The Theory of Relativity

[brian0918]

Don't worry Brian, you're still cool with me. Your spacetime diagram thing was dandy, to be sure! It's nit-picking perhaps, but this thing you implied about relativity somehow dictating maximums for your time-x-space product, or your time+space sum. Um, that seemed a gross departure from correct interpretation. Maybe I misunderstood your intent.

Well, the speed of light traces out a boundary that cannot be crossed. This is often called a "light cone". Also, please understand that it isn't "my spacetime diagram". That is just how it was taught to me in every relativity course I've taken.

[Capitalism Forever]

With the pre-SR understanding, if people had been able to travel close to the speed of light, they would have observed phenomena that would lead them to believe that there are multiple contradictory realities.

No, they would have applied the Lorentz transformations to their observations and gotten the same result.

[stuzal atla creala iuday]

I thought this forum page was dead... obviously, I'm wrong.

[poignant1]

...is just how it was taught to me in every relativity course I've taken.

Ahhh, you took courses; that would explain your confoundedness certainly. I can't say that I give much (credence) to the System, yeech. Too bad your investment. Alas, here's the skinny.

[brian0918]

No, they would have applied the Lorentz transformations to their observations and gotten the same result.

The only problem being they would not have understood why they couldn't find that pesky ether! (nor obviously could they find any variance to the speed of light) Even up to 1904 Poincare was referring to the reference frame of a "stationary observer" as being the actual time, whereas moving observers have "local times". Einstein showed that there is no preferential frame of reference, and this is definitely true given the gravitational acceleration that everyone in the universe experiences - ie, there can be no "stationary observer". The earlier understanding was (in retrospect) completely divorced from reality; Einstein brought them closer to reality.

Ahhh, you took courses; that would explain your confoundedness certainly. I can't say that I give much (credence) to the System, yeech. Too bad your investment. Alas, here's the skinny.

Ignoring the math makes everything look easy. The only problem is you don't learn anything. I remember reading Black Holes and Time Warps as a kid and liking it a lot, but realizing that I didn't really learn anything because there was little or no math behind it.

Edited April 11, 2008 by brian0918

[Capitalism Forever]

The only problem being they would not have understood why they couldn't find that pesky ether!

As I said, the fact that we cannot find something with technologies based on our current scientific level of development does not mean it does not exist.

[brian0918]

As I said, the fact that we cannot find something with technologies based on our current scientific level of development does not mean it does not exist.

You're misunderstanding the nature of what they were trying to find. Your statement would only be true if our current technology was incapable of reaching a certain required precision, however the technology of the time was more than capable of this, and our ever-increasing precision has backed up Einstein rather than supported the existence of an ether. What they were trying to find was variance to the speed of light caused by the motion of our planet. The speed of light should have changed by the amount of our speed at a given moment through the ether. They compared the speed of light moving with our direction to the speed of light moving in the opposite direction, and found no difference. They should have been able to find a difference with their technology, because that difference would have been well above the random noise of the equipment. They found no difference, and we still find no difference, to greater and greater precision. This variance, however, should have been discovered long ago given the predicted magnitude of it.

[Asimov]

As I said, the fact that we cannot find something with technologies based on our current scientific level of development does not mean it does not exist.

What reason is there to accept that an ether does in fact exist, though? Science, by its own nature, will not exclude with any absolute sense the existence of something unless it has been falsified. I don't think the SR group is stating that the ether doesn't exist, just that there's no evidence for its existence.

I could be wrong, though.

[agrippa1]

You're misunderstanding the nature of what they were trying to find. Your statement would only be true if our current technology was incapable of reaching a certain required precision, however the technology of the time was more than capable of this, and our ever-increasing precision has backed up Einstein rather than supported the existence of an ether. What they were trying to find was variance to the speed of light caused by the motion of our planet. The speed of light should have changed by the amount of our speed at a given moment through the ether. They compared the speed of light moving with our direction to the speed of light moving in the opposite direction, and found no difference. They should have been able to find a difference with their technology, because that difference would have been well above the random noise of the equipment. They found no difference, and we still find no difference, to greater and greater precision. This variance, however, should have been discovered long ago given the predicted magnitude of it.

