Why in the world would Einstein suggest....

@layman,

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I didn't understand your post.

Do you understand the difference between logical soundness, and logical validity, Ollie?

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If you want to say that "each is correct, given his assumptions," then that says nothing about reality. Yes each has a VALID argument, given his assumptions. His conclusion does follow from his premise(s). But each argument cannot be "sound."

Do you understand this, from the post before it?

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There is absolutely NOTHING illogical about saying that A believes B's clock is slower than his, and B believes A's clock is slower than his. Curious, but not illogical.

But it is completely illogical to then say "and both are correct."

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@layman,

No to all.

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@layman,

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The mutual attraction MUST be considered and accounted for in Newtonian mechanics.

In theory it'd be nice, but in practice I don't think that's how it's done. The calculations are just too complicated. Similarly, the effect of, say, Uranus on Venus or vice versa is not taken into account.

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@Olivier5,

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No to all.

No, you don't understand?

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@layman,

Correct.

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@Olivier5,

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In theory it'd be nice, but in practice I don't think that's how it's done. The calculations are just too complicated. Similarly, the effect of, say, Uranus on Venus or vice versa is not taken into account.

Ya think?

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Although this effect is very tiny, it can be measurable. In fact, before Neptune was discovered, 19th century astronomers noticed irregularities in Uranus’s orbit and realized that this was a result of the gravitational pull of a planet beyond Uranus (i.e. Neptune). They were even able to correctly calculate where this “new” planet should be.

http://scienceline.ucsb.edu/getkey.php?key=3396

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Although it is convienent to think of the Sun as the stationary anchor of our solar system, it actually moves as the planets tug on it, causing it to orbit the solar system's barycenter.

http://www.orbitsimulator.com/gravity/articles/ssbarycenter.html

You can also see computer simulations of the motions (caused by mutual gravity) of the entire solar system at the last site.

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@Olivier5,

What don't you understand? Do you want to make the same bet Parados did?

Try this (the same thing said a different way):

A and B are moving relative to each other, and they both acknowledge this, but, as between the two

1. A claims he is motionless and that only B is moving, whereas,
2. B claims he is motionless and that only A is moving.

Can they both be motionless, and still have relative motion between them?

I mean, there is a real world out there, isn't there? Or do you, like Parmenides, claim that all motion is an illusion?

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@layman,

Yes, i think. The case of Neptune's discovery is one of the very few cases (with a variety of Lagrange points) where the interaction between planets is/was taken into account. Even if we know and observe that the sun is also affected by planets, i still don't think we have a model of all the motions in the solar system that take into account all interactions between all planets, moons, asteroids, comets, etc. That'd be too complicated to calculate.

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@Olivier5,

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...i still don't think we have a model of all the motions in the solar system that take into account all interactions between all planets, moons, asteroids, comets, etc....

Then you might want to look at this software, eh?

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Here is the entire Solar System to scale for the orbits, constructed with the Solar System Live software

http://csep10.phys.utk.edu/astr161/lect/solarsys/revolution.html

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@layman,

I don't understand the difference between logical soundness, and logical validity, for one thing.

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A and B are moving relative to each other, and they both acknowledge this, but, as between the two

1. A claims he is motionless and that only B is moving, whereas,
2. B claims he is motionless and that only A is moving.

Can they both be motionless, and still have relative motion between them?

The only thing they can reasonably claim is to be moving relative to one another.

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@Olivier5,

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I don't understand the difference between logical soundness, and logical validity, for one thing.

This is a valid, but unsound logical argument.
1. All elephants are pink
2. This animal in an elephant
3. Therefore, this animal is pink.

Logically, the syllogism is impeccable. The conclusion must follow from the premises, so it is a VALID logical argument. But it is UNSOUND because (at least one of) the premises are false.

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The only thing they can reasonably claim is to be moving relative to one another.

That may well be, at least in some cases. But it doesn't really answer the question. IF they make those claims is it even possible that BOTH could be right? We know they could both be wrong, but it's at least possible that one could be right (whether he "reasonably" made such a claim or not).

But is it even possible for both to be right?

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@Olivier5,

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The only thing they can reasonably claim is to be moving relative to one another.

You have made similar statements in the past, Ollie, because you were using the term "moving" in an absolute sense. But motion can simple be relative. Let me give an example:

I buy a ticket, get on a train, and take seat. While I am sitting there, waiting for the train to get going, I see a guy leaning up against a lamp post about 50 yards away, directly across from me (at right angles to the train. He's not moving, neither am I (as least not relative to each other).

True, we are BOTH moving on a rotating earth, we are BOTH on an earth that is revolving around the sun, we are both on an earth that, together with the galaxy as a whole, is moving toward Leo at the rate of about a million miles an hour BUT, we are NOT moving with respect to each other. There is no relative motion between the two of us.

Then the train takes off. Suddenly things have changed between me and this guy. NOW there is relative motion between us when there wasn't a minute ago.

See the difference?

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@Olivier5,

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Even if we know and observe that the sun is also affected by planets, i still don't think we have a model of all the motions in the solar system that take into account all interactions between all planets, moons, asteroids, comets, etc. That'd be too complicated to calculate.

I think you kinda have it backwards, here, Ollie. We know the positions of the planets from observation (not from theory). It is by observing them that we can see a pattern and then posit a theory (formulate a mathematical relationship).. At that point, we apply our theory to every observable action and see if it fits. So, at bottom, we know how each influences the other by observing where they are (and where they were, and were they will be).

Newton admitted he had no "theory," just a math formula that fit all the observable data. Hypothesis non fingo (or something like that, in latin) he said. "I finger (point to) no hypothesis (regarding how and why gravity had the effects that it has).

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@layman,

You don't understand the point being made, but it's a minor point anyway so I won't belabor it.

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@layman,

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Olivier5 wrote:
The only thing they can reasonably claim is to be moving relative to one another.

you were using the term "moving" in an absolute sense. But motion can simple be relative.

What part of "relative to one another" did you not understand?

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@Olivier5,

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What part of "relative to one another" did you not understand?

This part:

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The only thing they can reasonably claim...

Back to me on the train. Would it be reasonable, once the train started moving, to insist that, instead of moving north, I have remained completely motionless while the man, the lamppost, and everything else attached to the earth started moving south? Would it be reasonable for me to say that, as between the two of us, I cannot possibly tell who started to move? Would THAT be reasonable?

I don't think so! Homey don't play dat. (Neither did Galileo, by the way).

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@layman,

Okay, if they are on earth, both are moving cause earth is moving... Didn't i explain that already?

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@Olivier5,

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Didn't i explain that already?

Yes, you did, as I aready did, also. But that is totally irrelevant to the question at hand.

You don't make the distinction and confound the two motions. That's what I was talking about, when I said that you want to bring in absolute motion.

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@layman,

All motion is relative.

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@Olivier5,

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All motion is relative.

Great. Even if true, it does not address the question. However, according to SR, at least, all motion is NOT relative. Accelerating motion is absolute.

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Why in the world would Einstein suggest....

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