All Questions
Tagged with gravity newtonian-gravity
404
questions
92
votes
7
answers
13k
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If dark matter only interacts with gravity, why doesn't it all clump together in a single point?
I'm a complete layperson. As I understand, dark matter theoretically only interacts with the gravitational force, and doesn't interact with the other three fundamental forces: weak nuclear force, ...
- 1,619
88
votes
8
answers
10k
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Could a "living planet" alter its own trajectory only by changing its shape?
In Stanislaw Lem's novel Solaris the planet is able to correct its own trajectory by some unspecified means. Assuming its momentum and angular momentum is conserved (it doesn't eject or absorb any ...
- 3,109
62
votes
5
answers
11k
views
Why is the Moon considered the major cause of tides, even though it is weaker than the Sun?
You have likely read in books that tides are mainly caused by the Moon. When the Moon is high in the sky, it pulls the water on the Earth upward and a high-tide happens. There is some similar effect ...
- 1,904
48
votes
5
answers
23k
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Why aren't there spherical galaxies?
According to the Wikipedia page on Galaxy Types, there are four main kinds of galaxies:
Spirals - as the name implies, these look like huge spinning spirals with curved "arms" branching out
...
- 615
39
votes
5
answers
34k
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Would you be weightless at the center of the Earth?
If you could travel to the center of the Earth (or any planet), would you be weightless there?
- 543
34
votes
4
answers
8k
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How can we recover the Newtonian gravitational potential from the metric of general relativity?
The Newtonian description of gravity can be formulated in terms of a potential function $\phi$ whose partial derivatives give the acceleration:
$$\frac{d^2\vec{x}}{dt^2}=\vec{g}=-\vec{\nabla}\phi(x)=\...
- 1,406
31
votes
4
answers
7k
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Why aren't the energy levels of the Earth quantized?
The Hamiltonian of the Earth in the gravity field of the Sun is the same as that of the electron in the hydrogen atom (besides some constants), so why are the energy levels of the Earth not quantized?...
- 1,523
27
votes
10
answers
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How does Newtonian gravitation conflict with special relativity?
In the Wikipedia article Classical Field Theory (Gravitation), it says
After Newtonian gravitation was found to be inconsistent with special relativity, . . .
I don't see how Newtonian gravitation ...
- 8,540
25
votes
2
answers
2k
views
How do spiral arms form?
Why aren't all spinning galaxies shaped as discs as my young mind would expect? I understand how the innermost parts of a galaxy spin faster than the outer parts, and that could explain why some ...
- 1,127
23
votes
4
answers
3k
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Is it possible that antimatter has positive inertial mass but negative gravitational mass? [duplicate]
Newtonian mechanics seems to allow for both positive and negative gravitational mass as long as the inertial mass is always positive. The situation is analogous to electrostatics but with the ...
- 2,403
22
votes
7
answers
5k
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The distance square in the Newton's law of universal gravitation is really a square?
When I was in the university (in the late 90s, circa 1995) I was told there had been research investigating the $2$ (the square of distance) in the Newton's law of universal gravitation.
$$F=G\frac{...
22
votes
2
answers
3k
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Can someone explain this Freeman Dyson quote about gravity and thermodynamics?
I was reading a book review by Freeman Dyson at http://www.nybooks.com/articles/2018/05/10/the-key-to-everything/ and he makes the following statement at the end of the 13th paragraph (3rd dropcap) ...
- 323
21
votes
2
answers
3k
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Is Newton's universal gravitational constant the inverse of permittivity of mass in vacuum?
Is it possible to consider Newton's universal gravitational constant, $G$, as inverse of vacuum permittivity of mass?
$$\epsilon_m=\frac {1}{4\pi G}$$
if so, then vacuum permeability of mass will be:...
user26425
20
votes
7
answers
7k
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Is Newton's Law of Gravity consistent with General Relativity?
By 'Newton's Law of Gravity', I am referring to
The magnitude of the force of gravity is proportional to the product of the mass of the two objects and inversely proportional to their distance ...
- 6,000
18
votes
3
answers
5k
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Gravitational force when standing on an infinite disc
If a person were to stand on a flat disc of thickness 1 meter but infinite diameter, would they experience finite or infinite downward force?
There is an infinite amount of mass, all of which ...
user55611