PM

There is a range of FTL speeds/distances that will always be allowed without paradox since they will never be able to arrive back at the original emission point "before" they were emitted in one frame. FTL occurs -- locally, for instance, in the faster than light travel of beta particles from nuclear decays ( the local speed of light is slower than the speed of the electron, hence the blue glow of light from the pools under which they store nuclear fuel). However, avoiding the paradox in one frame doesn't solve the problem in all frames, in some frame (in a lot of frames) the signal may arrive at the next clock at t+epsilon, but if the signal was traveling faster than light in at least one frame there would be a backwards in time problem. Defining that in all frames you have the signal arriving at some t+epsilon(1,2,3,4...), I think will force you to reach a mathematical paradox in which the assumption that the t+epsilon(1,2,3,4...) cannot be true.

sorry :/

You should know that GR doesn't have a real way of defining a universal speed of light, ie it the local speed that matters...

shetline

02-17-2004, 09:09 PM

Originally posted by billybobsky
but if the signal was traveling faster than light in at least one frame there would be a backwards in time problem. Defining that in all frames you have the signal arriving at some t+epsilon(1,2,3,4...), I think will force you to reach a mathematical paradox in which the assumption that the t+epsilon(1,2,3,4...) cannot be true.
I'm not trying to hide the fact that an FTL signal will appear to move backwards in time in some frames of reference. I plainly admitted to that.

My point was about loops is causality -- does the backward-through-time timeline of an FTL effect ever result in a loop such as sending yourself a message telling yourself not to send the message. What I believe is that the artificial constraint of a preferred frame for FTL signals prevents such loops from being formed.

billybobsky

02-17-2004, 09:59 PM

causality will be broken in at least one frame -- time moving backwards is inherently reversing the properties of the event.
i don't have issues conceiving of things moving faster than light locally. but the things that do cannot carry info (for instance entanglement of quantum particles).

shetline

02-17-2004, 11:11 PM

Originally posted by billybobsky
causality will be broken in at least one frame -- time moving backwards is inherently reversing the properties of the event.
i don't have issues conceiving of things moving faster than light locally. but the things that do cannot carry info (for instance entanglement of quantum particles).
The notion of causality gets bent a little, but not broken. Time in the preferred frame becomes the preferred measure of past and future, for ordering one's sense of causality. Again, consider that the lack of loops in the preferred frame can't be contorted into loops in any frame.

Now, if you don't agree with my notion of a "loop" being necessary to create a paradox, that's another matter.

Causality isn't broken because even when, in a non-preferred frame, an effect would seem to precede its own cause, there's always a space-like interval between anomalously ordered events.

In terms of what you might literally see, that is observe happening in the world around after waiting for light from such events to reach your eye, you wouldn't ever see anything out of the ordinary. You would always see an effect come after its cause, and you would only arrive at the weirdness of measuring that an effect came "first" by compensating for light delay, by computing time coordinates of cause and effect events within your own frame.

billybobsky

02-18-2004, 09:41 AM

As I said lack of causality or even misordering of causality is break of the first axiom of relativity -- the basic idea that physical properties are the same in all frames. A loop is not the paradox -- if any connectivity is broken in any frame relativity fails. If you could get something to move FTL then the info it carries would be giberish.

shetline

02-18-2004, 09:57 AM

Originally posted by billybobsky
As I said lack of causality or even misordering of causality is break of the first axiom of relativity -- the basic idea that physical properties are the same in all frames. A loop is not the paradox -- if any connectivity is broken in any frame relativity fails. If you could get something to move FTL then the info it carries would be giberish.
In case you didn't notice, I'm casually tossing aside the idea that physical properties are the same in all frames. From the beginning, I said that this FTL hack was against the spirit of relativity. Whether it's a fictitious must-be-one-of-a-kind magical lattice that sends FTL signal, or an only somewhat less whimsical "hyperaether" which can transmit FTL signals, I do not deny the idea that there would be introduced new physical properties of the universe that would measure differently in different frames.

The question is, does this FTL concept run contrary to currently measured confirmations of relativity, or merely to a higher notion of frame-of-reference egalitarianism, which inspired the development of relativity, but might not actually have to be true in order to get the results we've gotten so far from what relativity predicts.

billybobsky

02-18-2004, 10:06 AM

you can always throw in more properties, the problem is there seems to be a requirement that properties are the same in all frames. sure we can throw away relativity but what good does it do? the replacement theory has to cover the properties observed within relativity. there is also a truism and perhaps at some point a law which states that nature acts with the least number of assumptions, making a specific frame in which only one property is observed is adding unnecessary complexity -- theory follows observation and there have been no observations of anything with regard to the hypothetical universe you propose.

