Relativity

[md65536]

The velocity composition formula is relatively simply derivable from the transformations, which should be the first thing one knows about SR after the postulates. So yes, I put in a bit of hyperbole, but no, "quite a bit" would not be the appropriate phrase there.

So first is the postulates.

Then the transformations.

Then the relatively simple derivables.

If you haven't yet got around to figuring out the simple derivables, you don't know anything about SR.

"To competently discuss the LHC experiment described in post #17, in terms of SR, you should at least be able to apply the composition of velocities formula."

 

 

If you know about the postulates of relativity you already know more than the average person about SR. I don't think people should feel they know nothing until they're able to pass your initiation test, but on the other hand I don't think it's helpful to believe that one knows enough about SR and doesn't need to figure out something like composition of velocities.

 

+1 for provoking me to try to derive it. Personally I don't think it's simple, it's certainly mind-boggling to figure out on your own, but the math isn't bad (high school level?).

 

But yes, it is definitely not a complicated matter to set out learning about the postulates, about the transformations and how they're derived and what they mean, and the composition of velocities and how it's derived.

[swansont]

If you know about the postulates of relativity you already know more than the average person about SR. I don't think people should feel they know nothing until they're able to pass your initiation test, but on the other hand I don't think it's helpful to believe that one knows enough about SR and doesn't need to figure out something like composition of velocities.

The issue here, however, is that someone who is adamant that relativity is WRONG (and a religion, to boot) had better be pretty conversant with the theory itself, if they hope to appear in any way credible in voicing their critique.

[newts]

SR says that velocity addition is not Newtonian. Two particles moving at 0.5c have a closing speed of 0.8c as measured by either particle. A particle moving at 0.999c and the other at rest will have a closing speed of 0.999c. IOW, SR predicts that these will not be equivalent.

If 2 electrons head towards each other, both at ½ lightspeed; then after 1 second, they will be 1 light-second closer. So based on the definition of speed as distance/time, the closing speed must be lightspeed. If you had never been taught relativity, you would agree with that, and say anybody who disagreed was crazy. That is why I say SR is religion, because it involves people believing in nonsensical things, merely because they have been taught to.

 

SR, like Newtonian mechanics, allows one to calculate things that would be impractical using LET; but it does not describe a possible universe. LET is simple and intuitive, and since it gives similar results to SR, only somebody who prefers to believe in mysticism would favour SR. Uncool, for all his vices, does at least freely acknowledge the equivalence of SR and LET, presumably because he understands the maths. The most vociferous proponents and opponents of SR, surely do not understand the maths; that is why the proponents claim all relativity-deniers must be intellectually inferior, and why the opponents advocate absurdities like aether-dragging and a moving local gravitational field.

 

You are the one who is in error; swansont is correct.

Well done for correctly interpreting my answer, it was not till I got to bed that I realised it was nonsense. I see why SR and LET are the same for the GPS, but I am not sure about particle collisions.

 

If 2 protons are going at ½ lightspeed, their combined energies would be 2 times (sqrt 4/3 minus 1) = 0.309 times the mass of a proton. So if they were to collide and end up stationary, they could theoretically emit that in the form of photons at right angles to the impact.

 

If a proton was going at 4/5, its mass would be 5/3, thus its momentum 4/3. If it collides with a stationary proton, and they end up moving through space at the same speed, and the emitted photons also remain in line; then by the conservation of momentum: 4/3 = (5/3 + 1)V. so V = ½. The energy of 2 protons going at ½ is 0.309, the original energy was 2/3, therefore .358 could be emitted in photons. Not the same as in the first case?

 

You claimed "The experimental evidence clearly shows that motion is absolute not relative. If you were to fire 2 protons in opposite directions round the LHC both at ½ lightspeed; then repeat the experiment with one going at nearly lightspeed and the other barely moving, the particles produced in the 2 collisions would be very different." The implication of that statement is that the experiment had been done and the outcome had been different particles. In other words, deceptive phrasing at best.

You surely know of many experiments where high energy particles are collided with stationery atomic nuclei to produce exotic particles. You also know this could not happen if the particles and nuclei were heading in opposite directions at ½, so why nitpick?

