The Relativity of Simultaneity

[Motor Daddy]

So, if light expands as a sphere on earth, you have two choices:
1. You can proclaim that the earth has a zero velocity
OR
2. You can admit you are wrong

Do you agree to that idea?

What do you mean a light sphere expands as a sphere on earth?

Are you implying that the sphere expands as it travels with the earth?

 

[Neddy Bate]

I haven't done the math but I presume you are using my method so yes, I agree.

Okay, that will work. We know the cube is 1.00 lightsecond long along each edge, right? We can measure this with a metal measuring rod. So the speed of light inside the cube is measured to be:

c_forward = 0.50 / 2.50 = 0.20c
c_backward = 0.50 / 0.28 = 1.79c

Do you agree?

 

[Motor Daddy]

Okay, that will work. We know the cube is 1.00 lightsecond long along each edge, right? We can measure this with a metal measuring rod. So the speed of light inside the cube is measured to be:

c_forward = 0.50 / 2.50 = 0.20c
c_backward = 0.50 / 0.28 = 1.79c

Do you agree?

Again, I haven't done the math, but will assume for the moment your numbers are correct, so yes, I agree.

I will also note those measured speeds of light are along the x axis. If you measured the speed of light along the y and z axis, the speed of light will be measured to be different. I will also note that even though the y and z component velocities are zero, the times will not be .5 seconds to the y and z receivers.

 

[Neddy Bate]

What do you mean a light sphere expands as a sphere on earth?

Are you implying that the sphere expands as it travels with the earth?

Yes, experiments show that light expands as a sphere. That follows from the fact that light speed is always measured to be c in all directions.

 

[Neddy Bate]

Again, I haven't done the math, but will assume for the moment your numbers are correct, so yes, I agree.

My point is that light would be measured at various speeds such as:
c_forward = 0.20c
c_backward = 1.79c

if your theory were correct. But it is always measured to be 1.00c in reality. So now you need to add something to your theory to explain why this is the case. For example, you were saying that the synch method is different. So, perhaps you can show how using the wrong synch method would make the speeds come out to be 1.00c.

 

[Motor Daddy]

Yes, experiments show that light expands as a sphere. That follows from the fact that light speed is always measured to be c in all directions.

Good, the light sphere expands at c in all directions from the point in space it is emitted. But you say that as the sphere is expanding, it is also traveling along with the earth?

 

[Neddy Bate]

Agreed. That is exactly how I understand the SR position on this.

What I'm replying with is that you can conceive of the light sphere in one frame expanding into space and that same light sphere being encountered out there in space by receptors. With the knowledge of the duration of the expansion of the light sphere on a clock as if the clock was in the rest frame, then the distance from the point of emission to the receptor can be calculated. It is a thought experiment after all.

Start with the idea that light expands as a sphere in all frames. Now it is easy to see how receptors in the cube could be moving away from the light or toward the light. That does not violate SR, because you are just looking at it from a different frame. But when you are inside the cube, you should find that light reach the receptors at the same time, because the light is expanding as a sphere in the cube frame.

 

[Motor Daddy]

My point is that light would be measured at various speeds such as:
c_forward = 0.20c
c_backward = 1.79c

if your theory were correct. But it is always measured to be 1.00c in reality. So now you need to add something to your theory to explain why this is the case. For example, you were saying that the synch method is different. So, perhaps you can show how using the wrong synch method would make the speeds come out to be 1.00c.

You say it is always measured to be 1 c in reality. You provided a link previously and I showed you were the error was in that link. You overlooked it, and now you bring up the same point. What is your response to the error in the link you provided? You ignored my response, and now you pretend the issue is still valid.

 

[quantum_wave]

Start with the idea that light expands as a sphere in all frames. Now it is easy to see how receptors in the cube could be moving away from the light or toward the light. That does not violate SR, because you are just looking at it from a different frame. But when you are inside the cube, you should find that light reach the receptors at the same time, because the light is expanding as a sphere in the cube frame.

Lol, we've been there. I'll let you and MD finish your current conversation.

 

[Neddy Bate]

But you say that as the sphere is expanding, it is also traveling along with the earth?

Well, I don't know if the light is traveling along with the earth, but I do know that we never find anything like this:
c_forward = 0.20c
c_backward = 1.79c

Instead we always find this:
c_forward = 1.00c
c_backward = 1.00c
c_sideways = 1.00c

So either the light is traveling with the earth, or the earth has zero velocity, or something. One thing that is certainly not happening is this:

Good, the light sphere expands at c in all directions from the point in space it is emitted.

That is not what they mean when they say the speed of light is constant. They mean this:
c_forward = 1.00c
c_backward = 1.00c
c_sideways = 1.00c

 

[Neddy Bate]

Lol, we've been there.

So you understand that there is nothing special about watching the receptors move away from or toward the light? That is fully explained by SR?

 

[Neddy Bate]

You say it is always measured to be 1 c in reality. You provided a link previously and I showed you were the error was in that link. You overlooked it, and now you bring up the same point. What is your response to the error in the link you provided? You ignored my response, and now you pretend the issue is still valid.

Sorry, I did not see you point out any error in any link. I will go back and search.

 

[quantum_wave]

So you understand that there is nothing special about watching the receptors move away from or toward the light? That is fully explained by SR?

Sure, if what you are saying is that all of the calculations of SR are mathematically sound and you are saying that the speed of the receptors relative to the point of emission can be calculated by knowing the duration between the flash and the reception given the described motion of the receptors. But please, let's come back to this after MD and you resolve everything .

 

[Neddy Bate]

You say it is always measured to be 1 c in reality. You provided a link previously and I showed you were the error was in that link. You overlooked it, and now you bring up the same point. What is your response to the error in the link you provided? You ignored my response, and now you pretend the issue is still valid.

