Michelson–Morley experiment using objects with mass?

[guss]

Has anyone tried to do something similar to the http://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment" using an object with mass (protons probably being the best bet)? In theory, we could determine our speed relative to the "ether", could we not?

You could have three tubes, one for each dimension, and accelerate an object or set of particles for the right amount of time that would make them achieve the speed of light, then measure their speed and figure out your speed relative to the ether.

Would this work?

If it did work (or not work), and yielded results, what would the results tell us?

 

[soothsayer]

Particles with mass can't attain the speed of light.

 

[ghwellsjr]

Why do you think massive particles would be any better than light? We already know what speed light travels at and we still cannot determine how long it takes for light to travel a given distance one-way. All we can know is the round-trip time it takes to go a particular distance to a mirror and come back. We cannot know how long each leg of the trip takes. Using particles with mass would be much more complicated and wouldn't provide any additional information.

 

[atyy]

See eg. section 5.7 for a limit on the sidereal variation of a muon property: http://arxiv.org/abs/grqc/0502097

Another test of Lorentz invariance using massive particles: http://arxiv.org/abs/0902.1756

A failure of Lorentz invariance would tell us a lot! At present it has passed all tests (and there are very many indirect ones, basically all accelerator experiments thus far are consistent with the standard model of particle physics, which assumes Lorentz invariance).

 

[grav-universe]

Massive particles will also travel away and back at perpendicular angles over the same distance in the same time the same way as light does if the particles are ejected in the same way for both angles, but that is not all the M-M experiment is based upon. It was preceded by experiments with aberration, where light emitted from different moving sources will travel the same one way distance in the same direction over the same time. Classical ballistic theory says that the speed of particles should vary with the motion of the source, but no experiments with aberration showed any indication of this, so popular theory then became that light travels not ballistically as particles do, but with a constant speed in the same direction as a wave relative to an aether medium, so it was thought there must be some preferred frame for the aether. That was what the M-M experiment set out to determine, but that experiment failed to show any indication of an absolute aether either. So finally, we have SR and LET, along with quantum mechanics, to explain the motions of particles.

 

[MikeLizzi]

... and we still cannot determine how long it takes for light to travel a given distance one-way...

What makes you think that? See the link below. Roemer's measurement ws not very accurate but that doesn't mean a very accurate measurement cannot be made.

http://www.amnh.org/education/resources/rfl/web/essaybooks/cosmic/p_roemer.html

 

[MikeLizzi]

Has anyone tried to do something similar to the http://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment" using an object with mass (protons probably being the best bet)? In theory, we could determine our speed relative to the "ether", could we not?

You could have three tubes, one for each dimension, and accelerate an object or set of particles for the right amount of time that would make them achieve the speed of light, then measure their speed and figure out your speed relative to the ether.

Would this work?

If it did work (or not work), and yielded results, what would the results tell us?

The Michelson-Morley experiment did not measure the speed of light.

 

[ghwellsjr]

... and we still cannot determine how long it takes for light to travel a given distance one-way...

What makes you think that? See the link below. Roemer's measurement ws not very accurate but that doesn't mean a very accurate measurement cannot be made.

http://www.amnh.org/education/resources/rfl/web/essaybooks/cosmic/p_roemer.html

If we could measure the one-way speed of light, we wouldn't need Einstein's second postulate which defines the one-way speed of light to be exactly one half of the measured round trip speed of light.

Or to put it another way, if we could measure the one-way speed of light, we could identify an absolute ether rest frame and Special Relativity would be out the window.

All so-called measurements of the one-way speed of light are based on an unavoidable assumption of synchronizing remote clocks and however you do that determines the result of the "measurement".

 

[MikeLizzi]

If we could measure the one-way speed of light, we wouldn't need Einstein's second postulate which defines the one-way speed of light to be exactly one half of the measured round trip speed of light.

I have 11 textbooks on relativity. I cannot find a single reference to this postulate. Can you provide one?

 

[ghwellsjr]

It's in Einstein's 1905 paper:

http://www.fourmilab.ch/etexts/einstein/specrel/www/

 

[ghwellsjr]

The Michelson-Morley experiment did not measure the speed of light.

But it did measure the difference in the round-trip speed of light in different directions and found it to be a constant in all directions.

 

[MikeLizzi]

It's in Einstein's 1905 paper:

http://www.fourmilab.ch/etexts/einstein/specrel/www/

I'm sorry I don't see a reference to the two way speed of light. All I see is a reference to the speed of light. Can you provide a line number or quote?

