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4 votes

Why is gravity constrained to speed of light of gravity itself affects space time?

In the theory of general relativity, gravity is equivalent to inertia as the equation of motion is given by the free-fall/geodesic equation in a curved 4-dimensional spacetime. The gravitational ...
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10 votes

Is a black hole really a neutron star with a gravitational time dilation factor of 1.0

I'm not sure what you mean by gravitational length contraction, and the time dilation formula you are using is only approximately correct for weak gravitational fields. Observed neutron stars are ...
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6 votes
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Do any equivalent of Lagrange points exist between galaxies?

Short answer: likely sometimes. The gravitational potential of a galaxy is not going to be a spherically symmetric $1/r$ potential, since it is the sum of the potentials of all the stars, plus from a ...
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2 votes

Why are pseudo-Newtonian potentials used in studies of accretion processes around black holes?

What is $V_\mathrm{eff}$? The effective potential from S&T isn't the gravitational potential, $V$, that appears in places like $\vec{F}_g = -m \nabla V$. That effective potential comes from a ...
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8 votes
Accepted

If Earth was a moon of Jupiter orbiting at the same distance as Metis (Jupiter's innermost moon), then how much lighter would a 100 kg person feel?

TL; DR Around $8$ kg. You can calculate the tidal force using Newton's law of gravitation, $$F = G\frac{m_1m_2}{r^2}$$ where $G$ is the universal gravitational constant, $m_1$ and $m_2$ are the ...
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5 votes

Do Einstein's ten field equations use 20 or 40 variables? (2 or 4 for each tensor equation?)

A single vector equation like $\vec{F} = m \frac{d^2 \vec{r}}{dt^2}$ is actually three equations one for each of the $x,y,z$ components of the 3-vector $\vec{r}$. In the spacetime of general ...
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