While it would be cool if ftl signals were possible, the same as it would be cool if i could move objects with my mind, you toss aside relativity with too much easy.

shetline

02-18-2004, 11:24 AM

Originally posted by billybobsky
you can always throw in more properties, the problem is there seems to be a requirement that properties are the same in all frames.
"Seems to be a requirement" in what sense? What actually breaks by introducing a preferred frame, other than the "purity" of the idea of relativity? Does something utterly break, does an equation suddenly divide by zero or tell you 3 = 5?

Relativity is a good guiding principle -- I don't argue with that. One should be suspicious of anything that violates the principle that all physical properties will measure the same in all frames of reference. A lot of insight was gained by adopting the relativity principle, and measurements of known phenomena have fit as predicted into that framework.

Regardless, you can overstate relativity's case. Einstein did not disprove the existance of something like the aether, he merely made it arbitrary and superfluous. It's not that the aether didn't work or couldn't exist, but that any aether in any arbitrary frame of reference would work, and you wouldn't be able to measure it. If the laws of physics would conspire to make the aether totally undetectable, why even bother to suppose it's there at all?

But now I'm proposing (for sake of argument -- not because I think it's really there!) an kind of aether that would be detectable if it existed. Detecting it would involve discovering some kind of informating-bearing FTL phenomena that allows non-local causality. Obviously, we've never encountered such a thing, and may never do so.

My only concern here is "With the right set of rules, with the right set of tricky loopholes, is non-paradoxical, information-bearing FTL that produces non-local cause-and-effect relationships even imaginable in a world where relativity (with a small "r") is also true?"

By "relativity with a small 'r'" I mean a Minkowskian spacetime geometry, known non-FTL phenomena in accord with Einstein's relativity, but allowing for the philosophical bias toward total equivalence of all reference frames to be bent as needed.

billybobsky

02-18-2004, 12:29 PM

the thing is that you arent saying anything. What do you mean by preferred frame of reference? How exactly will having one allow FTL communication?
Until you define preferred frame of reference, I cannot say how the theory responds to that mathematical entry.

And if by prefered frame of reference you mean the only frame in which FTL communication can occur, you have your break right there -- FTL communication needs to be able to occur in a frames or else relativity is broken.

You are right about the aether -- Michealson-Morley experiment disproved the existence of the aether before Einstein.

Edit: and there is no such thing as non-local (ie global?) causality -- this is from GR.

shetline

02-18-2004, 02:07 PM

Originally posted by billybobsky
the thing is that you arent saying anything. What do you mean by preferred frame of reference?
The message-sending lattice we talked about is an example of a preferred frame. After using that idea of a fanciful physical artifact to get the thought experiment going, substitute the fictional one-of-a-kind artifact with an "aether", which has a frame of reference which can be defined by the way its hypothetical ability to transmit FTL information operates.

How exactly will having one allow FTL communication?
I'm not saying that having a preferred frame of reference causes FTL phenomena to spring into being. I'm saying that, starting with the presumption that FTL communication exists, anchoring the time flow of those messages to always be forward in time within one special preferred frame helps get you around paradoxical outcomes.
Until you define preferred frame of reference, I cannot say how the theory responds to that mathematical entry.
The preferred frame is defined as the frame in which all FTL message are guaranteed to move forward in time, the frame in which a message sent at time t will arrive no sooner than t + epsilon, where epsilon is an arbitralily small positive value. By definition, the behavior of these FTL messages is plainly, clearly, undeniably and deliberately not in tune with relativity. This is the starting point for further speculation.

If you treat that starting point as if it's the very definition of the ending point, we'll obviously not get anywhere.
And if by prefered frame of reference you mean the only frame in which FTL communication can occur, you have your break right there -- FTL communication needs to be able to occur in a frames or else relativity is broken.
Must... not... lose... patience... grrrrrrr...

How many times and in how many different ways do I have to say that I KNOW that making any frame of reference preferred goes against what's normally meant by relativity???

My point is that, I think with the right tricks, you can keep the outcomes predicted by relativity insofar as known phenomena are concerned, still use the same math for those phenomena, yet imagine information-bearing FTL communication that doesn't cause causality paradoxes, like sending yourself a message telling yourself not to send yourself a message.

FTL communication would be able to occur in other frames of reference... I'm not setting any weird hypothetical restriction such having to come to rest in the preferred frame before you're allowed to send a message. But only in one frame are you guaranteed that messages will always go forward in time. In all other frames, it's possible to send messages backward in time.

Again, if you immediately yell "paradox! that's broken!" the moment you hear the idea of an information-bearing signal going backward in time, we'll not get anywhere. My premise is that it takes more than information going backward in time to cause a paradox. It takes a closed loop of information-bearing signals or actions, where a chain of events can close back on itself, to cause a paradox.

A mere one-way sending of information backward in time doesn't in-and-of itself created such a loop. I believe that a preferred-frame kludge prevents such a loop from forming.