 

Neither. Heretic implies religion. Sparring partner implies some kind of equivalence. Neither are true. At best, I'd feel bad that you had rejected yet another chance to understand anything of what science is about.

I agree it is not an equal contest. I give your pet theories such a pummelling that the referee has to step in to spare you from further punishment; and then, like Simplicio, you get declared the winner.

[uncool]

If 2 electrons head towards each other, both at ½ lightspeed; then after 1 second, they will be 1 light-second closer. So based on the definition of speed as distance/time, the closing speed must be lightspeed. If you had never been taught relativity, you would agree with that, and say anybody who disagreed was crazy. That is why I say SR is religion, because it involves people believing in nonsensical things, merely because they have been taught to.

And that is why I feel free to call you a liar: because you repeatedly have been shown that it's not just "because they have been taught to"; you have been shown the evidence and the reasoning time and again.

SR, like Newtonian mechanics, allows one to calculate things that would be impractical using LET; but it does not describe a possible universe. LET is simple and intuitive, and since it gives similar results to SR, only somebody who prefers to believe in mysticism would favour SR. Uncool, for all his vices, does at least freely acknowledge the equivalence of SR and LET, presumably because he understands the maths.

More accurately, because I understand that LET has the same involves the Lorentz transformations, which are sufficient for relativity. In other words, LET satisfies the postulates of special relativity, and therefore everything that can be shown in SR is necessarily true in LET. In effect, LET directly implies SR. Honestly, SR doesn't care about the ether, if you can't tell - what SR has done is made the ether unnecessary.

 

While it is true that I understand the math, that isn't the specific reason. It's because I understand the derivations.

The most vociferous proponents and opponents of SR, surely do not understand the maths; that is why the proponents claim all relativity-deniers must be intellectually inferior, and why the opponents advocate absurdities like aether-dragging and a moving local gravitational field.

 

 

Well done for correctly interpreting my answer, it was not till I got to bed that I realised it was nonsense. I see why SR and LET are the same for the GPS, but I am not sure about particle collisions.

 

If 2 protons are going at ½ lightspeed, their combined energies would be 2 times (sqrt 4/3 minus 1) = 0.309 times the mass of a proton. So if they were to collide and end up stationary, they could theoretically emit that in the form of photons at right angles to the impact.

Specifically, emitting something (probably a bunch of particles) that has a total of 0.309 times the mass of a proton in energy and 0 momentum relative to this frame.

If a proton was going at 4/5, its mass would be 5/3, thus its momentum 4/3. If it collides with a stationary proton, and they end up moving through space at the same speed, and the emitted photons also remain in line; then by the conservation of momentum: 4/3 = (5/3 + 1)V.

Where are you getting this equation? p = mv? Remember, m depends on v. You can't simply use the original masses.

 

You've also forgotten the momentum that the other particles are carrying with them. Energy in one frame means momentum in other frames.

so V = ½. The energy of 2 protons going at ½ is 0.309, the original energy was 2/3, therefore .358 could be emitted in photons. Not the same as in the first case?

Given how much you've forgotten or misunderstood, not surprising.

 

Using the convention you've chosen, we'll let proton masses and the speed of light be 1 (there is some system of units for which this is true, so we can just work within that system). Then in the original frame, .309 was emitted from the reaction at speed 0. For the sake of ease of writing, I'll assume it's one particle; then this particle has rest mass of .309. In our new frame, then, this particle has velocity 1/2, and therefore momentum .179 and energy .359. Our original protons do, of course, end up with velocity 1/2, which does (as you said) end up with .359 energy missing. Note, however, that their total momentum is 1.157, rather than the original momentum of 4/3 - and the missing momentum there is .179.

 

So in both cases, the energy that has been extracted is in the form of this particle (or system of particles), which has rest mass .309. The rest mass is all of the energy that can be extracted from the system without having something else massive there to "bleed the momentum" of the particle (or system of particles), i.e. to act as a momentum sink; I apologize if the phrasing I used earlier confused you.

 

You surely know of many experiments where high energy particles are collided with stationery atomic nuclei to produce exotic particles. You also know this could not happen if the particles and nuclei were heading in opposite directions at ½, so why nitpick?

