J.C.MacSwell

Except time slowing down, correct? And a mass decrease for anything inside? (compared to the same matter with no shell there)

I am not suggesting Newtonian never differs from reality or GR. I am saying Newtonian results are always consistent, regardless of what frame you choose. They give the same result. This would also be true in GR compared to the calculations from different frames in GR (not that I could do them), and, I would like to think, in reality as well. If you could somehow quickly shift the Sun to where Mercury is (or have it disappear) you would get different results in Newtonian or in GR, but in each case you would get consistent results for each, independent of choice of frame. Newtonian would instantly shift the gravitational vector to the new position of the Sun (or force would disappear). GR would do the equivalent (approximately) but only after a lag...the effect would remain in the direction toward where the Sun was going to be until after the lag. This is I think approximately right, and assuming an equivalent set of assumptions for each frames calculations. In reality the Sun shift would have to have some cause, and of course a disappearance impossible.

It doesn't happen (in reality, GR, or Newtonian) "otherwise" there would be different results in different frames

Keep in mind that using the CoM is based on a spherical distribution of mass. Other distributions won't always sum to the same thing. The gravitational vectors for Newtonian Gravity point directly to current position (no lag), and for GR they tend to the equivalent of that for lower speeds and where no abrupt changes take place, even though their is a lag in GR. For, say, two masses some distance apart stationary in the same inertial frame, the gravitational effect would be directly toward each other. It would not be any different in other frames of reference...(measurements of what is considered "current" or simultaneous aside)...otherwise the two mass system could have a net self drag effect in a frame measuring them to have velocities parallel to each other due to the lag, and of course this does not happen. Just saw MigL's post...same example

Now...you guys are going off on a tangent

The spin is not accelerating, but all points off the rotational axis are. There is a net centripetal force as the resultant of gravity and other forces. There are tidal effects as well, so the effective gravity is not constantly the same at any point.

"If you build it...they will not come back"

Thanks. Nice to know my contributions have not gone unnoticed...(and here I always thought it was you helping me)

Essentially same as Swansont except, as you can tell from my last few posts, I am not clear on how the GE is accounted for with regard to mass. If say, you took a kg of lead from Earth and dropped it off on the moon at the same temperature I would have assumed it was the same mass, 1 kg, (but say warmed up to a higher temperature, then over 1 kg, which I am sure is correct) So I'm thinking I have to do some...thinking

So without the moon changing materially, or with regard to KE, it's mass increases due to it's change in position with respect to the Earth?

Are you referring to the mass of the moon, or to the moon's contribution to the mass of the Earth/Moon System?

That is the problem I would have with the example you gave. How can the mass of a system be less than the sum of it's parts?

Possibly. I have always had a problem with what seemed to me an arbitrary (though convenient at times) choice of having gravitational PE as negative. It's something I would like to have a better grasp of.

Keep in mind that the mass of the system is greater than the sum of the masses of it's constituent parts. The system has a different rest frame than M1, which is different again from M2.

I think that would have to be correct. If gravitational radiation is detectable as per recent news, then their has to be associated energy in the detection. No matter what the source of the Earth's movement, "Theia whacking" or whatever, the satellite will be responding to the changes in Earth's position.

Like a satellite going around the Earth as the Earth accelerates toward the Sun?

Essentially Feynman showed that, at the same temperature throughout, the mechanism is as at least as likely to slip as it is to consolidate a gain in potential energy. It can be hard to pick out the flaws, but generally every scheme that tries to beat the second law of thermodynamics to produce useful energy at a macroscopic level can be shown why it won't work...and of course no one has ever built a mechanism of that type that works

Sounds similar in objective to a Maxwell's Demon or Brownian Ratchet, trying to beat the second law of thermodynamics... https://en.wikipedia.org/wiki/Maxwell%27s_demon https://en.wikipedia.org/wiki/Brownian_ratchet

Line 1: Two different circumstances 1)The 1:1 change between PE and KE is with no drag for an elliptical orbit...add a drag component and you change the ratio, generally not to any special 2:1:1 PE:KE:Drag split 2)The 50:50 ratio between KE and drag losses, which split the PE change, is generally approximate for a slowly decaying, substantially circular, orbit Line 2: It does not have to be that way. The ratios depend on the resultant forces at any given point. Quantum considerations are insignificant here Line 3: You can get other ratios Line 4: A decaying long elliptical orbit will have varying ratios. This can be readily seen by comparing the resultant forces and velocities at various points. It's fairly simple Newtonian mechanics at any given point, even if more complex to track over time.

In a slowly decaying almost circular orbit there is a approximate 50:50 split of the PE change(100%), between drag loss(50%) and KE gain(50%). A change in the drag will, at least temporarily, change these ratios, and of course in elliptical orbits they are changing in (almost) any case.

Studiot was just trying to keep up with the "dirtyness" of the thread...

That's right. Same speed but different direction.

Except of course, like a broken clock being right twice per day...for elliptical orbits KE = 1/2 |PE| holds twice per orbit

I assumed an instantaneous slowing with no change in direction...an idealized impulse in the same direction as any would be drag. Once this takes place the body is free in the elliptical orbit, and will follow the path of that orbit.

After impact and forever in an ideal Newtonian case, once per elliptical orbit, until something changes the system. GR is different but that would be off topic.