Louis Essen discusses Einstein's theories. (Another attempt.)

The thought experiment is after the colon. As mentioned before.

 

Log in or Sign up to hide all adverts.

After the colon comes Uranus.
Scaramouche, no thought experiment is described "after the colon". I don't think you have any idea what Essen is even saying, let alone whether he is right or wrong.

 

Log in or Sign up to hide all adverts.

Here it is, with the colon:

 

Log in or Sign up to hide all adverts.

"B is slower than A as seen from A.

And since velocity is only relative and either of the clocks can be regarded as the moving one:

A is slower than B as seen from B.

This is certainly strange although not logically impossible. It implies that something happens to the signals during their transmission."

Ok, going with your version of the experiment, which since it includes no introduction of the setup I can only assume is one in which A and B are in uniform relative motion, everything is fine up to here.

"He then outlines his experiment without giving any details of how the measurements are made and concludes that:


B is slower than A."

Well if the experiment was a twin-type situation as most people, except you, read the article to be about, then this statement is also fine. If however, it is the experiment I described which seems the only alternative, then this conclusion is wrong. One would have to find whatever source of Einsteins Essen is referring to and find out what exactly it was that Einstein was saying, because I highly doubt this is the conclusion he came to.

"And although he does not specifically say so:

A is slower than B.

In accordance with the relativity principle."

This part is simply not in accordance with the relativity principle at all, in either thought experiment. Which presumably is why Einstein did not "specifically say so".

 

That's Essen's analysis of the thought experiment. It doesn't describe the experiment at all.
Here is the experiment description:

Did you bother to read Essen's RELATIVITY - joke or swindle? which repeats the same argument more concisely?

It is perfectly clear what thought experiment Essen is talking about. It is completely unclear what thought experiment you are thinking of.

 

Just to clarify: If A and B are clocks moving relative to each other and both are moving uniformly (ie they don't change speed or direction), then relativity says that:
In a system in which A is at rest, B is slower than A.
In a system in which B is at rest, A is slower than B.


The sources Essen is working from certainly includes Einstein's On the electrodynamics of moving bodies, the seminal work on relativity. See the latter half of section four for the clocks thought experiment.


On a side note:
A second point of confusion for Essen (and others) arises from Einstein's use of the word "viewed" in this paper, eg "What is the rate of this clock, when viewed from the stationary system?"
Essen understandably, but mistakenly, interprets this to mean a visual record recorded from a single stationary location, which may be affected by the signal delay. It would have been clearer and more correct if Einstein had instead used "measured". But, Einstein's intention is clear enough if you wade through the first sections of the paper where he describes systems of coordinates (Einstein always uses 'viewed' in conjunction with 'from a system', rather than from a location), and stresses that time measurements of events can only be directly measured at the location at which they occur.

 

You can say it that way if you like but it is dangerous imo because the phrase "is slower than" can be easily misunderstood, unless one is throughly familiar with the relativity way of thinking. Essen certainly doesn't appear to be using it the way you are because he is careful to quality the first version he uses, that being "B is slower than A when viewed by A". I know yours has the "In a system in which A is at rest" qualification, but it is not as explicit that this is a statement about how the clocks are measured. One could easily think the "B is slower than A" part had some kind of absolute meaning, which is how Essen is using it the second time around. It is in this sense that I meant that the final inference of Essen "A is slower than B" is not in accordance with relativity as he thinks it is. If you disagree with this assessment of Essen's usage of this phrase then perhaps the passage can be read differently to how I read it.

 

Recall that "at rest" can only mean with respect to a clock, which is keeping regular time. So how do you "know" the clock does this? Because the surface it's on isn't changing? Only the "time" on the clock is?

 

It's a logical deduction. All things being equal, if all motion is relative, and you're looking at motion between two objects, the same rules apply to one as the other. It is impossible in relativity to state that either one of those clocks is stationary and only the other clock is moving (although you can pretend one is stationary and the other is moving).

 

It's Essen's thought experiment, based on Einstein's work and the twins paradox. I did not say it was Einstein's thought experiment.

Certainly. You?

He's talking about the twins experiment, obviously. And it starts after the colon.

 

No, not at all. The clock is in it's own inertial time frame and you simply have designated it as your reference point. Nothing more is required than that.

 

Yes. at all. Designating a clock as being in an inertial frame is saying the surface it's on isn't changing, only its time is.

So the nothing more required is the same thing as requiring that the surface of the "clock" not change, only the "time" it keeps.The only way it keeps time regularly is if its in an local inertial frame.

 

I think the whole clocks thing deserves its own topic, for comprehensive description.

 

Ok, so now you agree that he is talking about the twins experiment? Pete has already corrected the error if this is the experiment in question. The symmetry required to make the "logical deduction" that "A is slower than B" and "B is slower than A" doesn't exist in the twins experiment. It has nothing to do with whether or not one clock is "stationary" and the other moves, as you agree is nonsense in relativity. It has everything to do with the fact that the older twin stays in the same inertial frame for the whole experiment, while the younger twin has to move between at least two different frames (not including the older twin's frame, specifically the "leaving" frame and the "returning" frame) depending on how you formulate the experiment. Thus there is no symmetry.

Why are you talking about "the surface it's on"? This is totally irrelevant. Put the things in space, then there is no surface. As long as no inertial (or gravitational) forces are acting on the clock you are fine, it is in an inertial frame, and everything in that frame is at rest relative to each other.

 

IF you have the observed twin/clock going both directions. Which Essen did not use. Like Einstein, he simply used A moving directly relative to B.

 

You are missing the whole point - it IS in a local inertial frame, it's own. Can you not see that??

 

For physicists, explaining why means explaining how something works, or acts. Why is a clock in an inertial frame, how does it get there?

WE simply assign it to one. So what then is an inertial frame assuming we know how to make a clock keep regular or "proper" time in one?

Can you see that?

 

No, it's Einstein's thought experiment, and Essen is criticizing it.

Yes, he's talking about the 'twin paradox'. One twin stays home. The other goes away and returns. Just as Essen says:

"He imagined that two clocks were initially together and that one of them moved away in a number of straight line paths, at a uniform velocity, finally returning to the starting point. He concluded that on its return the moving clock was slower than the stationary clock.

Moreover, since only uniform motion is involved there is no way of distinguishing between the two and each clock goes more slowly than the other. This result is known as the clock paradox or, since the clocks are sometimes likened to identical twins, one of whom ages more slowly than the other, the twin paradox."​

According to Essen, the predictions of Einstein's thought experiment start after the colon. "...the predictions are: ..."

I really don't know why you're having such difficulty with this. Perhaps if you explained what thought experiment you think Essen proposed? I'm honestly baffled by what you could possibly have read 'after the colon' that you interpreted as a description of a thought experiment.

 

I really can't tell what you mean.

 

Being that's it's different from Einstein's...

Look, I'm not going to teach you elementary English as well. For fuck's sake.

I'm having no difficult. Essen introduces what he's going to show, then has a colon, then shows it. Somehow you've been unable to grasp that simple fact. Either way, you're very tiresome and obviously determined to harp on about your misunderstanding of basic English rather than focusing on anything of substance. That being the case, do not expect any further replies until or unless you can post something worthwhile, or until you post something I find funny enough to mock.