The Relativity of Simultaneity

[Neddy Bate]

You've not proven anything about GPS because it has so many variables, and it is constantly updated. I don't know enough about GPS to tell you where you go wrong, and you are no GPS expert either.

I asked you to tell me how far away from the surface of the earth a GPS satellite is. You never responded. If you think I'm just going to throw my hands up in the air because you said GPS says the earth has an absolute zero velocity you are mistaking. Do you actually believe the Earth has an absolute zero velocity???No, you don't, so you've proven yourself wrong by saying GPS wouldn't work if the earth had an absolute velocity greater than zero.


Now onto more important matters. What direction in the cube can you measure the speed of light to be c??

I told you the distance to the satellites is 20,200km in post #869.http://sciforums.com/showpost.php?p=2759648&postcount=869

Then I calculated that, if your theory is correct, the absolute speed of earth must not be more than 0.003km/s in post #875. http://sciforums.com/showpost.php?p=2759670&postcount=875

But of course the earth moves about 29km/s relative to the sun, which completely disproves your theory. Thus, the answer to your question

What direction in the cube can you measure the speed of light to be c??

is "all directions."

 

[Neddy Bate]

I do have a question. In the link I just gave Origin, to chapter 11, the equations use the square root of I minus v^2/c^2. I am assuming that I is 1. Is that right?

Yes. The fonts were strange back then. The term "one over the square root of (1 minus v^2/c^2)" is called the Lorentz factor. That term shows up a lot in relativity equations.

 

[Motor Daddy]

Thus, the answer to your question is "all directions."

So you say the speed of light is measured to be c in all directions in the cube.

All directions must include from the source to the y receiver, correct?

So it took .65 seconds to get from the source to the receiver, and the distance from the source to the receiver is .5 light seconds.

That means the speed of light to the y receiver is 0.76923076923076923076923076923077 c.

So how do you conclude that the speed of light is measured to be 299,792,458 m/s from the source to the y receiver?

 

[Neddy Bate]

So you say the speed of light is measured to be c in all directions in the cube.

All directions must include from the source to the y receiver, correct?

So it took .65 seconds to get from the source to the receiver, and the distance from the source to the receiver is .5 light seconds.

That means the speed of light to the y receiver is 0.76923076923076923076923076923077 c.

So how do you conclude that the speed of light is measured to be 299,792,458 m/s from the source to the y receiver?

I think we agreed to use a cube that was one light-second long along each edge, as measured from inside the cube. That means the correct one-way light travel times should be 1 second for each full edge of the cube, or 1/2 second from center-point to center-point. This would hold true for any face of the cube.

Note: The above describes what the person inside the cube measures. If you look at it from some other reference frame, the cube will be shorter along its direction of motion, and the clocks inside the cube will tick slower, etc. We can work it all out if you want to see how it looks from some other reference frame.

 

[quantum_wave]

Yes. The fonts were strange back then. The term "one over the square root of (1 minus v^2/c^2)" is called the Lorentz factor. That term shows up a lot in relativity equations.

Thanks Ned. And I would like you to know that my interest is not in questioning that nature does it. I know the math works perfectly and I've of course heard the buzz words and phrases like mass/energy warps spacetime, Gravitational time dilation is an effect of relativity theory, and SR time dilation is an effect of relative motion. But I'm interested in the physics of how, i.e. the mechanics of SR, the means of curving space :shrug: .

 

[origin]

If by "round trip" you mean the light traveling from earth to the moon and back again, your experiment doesn't work. It is not able to differentiate between an absolute reference frame and relativity. In relativity, the light beam will simply take the same amount of time back and forth, but in an absolute frame the first part of the trip will be longer and the second will be shorter. The total round trip time will be the same.

That's my understanding anywho.

You are right it wouldn't really work for a number of reasons. I just wanted to further confuse MD and have him ignore a post that he thought proved him wrong. Just having a little fun.

 

[Motor Daddy]

I think we agreed to use a cube that was one light-second long along each side, as measured from inside the cube. That means the correct one-way light travel times should be 1 second for each full side of the cube, or 1/2 second from center-point to center-point. This would hold true for any face of the cube.

Note: The above describes what the person inside the cube measures. If you look at it from some other reference frame, the cube will be shorter along its direction of motion, and the clocks inside the cube will tick slower, etc. We can work it all out if you want to see how it looks from some other reference frame.

We are inside the cube, and we sent a light to the y receiver .5 light seconds away from the source at the center of the cube. The light made it to the receiver in .65 seconds. There is no external frame to relate to, and we don't know if the box is in motion or not.

How do you come to the conclusion that the speed of light was c from the source to the y receiver, when it clearly took .65 seconds for the light to travel .5 light seconds in our frame, the cube?????

 

[Neddy Bate]

You are right it wouldn't really work for a number of reasons. I just wanted to further confuse MD and have him ignore a post that he thought proved him wrong. Just having a little fun.

Your experiment would work pretty well. I think it should take about 2-1/2 seconds for light to make a round-trip from earth to the moon and back. DonQuixote's objection that the "fast time" would cancel out the "slow time" is a good approximation for slow speeds, but it really fails for faster speeds. The one-way travel times in each direction would look like this:

t_1 = d / (c+v)

t_2 = d / (c-v)

Look what happens to t_2 for the case where v is close to c. The denominator approaches zero, and you get a really, really long travel time. This cannot be "canceled out" by t_1 being a very short time.

