Why in the world would Einstein suggest....

@parados,

I said, to Dale:

Quote:

You keep asking how the "turn-around" can make any difference at all in explaining why one clock slows down and another doesn't. The answer is simple: It doesn't.

You responded with this claim:

Quote:

Actually, the turn around does play a part. The Minkowski diagram would show how it plays that part.

If you care to know anything about the actual PHYSICS of the matter, Parados, try googling "the clock hypothesis" and read what wiki says about it.

In the meantime, don't try to deny your own statements about minkowski diagrams and to then use that false "denial" to accuse me of "not paying attention."

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@layman,

Quote:

If you care to know anything about the actual PHYSICS of the matter, Parados, try googling "the clock hypothesis" and read what wiki says about it.

Here, I'll even help you out (even though this has already been posted in this thread):

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....it has become a standard assumption and is usually included in the axioms of special relativity, especially in the light of experimental verification up to very high accelerations in particle accelerators.

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

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@parados,

Quote:

The relative motion is there no matter which one you decide is moving

Yes, that's correct.

Now what? Do you have any kind of point?

How does that support your claim that "both are correct" when each claims to be motionless?

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@layman,

Sometimes the claim you are trying to make is put in negative form, such as: Neither is motionless, or, either could properly said to be motionless or, as the woeful positivist might say: The question is meaningless.

I have already addressed this form of claim in my "flipped coin" example.

To reiterate: Someone flips a coin, it lands, but before I can see if it came up heads or tails, it is covered.

Now, under those circumstances, is it accurate for me to say that "it could be either heads or tails?"

No, it isn't, that would be inaccurate.

It would be accurate for me to say "As far as I know, it could be either heads or tails." Sure, that's correct. I might even go on to add that the odds of me correctly "predicting" (not really predicting, but guessing) what it is are 50%

But, if that coin came up tails, then the odds of it being heads are exactly zero, not 50%. My ignorance of the actual facts does not mean the facts are merely "probable." Nor, needless to say, does it mean that the question of whether the coin came up heads or tails is "meaningless."

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@layman,

I think Parados is right. The travelling twin needs to make a course change at some point so it is incorrect to say his trajectory is just another frame of reference. It's not inertial.

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@Olivier5,

Quote:

The travelling twin needs to make a course change at some point so it is incorrect to say his trajectory is just another frame of reference. It's not inertial.

He is right about that, sure. But that's not the point in issue. The travelling twin has, indeed, changed reference frames. So what?

What does that have to do with who ages slower? Nothing whatsoever, according to SR itself.

http://able2know.org/topic/265997-29#post-5892686

http://able2know.org/topic/265997-28#post-5892216

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@Olivier5,

As I've already said numerous times in this thread:

Acceleration, per se, has no effect whatsoever on time dilation. This is an axiom of SR.

It does have an indirect effect. SR treats accelerating motion as "absolute." It is not relative, according to SR. The acceleration causes the travelling twin to move, absolutely.

He is the one moving. SR says the moving clock will run slow. Therefore SR says that it is his clock that runs slow.

What SR does NOT say is that the earth twin's clock ALSO runs slow. It does not say that "both are correct" when they each claim that it is "the other guy" who is moving. One is WRONG when he says that (the travelling twin). One is RIGHT when he says that (the earth twin).

The travelling twin does not age slower "because he has changed reference frames." He ages because he has a higher "instantaneous speed." He can't reach that higher speed without an incidental (but non-causal) change of reference frame.

To claim otherwise is akin to saying the air temperature gets hot because your body sweats. It's the other way around.

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@layman,

I'm not talking about whether it features in the formula or not. I am saying the frame of reference is not inertial, thus not considered a valid frame of reference for galilean or Einstein's relativities to apply. You can't treat an accelerated object as just as valid a frame of reference as any other. When i bounce a ball on the floor, you can't scientifically describe what's happening as: the rest of the universe is bouncing against my stationary ball.

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@Olivier5,

Quote:

You can't treat an accelerated object as just as valid a frame of reference as any other.

How is that relevant to the question, which relates only to time dilation?

Quote:

It's a common misconception that special relativity cannot handle accelerating objects or accelerating reference frames. Sometimes it's claimed that general relativity is required for these situations, the reason being given that special relativity only applies to inertial frames. This is not true...