This isn't a nitpick. Your claim was pretty clear in stating that you had evidence that what relativity predicts was false.

 

I agree it is not an equal contest. I give your pet theories such a pummelling

And again, this is why I feel free to call you a liar.

=Uncool-

Edited October 13, 2012 by uncool

[swansont]

If 2 electrons head towards each other, both at ½ lightspeed; then after 1 second, they will be 1 light-second closer. So based on the definition of speed as distance/time, the closing speed must be lightspeed. If you had never been taught relativity, you would agree with that, and say anybody who disagreed was crazy. That is why I say SR is religion, because it involves people believing in nonsensical things, merely because they have been taught to.

On the contrary, it is the extrapolation of Newtonian calculations at high speeds that is nonsensical and done only because people were taught to do it. When you do an actual experiment, you find that SR is correct. And in science, that's what matters — models that agree with nature. GPS works. Particle accelerators are designed by applying relativity, and they work. The model agrees with nature.

 

It is religion when you decide a world view and then cling to it, ignoring contradictory data. If the problem is just that you don't understand SR, that's too bad, but it doesn't make it a religion. There is no caveat that science must get your approval.

[A-wal]

Read this: Link removed by moderator

 

If the speed of light is constant then if two objects with different velocities relative to each other are measuring light moving at the same speed relative to both of them then time and space have to be relative, not a fixed background. Now leave special relativity alone! What's it ever done to you? If you want a theory of relativity to bash then have a go at general relativity. It superceded special relativity, by far the most beautiful thing I've ever seen in my life. It must be punished! (:

Edited October 14, 2012 by Phi for All
Advertising another thread - link removed

[newts]

Specifically, emitting something (probably a bunch of particles) that has a total of 0.309 times the mass of a proton in energy and 0 momentum relative to this frame.

 

Where are you getting this equation? p = mv? Remember, m depends on v. You can't simply use the original masses.

 

You've also forgotten the momentum that the other particles are carrying with them. Energy in one frame means momentum in other frames.

 

Given how much you've forgotten or misunderstood, not surprising.

 

Using the convention you've chosen, we'll let proton masses and the speed of light be 1 (there is some system of units for which this is true, so we can just work within that system). Then in the original frame, .309 was emitted from the reaction at speed 0. For the sake of ease of writing, I'll assume it's one particle; then this particle has rest mass of .309. In our new frame, then, this particle has velocity 1/2, and therefore momentum .179 and energy .359. Our original protons do, of course, end up with velocity 1/2, which does (as you said) end up with .359 energy missing. Note, however, that their total momentum is 1.157, rather than the original momentum of 4/3 - and the missing momentum there is .179.

 

So in both cases, the energy that has been extracted is in the form of this particle (or system of particles), which has rest mass .309. The rest mass is all of the energy that can be extracted from the system without having something else massive there to "bleed the momentum" of the particle (or system of particles), i.e. to act as a momentum sink; I apologize if the phrasing I used earlier confused you.

Instead of talking about the energy being emitted as photons; I could have assumed that the collision between the 2 protons going at ½, produced a particle of mass 0.309. In the collision between the proton moving at 4/5 and the stationary proton; if a particle of rest mass 0.309 were produced, and were to end up moving alongside the 2 protons at speed ½, then it would have a total mass/energy of 0.359. So the same particle could be produced in each collision, but the energy emitted would be different.

 

So in the first collision, a relativity-believer would measure the speed of both protons approaching each other, as ½ lightspeed; then decide to believe that the closing speed is actually 4/5, because the collision would produce the same particles as a proton moving at 4/5 colliding with a stationary proton. But the reason for such shenanigans, is that the concept of relative motion is invalid; because the speed of light is constant relative to the aether and not constant relative to anything else.

 

On the contrary, it is the extrapolation of Newtonian calculations at high speeds that is nonsensical and done only because people were taught to do it. When you do an actual experiment, you find that SR is correct. And in science, that's what matters — models that agree with nature. GPS works. Particle accelerators are designed by applying relativity, and they work. The model agrees with nature.

