# Thread: On Einstein's explanation of the invariance of c

1. Originally Posted by arfa brane
If the train has a velocity which is much less than the velocity of light, yes, the distance between the fixed clocks remains constant, so does the length of the train.
Good, now on to bigger and better things. Do you understand that just because the distance is 20 feet between the clocks doesn't necessarily mean light travels 20 feet in space to go from one clock to the other???

Originally Posted by arfa brane
Do you acknowledge that you were wrong about Einstein using light to measure the distance between stationary clocks?
Absolutely not, he gets the length wrong for anything other than a zero velocity.

2. Do you understand that just because the distance is 20 feet between the clocks doesn't necessarily mean light travels 20 feet in space to go from one clock to the other???
Do YOU understand that you need to measure the 20ft distance somehow? Say you use light to measure this distance, and you get the result: 20ft.

How far did the light travel between the clocks? If it wasn't 20ft, how do you "know" the clocks are 20ft apart??

One more detail:
Do you acknowledge that you were wrong about Einstein using light to measure the distance between stationary clocks?

Absolutely not, he gets the length wrong for anything other than a zero velocity.
So, you're saying that unless Einstein uses a stationary frame of reference (viz: clocks fixed to a train) he doesn't get the length right? So using the rest frame means: Einstein gets the length right?

That is exactly what Einstein says in his paper--you require a stationary frame of reference to synchronize clocks.

3. Originally Posted by arfa brane
Do YOU understand that you need to measure the 20ft distance somehow? Say you use light to measure this distance, and you get the result: 20ft.

How far did the light travel between the clocks? If it wasn't 20ft, how do you "know" the clocks are 20ft apart??
You measure the time the light travels and figure out the distance the light traveled, then figure out the velocity, and then figure out the distance, just as I did. Einstein just assumes the distance to be 20 feet because he assumes a zero velocity. He thinks the distance between the clocks always equals the distance that light travels. Dead wrong, unless the frame has an absolute zero velocity.

4. Originally Posted by arfa brane
So, you're saying that unless Einstein uses a stationary frame of reference (viz: clocks fixed to a train) he doesn't get the length right? So using the rest frame means: Einstein gets the length right?

That is exactly what Einstein says in his paper--you require a stationary frame of reference to synchronize clocks.
I'm saying that because he assumes the distance the light has to travel from one clock to the other in space is the same distance that is between the clocks is a fatal mistake!

5. Originally Posted by Motor Daddy
You measure the time the light travels and figure out the distance the light traveled, then figure out the velocity, and then figure out the distance, just as I did.
just because the distance is 20 feet between the clocks doesn't necessarily mean light travels 20 feet in space to go from one clock to the other???
How can you measure "the distance light travels" if it "doesn't necessarily" travel a given distance--in this case 20 feet? How do you determine the distance light travels if there is this discrepancy?

6. The arguments on this thread are just going round and round. Citing Einstein and Relativity is useless, because MD denies relativity, denies Einstein, and is convinced that he is the only one who understands.

According to MD, 105 years of physicists are all wrong, and he's the only one who is correct. This is the very heights of crankdom.

7. In the case of physical principles--the conservation of mass and energy, the constant velocity of light, how time is measured, etc--I try to place them in a frame that boils everything down to "meet" and "join" relations, a Boolean kind of matrix. Like reducing things to the toss of a fair coin that gives a balanced distribution, say. Or an 'unfair' coin with a constant bias. . .

In the case of arguing the toss with someone who has serious misconceptions about those principles it's a relation like: "face, meet palm".

8. Originally Posted by AlexG
The arguments on this thread are just going round and round. Citing Einstein and Relativity is useless, because MD denies relativity, denies Einstein, and is convinced that he is the only one who understands.

According to MD, 105 years of physicists are all wrong, and he's the only one who is correct. This is the very heights of crankdom.
So he might have to self publish his own work...

I gave you the step by step method. I told you the velocity of a frame, and the length of a frame.
In my train example, can you tell me the absolute speed of the tracks? If so, please outline the method by which you determine that, briefly.

