Why in the world would Einstein suggest... 2

@layman,

Quote:

Al stole Lorentz's concept of "local time" and said (in positivistic fashion) that it WAS time.

And that's true genius right there...

0 Replies

@Olivier5,

Quote:

You got that wrong.

We are talking about the supposed phenomenon of reciprocal time dilation here, right?

For example, if A claims that B's clock is slow, then B will "reciprocally" claim that A's clock is slow.

That's what we're talking about, right? Or do have something else in mind?

1 Reply

@Olivier5,

Quote:

One centred on the sun (or the solar system center of mass, to be precise) would work too but makes the computation much more complicated

Would "work" using WHAT theory of relative motion? Lorentz's, you mean? Or do you mean SR?

1 Reply

@layman,

Both theories are equivalent, in my understanding. They use the same math and make the same predictions. So the answer to your question is: in both.

1 Reply

@layman,

The 'reciprocity' would be true in SR (ie consistent with SR) only if both observers' motions are inertial. It does NOT hold true in SR if one or both observers go through an accelerated motion. This is a central point which apparently many people miss.

2 Replies

@Olivier5,

Quote:

Both theories are equivalent, in my understanding.

I've already addressed this claim. They use the same mathematical formalism, but they are not, by any means, equivalent theories.

What would SR predict the time differences ultimately shown on the respective clocks to be
1.IF you used the naval station clock as the frame of reference from which you were doing the calculation?
2..IF you used the westbound clock as the frame of reference from which you were doing the calculation?
3. IF you used the eastbound clock as the frame of reference from which you were doing the calculation?

Would you get the same "predictions" in every case? (the answer is no, they would all be different).

Which one would be "right?" Would ALL of them be right? (the answer is no, they would all be wrong). They would all be "right" according to the theory of SR, but those predictions would NOT correspond to the ACTUAL time differences shown on the clocks themselves.

Try it, if you think otherwise.

0 Replies

@Olivier5,

Quote:

The 'reciprocity' would be true in SR (ie consistent with SR) only if both observers' motions are inertial. It does NOT hold true in SR if one or both observers go through an accelerated motion. This is a central point which apparently many people miss.

According to a fundamental premise of SR (later determined to be an "axiom") time dilation is NOT changed by acceleration (although other things might be, in SR).

Quote:

The clock hypothesis is an assumption in special relativity. It states that the rate of a clock doesn't depend on its acceleration but only on its instantaneous velocity....The clock hypothesis was implicitly (but not explicitly) included in Einstein's original 1905 formulation of special relativity. Since then, it has become a standard assumption and is usually included in the axioms of special relativity...

http://en.wikipedia.org/wiki/Clock_hypothesis

Look, I've been through all this a dozen times in the prior thread. You have never read any of it. You don't know what the differences in LR and SR are, you don't know what authorities on the topic say about reciprocal time dilation, or anything else. I have to go now. Read the old thread. I have responded to all these misunderstandings there already.

1 Reply

@layman,

Quote:

Quote:
The 'reciprocity' would be true in SR (ie consistent with SR) only if both observers' motions are inertial. It does NOT hold true in SR if one or both observers go through an accelerated motion. This is a central point which apparently many people miss.

According to a fundamental premise of SR (later determined to be an "axiom") time dilation is NOT changed by acceleration (although other things might be, in SR).

That is a totally different issue, which has nothing to do with frames of reference. It's neither here nor there. The point is that a frame of reference "anchored" on an accelerated object is not equivalent to an inertial frame. There is no reciprocity between those. SR never said that any frame of reference is equivalent to describe the laws of motion, only that inertial ones are.

Until you get that, you have understood nothing of SR.

2 Replies

@Olivier5,

I will make one short, simple, post explaining the difference between SR (relative simultaneity) and LR (absolute simultaneity).

Take two "observers," one on a train moving at a uniform speed, and one standing on the earth, next to the tracks. Who's clock is "really" running slower (i.e., who is "really" moving--in SR and LR it is "always" the moving clock which runs slower--there is an (quasi) exception to this in SR--accelerating motion, but that's not important right now).

