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Old Mar 10th 2019, 10:22 AM   #1
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Little g without Big G

Anyone know how to find the gravity of a planet without using the gravitational constant?
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Old Mar 10th 2019, 11:50 AM   #2
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Originally Posted by JDDuncan View Post
Anyone know how to find the gravity of a planet without using the gravitational constant?
By "gravity" I presume you are referring to "acceleration due to gravity?"

Nope. I suppose there many sophisticated method you could employ but all of them are based on Newton's theory of gravitation and all would eventually depend on G.

The simplest equation would be: $\displaystyle g = \dfrac{GM}{r^2}$.

Think of it this way: If G were bigger we'd expect that the force on an object would be larger than it is now. So g would be larger as well. So there has to be a connection between the two.

-Dan
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Old Mar 10th 2019, 05:34 PM   #3
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Yes, the acceleration of gravity. Thanks.
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Old Mar 10th 2019, 06:53 PM   #4
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Originally Posted by topsquark View Post
Nope. I suppose there many sophisticated method you could employ but all of them are based on Newton's theory of gravitation and all would eventually depend on G.
-Dan
Would it be big news if someone did find a way?
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Old Mar 10th 2019, 08:00 PM   #5
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What would be wrong with determining g experimentally and determining the mass of the planet from that?
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Old Mar 10th 2019, 09:59 PM   #6
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Originally Posted by HallsofIvy View Post
What would be wrong with determining g experimentally and determining the mass of the planet from that?
Thereís nothing wrong with that. Iím just asking to see what ways we have.
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