When you come to the realization that the tracks can be in motion, then you MUST realize you need to know that motion before you can start to measure length in that frame.
If this is correct, then you are not in a position to measure length in any frame, since you can't establish the absolute motion of any frame.

Trying to prove a zero velocity doesn't exist by using a thought experiment that bases all its measurements on a zero velocity track is absurd!
I have nowhere tried to prove that an absolute zero velocity doesn't exist.

I'm just waiting for you to establish that such a thing does exist. So far, I've seen no evidence of it from you.

What more can I say? I tell you everything you need to know, Einstein doesn't, and you stick to his methods. People believe what they want to believe. All I can say is prove it to yourself. Ask yourself how he can possibly determine the length of a meter when he doesn't know the velocity of the frame? To assume a zero velocity of a frame is absurd!
But you think you know a frame that has zero velocity, don't you?

The definition of a meter is how far light travels in space. That doesn't mean if it takes 1⁄299,792,458 of a second for light to travel from one clock to the other that the distance between the clocks is one meter. It means that in that 1⁄299,792,458 of a second of light travel time, light traveled 1 meter in space.
I agree. Moreover, I believe this must be true in ALL frames of reference.

You say you agree with Einstein's speed of light postulate, but then you constantly talk as if you don't agree with it, and you avoid all direct questions asking you to confront and express your beliefs about that.

10. Physics, according to Motor Daddy:

1. Don't use light to synchronize clocks. That would be a fatal mistake! You should pull mechanical levers, wires, or strings.

2. Make sure to measure the "one-way" speeds of light in both directions between the clocks. Don't use a mirror and a "round-trip" time. (Fatal.)

3. The two "one-way" times are never equal to each other anywhere on earth, because the earth is not at absolute rest.

4. From the two different one-way times, you can determine the absolute speed of the clocks, AND the distance between the clocks!

v = (cT - ct) / (T + t)
d = T(c - v)
where:
v is the absolute speed along the line between the clocks
d is the distance between the clocks
T is the greater time
t is the lesser time

5. The physics community should perform this simple experiment, and we will finally know the absolute speed of the earth! Of course this speed only holds good for one instant in time, but who cares, just keep repeating the experiment.

6. If this experiment should reveal that the absolute speed of the earth is zero, this does not mean the Motor Daddy theory is wrong. The Motor Daddy theory is a FACT! So I guess you'll just have to rewrite all laws of physics to explain why everything in the entire universe is orbiting the stationary earth.

7. Get to work, you slacker physicists! Does Motor Daddy have to do everything for you???!!!

11. Originally Posted by Neddy Bate
Get to work, you slacker physicists! Does Motor Daddy have to do everything for you???!!!
Yeah, get to work you slacker physicists! Do I have to do everything for you??

12. Originally Posted by James R

In my train example, can you tell me the absolute speed of the tracks? If so, please outline the method by which you determine that, briefly.
James R, I have repeatedly told you the steps to find the absolute motion of any frame. You measure the one-way light times and go from there. Put two clocks on the track and measure the one-way times between the clocks. It doesn't matter how far apart you space the clocks, the velocity will be correct, and the length will be correct.

Originally Posted by James R
If this is correct, then you are not in a position to measure length in any frame, since you can't establish the absolute motion of any frame.
What do you think this thread is all about? I am telling you how to measure the velocity of a frame. Do you understand what "inside the box" means?

Originally Posted by James R
I have nowhere tried to prove that an absolute zero velocity doesn't exist.

I'm just waiting for you to establish that such a thing does exist. So far, I've seen no evidence of it from you.
When you don't know your own frame's velocity you assume it to be zero if you take measurements from that frame. You can not sit in a train and be in a position to measure anything unless you know your own velocity first.

Originally Posted by James R
But you think you know a frame that has zero velocity, don't you?
I'm not saying there is a zero velocity frame, I am telling you how to recognize one when you see one. If the one-way times are the same in each direction, that is a zero velocity frame. Period! If the times are different, the frame has a velocity, and you can find that velocity using my method.

