Why in the world would Einstein suggest... 2

So no evidence. Like for Popper, you're probably pulling that idea of a late-days relapse of Einstein from your rear end. And no, the LET was not just about electrons. It was an attempt to explain the Michelson Morlet experiment. But you know since you mentioned it yourself in that context. You just try to evade reality now.

Willfully maintaining your abject ignorance, yet again, eh?



Yes, of course it was. It was the attempt at a constructive theory of time dilation, the kind that Al despaired of and gave up on. It was about how the ether altered the motions of electrons.

Have an answer to Dingle's question?

What Dingle question EXACTLY?

What Dingle question EXACTLY?

See my last post (before yours).

Why does a clock at the equator moves faster than a clock at the pole, in SR? Because there is NO possible inertial frame of reference in which the earth would not be spinning around a north-south axis passing through the pole. Any inertial frame one can think of will show the same picture, consistent with modern cosmology: earth spins on its axis when cruising along its orbit around the sun. Therefore, calculating time dilatation in any convenient inertial or quasi-inertial frame of reference, one is bound to find that the equator clock moves faster than the north pole one. Always. Whatever the inertial frame chosen to make the computation.

Let's take this one step at a a time.



Why do you say this? Why couldn't the earth, at it's equator, be motionless, with the clock at the pole rotating?

Along the same lines, why couldn't the entire earth be motionless, with the Sun and the stars revolving around it (as was believed for many centuries)?

Note that, in any frame of reference anchored anywhere on the equator, the poles are not moving. From any point of view (any frame) anchored anywhere ON THE PLANET SURFACE, the whole planet is at rest (except for seismic and tectonic activity).

So both clocks are at rest as viewed from the earth surface.

Such a frame of reference anchored, say, in the Perpignan railway station, which Dali said was the center of the universe, is not inertial because of half a dozen reasons, eg:

Observation: a pendulum suitably tied to the ceiling of the main hall and allowed to oscillate for an entire year would do so along a plane that would rotate an entire 360• during that time.

Theory: SR says nothing can move faster than the speed of light in any inertial frame of reference, yet in an earth-bound frame all the stars would daily break the speed of light many times over.

One can perfectly represent the universe from an earth-centric view point. We know how to predict how the sky will look like over Perpignan. In fact it's done all the time when drawing sky maps. But such a point of view is not inertial in SR nor in Newtonian mechanics. Sky maps are BACKED by computations done in inertial frames (sun-centric), but they translate the result of these computations into a non-inertial point of view (rotating, on orbit).

Err... The pendulum only needs 32.7 hours to turn 360 degree... Ooops

OK. New York never moves with respect to Los Angeles, I agree. So how does that square with what you first said:



You've said a lot of stuff in this post, but, like I said, let's just take it one step at a time.

So which is it? Both are at rest, or the earth would always be spinning? Remember, now, the question is how and why Al can say one clock is moving, and one isn't.

I told you already: Foucault's pendulum. The rotation of its plane of oscillation could not happen if earth movement was inertial. I suppose he could also use a gyroscope, including one based on the Sagnac effect, ie on SR.

You already told me what? I understand you to be saying that, by interpreting the motion of a Foucault pendulum in a certain way, we can conclude (even if we don't "see" or "feel") that the earth is rotating. But I asked you which of the two statements you made about "frames" was correct. Have you "told" me that?

What two statements?

If a frame rotates, ergo it is not inertial. Inertial stuff don't rotate. What's so hard with that?

Why would you ask that? The ones I quoted. These:

#1:

#2

Which one of those two are you now claiming is correct?

As I said before:



You go from talking about frames of reference to talking about a Foucault pendulum without explaining how and why that's relevant. Not saying that this is necessarily relevant either, but we are talking about one clock being at the equator and, with respect to a Foucault pendulum at the equator:



http://www.si.edu/Encyclopedia_SI/nmah/pendulum.htm

With respect to a Foucault pendulum at the north pole, if you viewed the scene from a distant star, the earth would be rotating and the pendulum would not (it would remain in the same plane). From the perspective of a person standing at the pole, the earth would NOT be moving, but the pendulum would. Is one of these two views "correct?"



http://www.juliantrubin.com/bigten/foucaultpendulum.html

Both statements are correct. They don't contradict one another.