If you can send a message backward in time, how do you avoid causality problems? It works out that if a message goes back in time one year, that the message can only be received somewhere at least one light year away. As a consequence of FTL messages always moving forward in time in the preferred frame, I can't send a message backward in time one year to a place that's only a mile away.

A return message can't get to me sooner than my outgoing message because, moving the other way "against the aether", the return message will take at least a year to get to me.

As a practical matter, round-trip communication to distant places would be essentially instantaneous regardless of your frame of reference, regardless of your motion relative to the aether.
You are right about the aether -- Michealson-Morley experiment disproved the existence of the aether before Einstein.
MM failed to find an aether, but only disproved one particular notion of it. There were ways to rescue the aether, but only by the self-defeating modifications to the concept that made would save the aether while making it impossible to detect at the same time. Why have a theory about something you can't by definition ever test?

Don't get too hung up on the original idea of the aether... I'm partly using the word "aether" as a quaint homage to the past. My aether is not for the tranmission of light, but for the transmission of FTL signals. It does share in the idea of being a medium that permeates all space, and it would represent its own intertial reference frame. It would be detectable, therefore not a difference that makes no difference.

Edit: and there is no such thing as non-local (ie global?) causality -- this is from GR.
And yes, the Earth is not flat. I see that looking at the globe on my desk and looking it up in the encyclopedia. Definitions and assumptions are being bent and tweaked here. The question is do SR and GR completely break down under the assumption of non-local causality -- not free-form non-local causality, but a causality with a new set of constraints -- faster than light being possible, but always moving forward in time within one special frame of reference.

curiousuburb

02-18-2004, 03:33 PM

some fascinating writing in this thread, if a bit confused at times.

maybe some links will help...

NASA links on quantum entanglement (http://science.nasa.gov/headlines/y2004/23jan_entangled.htm)

Queensland University research (http://www.physics.uq.edu.au/people/pope/sci_comm/writing/writing_teleport.html)

New Scientist magazine (http://www.newscientist.com/hottopics/quantum/foryoureyes.jsp) - downplaying time travel, leaning in on quantum entanglement for cryptography

Nauture Magazine trumpets a "Trillion-atom triumph" in entangled physics (http://www.nature.com/nsu/010927/010927-11.html)

WIRED comments on the Danish entanglement research (http://www.wired.com/news/technology/0,1282,47191,00.html)

still searching for the link to a story last year or two claiming actual success,
not sure if it was via Bose-Einstein Condensate (slowing light) or independent of the BEC medium

<returns to dig through archived links>

billybobsky

02-18-2004, 07:15 PM

You are killing me shetline.

Simple proof. Time moves forward in all frames (true? -- it is a universal assumption in all science). Forward time is defined by increased entropy. The amount of information in a system can be defined by its entropy (this 'can be' has been shown to mean that entropy is fully equivalent to information). Information cannot be sent backwards because that would itself be a decrease in information (entropy) of the universe of some future point going against all sorts of laws that have nothing to do with relativity.

Think of this as a conservation of mass issue -- something has to come from the past to the present at the same time (that is precisely instantaneously) that we try to send stuff backwards.

(I believe the above requirements causes a causality loop)

With your assumptions of FTL, you have to ignore the issue of forward time and the fact that in all frames the entropy of the universe should be the same. You are not merely talking about the property of FTL being special, you are saying that the frame in which FTL is found is special in more ways than just allowing FTL to exist nonparadoxically. This is a frame in which none of the laws of the universe are known to apply, not even the direction of forward time. It is an intriguing construction but utterly useless for individuals who live outside of it -- is there even information in the FTL frame?

shetline

02-18-2004, 09:03 PM

Originally posted by billybobsky
You are killing me shetline.

Simple proof. Time moves forward in all frames (true? -- it is a universal assumption in all science). Forward time is defined by increased entropy. The amount of information in a system can be defined by its entropy (this 'can be' has been shown to mean that entropy is fully equivalent to information). Information cannot be sent backwards because that would itself be a decrease in information (entropy) of the universe of some future point going against all sorts of laws that have nothing to do with relativity.
At least now we're getting somewhere more interesting than "You're violating relativity because you're violating relativity." :)

Einstein's physics violated Newtonian conservation of energy. Einstein created a new conservation of energy by creating the idea of mass/energy equivalence, specifically by equating the rest mass of an object to a specific amount of energy -- the famous E=mc^2.

This kind of FTL already starts playing with how time is defined anyway, because time in the preferred frame would become the most important measure of time. In that frame, nothing goes backward in time. Backwardness in time in other frames can be measured, but it's a very academic backward motion in time since it's always non-local.