Originally Posted by James R
You say you agree with Einstein's speed of light postulate, but then you constantly talk as if you don't agree with it, and you avoid all direct questions asking you to confront and express your beliefs about that.
I agree the speed of light is always a constant, because by definition it has to be a constant. I don't agree with how Einstein measures length using light, as he can't find the velocity of a frame, so he ignores it, which is ultimately the same as assuming the frame is a zero velocity.

13. Long past time this thread was moved to pseudoscience.

14. Originally Posted by Motor Daddy
If the one-way times are the same in each direction, that is a zero velocity frame. Period! If the times are different, the frame has a velocity, and you can find that velocity using my method.
Surprisingly, MD has just described the method Einstein defines in his 1905 paper, although along with a description, Einstein uses mathematical formulas to support the definition.
He goes on to define a method to determine the "times" between a stationary frame of reference and a moving frame, after defining a stationary frame as one in which the one-way times are the same in each direction!

Just translate "zero velocity" into "stationary", and you're on it! He appears to be in agreement with Einstein. Wait, didn't he say Einstein was wrong?? Are there Klingons on the starboard bow, Jim?

15. Originally Posted by arfa brane
How can you measure "the distance light travels" if it "doesn't necessarily" travel a given distance--in this case 20 feet? How do you determine the distance light travels if there is this discrepancy?
When you know how much time light travels you know the distance light traveled in space, as by definition light travel time is distance. You do not separate light travel time and the distance that light travels in space. There is however a big difference between the distance between clocks and the distance light travels in space, if the velocity of the frame is anything but zero.

16. Originally Posted by arfa brane
Surprisingly, MD has just described the method Einstein defines in his 1905 paper, although along with a description, Einstein uses mathematical formulas to support the definition.
He goes on to define a method to determine the "times" between a stationary frame of reference and a moving frame, after defining a stationary frame as one in which the one-way times are the same in each direction!

Just translate "zero velocity" into "stationary", and you're on it! He appears to be in agreement with Einstein. Wait, didn't he say Einstein was wrong?? Are there Klingons on the starboard bow, Jim?
So using Einstein's methods, tell me the velocity of a frame if the one-way times are .1 sec and .2 sec??

Better yet, since Einstein uses two-way times, tell me the velocity of the frame if the two-way time is .3 seconds???

17. Motor Daddy: a stationary frame is one in which you can measure identical one-way travel times for light. This is independent of the velocity of the frame, it depends ONLY on the one-way paths for light.

The velocity of light is independent of the velocity of the frame, which if it's a "stationary frame" means the clocks stay at the same distance. Clocks fixed to a train don't move relative TO EACH OTHER, even when the train is moving. The clocks stay in a stationary frame, and the one-way paths for light "communication" stay the same.

18. Originally Posted by arfa brane
Motor Daddy: a stationary frame is one in which you can measure identical one-way travel times for light. This is independent of the velocity of the frame, it depends ONLY on the one-way paths for light.

It is not independent of the velocity of the frame. The only possible way that light can take the same amount of time each way is if the frame has a zero velocity.

Originally Posted by arfa brane
The velocity of light is independent of the velocity of the frame, which if it's a "stationary frame" means the clocks stay at the same distance. Clocks fixed to a train don't move relative TO EACH OTHER, even when the train is moving. The clocks stay in a stationary frame, and the one-way paths for light "communication" stay the same.
The speed of light is constant, and independent from the velocity of the frame. I'm not talking about moving clocks around on the train, I am talking about the train moving, and the clocks moving with the train, stationary to the train.

19. Originally Posted by Motor Daddy
[the velocity of light] is not independent of the velocity of the frame.
So the velocity of light increases if the source (which is in a frame) is moving?

Oops, no it doesn't apparently:
The speed of light is constant, and independent from the velocity of the frame.

20. Originally Posted by arfa brane
So the velocity of light increases if the source (which is in a frame) is moving?
NO, the speed of light is a constant.