 

[ghwellsjr]

I'm sorry I don't see a reference to the two way speed of light. All I see is a reference to the speed of light. Can you provide a line number or quote?

This what the entire section 1 is all about.

 

[MikeLizzi]

This what the entire section 1 is all about.

Not really. I don't like referening wikipedia because they are sometime wrong. But in this case they have it right. What is referenced below is repeated all over the internet and in my textbooks.

http://en.wikipedia.org/wiki/Postulates_of_special_relativity

"2. Second postulate (invariance of c)
As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body."

There is no requirement in the second postulate that the measurement be two way. You are referencing a methodology Einstein used to describe how to synchronize clocks.

 

[guss]

Why do you think massive particles would be any better than light? We already know what speed light travels at and we still cannot determine how long it takes for light to travel a given distance one-way. All we can know is the round-trip time it takes to go a particular distance to a mirror and come back. We cannot know how long each leg of the trip takes. Using particles with mass would be much more complicated and wouldn't provide any additional information.

The velocity of light relative to the ether is not necessarily equal to what we know as the maximum velocity of light in a vacuum, for many obvious reasons. But can't the velocity of a certain light be faster, because what if the source of the light (eg. the earth) is moving toward where the light is moving? Isn't this why the Michelson-Morley experiment failed?

But I thought the same principle cannot be applied to massive particles or objects. The velocity of, say, the ground that a train that can travel at the speed of light is traveling on must be taken into account if you wanted to find the velocity of the train. Although maybe I'm misunderstanding this.

Note that I don't want to do something exactly like the Michelson-Morley experiment but with mass, just something similar.

 

[ghwellsjr]

Not really. I don't like referening wikipedia because they are sometime wrong. But in this case they have it right. What is referenced below is repeated all over the internet and in my textbooks.

http://en.wikipedia.org/wiki/Postulates_of_special_relativity

"2. Second postulate (invariance of c)
As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body."

There is no requirement in the second postulate that the measurement be two way. You are referencing a methodology Einstein used to describe how to synchronize clocks.

The second postulate is not about the two-way speed of light and it is not about a measurement of anything. It's about the one-way speed of light which cannot be measured, that's why it is a postulate of Special Relativity.

Please read section 1 of Einstein's paper. He very clearly states that it is impossible to measure or know the one-way speed of light. He very clearly states that we can only arbitrarily define how the times of the two one-way trips add up to the time of the round-trip and he uses the arbitrary definition that they are equal to establish his theory of Special Relativity.

Do you want me to give you a commentary on section 1 of Einstein's paper? Is it that you understand it but you don't agree with it or is it that you don't understand it?

 

[Dale]

ghwellsjr is correct. The second postulate refers to the one-way speed of light, which is unmeasurable in principle since it depends entirely on your synchronization convention.

The two-way speed of light does not depend on the synchronization convention, it is measurable, and has been measured to be isotropic and frame-invariant.

 

[ghwellsjr]

The velocity of light relative to the ether is not necessarily equal to what we know as the maximum velocity of light in a vacuum, for many obvious reasons. But can't the velocity of a certain light be faster, because what if the source of the light (eg. the earth) is moving toward where the light is moving? Isn't this why the Michelson-Morley experiment failed?

But I thought the same principle cannot be applied to massive particles or objects. The velocity of, say, the ground that a train that can travel at the speed of light is traveling on must be taken into account if you wanted to find the velocity of the train. Although maybe I'm misunderstanding this.

Note that I don't want to do something exactly like the Michelson-Morley experiment but with mass, just something similar.

You have a lot of interesting comments here but I'm wondering where you got these ideas from. For example:

"The velocity of light relative to the ether is not necessarily equal to what we know as the maximum velocity of light in a vacuum, for many obvious reasons."

The velocity of light is not relative to anyone thing, like an ether, and it is an exact constant value, so I have no idea what you are trying to say here or what it is that is obvious to you. It's not obvious to me.

Another example:

"But can't the velocity of a certain light be faster, because what if the source of the light (eg. the earth) is moving toward where the light is moving?"

What do you mean by "a certain light"? It doesn't matter what the relative motion of the source of light is or "where" it is moving, anybody who measures any light will always get the same constant value.

"Isn't this why the Michelson-Morley experiment failed?"

I'm not sure what your reasoning is but MMX could not measure an ether wind for the "reason" I just stated, which is that anybody who measures any light will always get the same constant value. It was "explained" by Lorentz and others by presumming that the length of their measuring apparatus shrunk in the direction of the ether wind by just the right amount so that it took the same time for the light to make its round trip along the direction of motion as it did to make its round trip at right angles to the direction of motion.