SR and LR give different answers to this question. The Lorentz transformations always give the SAME answer--it is always the moving clock which runs slower--but the LT cannot, by themselves, tell you which one is moving). So,

1. In SR, each will insist that it is only the OTHER clock which runs slower. This is inherently contradictory, if taken to be factual. But, all the same, each observer will INSIST that he is not moving. Nothing will ever get them to agree that THEY are (or even could be) the one moving. It's the other guy, dammit!

2. In LR, the guy on the train will freely acknowledge that, relative to the earth, he is the one moving. So what does this mean? Because he knows how the LT work, and what they imply, he will acknowledge that it is HIS watch, NOT the other guy's that is really running slow. Such an acknowledgment is PROHIBITED by SR. In SR each party must contradict each other's claims about who (which clock) is moving.

I have put this in "personal" terms (in terms of "claims made by observers"), because that's exactly what Al did. However, it is actually just a function of the mathematical protocols which SR requires when applying the LT.

1 Reply

@Olivier5,

Quote:

Until you get that, you have understood nothing of SR.

I get that. COMPLETELY. I have brought it up and discussed this fact many times in the other thread.

What I also "get," which you don't, it what that implies about the theory. I get why Al MUST say that, even though he hated to concede it. He was NEVER satisfied with SR, and had rejected it as insufficient (for a number of reasons) within a couple of years. With GR he hoped to developed a "general" (not "special") theory of relative motion. According to the math experts, GR failed to achieve this goal. It did, however, provide a very useful theory of gravity.

1 Reply

@layman,

Quote:

in SR and LR it is "always" the moving clock which runs slower--there is an (quasi) exception to this in SR--accelerating motion, but that's not important right now).

To elaborate on this exception. In SR, where one of two objects is accelerating, then the non-accelerating observer will claim (as always) that it is the "other guy" who is moving. The difference is that, even in SR, the accelerating guy will agree. He will ALSO say that "he" is the one moving, not the stationary (inertiallly moving) guy. As a result, the speed of light is NOT isotropic and constant in his frame. It never is, or can be, isotropic in all frames if you allow for the possibility that one of the two is moving and both agree on who it is (although, needless to say, the "agreement" is not crucial here--it will be that way, as a matter of math, whether or not all agree).

0 Replies

@Olivier5,

Now given the above (you seem to agree with all the experts who say that, when accelerating, all parties agree that it is the accelerating party who is "really" moving), let's apply to a particular example.

Take a train, parked at a station, which suddenly begins to accelerate, at a VERY slow rate (say 1 mile per hour). After 60 hours it will be travelling 60 miles an hour. In the meantime, during those 60 hours, even SR will adopt an LR view of the deal. SR will say that the train is the one "really" moving during that time, and will therefore say that it is a clock on that train that is "really" running slow. In other words, according to BOTH a passenger on the train AND a stationary observer on earth, it is the train that is moving, and therefore both would assert that the train clock is the one running slower.

Now, the train stops accelerating, and moves at the uniform speed of 60 mph relative to the earth for one minute.

How would SR and LR treat that one minute differently? As we all know, the law of inertia says that a body in motion tends to stay in motion, unless it is acted upon by an outside force. So it would tell us that the train is STILL going 60 mph, even though it has now stopped accelerating. LR would say the exact same thing.

SR would NOT say that. In SR, the train passenger will now say (since it is moving at a uniform speed) the train is NOT moving, but that NOW it is the earth that is moving instead (again, according to a train passenger). In LR, the train passenger would concede that he is still moving, that's the difference.

To complete the example, let's now suppose that, after one minute of maintaining a uniform speed, the train begins slowing down at the same slow rate of 1 mph. So, at the end of another 60 hours, it will once again be motionless relative to the earth (it will have come to a complete stop). Here again, SR will concede that, during these 60 hours, it is the train, not the earth, that is relatively moving.

So after 120 hours and one minute, the train was, according to SR, "really moving" for 120 hours. For LR it would also be the one moving for the one minute--i.e, for the whole time.

0 Replies

@layman,

No, you don't get that, since you still speak of reciprocity between NON-INERTIAL frames such as planes and naval stations... So obviously, something doesn't click.

