# Thread: The Relativity of Simultaneity

1. Originally Posted by quantum_wave
Let me test my understand here, MD. You have this box in space and it is in motion relative to a fixed point in space somewhere distant. You transmit light from the center of the box and you can determine the motion of the box by the readings you get of the speed of light at the receivers.

Motion is therefore in the direction of the shortest time recorded by the receivers. This is all in line with your postulate, right.
You got it!

2. Originally Posted by Neddy Bate
Only in your imagination can light take 0.65 seconds to travel 0.50 lightseconds. Because that would mean the speed of light relative to the cube is 0.50/0.65=0.77c in that one direction. That never happens in reality.

In reality, the light would only take 0.50 seconds to travel 0.50 light seconds. That is how the speed of light relative to the cube is measured to be 0.50/0.50=1.00c in all directions. That is reality.

If we entertain your imagination, we can calculate the absolute speed of the cube using the equations that you and I worked on a long time ago. But considering that "GPS" works on earth, I think it is perfectly natural to assume that "CPS" works in the cube. That means your equations are not matching reality. I'm sorry to break this to you.
In reality, objects can and do have motion in space. Only in Einstein's fantasy world does everyone get to assume to be at rest.

The only way it takes .5 seconds for light to get to all the receivers, simultaneously, is if the cube has an absolute zero velocity. If the cube has a velocity, it is impossible for light to arrive at each receiver simultaneously.

Furthermore, if the cube has a velocity in space in the x direction, the time it takes light to reach the y and the z receivers is different, even though they have zero component velocities.

Tell you what, Neddy Bate, you live in Einstein's fantasy world and keep thinking everything else in the universe is moving, and you are the only one not moving, and I'll live in my world, where all object are in motion in space!!!

3. Originally Posted by quantum_wave
Let me test my understand here, MD. You have this box in space and it is in motion relative to a fixed point in space somewhere distant. You transmit light from the center of the box and you can determine the motion of the box by the readings you get of the speed of light at the receivers.

Motion is therefore in the direction of the shortest time recorded by the receivers. This is all in line with your postulate, right.
It is not in motion relative to a fixed point in space somewhere distant it is in motion relative to the point in space the source emits light, which is at the center of the cube.

4. Originally Posted by Neddy Bate
You got it!
I'll just bask in the warmth for awhile, assuming MD confirms.

Oh wait, I stand corrected. The fixed point is at the center of the box, and the light source is in motion along with the box, but an emitted light wave front is assumed to move at the speed of light in all directions from the point of transmission. The motion of the box makes the measurements based on the point back where the light was emitted. In other words the light wave is not moving along with the box, it is expanding spherically from its point of origin and the box is in motion relative to the point that the light was emitted (the point of origin).

5. Originally Posted by Motor Daddy
In reality, objects can and do have motion in space. Only in Einstein's fantasy world does everyone get to assume to be at rest.
We know the earth is not at rest, because it moves relative to the sun. Yet GPS cannot even detect the 29km/s speed of the earth around the sun. Light signals simply do not work the way you think they do.

The only way it takes .5 seconds for light to get to all the receivers, simultaneously, is if the cube has an absolute zero velocity. If the cube has a velocity, it is impossible for light to arrive at each receiver simultaneously.
The signals from GPS satellites all arrive at the nearest point on earth simultaneously, (after factoring our different altitudes of the land). Yet you continue to say that is impossible.

Furthermore, if the cube has a velocity in space in the x direction, the time it takes light to reach the y and the z receivers is different, even though they have zero component velocities.
Yes, you and I determined that would be the case, if your theory were correct. That is why we had to consider the whole 3D scenario.

Tell you what, Neddy Bate, you live in Einstein's fantasy world and keep thinking everything else in the universe is moving, and you are the only one not moving, and I'll live in my world, where all object are in motion in space!!!
I am not the one who says that the earth is at absolute rest, YOU ARE!!! You keep saying that the only way all of the GPS signals can reach earth at the same speed is if the earth is at absolute rest. Yet, that is exactly what happens with GPS. So either your theory is wrong, or the earth is at absolute rest. Relativity says your theory is wrong and the earth is not at absolute rest.

6. I swear this thread should be renamed "blue collar physics".

You may be a hillbilly physicist if you think advanced math is long division.

You may be a hillbilly physicist if you think length contraction is what happens when you jump into a creek in winter.

You may be a hillbilly physicist if your theoretical proof consists of "well that thar other stuff don't make no sense to me no how"!

You may be a hillbilly physicist if you think the tools for quantum mechanics are an impact wrench and a screw driver.

Which reminds me

Reintarnation: When you die and come back as a hillbilly.