OK, I didn't find anyplace where you showed me where there was an error. If you can tell me the post number or something, I'd be happy to look into it. Meanwhile, I know you have claimed these things are problematic:

1. The distance is measured wrong. They measure distance with light instead of metal measuring bars.

The reason this doesn't hold water is that the metre was originally a metal bar made out of 90% platinum. The only reason they were able to switch to using light was because the light always traveled this exact length in 1/299792458 seconds. So obviously they did use a metal bar.


2. The synch method is wrong.
What method do you think they use, and how do you think it can be improved?

 

[Motor Daddy]

Well, I don't know if the light is traveling along with the earth, but I do know that we never find anything like this:
c_forward = 0.20c
c_backward = 1.79c

Instead we always find this:
c_forward = 1.00c
c_backward = 1.00c
c_sideways = 1.00c

Again, if a cube is in space, and you say regardless of the motion of the cube the light always hits all the walls simultaneously, then what you are saying is that the light sphere is expanding in the cube while it is traveling with the cube.

So for instance, say a train car is a cube traveling down the tracks at 60 MPH. You say the light hits all the receivers in the same time in the cube. Now redo the test, but this time increase the speed of the train to 200 MPH. Again, you say the light sphere expands and hits all the receivers in the same amount of time.

So what you are saying is that the light sphere expands as it travels along with the train. That is simply impossible, Ned.

 

[Neddy Bate]

Sure, if what you are saying is that all of the calculations of SR are mathematically sound and you are saying that the speed of the receptors relative to the point of emission can be calculated by knowing the duration between the flash and the reception.

If you are in a reference frame where you see the cube moving relative to the expanding sphere of light, you can easily calculate the speed of the cube. All you have to do is use your own clocks to measure the light transmission times, and use your own measuring rods to measure the size of the cube. Then you can calculate how fast the cube is moving. You don't even need to know SR. This is what MD has been doing.

But if you are in the reference frame of the cube, the cube is not moving. The expanding sphere of light is still a sphere, expanding relative to the center of the cube. Now, if you use your own clocks to measure time, and you use your own measuring rods to measure distance, you can't figure out how fast the cube is moving. All experiments tell you that the cube is at rest.

Is that how you understand it?

But please, let's come back to this after MD and you resolve everything .

I don't mind carrying on two conversations at once. I drank a diet cola, and now I am all sped up on caffeine.

 

[Neddy Bate]

Again, if a cube is in space, and you say regardless of the motion of the cube the light always hits all the walls simultaneously, then what you are saying is that the light sphere is expanding in the cube while it is traveling with the cube.

You can't really say the light travels with the cube, because someone not moving with the cube also sees the light as an expanding sphere. So the light would have to be traveling with everyone, and that doesn't make much sense.

So for instance, say a train car is a cube traveling down the tracks at 60 MPH. You say the light hits all the receivers in the same time in the cube. Now redo the test, but this time increase the speed of the train to 200 MPH. Again, you say the light sphere expands and hits all the receivers in the same amount of time.

That is correct!

So what you are saying is that the light sphere expands as it travels along with the train. That is simply impossible, Ned.

As explained above, I wouldn't really say the light travels with the train. The light expands as a sphere in all reference frames. I know it's strange, but it is not self-contradicting. If you studied relativity for awhile, you'd understand it.

 

[Motor Daddy]

As explained above, I wouldn't really say the light travels with the train. The light expands as a sphere in all reference frames. I know it's strange, but it is not self-contradicting. If you studied relativity for awhile, you'd understand it.

Neither would I say the sphere travels with the train, but you have to concur to that statement in order for the light to always be measured at c in the train, regardless of the velocity of the train.

So, you either agree that the sphere expands as it travels with the train, or you agree that the sphere expands independent of the train. Which is it. Don't pretend that if I studied relativity I would understand it. If you pretend to understand relativity, explain your point. Which is it??

Sorry, I have to go now. I'll be back...

 

[Neddy Bate]

Neither would I say the sphere travels with the train, but you have to concur to that statement in order for the light to always be measured at c in the train, regardless of the velocity of the train.

So, you either agree that the sphere expands as it travels with the train, or you agree that the sphere expands independent of the train. Which is it. Don't pretend that if I studied relativity I would understand it. If you pretend to understand relativity, explain your point. Which is it??

The light expands as a sphere in all reference frames. So, according to the cube frame, the light sphere reaches all the walls simultaneously. Yet, according to the "embankment" frame, the light also expands as a sphere, so it behaves the way your theory says it would. The light hits the rear wall of the cube first, because that wall is moving toward the light sphere. The light does not hit the front wall of the cube until later. Hence the name of this thread, "The Relativity of Simultaneity". (Events which are simultaneous in one frame are not necessarily simultaneous in some other frame.)

 

[quantum_wave]

If you are in a reference frame where you see the cube moving relative to the expanding sphere of light, you can easily calculate the speed of the cube. All you have to do is use your own clocks to measure the light transmission times, and use your own measuring rods to measure the size of the cube. Then you can calculate how fast the cube is moving. You don't even need to know SR. This is what MD has been doing.

But if you are in the reference frame of the cube, the cube is not moving. The expanding sphere of light is still a sphere, expanding relative to the center of the cube. Now, if you use your own clocks to measure time, and you use your own measuring rods to measure distance, you can't figure out how fast the cube is moving. All experiments tell you that the cube is at rest.

Is that how you understand it?

Yes, the first paragraph is MD and the second is SR.

I don't mind carrying on two conversations at once. I drank a diet cola, and now I am all sped up on caffeine.

I'm behind on my espresso, lol.

Now what we have to do is test at relativistic speeds relative to a cooincident point of emission in space to see if the light sphere moves with the source or from a point of emission.