If that sounds a bit dismissive, consider this real-world consequence of how time is defined under relativity: Say a billion years from now, a star in a galaxy a billion light years away is seen, from telescopes on Earth, exploding from into a supernova. One could say that the star is exploding right now, but that we won't see the event for a billion years because of how long it takes for light to reach us.

Remember, however, that the notion of simultaneity, of "right now" is relative to a frame of reference, and that even small changes in velocity change your reference frame. You can almost think about a frame of reference "pivoting" around an object as it changes velocity, and the three-dimension slice of four-dimensional space-time called "now" for that object sweeps through difference slices of space time as the object changes velocity. The greater the distance between you and an event, the greater the effect a small change in your velocity makes in how you would notate the time coordinates of that event, just like when you swing a long pole the end that's far away from you moves much farther than the part of the pole near your body.

Merely by walking around in my room I can swing the moment of the star's explosion around in time. If the star is exploding "now" while I'm standing still, I take a step away from the star, and now it exploded a few years ago in my new reference frame. Turn around and walk towards star, and in this third reference frame, the star won't explore for a few more years.

This is all very academic, however, because this strange fluctuating dating of the event can only happen once I really know that the event has occurred, around a billion years from now.

So, yes, my FTL scheme violates a full relativistic sense of entropy, but only in the same sense that I'm really changing when a star explodes by walking around in my room. Entropy would be perfecting preserved within the preferred frame of reference, and go more and more out of whack as your velocity relative to the preferred frame increases, but even then, the violation of entropy would be non-local, sealed off from you at a safe distance.
Think of this as a conservation of mass issue -- something has to come from the past to the present at the same time (that is precisely instantaneously) that we try to send stuff backwards.

(I believe the above requirements causes a causality loop)
I don't see a loop here, just a non-local violation of entropy as discussed above. The violation would have to "catch up" with its precipitating event to cause a loop, and it can't do so as far as I can see.
It is an intriguing construction but utterly useless for individuals who live outside of it -- is there even information in the FTL frame?
Go back to the original image of the lattice of clocks, adding to each clock a little data terminal where you can pick up and receive messages sent along the lattice from any clock to all other clocks. Further, suppose you can use these data terminals by radio control, so you don't have to physically stop relative to the lattice to use one of the terminals, but can even pick up and drop off message while flying by at high speed.

Living "outside the frame of reference" of the lattice doesn't mean the lattice is hidden or inaccessible to you, all it means is that you are moving relative to the lattice. You can send a message to a distant friend while remaining in motion by sending it to your nearest lattice terminal, she can pick the message up from her nearest terminal while also in motion, and similarly draft a response and return it to you.

The lattice remains quite useful to you, even though you aren't in its frame of reference. The important thing in communication is round-trip message time, and even for people moving relative to the lattice, round-trip message times can be arbitrarily close to instantaneous. Sent in one particular direction along the lattice, a message might take a whole year to get where it's going, but the return message will be able to go backward in time nearly a year, so the benefit if instantaneous round-trip communication is preserved.

billybobsky

02-18-2004, 09:51 PM

I don't think you understand my entropy argument -- the entropy of the universe is something you can "measure" at any time; it increases in all frames as time goes forward -- yet in all frames it is the same at any point. If it appears that information is sent back in time in one frame -- which is to say that the entropy of the universe has decreased (which is a violation of physical properties outside of relativity but we will go with it) -- then the measurement of the entropy of the universe in all frames will necessarily be less than it was in the previous time it was measured causing the violation to be true in all frames. There is no preferred frame in which this is not true. Hence you cannot send information backwards in time even if it appears that it goes back in time in only one frame.

If you want FTL signaling you will need to do it in a frame which is not a part of the universe -- meaning it cannot receive information from the universe since it is necessarily decoupled from the measurement of entropy in order for FTL signaling to actually occur (it would be like a rip in time -- but since it is a frame and not an actual event it would be a "subspace" heh.). What this effectively means is that our universe cannot do anything to the FTL subspace -- we cannot send signals through it, etc etc.

The loop of causality is a two body loop -- the minimal size necessary -- the future event is as necessary as the past event.

shetline

02-18-2004, 10:30 PM

Originally posted by billybobsky
I don't think you understand my entropy argument -- the entropy of the universe is something you can "measure" at any time; it increases in all frames as time goes forward -- yet in all frames it is the same at any point.
You're right... I don't understand what you're saying here.

I understand that entropy is supposed to increase going forward in time. That I know.

I understand that entropy should increase in all frames. I'm willing to tweak the rules for sake of argument that the preferred frame is the only frame where entropy always increases, but that's another matter.

What I don't get is what you mean by "yet in all frames it is the same at any point". Entropy is the same at any point in time? In space?

I'd have to know more about how "the entropy of the universe" is defined as a measurable property to make more sense of this. I find myself thinking about the exploding star I mentioned earlier -- clearly, a star blowing up represents a major increase in entropy. Yet just by walking around my room, I can place such an increase of entropy into my past, present, or future.

