Why in the world would Einstein suggest....

One might view the statement, "A sees B's clock running slow, and also B sees A's clock running slow," as somewhat unsettling. But in fact, it would be a complete disaster for the theory if A and B viewed each other in different ways. A critical fact in the theory of relativity is that A sees B in exactly the same way that B sees A.

I have no problem with that

Your hypothetical is about acceleration and mass, not just movement.

OK, great. Now let's look at what this is saying. Let's take A to be a railside observer and B to be a passenger on a moving train.

If A claims he is not the one moving, and if B agrees, then now they are NOT seeing each other "in exactly the same way." This constitutes "a complete disaster for the theory," according to Prof. Morin.

and acceleration presumes some resulting movement, in most cases.

When you do, I trust you will find that if both observers are in an inertial frame of reference each sees the other one's clock run slower.

Of course. I have not assumed otherwise. In fact, that's what I see as the problem.

Acceleration does not imply a resulting movement, only a change in the rate of movement.

an observer on the sidewalk will see your car accelerate (in the direction opposite to its movement),

I'm not really concerned about how any particular observer might "see" anything. The motion is absolute, right?

It's a good thing, then, that B will disagree that A is not the one moving. B will observe that A is moving in the same direction as the city of Chicago is.

...[it is] equally valid to ask "will this train stop in Chicago?".

No, the motion is relative. The acceleration is absolute.

However, the term 'absolute acceleration' _does_ have a meaning. If you were on a roller coaster, even on one which has closed cars with no windows, you would still be able to tell you were moving -- you'd be thrown every which way, and you would even be able to feel the motion in your guts, given you were securely fastened in your seat. Now, when riding a roller-coaster, you definitely know it is YOU that is moving, and not your friend standing on the ground waving to you...

Similarly the same kind of situation exists between the earth and the moon -- the two rotate around the center of mass of the earth-moon system, but this point lies well within the earth, so it makes sense to say the moon is moving around the earth, and not vice versa.

But, haven't you just conceded that this claim of yours was inaccurate?:

Quote:

...[it is] equally valid to ask "will this train stop in Chicago?".

Physically speaking, waysidism and trainism are still equally valid worldviews. If we seem to be living in a waysidist world, that's a matter of social convention, not physics.

No I haven't, but I do admit to phrasing my reply sloppily. I re-phrase as follows: When A on the wayside says, "I'm resting; you, B, are moving", B on the train replies, "oh yeah? Maybe relative to your frame of reference you are, you waysidist-chauvinist pig! But relative to my frame of reference, I am the one who's resting and you are the one who's moving."

Won't my motion be seen, as such, as "real motion" by everyone, including myself?

The point being that you can't claim that "you can't tell who's moving" when accelerated motion is involved.

Or do you still disagree with that proposition? Is it your claim that such knowledge CANNOT inform you about which one is moving (relative to the other)?

No I haven't [conceded that]

But what is "equally valid" even supposed to mean?

You have now conceded other points which establish that what I said about SR was accurate.

Then imagine[ yourself in the role of the train, and the treadmill in the role of the rails.

This puts you all back in relativity-land, where no physical experiment can tell the difference between you speeding forward past the spectators and the spectators speeding backwards past you.

Whenever we go, say, downtown, then the moment we make that decision, the earth 'suddenly" starts moving under us while we remain motionless, and then stops doing so once it brings "downtown" to us?

Once again, you seem to be implying that the only way anyone can ever know anything is by conducting physical experiments in his own frame of reference.