Newtonian mechanics, like SR, does not make sense as a description of the universe at any speed. LET makes perfect sense, and agrees with experiment. That is why proper scientists who want to make sense of the universe favour LET; whilst only the fantasists, who prefer to think the universe is mystical and mysterious, choose to believe in SR.

[uncool]

Instead of talking about the energy being emitted as photons; I could have assumed that the collision between the 2 protons going at ½, produced a particle of mass 0.309. In the collision between the proton moving at 4/5 and the stationary proton; if a particle of rest mass 0.309 were produced, and were to end up moving alongside the 2 protons at speed ½, then it would have a total mass/energy of 0.359. So the same particle could be produced in each collision, but the energy emitted would be different.

Yup. But the magnitude of the 4-momentum of the emitted material (which is the same as the extractable energy) would be the same. Which is what relativity predicts.

 

So in the first collision, a relativity-believer would measure the speed of both protons approaching each other, as ½ lightspeed; then decide to believe that the closing speed is actually 4/5, because the collision would produce the same particles as a proton moving at 4/5 colliding with a stationary proton. But the reason for such shenanigans, is that the concept of relative motion is invalid; because the speed of light is constant relative to the aether and not constant relative to anything else.

Congratulations; you're going in circles.

 

What you have managed to demonstrate is that you still have no idea what relativity says, or how it works. Nor do you even know what LET says, because everything that was true about the protons going at 1/2 c remains true in LET. When you want to criticize a theory, or claim that another theory is correct, at least try to have some basic understanding of what the theories say.

Newtonian mechanics, like SR, does not make sense as a description of the universe at any speed. LET makes perfect sense, and agrees with experiment. That is why proper scientists who want to make sense of the universe favour LET; whilst only the fantasists, who prefer to think the universe is mystical and mysterious, choose to believe in SR.

Once again:

 

In effect, LET directly implies SR. Honestly, SR doesn't care about the ether, if you can't tell - what SR has done is made the ether unnecessary.

=Uncool-

Edited October 14, 2012 by uncool

[swansont]

 

Newtonian mechanics, like SR, does not make sense as a description of the universe at any speed. LET makes perfect sense, and agrees with experiment. That is why proper scientists who want to make sense of the universe favour LET; whilst only the fantasists, who prefer to think the universe is mystical and mysterious, choose to believe in SR.

SR does not make sense to you, perhaps, but then, there is no requirement that it needs to. It's not a valid objection.

[md65536]

Newtonian mechanics, like SR, does not make sense as a description of the universe at any speed. LET makes perfect sense, and agrees with experiment. That is why proper scientists who want to make sense of the universe favour LET; whilst only the fantasists, who prefer to think the universe is mystical and mysterious, choose to believe in SR.

Do you have a reference for that?

 

http://en.wikipedia.org/wiki/Lorentz_ether_theory says the opposite: "However, in LET the existence of an undetectable ether is assumed and the validity of the relativity principle seems to be only coincidental, which is one reason why SR is commonly preferred over LET."

 

 

The preceding sentence is, "Because of the same mathematical formalism it is not possible to distinguish between LET and SR by experiment." So it is metaphysics to speak of one being real while the other is not. Wouldn't a reasonable scientist let evidence falsify a theory? What does it mean to say that one theory is correct while an equivalent theory, with equivalent evidence, is wrong?

[uncool]

On a side note, swansont:

 

Closing speed means the derivative of the distance between the two objects as measured in a chosen frame, not necessarily as measured in the frame of either object. This means that by definition, the closing speed between the two objects still is the speed of light (since the chosen frame is the one where they are both moving at c/2). This doesn't change any of what physically happens; just a note on the definition of "closing speed".

=Uncool-

[swansont]

On a side note, swansont:

 

Closing speed means the derivative of the distance between the two objects as measured in a chosen frame, not necessarily as measured in the frame of either object. This means that by definition, the closing speed between the two objects still is the speed of light (since the chosen frame is the one where they are both moving at c/2). This doesn't change any of what physically happens; just a note on the definition of "closing speed".

=Uncool-

I specifically mentioned the frame in which the speed was being measured was that of the particle.