Since I doubt that such small local motions are supposed to affect what's meant by the measured entropy of the universe, I'd be inclined to think that the proper measure is somehow related to the local circumstances of the one doing the measuring, and if that's the case, sending information back into time non-locally shouldn't cause any problems.

billybobsky

02-18-2004, 10:41 PM

The total entropy in the universe is "measurable" in the sense that it could be measured but not easily. What I mean when I say it is the same in all frames is that irrespective of the motion of a frame, the total entropy measured at a given moment in time (this is not looking at the stars and counting some measure of entropy but in essence "measuring" entropy at every point in the universe at one time) should be identical to the total entropy measured at the same point in another frame moving at some different velocity.

shetline

02-18-2004, 10:56 PM

Originally posted by billybobsky
The total entropy in the universe is "measurable" in the sense that it could be measured but not easily. What I mean when I say it is the same in all frames is that irrespective of the motion of a frame, the total entropy measured at a given moment in time (this is not looking at the stars and counting some measure of entropy but in essence "measuring" entropy at every point in the universe at one time) should be identical to the total entropy measured at the same point in another frame moving at some different velocity.
If entropy is always increasing, then the measure of entropy is time dependant.

Time is relative across frames, so you can't say the total entropy in the universe in one frame is the same as it is in another frame "at the same time", because there is no such thing as "at the same time" (except for "at the same time and place").

At any rate, I'm not seeing any troubling violations of causality yet -- and by "troubling" I mean leading to a clear paradox.

I'm the one with the crackpot hypothetical idea, so I know that the burden of proof is on me, but if you'll humor me, I'd like to see if you can follow my rules (as best you understand them) and come up with a shoot-your-own-grandpa type of paradox that I can't prevent by my rules. This would include problems with entropy that lead to clear local violations of entropy, like seeing the (absolute) future or running a machine off its own waste heat or something like that.

billybobsky

02-19-2004, 02:18 PM

shetline, the total entropy of the universe is a physical property of the universe. while it increasing does define forward time, it does not have a set law saying it increases at a certain rate with time, so it is not time dependent as such -- it defines forward time. There is a concept of same time in relativity, an event that begins in one frame and ends some time later will appear (when considering the speed of the signal) to begin at the same time and end at the same time in another frame (the time the event takes to occur will of course vary in the two frames but the beginning and ending of the event occurs identically -- this allows interconversion between frames of reference, if this were not true then well none of this would matter). You can measure entropy in two frames at the same time and they should read the same number because it is a universal property. In other words, think of the universe as a adiabatic box on your lab bench, you measure the entropy of the contents of the box and that value should be identical to that of someone who measured the value of the same box at the same time but while driving by at 0.5c.
I am trying to convince you without using relativity (other than fundamental properties remain the same in all frames) that a signal that appears to go back in time in one frame is thermodynamically impossible in all frames.

By showing you this, I hope I can make you realize that a frame in which FTL signalling is allowed is essentially a frame that is not in contact with our universe.

I can show you a paradox simply. Deterministic physics is not a full description of what occurs (ie there is chaos). In order for me to send a signal backwards in time (in any frame), I need to obtain at least the amount of entropy i send back back from the place I sent. This requires all events between the past and the future to be fully determined such that any and all information that signal carries is identical, which we know is not observed let alone theoretically possible.

Local violations of entropy are allowed, btw. The machine example is an adiabatic system, ie its a minature mock up of the way the universe works.

shetline

02-19-2004, 03:33 PM

Originally posted by billybobsky
There is a concept of same time in relativity, an event that begins in one frame and ends some time later will appear (when considering the speed of the signal) to begin at the same time and end at the same time in another frame (the time the event takes to occur will of course vary in the two frames but the beginning and ending of the event occurs identically -- this allows interconversion between frames of reference, if this were not true then well none of this would matter).
Conversion of time coordinates between frames is something that I know reasonably well, and what you've said above makes no sense.

An event in frame A starts at time ta_0 (damn the lack of subscripts and superscripts in vB code!), and ends at time ta_1, taking a duration da. It follows that...

ta_1 = ta_0 + da

In other words, the end time equals the start time plus the duration.

You're telling me that the duration in frame B can be different from frame B (which is correct -- time dialation), but that after allowing for light travel time, the start time and end time in both frames will be the same. Therefore...

tb_0 = ta_0
tb_1 = ta_1
db != da
tb_1 = ta_0 + da = ta_0 + db, where da != db???