This idea that special relativity cannot handle acceleration or accelerated frames often comes up in the context of the twin paradox, when people claim that it can only be resolved in general relativity because of the acceleration present. Their claim is wrong.

http://math.ucr.edu/home/baez/physics/Relativity/SR/acceleration.html

BTW, there is nothing the least bit "invalid" about an accelerating frame. If you are standing on the sidewalk, talking to friends and then start walking home, you are "accelerating." Does the whole world suddenly change, or become "invalid" for you?

1 Reply

@layman,

I said:

Quote:

What SR does NOT say is that the earth twin's clock ALSO runs slow. It does not say that "both are correct" when they each claim that it is "the other guy" who is moving. One is WRONG when he says that (the travelling twin). One is RIGHT when he says that (the earth twin).

Are you claiming otherwise, Oliver? Do you think SR says "each clock runs slower than the other, and therefore each twin is younger than the other," or anything like that? Do you think the mainstream physics community says "there is no way to say which one ages less, therefore there is no answer to the question of which one ages less?"

Or are you just pointing out a distinction without a difference? If I said the twins were not completely identical, because one had a scar on his foot incurred when falling off his bike, and one didn't, would that change any answer given about who aged slower? It would be a distinction, but not one which would make any difference in answering the question being asked.

1 Reply

@layman,

I said:

Quote:

The travelling twin does not age slower "because he has changed reference frames." He ages because he has a higher "instantaneous speed."

Are you disagreeing with that, Oliver? Are you saying it is the change of reference frame which causes the aging difference, NOT the difference in speed?

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@layman,

Special relativity says two inertial frames of reference are equivalent re. calculating and expressing the laws of nature. It does not extend that similarity to accelerated ones. Of course one can calculate what happens to accelerated objects in general or special relativity.... but one has first to adopt an inertial frame of reference. In the case of the twins, the right frame of reference to calculate their respective time dilatation would be centred on the sun (assuming the traveling twin remains in the solar system).

1 Reply

@Olivier5,

If you want to say that the situations of the two twins are not "symmetrical," then I would agree with you 100%. One is moving, one isn't (relative to each other, I mean, of course).

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@Olivier5,

Quote:

In the case of the twins, the right frame of reference to calculate their respective time dilatation would be centred on the sun (assuming the traveling twin remains in the solar system).

Yes, I agree (except it would not be the sun, it would be the barycenter, which is near the sun, but which point the sun ALSO revolves around).

The problem SR would purport to have with this is that you have established a "preferred frame." That would be the one frame that would give you the correct answer, with respect to each twin (and not just with respect to one versus the other).

But that objection would be hollow. In "solving" the twin paradox issue, relativists simply establish the earth as the "preferred frame."

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@layman,

Both are moving, but one more rapidly than the other. The earth is also moving. If you adopt the right (thus inertial) frame of reference to compare their respective speed, you can accurately calculate the time dilatation accumulated by the twin traveling in the space craft, as compared to the twin traveling on earth. I would imagine that choosing an heliocentric frame of reference would also ease the calculation of gravitational time dilatation, except perhaps immediately around the earth.

1 Reply

@Olivier5,

Quote:

. If you adopt the right (thus inertial) frame of reference to compare their respective speed, you can accurately calculate the time dilatation accumulated by the twin traveling in the space craft, as compared to the twin traveling on earth.

Again, I agree, Oliver. So far, we have not disagreed on anything. Do we disagree on other things? I have asked you several specific questions, and asked you if you disagree. You have not responded to any of those questions yet.

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@layman,

Which questions, if you don't mind repeating?

1 Reply

@Olivier5,

Repeating gets messy. They are all right on this page, and are presented after your first post.

Here is a link to one, and the post immediately following contains others:

http://able2know.org/topic/265997-29#post-5893004

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@layman,

layman wrote:

I said:

Quote:
What SR does NOT say is that the earth twin's clock ALSO runs slow. It does not say that "both are correct" when they each claim that it is "the other guy" who is moving. One is WRONG when he says that (the travelling twin). One is RIGHT when he says that (the earth twin).

Are you claiming otherwise, Oliver? Do you think SR says "each clock runs slower than the other, and therefore each twin is younger than the other," or anything like that? Do you think the mainstream physics community says "there is no way to say which one ages less, therefore there is no answer to the question of which one ages less?"

No. I say that they are both moving, but one faster than the other.

1 Reply

@Olivier5,

Quote:

No. I say that they are both moving, but one faster than the other.

OK, good. We agree on that too. I don't think you were aware of what the dispute was when you first posted and said Parados was "right." You also disagree with his claims, obviously.

You have changed the question, which is fine--it's just that it's a different question.

1 Reply

Why in the world would Einstein suggest....

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