It sounds like you've looked at some of the math involved in SR. Does it seem strange to you that Einstein combined the forward trip (in the direction of u) of light with the reverse trip for a total round trip time, rather than treating them individually?

Edited April 13, 2008 by agrippa1

[Adrian Hester]

It sounds like you've looked at some of the math involved in SR. Does it seem strange to you that Einstein combined the forward trip (in the direction of u) of light with the reverse trip for a total round trip time, rather than treating them individually?

First, there were two different beams involved simultaneously in the experiment at 90 degrees to each other on a platform that could be rotated to any desired orientation. Second, this experiment was performed in 1879, long before Einstein explained the results with special relativity; it was the most precise way of determining whether there was an ether wind. There's a good overview of the experiment here.

[brian0918]

It sounds like you've looked at some of the math involved in SR. Does it seem strange to you that Einstein combined the forward trip (in the direction of u) of light with the reverse trip for a total round trip time, rather than treating them individually?

I wasn't talking about Einstein, but the Michelson-Morley experiment which took place well before his work. IIRC, they had a platform floating on a pool of mercury, and they split a single beam of light into two, and sent them in opposite directions. Because the motion of the Earth through the ether should have affected the speed of light, one beam should have been pushed to a greater speed, while the other should have been slowed down. They then recombine the two waves together into a single wave. Given the frequency of the light, and the distance and angles that the separate beams travel, this would allow them to see if the resulting wave showed any signs of a phase shift, ie, that the light beams had come out of synch, which would be true if one had temporarily been moving faster than the other. No such evidence was found.

On a side note, Dayton Miller (who also went to Case, where the experiment took place) refused to believe these results, and spent the next half a century conducting more and more precise experiments, trying to find the ether. He only succeeded in showing with greater and greater precision that there is no evidence of an ether. With modern technology it becomes trivial to show this to an (almost) arbitrary precision.

The original experiment is still on display at the Rockefeller physics building at CWRU, and I've seen some of Michelson's hand-written records documenting his earlier measurements of the speed of light a decade earlier. (not that that has anything to do with this discussion...)

Edited April 13, 2008 by brian0918

[y_feldblum]

The mathematical equations used in relativity to describe the fact that two observers moving at different speeds see different phenomena are almost exactly identical to the mathematical equations used to describe the fact that two observers looking in different directions see different phenomena.

We all know that when two observers look in different directions, they see the same actual phenomena, although they may measure the component parts of the actual phenomena differently. For example, one person may say "the Starbucks is one block forward" while another person standing in the same spot but facing a different directio may say "the Starbucks is one block to my right."

The standard interpretation of relativity - the one you learn when you study relativity at anything beyond a 101 level - says that we should treat space and time as interrelated in the same way that we treat forwardness and rightness as interrelated. As you turn to your left, that which was forward becomes that which is to your right. As you speed up, space and time are interrelated in a similar way. The reason for this interpretation is that the equations describing turning about an angle are almost identical to the equations describing speeding up.

The next time you hear "objects get shorter and heavier when they go faster and their clocks slow down", understand that it's nonsense and is nothing at all like what the standard interpretation of relativity states. It is the naive interpretation of the Lorentz transformation, but of course that is only the naive interpretation, and the Lorentz transformation predates relativity theory, which gave the foundation for a vastly different interpretation: that speeding up is a kind of analog of turning about an angle. The standard interpretation says that as an observer's speed relative to the observed changes, he will measure changes in various interrelated quantities such that the combined sum of these quantities remains the same. The measures of the various interrelated quantities are, taken separately, affected by the speed relationship between observer and observed. But the actual physical quantities involved can always be calculated from the measures of the various interrelated quantities. The matter is analogous to observing an object through a magnifying glass: the measure of the object's size changes, but we know there is a magnifying glass in the way, so given the object's measured size and given certain information about the magnifying glass, we can always calculate the object's actual size.