How can the start and end times of an (extended) event be the same when the duration in between the start and the end times is different? (The reason I added the parenthetical "extended" is because the typical use of the word "event" is for a single point in space time of zero duration.)
I can show you a paradox simply. Deterministic physics is not a full description of what occurs (ie there is chaos). In order for me to send a signal backwards in time (in any frame), I need to obtain at least the amount of entropy i send back back from the place I sent.
I don't think you're getting what I mean by a paradox. I mean something like "This statement is a lie", where the logic runs in self-contradictory circles.

Breaking the standard definition of entropy is not to be taken lightly, but it's not a paradox. As far as I can tell so far, time defined by increasing entropy survives my FTL scheme -- with a little modification. It doesn't break down in a "man who shaves all men who do not shave themselves" heap of inconsistencies.

I'm also not sure you're getting what I mean when I say that nothing goes backward in time in the preferred frame, but things can go backward in other frames. I'm beginning to get the impression that you're coming from the other direction and saying "If something goes backward in a non-preferred frame, it sure as hell can be seen as going backward in the preferred frame, unless you put that preferred frame in a separate universe." If that's where you are, then I've got some more explaining to do, because that's not how what I'm trying to describe works.

I'm not saying that willy-nilly, anyone in a non-preferred frame can wildly send information back in time however they like, just because they aren't in the preferred frame. The only backwardness I'm allowing comes from translating forward-marching, preferred frame FTL events into time coordinates of other frames. The backwardness seen from doing such event coordinate translations is the only backward-through-time causality that my FTL rules allow.

By definition, no sending of information, no causal event, runs backward in the preferred frame. As long as that condition holds, then at the very least entropy always increases in the preferred frame.

billybobsky

02-19-2004, 04:13 PM

you are right -- you just dont get what i am saying.

If I am looking at an experiment happening in another moving frame, I and i was able to talk to a person in that frame we would both agree that the event started and stoped at the same time -- not t=5.2 s after midnight, but the same time (remember there is no absolute scale). The duration of the event would be different in both frames but the point at which it began and ended would be the same.

I understand completely your argument, and you are simply wrong. Uncoupling your frame is necessary for your argument to work, ANY percieved backwards in time motion causes the entropy of the universe to decrease in all frames because it has to be the same in all frames. This a violation of thermo.

Its not that the rules of the universe simply apply to all frames, its that all frames are intrinsically coupled causing the rules of the universe to apply to all frames. Basically I am getting a sense that you dont understand the premise behind my first paragraph in this post. The observed events are the same in relativity -- their space time durations differ in different frames, but they are the same.

Fundamentally, if something appears to go back in time in any frame, it cannot occur. Period. This can be shown through several other theories, but I choose thermo because its relatively easy to argue and you werent accepting relativistic arguments.

You cannot have a special frame in which events occur that arent observed in other frames. That is relativity. You cannot send stuff back in time because that causes a decrease in the universe's entropy. That is thermo.

Your condescension is not unexpected due to my confusion with the whole setting the clocks argument, but it is unwarented, I assure you. I am not the first to make these arguments and you are no doubt not the first to think you can make a special frame that has special properties. You dont understand what a frame is -- it is merely an observation point -- it doesnt change the properties of the universe; certain frames make CALCULATIONS easier but the same CALCULATIONS can be done in other frames.

Thinking a frame is a special place is sweet, really, but its not.

shetline

02-19-2004, 04:50 PM

Originally posted by billybobsky
You cannot have a special frame in which events occur that arent observed in other frames.
When or where did I ever say that events in the preferred frame couldn't be observed in any other frame?

Think back to the clock lattice with its FTL data terminals... The lattice would be "out there", floating around in space, and anyone in any frame of reference can look at, fly up to and touch it, stare at the clocks through a telescope while flying by in a different frame of reference, send and received messages sent through the lattice, again while in motion relative to the latice, and hence in a different frame. Of course it’s observable – it wouldn’t be very useful if it were invisible! :D
Thinking a frame is a special place is sweet, really, but its not.
Again, consider the example above. I'm not calling the preferred frame a "special place". The only meaning of the preferred frame is that, if you plot out a sequence of FTL events, when you look at events translated into coordinates for that frame, cause always precedes effect, send always precedes receive. When you send a message from one place along the lattice to another, the message isn't allowed to show up until the next arbitrarily small forward tick of all of the synchronized clocks in the lattice.

billybobsky

02-19-2004, 05:04 PM

sorry not events. i meant physical property. frames cannot hold properties yet you clearly indicated that in the prefered frame FTL signalling was possible. you cannot do that. the properties are intrinsic to the universe not to the frames used to observe them.

that lattice work of clocks is a teaching tool. its great that you have your construct based around it, but it doesnt show that you have any understanding of what einstein was getting at. you cant give frames physical properties. just having a frame in which something is possible (like it doesnt appear to go back in time) doesnt mean the event is possible, there is a paradox intrinsic to the fact that you are just using a frame to measure a property and the event must be the same regardless of frames. Toss away relativity and you still have the problems with thermo etc etc. There is something intrinsic to the fact that nothing can go back in time.