 

[Neddy Bate]

We are inside the cube, and we sent a light to the y receiver .5 light seconds away from the source at the center of the cube. The light made it to the receiver in .65 seconds.

No it wouldn't take 0.65 seconds in reality. It would take 0.50 seconds. That is because the speed of light is c relative to the cube in the cube's own reference frame.

 

[Enmos]

I win Enmos.

You win me? :bugeye:
I mean.. What is thy bidding, master Quantum?

Seriously though. I didn't realize there was any sort of contest going on..

 

[Motor Daddy]

No it wouldn't take 0.65 seconds in reality. It would take 0.50 seconds. That is because the speed of light is c relative to the cube in the cube's own reference frame.

We just established that it would take .65 seconds for light to travel from the source to the y receiver. You are now saying it would take .5 seconds?

It can't take .5 seconds, period!

If the time to the x receiver is more than .5 seconds, then the y and z times must be more than .5 seconds, even though their component velocities are zero.

 

[Neddy Bate]

We just established that it would take .65 seconds for light to travel from the source to the y receiver. You are now saying it would take .5 seconds?

It can't take .5 seconds, period!

If the time to the x receiver is more than .5 seconds, then the y and z times must be more than .5 seconds, even though their component velocities are zero.

In your world, it can take 0.65 seconds, but reality has its own rules. Let's say the person in the cube decides to set up a system similar to GPS. He calls it the "Cube Positioning System", or "CPS". He arranges some transmitters around the centers of all the sides of the cube, and puts synchronized clocks with each transmitter. Now he walks around the cube, carrying a CPS device that tells him his current location inside the cube. According to you, this system would not work if he assumes the travel times are 0.50 seconds to the center of the cube. But in reality, the system does work, just as the GPS system works on earth.

 

[quantum_wave]

You win me? :bugeye:
I mean.. What is thy bidding, master Quantum?

Seriously though. I didn't realize there was any sort of contest going on..

Welcher. (I hope that term is politically correct, lol).

OK, maybe there was no formal bet but you did say you were willing to give odds ... we just didn't have time to consumate the deal .

 

[Motor Daddy]

In your world, it can take 0.65 seconds, but reality has its own rules. Let's say the person in the cube decides to set up a system similar to GPS. He calls it the "Cube Positioning System", or "CPS". He arranges some transmitters around the centers of all the sides of the cube, and puts synchronized clocks with each transmitter. Now he walks around the cube, carrying a CPS device that tells him his current location inside the cube. According to you, this system would not work if he assumes the travel times are 0.50 seconds to the center of the cube. But in reality, the system does work, just as the GPS system works on earth.

We are not measuring our positions in the cube, we are measuring the absolute velocity of the cube in space. You are being intellectually dishonest, and you know it!!!

We don't know the velocity of the cube in space. We send a light signal to the receivers on each of centers of the x, y, and z wall. The first receivers to be impacted by the light are the y and z receivers, and the clocks read .65 seconds. How do you explain that, and how do you come to your conclusion that .65 seconds to travel the distance of .5 light seconds is somehow traveling at c???

 

[Enmos]

Welcher. (I hope that term is politically correct, lol).

OK, maybe there was no formal bet but you did say you were willing to give odds ... we just didn't have time to consumate the deal .

Oh.. lol
I think I misunderstood the odds thing then.
Sorry, this happens to me every once in a while. English is not my first language.

 

[quantum_wave]

Oh.. lol
I think I misunderstood the odds thing then.
Sorry, this happens to me every once in a while. English is not my first language.

Now its excusses is it? Translation: Just kidding friend.

 

[Enmos]

Now its excusses is it? Translation: Just kidding friend.

Oh great, now everything is going to be translated for me?

 

[arfa brane]

How do you know what the speed of light is?

Since light travels at a constant speed in a vacuum, I can use light travel time to define a unit of measure of distance.

So you see, Motor Daddy thinks he knows what the speed of light is "since light travels at a constant speed in a vacuum".

I would not advise asking Motor Daddy how he knows light travels at a constant speed in a vacuum, it will just confuse the poor lad.

 

[Neddy Bate]

We are not measuring our positions in the cube, we are measuring the absolute velocity of the cube in space. You are being intellectually dishonest, and you know it!!!

We don't know the velocity of the cube in space. We send a light signal to the receivers on each of centers of the x, y, and z wall. The first receivers to be impacted by the light are the y and z receivers, and the clocks read .65 seconds. How do you explain that, and how do you come to your conclusion that .65 seconds to travel the distance of .5 light seconds is somehow traveling at c???

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.

 

[quantum_wave]

We are not measuring our positions in the cube, we are measuring the absolute velocity of the cube in space. You are being intellectually dishonest, and you know it!!!

We don't know the velocity of the cube in space. We send a light signal to the receivers on each of centers of the x, y, and z wall. The first receivers to be impacted by the light are the y and z receivers, and the clocks read .65 seconds. How do you explain that, and how do you come to your conclusion that .65 seconds to travel the distance of .5 light seconds is somehow traveling at c???

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.