Why in the world would Einstein suggest....

@FBM,

Quote:

Depends on which frame they meet in.

How?

@oralloy,

Quote:

Once the bullet accelerates it will no longer be in its original inertial frame of reference

True. So you mean they are at rest, before they accelerate? Is THAT really what you're saying? BOTH of them!?

When they BOTH perceive relative motion between them!?

How does THAT work?

I guess you're just talking about the two clocks at the Naval Station, before take-off, eh? That is, at a time when there is NO relative motion between them.

I think FBM had a different situation in mind, though.

1 Reply

@layman,

layman wrote:

Quote:
Depends on which frame they meet in.

How?

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/airtim.html#c2

The two airborne clocks were measured in a third frame, the Observatory. They read differently depending on which frame they were measured in. While the clocks are still in their respective airborne frames, neither of them has lost or gained any time inside that frame. It's always the other one. Take one clock and put it in the other frame and the time gain or loss is measureable.

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@FBM,

Quote:

While the clocks are still in their respective airborne frames, neither of them has lost or gained any time inside that frame.

Who told you that? In the GPS system satellite clocks are, every day ( or would be, if not adjusted) losing time to earth clocks.

1 Reply

@layman,

layman wrote:

Quote:
While the clocks are still in their respective airborne frames, neither of them has lost or gained any time inside that frame.

Who told you that? In the GPS system satellite clocks are, every day ( or would be, if not adjusted) losing time to earth clocks.

"to earth clocks." Precisely. A different frame. I'm inside a frame now, sort of. My clock doesn't tell me that I'm either losing or gaining time.

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@FBM,

Quote:

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/airtim.html#c2

This site says (last sentence):

Quote:

It gives an experimental answer to the twin paradox.

The answer to the twin paradox, if you'll recall, is that the travelling twin ages less, and that, he lost gained every bit of that time in HIS frame, not the earth's.

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@layman,

You're in a frame right now, sort of. Are you gaining or losing any time?

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@FBM,

I think this is where you're going wrong, FBM:

Quote:

My clock doesn't tell me that I'm either losing or gaining time.

What your frame "tells" you is not always what's really happening. Again, think travelling twin.

1 Reply

@layman,

Then knowledge is impossible and chaos ensues.

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@FBM,

Quote:

Then knowledge is impossible and chaos ensues

.

No, not at all. Let me repeat this, from an earlier tell.

You seem to be forgetting one thing, FBM, to wit: Fowler CLEARLY says they are moving relative to each other. Is it POSSIBLE, at all, for both to be at rest, under those circumstances? Notice he does NOT say that they "really are" each moving slower than the other, only that they "appear" to be.

Every physicist I've ever seen weigh in on the matter, starting with Al himself, says that it CAN'T be the case that "each clock is slower than the other."

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@FBM,

FBM wrote:

...I'm thinking I need to bow out of the discussion. I'm not getting much from it, nor contributing much to it.

Good idea. I think that's the best move.

3 Replies

@FBM,

Quote:

Then knowledge is impossible and chaos ensues.

No, not at all. Only self-deception causes that. If a guy gets on a train, feels himself accelerate, then ceases acceleration (without feeling deceleration) then he KNOWS, from the law of inertia, if nothing else, that HE is moving relative to the earth, and that the earth is not (the thing) moving relative to him, while he remains motionless. He knows that. No lack of knowledge, no chaos.

Now, if he tries to DENY the law of inertia, then, yeah....lack of knowledge, chaos.

Likewise, a guy boarding an airplane knows he is moving in the air. He doesn't think he is "standing still in space" while the earth moves under him, does he?

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@FBM,

Quote:

I'm thinking I need to bow out of the discussion.

It's a shame you want to "bow out" just before it all comes to an end.

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@FBM,

SR ITSELF gives you a way to know what's really happening. It tells you it's ALWAYS the moving clock which runs slow.

If there was otherwise any doubt (which there shouldn't be to begin with) about whether it was the plane which was (the one) moving relative to the earth, the answer to that question can be given empirically. Just look to see which clock recorded less time elapsed. THAT will be the clock that was moving.

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@layman,

layman wrote:

True. So you mean they are at rest, before they accelerate? Is THAT really what you're saying? BOTH of them!?

ALL objects are at rest with regard to their original inertial frame of reference before they accelerate.

layman wrote:

When they BOTH perceive relative motion between them!?
How does THAT work?

If two objects have been moving with regard to each other since the moment of the Big Bang, it is possible for them to both remain within their original inertial frame of reference while still moving relative to each other.

layman wrote:

I guess you're just talking about the two clocks at the Naval Station, before take-off, eh? That is, at a time when there is NO relative motion between them.
I think FBM had a different situation in mind, though.

The principle applies to all situations.

1 Reply

@FBM,

One more thing that might be worth mentioning, FBM: Having a frame of reference (which everybody--and "thing" does) does NOT mean you are absolutely motionless.

It just means you are where you are, moving or not. You have a frame whether you are going 100,000 miles a second, or absolutely motionless. Whether you're accelerating, or inertial.

There is NOTHING in the concept of a "frame of reference" which requires that you treat yourself as THE motionless "ether."

Well, except for in SR, I mean.

But, like, what's up with that?

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@layman,

layman wrote:

The answer to the twin paradox, if you'll recall, is that the travelling twin ages less, and that, he lost gained every bit of that time in HIS frame, not the earth's.

It depends on the details of the particular scenario being proposed for the twins.

If one twin accelerates while the other remains in his original inertial frame of reference, yes. The one that accelerates will be younger.

1 Reply

@oralloy,

Quote:

If two objects have been moving with regard to each other since the moment of the Big Bang, it is possible for them to both remain within their original inertial frame of reference while moving relative to each other.

Not sure what you mean by that. Didn't EVERYTHING, by definition, begin accelerating after the big bang. In other words their "original inertial frame" could ONLY be the so-called "cosmic egg" which "blew up?"

If so that frame is long gone--for every particle in the universe, isn't it?

1 Reply

@oralloy,

Quote:

If one twin accelerates while the other remains in his original inertial frame of reference, yes. The one that accelerates will be younger.

Yeah, that's the scenario I had in mind. I believe that's the classical way of setting the stage for looking at the "problem" (which it really isn't).

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@layman,

layman wrote:

Not sure what you mean by that. Didn't EVERYTHING, by definition begin accelerating after the big bang. In other words their "original inertial frame" could ONLY be the so-called "cosmic" egg which "blew up?"
If so that frame is long gone--for every particle in the universe, isn't it?

Expansion of the universe is not the same thing as acceleration within the universe.

1 Reply

Why in the world would Einstein suggest....

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