shetline

02-19-2004, 06:13 PM

Originally posted by billybobsky
sorry not events. i meant physical property. frames cannot hold properties yet you clearly indicated that in the prefered frame FTL signalling was possible. you cannot do that. the properties are intrinsic to the universe not to the frames used to observe them.
Didn't I say that I knew I was violating the frame-egalitarianism of relativity from the start? That's the premise... break the rules a little, see how far things get out of hand. Do I break only a bit of philosophy, do I produce consequences that runs counter to things that have actually been measured (and I don't think anyone has every actually measured the total entropy of the universe), do I create an internal contradiction in the special rules I propose?
that lattice work of clocks is a teaching tool. its great that you have your construct based around it, but it doesnt show that you have any understanding of what einstein was getting at. you cant give frames physical properties.
You can't, or else... what? That's the whole point of the hypothetical exercise. Break that rule, in a very particular, careful way, and see what happens.

It would be kind of a pointless exercise if all I was asking is which rules can I break without breaking any rules.
just having a frame in which something is possible (like it doesnt appear to go back in time) doesnt mean the event is possible
Again, I'm not saying the rule causes such an event to be possible. The game is merely to ask, if FTL is possible, and it follows these particular non-relativistic rules, what happens?
there is a paradox intrinsic to the fact that you are just using a frame to measure a property and the event must be the same regardless of frames.
That's a simple contradiction, not a paradox. I'm deliberately contradicting the assumption that everything has to be the same across all frame, to see what the contradiction buys me, and what's left of what we'd normally expect.
Toss away relativity and you still have the problems with thermo etc etc. There is something intrinsic to the fact that nothing can go back in time.
First of all, I'm not tossing relativity completely away... I'm keeping time dilation, the light-speed limit for all information-bearing interactions other than the special FTL messages, a Minkowskian spacetime geometry, etc.

I'm mostly keeping the idea that nothing can go backward in time. Nothing can go backward in time in the preferred frame, and in other frames, all backwardness is non-local.

Here's a painfully forced analogy for what I'm trying to do... Consider three proposals for changing the rules of baseball.

1) Replace the baseballs with oranges.
2) You aren't allowed to hit the ball.
3) Pitchers must bat for all team members, and only those team member, who don't bat for themselves.

Given Proposal 1, you could just dig in your heels and say "Well, if you don't use baseballs, it isn't baseball anymore, is it?" and stop there.

Or you could explore the idea, "Well, it would certainly be a messier game. I don't know if the outfielders would have much to do anymore, since it'd be hard to hit an orange very far. Say, can we freeze the oranges? Etc., etc." The game would be quite a bit different, but something still recognizably baseball would survive. Things wouldn't be so broken that you couldn't discuss consequences.

Given Proposal 2, with no options given for something else you're allowed to do instead of hit the ball, it's pretty clear that you’d outright kill the game off with the rule change. All players could do is stand there until they strike out, and no one would ever score.

Proposal 3 doesn't merely break the game, it leads to a logical paradox in which you can't define whether or not the pitcher must or must not bat for himself.

For my FTL proposal, I want to see if it can at least hold up on a Proposal 1 kind of level.

Harald

02-19-2004, 06:39 PM

An AI thread that starts with the hope of reasoned discscussion and debate about presiditential lunacy but descends after precious few replies into the same ping-pong flamewar about the relative merits of Einstein, space-time and violation of relativity's frame-egalitarianism.

Typical. Grow up.

:no:

shetline

02-19-2004, 06:47 PM

Originally posted by Harald
An AI thread that starts with the hope of reasoned discscussion and debate about presiditential lunacy but descends after precious few replies into the same ping-pong flamewar about the relative merits of Einstein, space-time and violation of relativity's frame-egalitarianism.
Damn, I hate the way that keeps happening. :err: :D

BuonRotto

02-19-2004, 06:52 PM

Originally posted by Harald
An AI thread that starts with the hope of reasoned discscussion and debate about presiditential lunacy but descends after precious few replies into the same ping-pong flamewar about the relative merits of Einstein, space-time and violation of relativity's frame-egalitarianism.

Nerd alert! Nerd alert! Only nerds get into heated pissing matches about space-time. :devil:

Typical. Grow up.

Indeed. Listen to the man.

Harald

02-19-2004, 07:07 PM

I will not derail this wonderful thread.

Originally posted by billybobsky
You are killing me shetline.

Simple proof. Time moves forward in all frames (true? -- it is a universal assumption in all science). Forward time is defined by increased entropy.

No, not true (as I understand it, IANATP).

Time is far more a human perception of the 'direction' of the tendency toward entropy.