2 Replies

@Olivier5,

Do you understand anything I've said here, Ollie?

http://able2know.org/topic/276564-2#post-5948239

1 Reply

@Olivier5,

Quote:

No, you don't get that, since you still speak of reciprocity between NON-INERTIAL frames such as planes and naval stations

Which is it, with you, Ollie? You want to have it BOTH ways, constantly jumping from one opposing stance to another, just depending on which one you think suits your current purposes. Is it:

1. As a practical matter, SR is a totally worthless theory which cannot tell anyone anything at all about motion because it doesn't apply anywhere in the "real world," or is it...
2. It does apply, at least as a close approximation?

According to the clock hypothesis (axiom), the fact that one object is moving non-inertially is of absolutely NO consequence to the issue of time dilation. Do you reject this axiom? If not, why do you pretend it doesn't exist?

If you choose #1, then you should definitely favor LR over SR because, unlike SR, LR is NOT limited to predicting the motion of ONLY inertial objects.

1 Reply

@layman,

I do. Do you understand what I am saying?

I am saying that your understanding of SR is wrong. You believe that it says things that it does not say, which is why you are under the mistaken impression that there is a significant difference between SR and what you call LR.

1 Reply

@layman,

Quote:

Is it:

1. As a practical matter, SR is a totally worthless theory which cannot tell anyone anything at all about motion because it doesn't apply anywhere in the "real world," or is it...
2. It does apply, at least as a close approximation?

2. we can use it as an approximation of reality, when the experiment or phenomenon observed is sufficiently short in duration that a quasi-inertial frame can be assumed.

Quote:

According to the clock hypothesis (axiom), the fact that one object is moving non-inertially is of absolutely NO consequence to the issue of time dilation. Do you reject this axiom? If not, why do you pretend it doesn't exist?

I have not mentioned this nor disagreed with it. It has no relevance to our discussion. I was talking of all inertial frames of reference being equivalent to calculate time dilatation, and about non-inertial frames not offering the same equivalence. This has nothing to do with the effect of acceleration on time dilatation. These are two different topics having no bearing with one another. You are confusing objects with frames of reference.

3 Replies

@Olivier5,

Quote:

I do. Do you understand what I am saying?

I am saying that your understanding of SR is wrong.

Yes I understand that. I also understand that, as always, you really can't explain why what I say is "wrong" (other that mentioning, in some vague way, some words that you don't understand). As always, you think that mere assertion, without argument, evidence, authority, or understanding is equivalent to "demonstration of indubitable truth."

YOU don't understand. Not a word of what I'm saying. If you do, and you think I am wrong, tell me how and where.

Do you agree with the difference I have shown between LR and SR in the 120 hour train example? If not, why not?

0 Replies

@Olivier5,

Quote:

I was talking of all inertial frames of reference being equivalent to calculate time dilatation, and about non-inertial frames not offering the same equivalence. This has nothing to do with the effect of acceleration...

Do you even understand that "accelerating" and "non-inertial" are synomyms, which mean the exact same thing? Do you? If you are talking about one, then you are ipso facto talking about the "other."

The clock hypothesis is QUITE relevant, because the nature of the frame is irrelevant for time dilation purposes. There is no need for "equivalence of frames," that's the whole point of the clock hypothesis.

1 Reply

@Olivier5,

Quote:

No, you don't get that, since you still speak of reciprocity between NON-INERTIAL frames such as planes and naval stations... So obviously, something doesn't click.

So, which is it? What you say above, or what you say now (below):

Quote:

we can use it as an approximation of reality, when the experiment or phenomenon observed is sufficiently short in duration that a quasi-inertial frame can be assumed.

By the way, all three are travelling in "inertial frames" from the standpoint of the earth. All three are maintaining a uniform rate of motion.

Relative to the station each plane is moving at a uniform speed (say it's 500 mph). This remains true EVEN IF they are both (jointly) also moving "through space" at the rate of a million miles an hour. That DOES NOT effect their speed relative to each other. It is relative speed between two objects, not absolute speed through space, which determines the time dilation, per SR.

1 Reply

Why in the world would Einstein suggest... 2

Related Topics

Quick Links

My Account

able2know