"But I thought the same principle cannot be applied to massive particles or objects. The velocity of, say, the ground that a train that can travel at the speed of light is traveling on must be taken into account if you wanted to find the velocity of the train. Although maybe I'm misunderstanding this."

Not sure what that same principle is, but you have a lot of misunderstandings here. First, no massive object, certainly not a train, can travel at the speed of light. Second, velocities have to be measured relative to some arbitrary reference frame. You could use the ground that a train is traveling on as your reference frame to analyze what is happening with the train and with the ground OR you could use the train itself as your reference frame to analyze what is happening with the train and with the ground. This is what Special Relativity is all about.

So it is very difficult to explain why your idea won't work because it is based on so many misunderstandings. I would suggest that you go through a lot of the threads on this forum and try to increase your understanding of how nature works and how Special Relativity is used to explain and analyze how nature works and then you will see that there is no hope of coming up with an experiment that could ever identify an absolute ether rest frame.

 

[guss]

Yeah sorry, the way I worded things were confusing.

So, let's say we are on a planet-like object that is not moving at all in an otherwise completely blank universe similar to ours. Now that that's out of the way, let's add a basic "spin" to the planet.

Let's say that on that planet, we have a train that can get to 99.999% of the speed of light on it's own, not counting the spin of the planet. The track happens to be around the planet in such a way that it matches up exactly with the "spin" of it. You can picture it like the track is on the equator.

If the train leaves the station, and begins heading in the direction the "planet" is "spinning" towards, the train will never be able to reach the speed it would be able to reach relative to the ground if the planet was not spinning. If the train was traveling in the opposite direction, against the spin of the planet, it would be able to exceed the speed of light, or at least travel faster than it normally could, relative to the ground because the rotation of the planet contributes to its total velocity.

Now let's say we shown a light down the track, and for the sake of this example let's say the light did not go off into space, but was able to curve around the planet the right amount so it would end up back at the source. Now, it wouldn't matter which way you shown the light down the track, because we are using a non-massive object. The speed of the light would always be the same relative to the ground.

That's where my ideas are coming from. Or am I wrong with my facts above (which I very well could be)?

 

[ghwellsjr]

Guss, you are still exhibiting so many misunderstandings, not the least of which is the relative addition of velocities. I don't want to go through the details of this new scenario (it's very time-consumming) but rather let me repeat my previous admonition to you:

So it is very difficult to explain why your idea won't work because it is based on so many misunderstandings. I would suggest that you go through a lot of the threads on this forum and try to increase your understanding of how nature works and how Special Relativity is used to explain and analyze how nature works and then you will see that there is no hope of coming up with an experiment that could ever identify an absolute ether rest frame.

 

[MikeLizzi]

ghwellsjr is correct. The second postulate refers to the one-way speed of light, which is unmeasurable in principle since it depends entirely on your synchronization convention.

The two-way speed of light does not depend on the synchronization convention, it is measurable, and has been measured to be isotropic and frame-invariant.

I agree. I was objecting to the inference that the second postulate was about the two-way speed of light. Are we all in agreement that it is about the one-way speed?

 

[Dale]

I think so. If ghwellsjr asserted that the second postulate was about the two-way speed of light then I must have missed it. I suspect a simple miscommunication.

 

[guss]

Alright then, thanks guys.

 

[ghwellsjr]

I agree. I was objecting to the inference that the second postulate was about the two-way speed of light. Are we all in agreement that it is about the one-way speed?

I think so. If ghwellsjr asserted that the second postulate was about the two-way speed of light then I must have missed it. I suspect a simple miscommunication.

Huh? Mike, I never said any such thing. Show me where I did.

 

[MikeLizzi]

Huh? Mike, I never said any such thing. Show me where I did.

I was referring to you posting quoted below

"If we could measure the one-way speed of light, we wouldn't need Einstein's second postulate which defines the one-way speed of light to be exactly one half of the measured round trip speed of light."

Perhaps I misunderstood.

 

[ghwellsjr]

I was referring to you posting quoted below

"If we could measure the one-way speed of light, we wouldn't need Einstein's second postulate which defines the one-way speed of light to be exactly one half of the measured round trip speed of light."

Perhaps I misunderstood.

OK, I see the problem now. I should have said:

Einstein's second postulate defines the time for the one-way transit of light to be exactly one half of the measured time for the round trip of light.

Thanks for catching this and I apologize for the confusion it created.