Something is not clicking, apparently...

"non-inertial" means "accelerating." So are you saying that both the clock at the equator and the clock at the pole are accelerating? I guess you are, but how do you know that? Aren't you just assuming your conclusion and begging the question when you assert that: "Inertial stuff don't rotate."

Again, for centuries it was assumed that the earth was motionless, and the heavenly bodies revolved around it. We no longer believe that. Do we have good reason not to believe it? You think we do, and I do too, but are you conceding then, prior to your countless prior assertions to the contrary, that all motion is NOT relative, i.e, that we have ways of detecting which of two objects is "really moving" (rotating)?

Ollie, for now, at least, I am going to withdraw the question of how you know the earth is non-inertial. But here's the question(s) I do want answered:

Do you now concede that all motion is not relative? Put another way, do you concede that we "know" the earth is moving, at least in a rotational way?

I guess you do, and that is itself a HUGE step forward from the position you have always taken before when you repeatedly claimed that all motion is relative (no matter how many times I told you that even SR said otherwise).

Just "yes" or "no" will be fine. I just want to know on what basis we can proceed without you claiming that I am wrong at every turn.

====
Now, then, back to this statement of yours:



Remember, the question is: how can Al know that a clock at the equator runs slower than one at the pole? Simply saying "the earth rotates" does not, in itself, answer that question, does it?

If a clock (or person) at the equator looks at a clock at the pole, it will not be moving, and vice versa, right? If that's true, how and why can Al say (in effect) that one is moving, and one isn't?

Yes, but "acceleration" in mechanics means something wider than in common language. It means any change in speed or direction of motion of an object, as the result of a force applied on the moving object. So when you slow down a vehicle, in a physician language you are accelerating your vehicle in the direction opposite to its motion... When you turn right, you accelerate you vehicle towards your right, etc. You can think of a spacecraft navigating, accelerating, turning or slowing down through the use of booster rockets located on the side and front of the spacecraft. Each rocket provides an acceleration in some direction or another. In this sense, slowing down and rotating are particular forms of acceleration.

Inertial means flying straight, without any kind of acceleration, with constant speed and with no rotation or turn whatsoever. The French technical term for this type of movement is "translation"--don't know if it errr translates... Hence the example of the train, to try and convey the meaning of an inertially moving object or frame to children, because a train running straight at constant speed is the closest thing to it in our daily life. It's only a metaphor of course, a real train rotates around the earth too and thus is not anymore inertial than our equatorial clock.

To rotate around something implies a force pulling you constantly towards what you rotate around. That force is a form of "acceleration", in physic speech. Ergo it makes the body turning non-inertial. When you make a pendulum rotate horizontally around your fingers, swinging it around your hand, you exert a force on the rope to make the pendulum turn around. That's your acceleration. As soon as you stop exerting that force, ie when you open your fingers and let the rope go, the pendulum will stop rotating around your hand and fly away, first in an apparent straight line (as an inertial object is supposed to do) then in a parabole, as gravity pulls it down. That, or it will hit you in the eye...

Under this understanding of acceleration as a change in direction or speed of motion, any object -- such as a clock -- rotating on earth surface is being constantly "accelerated" downward by gravity. Otherwise it would move in straigth lines, escaping gravity to fly straight into space.

So, to recap, if you can determine that the place you are in rotates around something or has any form of torque (and yes, we can easily determine this with a gyroscope, based on the same principle as the Foucault pendulum of conservation of angular momentum in all inertial frames), then it follows that the place has a non-inertial behavior.

You therefore cannot assume inertial any frame of reference immobile as compared to that place, aka anchored on that place.

