Why in the world would Einstein suggest....

@dalehileman,

Finally saw the bbcode editor location.

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@dalehileman,

Quote:

Yes, Con, no, I realize there's not supposed to be such a point

This seems to be a common conclusion (that there is not "supposed to be" any motionless object in the universe).

But even Einstein never made that claim. He simply claimed (as Newton did also) that such a point would be undetectable by us.

There is a big difference between "not seen" and "not existing," although some seem to think they are one and the same.

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@layman,

I think you are confusing the terms "knowing human"(a concept for psychologists and philosophers) with "standard observer" (a concept for physicists). Also, as I understand it, "acceleration" was excluded from "special relativity" although it was included in "general relativity".

NB The British childrens' classic "Worzel Gummidge" was about animated scarecrows one of whom believed that it was not the train that moved but the earth and trees. Presumably children who had sat on stationary trains and experienced the feeling that they were moving backwards when in fact it was an adjacent train next to them moving forwards would have identified with this character.

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@fresco,

Quote:

I think you are confusing the terms "knowing human"(a concept for psychologists and philosophers) with "standard observer" (a concept for physicists).

Maybe so. What is a "standard observer" as a physical conception, exactly?

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@fresco,

Quote:

Also, as I understand it, "acceleration" was excluded from "special relativity" although it was included in "general relativity".

I think it was "excluded" from SRT only in the sense that the SRT fails when one object is accelerating. Under those circumstances, it is no longer true that the speed of light is isotropic, etc.

Under those circumstances, the accelerating observer does not (and can not) assume he is motionless as is otherwise required by the theory.

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@layman,

A "standard observer" is hypothetical one who is observing "raw data" without any preconceptions or measurement bias. Such an observer would not for example be able to distinguish between states of "uniform motion" or "rest" if visual clues are excluded and there is no acceleration.

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@fresco,

Quote:

...although it was included in "general relativity

I'm no expert on GR by any means but it appears that Al aspired toformulate a theory of motion that encomplassed accelerating objects (and for a while thought he had succeeded).

However, all the experts I've read seem to agree that GR is NOT a theory of relative motion, but is simply a theory of gravity.

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@fresco,

Quote:

A "standard observer" is hypothetical one who is observing "raw data" without any preconceptions or measurement bias. Such an observer would not for example be unable to distinguish between states of "uniform motion" or "rest" since visual clues are excluded and there is no acceleration.

Hmmm, not sure I agree. Not sure why you say a "standard observer" is "without visual clues."

I think that Al, like Gallileo before him, made a clear distinction between what you could determine WITHOUT visual clues, and what you could determine WITH external information.

Gallileo said that, below the deck of a ship in uniform motion, you could NOT tell if you were moving. But, he said, this situation changed radically if you were on deck, watching places on the coast go by.

A guy who goes to the moon knows he was moving toward the moon (and back again). He doesn't assume, or for one minute believe, that he remained motionless while the moon came to him. Wouldn't he be a "standard observer" for physical purposes, fresco?

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@layman,

Sorry. I actually edited that slightly.

But you are missing the point that a "standard observer" theoretically brings no "knowledge" or" belief" to his observation (which of course may make no sense philosophically).

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@layman,

Quote:

then if the earth was moving "west" at 60 mph relative to the CMBR, a train moving at 60 mph westward on the earth would be moving 120 mph westward with respect to the CMBR, wouldn't it?

Yes it would. However Lay I recall having the train headed east

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@dalehileman,

Quote:

Yes it would. However Lay I recall having the train headed east

OK, sorry, Dale, I didn't read your posts that carefully. I see what you're saying now, but, again, I don't see how it's relevant to the train vis-à-vis the earth's surface.

The train and the earth are in relative motion. Which one is moving? I mean as between the two, not as possibly perceived by some hypothetical third party.

As contrex pointed out, we can, and do, have ways of knowing which one is "actually moving" (as between those two) and it aint the earth.

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@fresco,

Quote:

...that a "standard observer" theoretically brings no "knowledge" or" belief" to his observation (which of course may make no sense philosophically).

A professor named Hogg wrote a book on SR where he defined an "observer" as an INFORMED observer, one with perfect knowledge of the facts. An observer who would not, for example, confuse the travel time of light with the time dilation effects caused by relative motion.

