And yet lower down the page you seem to describe the principle of equivalence very well. Funny how you keep doing that, flatly deny something one minute, then write almost an erudite piece to the opposite effect a moment later.
Maybe its due to knowing when it applies, and when not.
You seem not to have understood, or at least acknowledged or spoken to, my argument. They do not cancel out, I believe, because the force on them is proportional to the combined mass:
F = GmM / r2but the acceleration on each body is inversely proportional to its own mass:
a = F / m,
a' = F / M
Hence, for two mutually attracting masses of great difference, such as yourself and the Earth, when you fall, you accelerate considerably more than the Earth.
Same applies for the ratio of the two falling masses. The Earth is the common source of the much greater gravity. You don't need to include the Earth itself.
The forces are the same between the objects and the Earth.
If you were perhaps interested in displacement, it may be necessary to consider the Earth, but of course, if one mass pulls the Earth towards itself, it moves towards the the mass by an equal amount.
For two different masses falling towards the Earth, the difference will be less obvious, since their masses are less obviously different in most experimental situations. Do you suppose a star will fall into a black hole at the same rate as an equidistant orange? I haven't been corrected on this yet, though I have to say I'm not absolutely sure of it. I have a feeling that if I google I'll find actual experimental data confirming this.
There are no simple answers to questions of black holes. You did say you wanted c.m.? Otherwise, same as above.
You forgot to mention what happens to very fast mesons as they enter the atmosphere...
It sounds like you don't know how you'd decide.
It means that nature does not go about trying to fit itself into human systems of classification.
Yes, it sounds very much like you don't know what, in between "relative" and "absolute" acceleration might be, if you could "do that".
There is no need to make the distinction.
Both are artificial. That is the point.
Brilliant.
I wrote about this myself not so long ago. Not particularly relevant here, but fine, we agree.
ETA: Oh no, it's actually a very good example of the different accelerations due to gravity, as I argue above. The big mass of the sun doesn't move as much as the Earth orbiting it.
But the Earth is falling, John. Why do your accelerometers work?
The "same goes for" it? What, acceleration orbits round its shared centre of mass? Absolute acceleration may be about to gain meaning, perhaps? Yea Dude, pass the Rizlas. I think you might be on to something.
Same as above. The Earth is falling towards the sun. Newton himself used this way of decribing orbit.
"Einstein liked to say that the Moon is "out there" even when no one is observing it.
Realism in the sense used by physicists does not directly equate to realism in metaphysics.[1] The latter is the claim that there is in some sense a mind-independent world."
Er, no thanks. Post that on Philosophy & Religion maybe.
Not speaking for Einstein this time, John? You do stress the role of the conscious observer. A fashionable idea, I think.
Shall I wikki wikki, or will you?
You.
This is all rather garbled, but seems to be refuting the P of Equivalence, y'know, that Einstein thing you described almost perfectly later? You even pose the wrong conditions in this - "stationary in a gravitational field" is not the condition, it is accelerating in a gravitational field that is indestinguishable from zero g.
There is no gravitational field that is indistinguishable from zero-g. It is distinguishable in free-fall or not.
Yes, plummeting towards the Earth. I criticised the idea that we can't tell the difference earlier, but by considering visual reference outside. You can't tell if the force on your arm is due to being in a vomit comet or out in the depths of space with no gravity, except by knowing that some other way. But as you have shown, you don't understand the importance or purpose of taking away information and asking what can be discerned. To you it just seems a cruel trick, I suppose.
Not a cruel trick, but pointless. You can ignore all knowledge by anesthetising yourself for the duration of the experiment.
To raise your arm, you must do work against gravity, falling or not. That is detectable.
You
can say there is no force on an object in free fall, but that force reappears as soon as it is opposed. That is not the case with zero-g. Zero is zero.
There is stress along any body that is in free fall. That too is detectable. The ISS hull is stressed by the same forces.
That's not what more reliable sources are telling me. When I say "more reliable", I mean ones who wouldn't suggest you "pour a glass of water" in either scenario. How? How do you even set that experiment up?!
You can do it on the vomit comet. The resulting stream will break up, and let you know that you are being accelerated. The drops will be separated by displacements that will not happen in zero-g.
Motion in such an environment can be misleading. You move a little, but to the outside observer, your actions are stretched over a much greater distance. This has consequences for the amount of apparent work expended. You don't appreciate those effects from the inside.
Acknowledged already. Nil points. That's like saying that the cart can tell the difference when it's on the treadmill because it can see the television.
Ridiculous. There is no other information necessary. You are building castles in the air.
Two standard mass-sensing accelerometers, one on each end of a bar. Spun in zero-g, they would show a constant output as a result of that acceleration.
In free-fall towards the Earth, each acclerometer will either be moving with gravity or against it, with each revolution. Easily detected.
