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Compressed Matter

@scotth

But did Newton (or anyone for that matter) ever explicitly say that gravity propagates at some speed or that the force vector points at where the planet is now or at some earlier point? I think not. I think it was centuries before anyone even came across a situation where it made a difference that prompted the question. And when the question did come up people had to try it both ways to find out that both approaches still had problems.

Basically I'm making a small point that I don't think Newton was prescient enough to have even considered the question or to even realize he might have implied something about the question. When 19th century scientists realized this previously unaddressed question made a difference they had to answer it.
 
RecoveringYuppy said:
Basically I'm making a small point that I don't think Newton was prescient enough to have even considered the question or to even realize he might have implied something about the question. When 19th century scientists realized this previously unaddressed question made a difference they had to answer it.
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That is not the impression that I had... I hope to be able to find the passages (probably of the Principia) that led me to believe otherwise.

I do think Newton considered it and instantaneous action was his conclusion. Now, can I support that? This will be a tough one I bet.
 
I've read Principia but probably not with this particular question in mind. I do remember reading something about some of the early attempts at explanations for the anomolous precession of perihelions. One early writer on that subject speculated about gravity taking time and pointed out they had no way to know and had to assume gravity was instantaneous.

I suppose it is also possible that Newton himself explicity thought or said it was instantaneous but that no one took him seriously. He was at odds with almost everyone of his time over how actions could propagate over distance.
 
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How does the speed of terminal velocity (falling through our atmosphere) relate to the speed of gravity?
 
ynot said:
How does the speed of terminal velocity (falling through our atmosphere) relate to the speed of gravity?
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I doesn't. The terminal velocity concept does not depend in any appreciable way on the speed of gravity.
 
ynot said:
How does the speed of terminal velocity (falling through our atmosphere) relate to the speed of gravity?
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Gravity is an acceleration, not a speed. Terminal velocity goes up with increasing gravity and down with increasing friction. On a planet with no atmosphere, terminal velocity would equal escape velocity.
 
Unnamed said:
I doesn't. The terminal velocity concept does not depend in any appreciable way on the speed of gravity.
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It most certainly does, although you mean acceleration of gravity. It is a balancing equation between air resistance and the force of gravity.
 
Zygar said:
It most certainly does, although you mean acceleration of gravity. It is a balancing equation between air resistance and the force of gravity.
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Maybe ynot meant the acceleration of gravity, but I meant the speed of propagation of the gravitational field, which was the subject being discussed for several posts until now.
 
Yes, it's not related to the speed of propagation of gravity, but is related to the strength of gravity.
 
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