[Thomas M. Miovas Jr.]

I wasn't talking about Einstein, but the Michelson-Morley experiment which took place well before his work.

Actually, all the Michelson-Morely experiment showed was that they were wrong to model the aether as some sort of mechanical fluid -- like wind or a river. It did not prove that the aether does not exist, but rather that their theories about its nature and how it must behave were pre-mature; sort of like an a priori idea trying to prescribe something to existence.

Reality is a full plenum, meaning that there is no nothing -- no absolute vacuum with absolutely no anything in it -- there is always something there.

And further, there must be some cause for things like gravitational fields, magnetic fields, and electric fields. In current physics theory, these are taken as a force that would act on a unit particle at a unit distance from the source, but something must be interacting with that unit particle or actual particle for it to change its position within the range of those forces. In other words, what is acting on the particles to bring about that force?

Further, in order to explain things like particle jumps on the quantum level and even the wave pattern of the double slit experiment, there must be some real thing there to bring about these effects. Even the De Broglie wave relationship must be explained somehow.

There is something there.

What is it?

[brian0918]

Actually, all the Michelson-Morely experiment showed was that they were wrong to model the aether as some sort of mechanical fluid -- like wind or a river. It did not prove that the aether does not exist, but rather that their theories about its nature and how it must behave were pre-mature; sort of like an a priori idea trying to prescribe something to existence.

Reality is a full plenum, meaning that there is no nothing -- no absolute vacuum with absolutely no anything in it -- there is always something there.

And further, there must be some cause for things like gravitational fields, magnetic fields, and electric fields. In current physics theory, these are taken as a force that would act on a unit particle at a unit distance from the source, but something must be interacting with that unit particle or actual particle for it to change its position within the range of those forces. In other words, what is acting on the particles to bring about that force?

Further, in order to explain things like particle jumps on the quantum level and even the wave pattern of the double slit experiment, there must be some real thing there to bring about these effects. Even the De Broglie wave relationship must be explained somehow.

There is something there.

What is it?

It sounds like your argument would eventually lead to the necessity of a "god" to take care of everything. You're essentially saying "we observe these phenomena, but do not know their root cause, so this root cause is the ether" - of course you don't take that last step, but it's implied by your sweeping rejection of both the prior understanding and the Einsteinian understanding. Why the need to reject any of this? What is the reason for this rejection? What is making you say, "I cannot accept these physical understandings in their current form."

An "ether", if there is one, would be a "medium", and by its very definition, a medium is made up of particles that get jostled. If and when these particles are discovered, you will have to ask, "how are these particles moving and interacting? There must be some ether through which these ether-particles are moving." and so you regress ad infinitum. Unfortunately, you eventually hit the limits of the uncertainty principle and it becomes impossible to verify your theory with experiment.

Edited April 13, 2008 by brian0918

[Capitalism Forever]

You're misunderstanding the nature of what they were trying to find. Your statement would only be true if our current technology was incapable of reaching a certain required precision, however the technology of the time was more than capable of this, and our ever-increasing precision has backed up Einstein rather than supported the existence of an ether.

I do not dispute the null result of the Michelson-Morley experiment. I just dispute the conclusion that this necessarily means there is no ether. (And Ayn Rand, as I pointed out, emphatically agrees with me.)

The Lorentz Ether Theory is one way in which the null result of that experiment (and any similar experiment with any greater precision in the future) can be consistent with the existence of an ether.

Edited April 13, 2008 by Capitalism Forever
spelling

[Capitalism Forever]

I don't think the SR group is stating that the ether doesn't exist, just that there's no evidence for its existence.

Well, some people seem to be quite positively convinced that there is no ether, and they base that on M-M.

