Why in the world would Einstein suggest....

@Thomas,

I asked:

Quote:

Is anyone "really" moving, or is all motion just an illusion?

Your (short) response was:

Quote:

Neither

So then you are saying that:

1. It is NOT the case that all motion is just an illusion, and also that
2. Nobody is really moving.

I don't get it, I'm afraid.

2 Replies

@layman,

Just my

on that question about whether anyone is really moving/illusion.

My limited knowledge of SR makes me think that this would be a nonsense question unless you specify a reference frame. Without doing that, you can answer both 'yes' and 'no' without contradiction, I think.

1 Reply

@FBM,

Well, FBM, why would it be a "nonsense" question?

A & B moving, relative to each other (and they agree on this)
A, in his frame of reference, says HE is motionless
B, in his frame of reference say HE is motionless

Is it logically possible for both to be right, given that there is relative motion between them?

1 Reply

@layman,

As far as I can tell, it's correct for A to say "No, I'm not moving, but B is."
It's also correct for B to say "No, I'm not moving, but A is."

It requires an objective/absolute frame of reference to make a 3rd-party judgement about any absolute truth to any of those statements, I think.

2 Replies

@FBM,

Quote:

As far as I can tell, it's correct for A to say "No, I'm not moving, but B is."

What do you mean by "correct?" Thinks he is correct? Or simply IS correct?

0 Replies

@FBM,

I'm trying to understand your response, FBM, but, that said, it wasn't responsive to my question, which was simply one of logic, not one about "absolute truth."

You said:

Quote:

It requires an objective/absolute frame of reference to make a 3rd-party judgement about any absolute truth to any of those statements, I think.

That may or not be true, but you don't need to make any judgment about that whatsoever to answer a purely logical question.

1 Reply

@layman,

Well, I think I'm doing this logically.

How would you be able to judge whether A or B were "absolutely" correct or only think they're correct without a 3rd-person frame of reference? That's kinda the whole point of SR, I think.

By the way, I see that your and Thomas's discussion gets a bit heated now and again, but I'm not part of that. I'm not trying to be argumentative in the colloquial sense of the term; I'm just trying to make a logical argument.

2 Replies

@FBM,

Quote:

How would you be able to judge whether A or B were "absolutely" correct...

Once again, that wasn't my question. Let me put it another way:

SR advocates will routinely tell you that "A sees B's clock running slower, and B sees A's clock running slower." OK, fair enough.

But to the extent they address it at all, to a man, every physicist I've seen says it would be "absurd" and "impossible" to conclude that "each clock is running slower than the other."

How can they come to that conclusion? Because, its LOGICALLY impossible, irrespective of any particulars about A and/or B.

1 Reply

@FBM,

Quote:

By the way, I see that your and Thomas's discussion gets a bit heated now and again, but I'm not part of that. I'm not trying to be argumentative in the colloquial sense of the term; I'm just trying to make a logical argument.

Great, me neither. I didn't think the exchange between Thomas and me was "heated," although it's obvious that we disagree on a number of things.

0 Replies

@layman,

layman wrote:

Is anyone "really" moving, or is all motion just an illusion?

The "really" part of this seems to imply that there is an absolute truth independent of any observer. Am I wrong about that?

0 Replies

@layman,

layman wrote:

Quote:
How would you be able to judge whether A or B were "absolutely" correct...

Once again, that wasn't my question. Let me put it another way:

SR advocates will routinely tell you that "A sees B's clock running slower, and B sees A's clock running slower." OK, fair enough.

But to the extent they address it at all, to a man, every physicist I've seen says it would be "absurd" and "impossible" to conclude that "each clock is running slower than the other."

How can they come to that conclusion? Because, its LOGICALLY impossible, irrespective of any particulars about A and/or B.

The part I bolded is a statement made from an objective, 3rd-person, absolute frame of reference, which SR says doesn't exist.

3 Replies

@FBM,

Quote:

The part I bolded is a statement made from an objective, 3rd-person, absolute frame of reference, which SR says doesn't exist.

No, I don't think so. It is what relativists actually say. But again it is not even a matter of "motion" or even of SR. It is a question of logic only.

