# Tag Info

### If a planet or star is composed of gas, the center of mass will have zero gravity but immense pressure? I'm trying to understand fusion in stars

"Hydrostatic equilibrium" is how the force of gravity is balanced not by the mere presence of pressure itself but by pressure gradient. The center ends up having immense pressure due to the ...
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### If a planet or star is composed of gas, the center of mass will have zero gravity but immense pressure? I'm trying to understand fusion in stars

Gravity is the result of mass that is below you. (It's an interesting fact that in a sphere, the mass "above" you in the sense of being at greater distance from the centre pulls you in all ...
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### If a planet or star is composed of gas, the center of mass will have zero gravity but immense pressure? I'm trying to understand fusion in stars

TL;DR: The high pressure in the center comes from the outer regions where there is gravity, not from the zero gravity in the center. And yes, pressure is a factor driving fusion, while gravity is just ...
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1 vote

### If a planet or star is composed of gas, the center of mass will have zero gravity but immense pressure? I'm trying to understand fusion in stars

Gravity is not zero anywhere. In the center of a star it's balanced out, but even in your description it's not complete balance - it's just infinitesimally off balance from other planets, stars, etc. ...
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### Why does gravity make time go slower and warp light?

The answer you'll get to this question is that gravity occurs because space is curved. but it only looks curved in four dimensions, when you can look at the same space at more than one time. It's ...
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### In an expanding universe could black hole pairs keep orbiting each other forever?

The paper is Dias et al (2023), Phys. Rev. Lett. 131, 131401 (DOI, arXiv). From the abstract: We construct the first four-dimensional multiple black hole solution of general relativity with a ...
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### Earth’s orbit (JPL Horizon system)

What am I doing wrong? Lots and lots of things. You assumed that the Earth will orbit the solar system’s barycenter in a nearly perfect elliptic orbit with the barycenter as the focus point. That is ...
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Accepted

### Earth’s orbit (JPL Horizon system)

The Solar System as a whole orbits the SSB (Solar System Barycentre), but it's not actually the focus of the orbit of any individual planet. Instead, each planet orbits the point which is the ...
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