If you ask me, M-M and the Lorentz equations would suggest exactly that there IS an ether, since the only alternative explanation that has been offered--that "everything is relative"--doesn't seem to make sense to me.

[Thomas M. Miovas Jr.]

An "ether", if there is one, would be a "medium", and by its very definition, a medium is made up of particles that get jostled.

No, I'm not looking for "God" but I am looking for physical causes. There has to be a physical cause to any interaction occurring over a spatial distance. However, I do reject the idea that all this stuff must be particles, as I think that is an a priori stance and one of the mistakes made earlier with regard to the aether. We would have to discover what it is that is acting on a particle with mass or charge -- and further, what is mass or charge? In other words, why is there a resistance to change of motion (mass) and why is there an interaction between certain particles and what surrounds them (charge). I think the descriptive form of most modern equations insofar as they are predictive is good, but it doesn't identify the cause. They basically say this and this happens in this or that circumstance, but it doesn't get to a root cause of the interaction.

In other words, in order for the moon and the earth to be mutually attracted to one another via gravity, one ought to ask: What is going on in between these bodies that makes that possible? Mathematically, we can say what the amount of force there is in between the moon and the earth; but how does that force come about?

That's why the aether idea is not dead with me. Of course, whoever finds out what is going on in between bodies will have the right to name it what he will -- he may or may not call it the aether, but it has to be something that is active to bring about that effect. A similar argument can be made with regard to magnetic and electric fields. But, one ought not to state a priori that it must have the nature of a wind or a river or of particles. We have to discover what it is.

[poignant1]

Well, some people seem to be quite positively convinced that there is no ether, and they base that on M-M.

If you ask me, M-M and the Lorentz equations would suggest exactly that there IS an ether, since the only alternative explanation that has been offered--that "everything is relative"--doesn't seem to make sense to me.

If ever one espoused the antithesis of objectivism, you just did when you said that "M-M and the Lorentz equations would suggest exactly that there IS an ether" because the given explanation doesn't sit well with you personally.

I'll repeat that relativity sits just dandy with me and is entirely objective. I say that because I understand relativity at its core: Earth vicinity is not a privileged zone as once believed; but is only a peer to myriad (gazillions) of other conceivable vantage points. Despite what we or others might ascribe as absolute motion upon viewing a remote planet or craft, all observation stations are nevertheless blessed with normalcy of light signal behavior relative to their own vantage. That truth alone is quite an exhilarating emancipation IMHO.

----------------

Ironically, the word "objectivism" gets flagged by the spell-checker here.

[y_feldblum]

And further, there must be some cause for things like gravitational fields, magnetic fields, and electric fields. In current physics theory, these are taken as a force that would act on a unit particle at a unit distance from the source, but something must be interacting with that unit particle or actual particle for it to change its position within the range of those forces. In other words, what is acting on the particles to bring about that force?

Quantum mechanics answers this: gravitons sent from a mass interact with other masses, and photons from moving charges interact with other moving charges to induce the various effects of electromagnetism.

[y_feldblum]

Well, some people seem to be quite positively convinced that there is no ether

Me for one.

and they base that on M-M.

Yes, but for me it is primarily philosophical. MM is corroborating evidence.

If you ask me, M-M and the Lorentz equations would suggest exactly that there IS an ether

MM is: "given the expected properties of the ether which current theories predict, we performed experiments designed to detect these expected properties, but no evidence of these expected properties could be found." That does not suggest that there is an ether.

Neither do the Lorentz equations suggest that there is an ether. The Lorentz transformation requires a physical explanation - it is itself not a physical explanation - but it does not itself suggest the existence of an ether.

since the only alternative explanation that has been offered--that "everything is relative"--doesn't seem to make sense to me.

The "everything is relative" theory begins with Galileo and continues with Newton. It is a phenomenally objective and sound theory with vast quantities of evidence to back it. F = m A hinges entirely on "everything is relative."