Try this:

Al claims he is taller than Bob.
Bob claims he is taller than Al.

Is it logically possible for BOTH of them to be right?

You don't have to know how tall either of them is to answer the question.

You don't have to know who is taller (if anyone--they could be exactly the same height).

You don't need to know a single thing about them, really, to answer the question.

1 Reply

@FBM,

But let me take it one step further.

Suppose now, that Al is 6' 3" and Bob is 5' 4" tall.

Would that make Al right? To me it would.

But, I guess you could take the position that, regardless of the true facts, "both" are right, because whatever they choose to believe is "right for them."

That's why I asked in what sense you were saying they are "both correct," FBM.

0 Replies

@layman,

layman wrote:

Quote:
The part I bolded is a statement made from an objective, 3rd-person, absolute frame of reference, which SR says doesn't exist.

No, I don't think so. It is what relativists actually say. But again it is not even a matter of "motion" or even of SR. It is a question of logic only.

What the relativists say is that it's impossible/absurd to make that claim (I didn't highlight that part.) It is impossible/absurd for the very reason that there's no absolute frame of reference from which to make that statement.

Quote:

Try this:

Al claims he is taller than Bob.
Bob claims he is taller than Al.

Is it logically possible for BOTH of them to be right?

You don't have to know how tall either of them is to answer the question.

You don't have to know who is taller (if anyone--they could be exactly the same height).

You don't need to know a single thing about them, really, to answer the question.

Of course, it is logically impossible for those contradictory statements to both be correct, but I don't think this is a good analogy. The SR frame-of-reference issue is vital to the question about who is "really" moving or whether or not anybody is, but the question about height is relative to a ruler, which is a 3rd-person absolute measure. In SR, no such "ruler" exists, so no such truth statment can be made about "real" motion outside the perceptions of the agents, A and B.

1 Reply

@FBM,

Quote:

In SR, no such "ruler" exists, so no such truth statment can be made about "real" motion outside the perceptions of the agents, A and B.

Well, don't you think SR builds in it own "ruler" on this matter? SR says the moving clock runs slow. If you know who's clock is running slower, then you know who is (or was) moving.

All the relativists seem to agree, for example, that it is the "travelling" twin whose clock "really" runs slower in the twin paradox.

1 Reply

@FBM,

Excellent exposure of the straw man "God's Eye View". There are no "conclusions" made by physicists about reality of faster/slower. Only statements about the equivalence of appearances or "observational constraints" in inertial reference frames. THAT is what layman cannot get his head around. The twin paradox (so called) was a curiosity raised by Einstein himself referring to non-inertial reference frames in which the inextricability of space-time is the central issue, not concepts about "appearances" limited to non-inertial reference frames. And it is that first show of genius of the upsetting of "common sense" in physics which many find it difficult to cope with. The irony is that subsequent upheavals of common sense in physics were resisted by Einstein himself.

3 Replies

@layman,

I don't think SR is making its own "ruler." I think it's getting rid of all objective "rulers." I'll have to do some reading up to be more confident about my answer, though. I think that SR says the clock will "seem" be moving slower by the second observer, which is quite a different statement from saying that it IS moving slower. If the statement is that A's clock is moving slower "for B," then we still don't have a 3rd-person objective "ruler."

1 Reply

@fresco,

Thanks, fresco. SR is a bit out of my regular domain, so I'm not all that confident in my grasp of the details. I'm learning a good bit due to this discussion, though.

0 Replies

@FBM,

Quote:

I think that SR says the clock will "seem" be moving slower by the second observer, which is quite a different statement from saying that it IS moving slower.

I agree with this (that they are two different things). That said, someone else made the claim early in this thread that is was only an appearance., and I quoted Einstein verbatim in response (who said it wasn't "just an appearance"). Hold on, I can probably find it fairly quickly.

Here it is:
http://able2know.org/topic/265997-9#post-5878401

1 Reply

@layman,

I buggered the grammar in that sentence, didn't I? Let me try again: "I think that SR says the clock will "seem" to be moving slower to the second observer..." Like that.

0 Replies

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