The problem with that, is that the laws of motion as we know them can be easily described and calculated ONLY in inertial frames of reference. That's why we need them: the computations don't work well otherwise. The laws of motion as we know them apply in any inertial frame, but only in inertial frames. The conservation of kinetic energy, the conservation of angular momentum, etc. all these laws that we use to calculate the movement of stuff only work in inertial frames. Any torque, any acceleration of any sort, however small, in the frame of reference used to plot objects will introduces errors in the calculations.

So what is Einstein to do -- trying to verify his new theory of relativity but ignorant of earth rotation for the sake of the argument -- when he notices that various clocks placed in various locations on earth's surface accumulate different delays respective to one another, in spite of being seemingly immobile?

He must wonder if the frame of reference he uses is truly inertial... Could there be some torque in earth, that would explain this odd observation? He pulls his gyroscope out of the cupboard and looks at it for a very very long time... The axis of the gyroscope is slowly moving... Leaning towards the setting sun now... Proving that earth is not moving inertially but has some sort of rotation to it. He must calculate the speed of rotation and determine the axis!

To do this, Einstein will need to travel far and wide around the globe with his gyroscope in hand, to see how the "signal" changes as latitude changes. Wandering Einstein finally spots the north pole.... computes the angular momentum at that point and finds: one turn per 24 hours.

Eureka! says Einstein. That must be why the sky above us "turns" in the same 24 hours. The sky is not ACTUALLY turning! In fact our planet is turning... I wonder what they'll say about that back in the shtetl...

Sitting on the north pole, orienting his x, y and z axes so that are pegged pointing at suitable stars (now known to be fixed), Einstein builds another frame of reference in his mind that he hopes is inertial. This new frame explains the so far odd behavior of his gyroscope, at least... And when he calculates the time dilatation of the clocks placed at the equator and at the pole, calculating now that the one at the equator rotates at 40,000 km / 24 hours = 1,667 km/hour. Computing now the Lorentz transformations... it fits the clock data!!!... Einstein can rest, SR is consistent with all observed data, once the right (inertial) frame of reference is used.

If Michelson and Morlet had used a Sagnac interferometer (one where two rays of light turn around some space in opposite directions) rather than a cross-shaped interferometer, they would have found their "aether"... Or believed they did. They would have seen the sort of shift in the interferences that they were looking for. They would have proven the earth movement with lights and mirrors... But only rotation can be detected by a Sagnac interferometer, not inertial translation.

Does that mean that rotation is absolute, while translation is not?

(TBC)

Thanks for all the "information" about what acceleration is, but I really wasn't asking you that. I won't even go into what is considered to be "inertial" in GR, because it's completely irrelevant to what we're discussing here (SR).



Really? Who knew? That would, of course, depend on what the "laws of motion" are, wouldn't it? No one, from Newton on (and most before him) ever claimed that there are no "laws of motion" which would apply in a non-inertial frame. Are you suggesting that "motion" turns into some mysterious, completely incomprehensible, arbitrary, and unknowable thing as soon as some object accelerates?



Here's where you start contradicting yourself, Ollie, even though you're not aware that you are doing so, because you only have a shallow conceptual understanding of SR. You are suggesting that there is a "right" inertial frame of reference. What would be called a "preferred frame." SR says there is no such thing. LR says there is, of course.

So it is not SR that is "consistent with all observed data." I agree that his assertion that a clock at the equator would run slower is consistent with "all the known data. But that's not the question. The question is how is "all the known data" consistent with the contents of his theory. But that would be getting ahead of ourselves. Let's leave it aside for now.

Dingle's question remains: On what basis that is consistent with his theory can Al make the claim? Sure, he can determine it empirically. But how does his theory correspond to such empirically known truths? That's what we're seeking an answer to.

You say "TBC" which I take to mean "to be continued," but I will note that, so far, you have not given a direct answer to my simple "yes or no" question. But, given all you've said, I think you've answered it indirectly. To be sure, though, let me ask you again. Do you now concede that not "all motion is relative?"

You said:



In response, I said:



I may be misreading you here. If all you are saying is that in SR all inertial frames are "preferred" over all non-inertial frames, then I agree.