7. Originally Posted by quantum_wave
I'll just bask in the warmth for awhile, assuming MD confirms.

Oh wait, I stand corrected. The fixed point is at the center of the box, and the light source is in motion along with the box, but an emitted light wave front is assumed to move at the speed of light in all directions from the point of transmission. The motion of the box makes the measurements based on the point back where the light was emitted. In other words the light wave is not moving along with the box, it is expanding spherically from its point of origin and the box is in motion relative to the point that the light was emitted (the point of origin).
You got it!

8. Originally Posted by origin
I swear this thread should be renamed "blue collar physics".

You may be a hillbilly physicist if you think advanced math is long division.

You may be a hillbilly physicist if you think length contraction is what happens when you jump into a creek in winter.

You may be a hillbilly physicist if your theoretical proof consists of "well that thar other stuff don't make no sense to me no how"!

You may be a hillbilly physicist if you think the tools for quantum mechanics are an impact wrench and a screw driver.

Which reminds me

Reintarnation: When you die and come back as a hillbilly.
That's pretty good there, Origin. But you come across as if these threads should be at the professional level and laymen should keep quiet and learn from all the smart guys. Do you mean to sound like that?

9. Originally Posted by Motor Daddy
You got it!
Good. Have you done a graphic that shows this. Maybe start with a cube (square) with a point in the center as frame one. That would be the point of origin of the light wave. Then frame two shows the box moving away from the point of origin and shows the spherical (circular on the paper) wave expanding within the box. Then frame three could be the point where the wave front reaches the first receptor. BTW, as I think about it, the motion would cause the light wave to take longer to reach the front of the box than to reach the back of the box. It would reach the back of the box first wouldn't it, and then the sides, and finally the front.

10. It's pretty non-intuitive.

If you run towards a source of light, you would think the apparent speed of the light towards you would be greater than if you were at rest. Or if you run away from a source of light, the apparent light speed would be less than the at rest speed.

But it's always the same speed, c.
Measuring the speed of light contradicts the commonsense view.

Motor Daddy can't even explain how he knows that light "travels at c", and he doesn't think it matters that he can't.

11. How does this look, MD?

12. Originally Posted by quantum_wave
Good. Have you done a graphic that shows this. Maybe start with a cube (square) with a point in the center as frame one. That would be the point of origin of the light wave. Then frame two shows the box moving away from the point of origin and shows the spherical (circular on the paper) wave expanding within the box. Then frame three could be the point where the wave front reaches the first receptor. BTW, as I think about it, the motion would cause the light wave to take longer to reach the front of the box than to reach the back of the box. It would reach the back of the box first wouldn't it, and then the sides, and finally the front.

Yep, that's right, according to MD's theory. If you restrict the cube's motion to one axis, then MD has some simple equations that let you solve for the velocity of the cube based on light travel times. But if you let the cube move in three dimensions, it get's trickier to solve.

Here's an interesting side note. In relativity, you can interpret MD's "absolute reference frame" as if it is not a special frame at all. Just because the speed of light is constant in that frame does not make it special. The difference between this interpretation and MD's interpretation is you have to assign all your light-travel times to the reference frame through which the cube is moving. You cannot assign those measurements to the inside of the cube, as MD does. (Inside the cube should be just another reference frame where the speed of light is constant, like a box within a box).

13. Originally Posted by Neddy Bate
Yep, that's right, according to MD's theory. If you restrict the cube's motion to one axis, then MD has some simple equations that let you solve for the velocity of the cube based on light travel times. But if you let the cube move in three dimensions, it gets trickier to solve.
As it does in SR as well. And certain motion is not allowed, i.e. spinning as in Newton's bucket. I think we are restricted to the principle of relativity as described in the text we have been referring to.
Here's an interesting side note. In relativity, you can interpret MD's "absolute reference frame" as if it is not a special frame at all. Just because the speed of light is constant in that frame does not make it special. The difference between this interpretation and MD's interpretation is you have to assign all your light-travel times to the reference frame through which the cube is moving. You cannot assign those measurements to the inside of the cube, as MD does. (Inside the cube should be just another reference frame where the speed of light is constant, like a box within a box).
Yes, under current theory. But we are talking MD theory and we are about to see where it goes from here.

I suggest we start with MD's receptors and the measured speed of light at each receptor using his theory. Then we calculate those speeds with SR and quantify the differences. That list will provide us with data to start working with .

14. Originally Posted by quantum_wave
As it does in SR as well. And certain motion is not allowed, i.e. spinning as in Newton's bucket. I think we are restricted to the principle of relativity as described in the text we have been referring to.
Yes, under current theory. But we are talking MD theory and we are about to see where it goes from here.
I agree. Spinning is not required to achieve 3D motion though. The cube can remain upright as its x, y, and z coordinates all change at constant rates. But there is no need to make the problem any more difficult at this stage.