So his definition was different. For him an "observer" was one who did in fact look at more than just the sensual input he was receiving and who drew conclusions based on knowledge, not ignorance.

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Dale, I looked at a thread you started a couple years ago, entitled "uncertainty in relativity."

Among other things, you brought up the issue of a preferred frame of reference.

Al said, in 1905, or shortly thereafter, that a traveler would age slower than a motionless (or relatively motionless) party. The Lorentz transformations incorporate this presumption. They say that time slows down for the "moving" party.

Of course the transformations do not tell us who is moving. But, whoever it is, time will slow down for them.

And, of course, that is why the traveler ages less in the twin paradox. That is, because he is the one moving.

There's nothing paradoxical in that, per se. The paradox only enters when one tries to insist that there is no way to determine who is moving. If you make that claim, then you could never consistently claim (as relativists do) that the travelling twin would age less. To say that, you MUST know who is moving.

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@layman,

You see, he isn't talking about you being aware that you are moving, he means your body. It feels as if it is one place and not moving. And your brain would most likely take the moving trees, signs, cars, etc. as them moving rather than you.

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@Poseidon384,

Quote:

You see, he isn't talking about you being aware that you are moving, he means your body.

Yeah, Poseidon, I agree, and that's why I ask the question. Any false illusion a train passenger may have about being motionless is just that--a mistaken belief based on subjective misperception.

Why would we want to base a physical theory on the supposed "truth" of illusions? Isn't physics about "objective reality," as opposed to subjective perception? Psychology is more appropriate for explaining behavior using subjective belief as a basis for explanation, isn't it?

I really just don't get it.

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@neologist,

Quote:

If I am misquoted by someone speaking alone inside a soundproof closet, does that mean I never said anything at all?

Heh, Neo, good question. Of course the answer might depend on your philosophy. If you're a solipsistic subjectivist, the answer would be "yes, you never said anything."

Berkeley was an ingenious proponent of such a philosophy. His edict was that "to be is to be perceived." He argued that trees which existed when you were looking at them ceased to exist the second you looked away from them.

Not a very persuasive philosphy, if you ask me.

Back in Al's day, Ernst Mach was a strong proponent of employing such a "positivist" approach to the physical sciences. As a younger man, Einstein was a fervent admirer of Mach (and of David Hume who made similar arguments).

Later, Al came to see the errors of Mach's naïve ways, and basically ridiculed the Machian thesis.

But his early views were later used against him, all the same. Guys like Bohr, for example, cited his early decrees against him as a method of defending QM.

As a philosophy of science, positivism held strong sway for the first half of the 20th century, and was deemed to have encapsulated the essence of wisdom. Positivism has now been completely refuted and is almost universally rejected by thinking people.

Yet, there are still some, as evidenced by some of the replies in this thread, who believe they are profound when they assert that certain question/concepts are "meaningless."

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@layman,

Actually, even Mach seemed to realize the internal inconsistencies being generated.

Mach argued that a geocentric view of the solar system was just as "valid" as a heliocentric one.

Nonetheless, he also proclaimed that "the universe is only given once." In other words, its either one or the other, but not both. So, one of the views has to be "more valid" than the other, even if we don't have the means of determining which one it is.

In SR, two observer can both "see" the other as moving while they remain motionless. But, as a logical matter, they cannot BOTH actually be motionless while in motion relative to each other.

Hence, at least one of them has to be mistaken when asserting that he is motionless.

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@layman,

I have personally written reams on this forum regarding the philosophy of observation, which is what Hogg is talking about. That is not what the concept of a standard observer is about. It is a device like a mathematical axiom which forms a substrate for a subsequent mathematical model which turned out to be successful with respect to enhancing prediction and control of what we call "the world". Without such "success" we would not be having this conversation.

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@layman,

I suggest you read something like...
http://plato.stanford.edu/entries/scientific-realism/
or
http://books.google.co.uk/books/about/Arguing_about_Science.html?id=iGpd3xLGNbYC&redir_esc=y
You might discover that "logic" is a bit player in the debate.

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@layman,

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As contrex pointed out……. actually moving……... aint the earth.

Thanks Lay but I wonder if you might be persuaded to provide a link to the posting in which Con makes this assertion

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The train and the earth are in relative motion. Which one is moving?

I was proposing an imaginary point with which the average speed of everything else is minimized, which might serve as a reference

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Why in the world would Einstein suggest....

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