If one uses a concept of imaginary time, then the desired outcome of FTL for the communication of information becomes entirely moot. This *may* be what shetline is suggesting with his Orangeball.

Unfortunately you also need an imaginary set of 'people' to observe the communication.

Please ignore this if it is total horseshit.

billybobsky

02-19-2004, 07:14 PM

you know i didnt have to use the universe as the example of an adiabatic system, and furthermore just because no one has measured the entropy of the universe doesnt mean you cannot extend the results of all other adiabatic systems to the universe unless the universe is not adiabatic.
(and that seems to me to be a far more interesting question than what if FTL can exist but only in one frame, yea as if, giggle giggle).
But I have to refuse to play along stupidly (since i already showed that your system doesnt survive to point 3 in thermo).

You are not approaching this problem scientifically. Your so called "thought experiment" is not an experiment at all because you have systematically denied the validity of any "accepted property" of the universe that I have thrown at you. You have even denied Einstein's own thought experiments. Simply put, you are assuming properties before there is evidence of them, you are creating a hypothetical universe that does not share any of the major properties of the known universe. Your concept of a frame is bizarre, it recalls the sci fi equivalent of an alternate universe. If you want an alternate universe you might as well propose one since your definition of frame is so far removed from the accepted definition of a frame that all you are effectively doing is making an internal universe that is "somehow" accessible and useful to our universe.

its fine to play games shetline, but you keep changing the rules, in fact all that is basically left (since you now have abandoned thermodynamics to not be relevent between frames) is quantum and i am sure there are plenty of properties of quantum systems that just dont fit into your scheme.
btw, contradictions and paradoxes are effectively the same. it is a paradoxical to have contradictory properties -- 2=3 is a contradiction isnt it?.
So here is the deal -- define your rules. if your rules break a theory accept it -- so far thermo and relativity have fallen. once you have your rules have fun. but remember it has nothing to do with what actually occurs in the universe. a thought experiment is supposed to provide insight on few assumptions. your "experiment" provides no insight (or at least none offered from you) on a lot of unstated and stated assumptions.

This is my last response.

billybobsky

02-19-2004, 07:21 PM

Originally posted by Harald
I will not derail this wonderful thread.

No, not true (as I understand it, IANATP).

Time is far more a human perception of the 'direction' of the tendency toward entropy.

If one uses a concept of imaginary time, then the desired outcome of FTL for the communication of information becomes entirely moot. This *may* be what shetline is suggesting with his Orangeball.

Unfortunately you also need an imaginary set of 'people' to observe the communication.

Please ignore this if it is total horseshit.

yeah, horse and some cow too.

btw. while forward time is percieved (and provable within the context of perception in thermo) to follow increased entropy, we have to accept this if we are talking about time. otherwise we stare at a clock and its hands mean nothing.

shetline

02-19-2004, 08:42 PM

Originally posted by billybobsky
So here is the deal -- define your rules. if your rules break a theory accept it -- so far thermo and relativity have fallen. once you have your rules have fun. but remember it has nothing to do with what actually occurs in the universe. a thought experiment is supposed to provide insight on few assumptions. your "experiment" provides no insight (or at least none offered from you) on a lot of unstated and stated assumptions.
I did define my rules, and the only way theromodynamics and relativity have "fallen" so far that all you want to do is parrot back completely unmodified definitions of terms that my premises are clearly and admittedly going to play with. When a completely predictable collision occurs between the starting assumptions and rigid definitions, you say "See! It fails!"

By no means am I certain that what I'm thinking of will work in any sense of the word "work", but I was hoping for something a whole lot more interesting out of the discussion than inflexible repetition of rules that are broken, with no curiousity expressed about what room there might be to play with those rules and still come out with some kind of new consistency.

billybobsky

02-19-2004, 09:00 PM

i sound like a parrot because you are not listening.

this is final. you didnt define your rules. none of them. you have "predictable" collisions with every known theory of the universe that has supporting evidence out there. You cannot just randomly select the few things that could still agree and say "see, some of it is still there". You dont learn a damned thing working this way. Your wonderful properties that come out of a convoluted series of assumptions, have to jive with all that is known -- not theories but actual observations. You are like a string theorist. No you are worse. You are proposing an entirely untestable theory (like string theorist) that disbands everything before it without any evidence (like no one else). Einstein didnt work in a vacuum. Shetline evidently does.

What the hell do you think you are going to accomplish? Do you want to explain thermodynamics then in your new plane of reality? How a frame can carry properties?

Good god. I have just wasted my time trying to convince someone that they can't just toss aside parts of tested theories which do not line up with their pet theory. Worse, you havent offered a solution at all to these problems merely an "eh, it works/doesnt work; its all the same".

I am not being rigid. I accept that these theories probably do not explain all things but they certainly hold more water than your leaking dingy does.