Originally Posted by quantum_wave
I suggest we start with MD's receptors and the measured speed of light at each receptor using his theory. Then we calculate those speeds with SR and quantify the differences. That list will provide us with data to start working with .
There should not be any differences, PROVIDED you realize that you are not working in the reference frame of the cube. The cube is moving through the frame you are working in, and you are using clocks in that frame, not clocks in the cube frame. Likewise, if the cube is a true cube in the frame you're working in, then it is not really a cube in its own frame, etc.

15. Originally Posted by Neddy Bate
I agree. Spinning is not required to achieve 3D motion though. The cube can remain upright as its x, y, and z coordinates all change at constant rates. But there is no need to make the problem any more difficult at this stage.
That is true but let's use the KISS method first.
There should not be any differences, PROVIDED you realize that you are not working in the reference frame of the cube. The cube is moving through the frame you are working in, and you are using clocks in that frame, not clocks in the cube frame. Likewise, if the cube is a true cube in the frame you're working in, then it is not really a cube in its own frame, etc.
We have to realize it in terms of MD's theory. Did you see my graphic? If MD thinks that is how it would look in three frames as time passes and if motion is linear relative to the point of origin.

16. Originally Posted by quantum_wave
That is true but let's use the KISS method first.
It's pretty easy if the cube only moves in one dimension. I won't spoil the fun by giving you the equations, but MD has already worked out how you can solve for both the cube's length and its absolute speed, based only on light travel times in two directions parallel to the movement of the cube.

Originally Posted by quantum_wave
We have to realize it in terms of MD's theory. Did you see my graphic? If MD thinks that is how it would look in three frames as time passes and if motion is linear relative to the point of origin.
I'm pretty sure he would agree to it. I can tell the cube is moving left-to-right, but I can't tell if it is also moving up ever so slightly? Probably not based on the KISS approach, right?

17. Originally Posted by quantum_wave
That's pretty good there, Origin. But you come across as if these threads should be at the professional level and laymen should keep quiet and learn from all the smart guys. Do you mean to sound like that?
Absolutely not. I am not a physicist so I certainly do not think that this forum should be for physicist only. However, when someone says they do not beleive the speed of light is constant in all inertial frames when the evidence says other wise, and their only evidence for their belief is that they know it is true, well that is not physics at any level that pseudo science.

When someone says that there is no acceleration due to gravity because a beach ball does not have an increasing velocity through solid ground that is just ignorance.

Being a laymen does not make you stupid or irrational, but it sure doesn't preclude it!

18. Originally Posted by origin
Absolutely not. I am not a physicist so I certainly do not think that this forum should be for physicist only. However, when someone says they do not believe the speed of light is constant in all inertial frames when the evidence says other wise, and their only evidence for their belief is that they know it is true, well that is not physics at any level that pseudo science.

When someone says that there is no acceleration due to gravity because a beach ball does not have an increasing velocity through solid ground that is just ignorance.

Being a laymen does not make you stupid or irrational, but it sure doesn't preclude it!
OK then I took it wrong. You are a funny guy and you take your science seriously, at least to the extent that you don't suffer those who ignore what most people consider the obvious, .

I'm sure I'm covering the same ground again as I get up to speed with MD but to be honest I think there are some lessons to be learned here, at least on my part. And the topic is one which I find interesting because it is a collision between innate logic and accepted physics. It is somewhat philosophical to me in that respect.

19. Originally Posted by quantum_wave
OK then I took it wrong. You are a funny guy and you take your science seriously, at least to the extent that you don't suffer those who ignore what most people consider the obvious, .
The only part I would disagree with is the obvious term. Several aspects of physics are not obvious and are really counter intuitive to our everyday experiences. Many of the concepts (and the math) are very challenging. What is frustrating is when these concepts are patiently explained by some of the very smart people on this forum to no avail. I have no patience for someone who clings to there ideas when they are shown very clearly that there errors in there thinking.

Wrong again, James. There is no dispute that the y receiver is in a specific location at .65 seconds.
Apparently, there is, because I get a different answer to you.

Let's go back a step. What is the speed of the cube? Was I correct in using 0.63897c? That's a strange number to pick for an example, but I'm happy to use it if you want to.

Or is the speed of the cube some other number (in which case I need to re-do my calculation)?

What locations do you think the y receiver is at .65 seconds and .913 seconds?
If the speed of the cube is 0.63897c in the x direction, then at t=0.65 seconds the y receiver is at:

$(x,y,z)=(0.63897c \times 0.65 metres,0.5 light-seconds, 0)$

Again, I'm working on the assumption that the y receiver was at (0,0.5 light seconds, 0) at time t=0. Correct me if that's wrong.

You will not get your length contraction to work, even after I tell you the absolute velocity of the cube.
I haven't used length contraction. The above calculation (my previous post) is in a single frame - the frame of the source. Length contraction only ever becomes an issue when you're translating between two different frames.