[newts]

What you have managed to demonstrate is that you still have no idea what relativity says, or how it works. Nor do you even know what LET says, because everything that was true about the protons going at 1/2 c remains true in LET. When you want to criticize a theory, or claim that another theory is correct, at least try to have some basic understanding of what the theories say.

All my calculations were done on the basis of the earth being stationary in the aether. I did not state that, because I thought if I had done, you would likely have refused to discuss the maths. I do not claim to understand SR, indeed I think it is something that cannot be understood, just something to be believed in.

 

Do you have a reference for that?

 

http://en.wikipedia....tz_ether_theory says the opposite: "However, in LET the existence of an undetectable ether is assumed and the validity of the relativity principle seems to be only coincidental, which is one reason why SR is commonly preferred over LET."

 

 

The preceding sentence is, "Because of the same mathematical formalism it is not possible to distinguish between LET and SR by experiment." So it is metaphysics to speak of one being real while the other is not. Wouldn't a reasonable scientist let evidence falsify a theory? What does it mean to say that one theory is correct while an equivalent theory, with equivalent evidence, is wrong?

One major reason why relativity principle seems coincidental; is that physicists have spent the last 100 years assuming it is a gift from God, rather than trying to derive it from the aether model.

 

I favour LET because I have a mechanical model of the universe, based on compressible spheres, which requires that the speed of light be constant relative to this aether. It is really the relativists who muddy the water, by continually saying how Einstein changed our perception of the universe, by showing that that Newtonian concepts of space and time are wrong; when in actual fact LET accurately describes the universe based on absolute space and speed. LET is not practical for calculating things, so SR certainly has a use. But the relativity-believers are still much to blame by trying to sweep the aether under the carpet, by indoctrinating people into believing that SR is the one true faith.

 

I specifically mentioned the frame in which the speed was being measured was that of the particle.

The resident high priests of relativity, are now arguing over how many angels can dance on the head of a pin. Which is reminiscent of the Dingle affair, where the great minds of relativity argued not about the result of an experiment (the twins paradox), but rather about what SR should predict the result to be.

[uncool]

All my calculations were done on the basis of the earth being stationary in the aether.

And yet you came to conclusions that were wrong even within LET, which you constantly proclaim to be right.

I did not state that, because I thought if I had done, you would likely have refused to discuss the maths.

I'd have pointed out that I asked you to calculate things with respect to SR and that you therefore would have been answering an irrelevant question.

I do not claim to understand SR, indeed I think it is something that cannot be understood, just something to be believed in.

And as I have asked you before, is there anything which would falsify your belief? Because you seem to have a religious attachment to your belief that SR is incomprehensible.

 

You claim to understand LET. If you did, then you'd understand SR. As you have made clear, you don't understand either, and don't plan on understanding either.

=Uncool-

[swansont]

I do not claim to understand SR, indeed I think it is something that cannot be understood, just something to be believed in.

 

 

One major reason why relativity principle seems coincidental; is that physicists have spent the last 100 years assuming it is a gift from God, rather than trying to derive it from the aether model.

 

I favour LET because I have a mechanical model of the universe, based on compressible spheres, which requires that the speed of light be constant relative to this aether. It is really the relativists who muddy the water, by continually saying how Einstein changed our perception of the universe, by showing that that Newtonian concepts of space and time are wrong; when in actual fact LET accurately describes the universe based on absolute space and speed. LET is not practical for calculating things, so SR certainly has a use. But the relativity-believers are still much to blame by trying to sweep the aether under the carpet, by indoctrinating people into believing that SR is the one true faith.

 

 

The resident high priests of relativity, are now arguing over how many angels can dance on the head of a pin. Which is reminiscent of the Dingle affair, where the great minds of relativity argued not about the result of an experiment (the twins paradox), but rather about what SR should predict the result to be.

You don't understand it , yet you know it to be wrong. THAT, sir, is religion.

[md65536]

One major reason why relativity principle seems coincidental; is that physicists have spent the last 100 years assuming it is a gift from God, rather than trying to derive it from the aether model.

False.

 

You don't understand it , yet you know it to be wrong. THAT, sir, is religion.

It could also be straight lying, or delusion, or ignorance especially regarding how logical reasoning works, which can all occur independent of or in combination with religion.