[Capitalism Forever]

MM is: "given the expected properties of the ether which current theories predict, we performed experiments designed to detect these expected properties, but no evidence of these expected properties could be found." That does not suggest that there is an ether.

Neither do the Lorentz equations suggest that there is an ether. The Lorentz transformation requires a physical explanation - it is itself not a physical explanation - but it does not itself suggest the existence of an ether.

I meant that the two together would suggest to me the existence of an ether, for the simple reason that the Lorentz Ether Theory is the only coherent explanation that has been offered for them.

Of course, "suggest" is something very different from "prove," and we should not accept a theory as proven just because it is the only theory we currently have that works. (I keep getting back to that passage in the ITOE appendix...)

The "everything is relative" theory begins with Galileo and continues with Newton. It is a phenomenally objective and sound theory with vast quantities of evidence to back it. F = m A hinges entirely on "everything is relative."

You realize that it does not imply the non-existence of an ether, do you?

[Tensorman]

The next time you hear "objects get shorter and heavier when they go faster and their clocks slow down", understand that it's nonsense and is nothing at all like what the standard interpretation of relativity states.

It isn't nonsense, as the slowing down of the clocks is a real effect that will cause a permanent difference in elapsed time, even if the objects no longer move with respect to the observer. In other words, you can get physically younger than your grandchild by making a long trip through space with high speed. Of course this is in practice far beyond our current technology, but the principle has been experimentally verified.

[y_feldblum]

CF, on the one hand, to date there has never been physical evidence found for an ether. On the other hand, of the many theories of an ether that have been offered, they have generally all been disproven: the results which these theories predicted simply did not accord with the results of experiments designed to test these theories.

Tensorman, the nonsense is in stating that an object moving faster gets heavier, etc. It is not so. The observed mass of an object gets larger as the object moves faster with respect to the observer. That is because mass is not an independent, self-contained property of an entity. However, there is a certain combination of observed mass, velocity, and energy which is an independent, self-contained property of an entity. This combination is given the name momenergy (or momentum-energy or 4-momentum). The particular mass observed depends on the relationship between observer and observed; the particular momenergy observed is independent of the relationship between observer and observed, because it is an existential property of the observed. Mass observed depends on the momenergy of the observed and the relationship between observer and observed. (The same principle is true of the combination of time, space, and velocity.)

Yes, it is true that two objects which take different paths from A to B (to events, separated by time interval and space interval) will have different lengths, and the length of a path is the proper time interval of an object moving along that path. But the clock of an object moving along one path rather than another does not change. One path is simply shorter than the other. "Paradoxically," the curved path is shorter, so the grandfather accelerating and decelerating in his spaceship will travel a shorter path through space and time than his grandchild taking a nonaccelerating path through space and time, at rest on earth. Traveling a shorter path takes the traveler less time, so he ages less. This fact arises from the mathematical relationship between space and time.

[Tensorman]

I do not dispute the null result of the Michelson-Morley experiment. I just dispute the conclusion that this necessarily means there is no ether. (And Ayn Rand, as I pointed out, emphatically agrees with me.)

The Lorentz Ether Theory is one way in which the null result of that experiment (and any similar experiment with any greater precision in the future) can be consistent with the existence of an ether.

What Lorentz did was posing an ad hoc solution for the negative result of the MM experiment, that was expressed in his equations. The next thing he did, was trying to explain these with a primitive atomic theory (quantum mechanics with its precision to 12 decimal places was still far away), which was not very succesful. Of course that doesn't in any way diminish his genial contribution to the theory of relativity. Einstein's genial move was to find a much simpler explanation of the Lorentz equations, leading to his famous e = mc^2 equation and later to his graviational theory, of which the special theory is just a special case. That all many times experimentally confirmed over a century. The ether theory is really dead as a doornail.

[Capitalism Forever]

Einstein's genial move was to find a much simpler explanation of the Lorentz equations

Namely?