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submitted 2 years ago by [email protected] to c/[email protected]

(To be clear, I'm more interested in the reach and scaling of gravity.)

If we were to suddenly double earth's mass, but not it's size, would it's field double in size (I assume strength as well), to the extent that if I were to measure this increased gravity at the same place I measured earth's normal gravity, it would simply be double? If so, the least measurable point of both gravitates should also be the same?

Just wondering if there's diminishing returns or if mass and density affects a gravity field the same regardless of whether it's an asteroid or a billion Solar Masses.

Feel free to share any views I'm not taking into account in regards to gravity fields.

Thanks

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[-] [email protected] 9 points 2 years ago

Assuming a spherical earth, if you doubled its mass but kept the radius the same then the gravitational force on the earths surface would be twice that of the current earth.

As long as you keep the earths mass reasonable, you’re in the realm of Newtonian gravitation. Newton’s law of gravitation depends linearly on the mass of the attracting source. So doubling the mass doubles the gravitational force.

At 1 billion solar masses (firmly in the not-reasonable mass range for the earth), you’d need to consider the formation of a black hole. The Schwarzschild Radius for a 1 billion solar mass black hole (aka the event horizon) is almost 20 astronomical units or 2 billion miles. So in that case you wouldn’t be able to measure the change in gravity as you’d be within the event horizon of a black hole.

At an intermediate mass there might be some general relativity effects that could alter the linear relationship between earth mass and gravitational force as measured on the earths surface, but I’m not sure what that would be. If you were to measure earths mass from a large distance, then it should follow Newtonian dynamics and behave linearly with mass.

[-] [email protected] 1 points 2 years ago

Thank you so much for the reply.

My understanding is that most(all?) force fields are made up of waves (as is everything?), so  hypothetically, a Gravity field should be as well? 

[-] [email protected] 7 points 2 years ago* (last edited 2 years ago)

No.

A field is a value assigned at every point in space. It is not "made of waves". But if the field is perturbed by an acceleration, then the perturbation is propagated as a wave.

Simple analogy: every point in the sea has a "depth". That's like a field. If a motorboat creates a wake, the "depth" changes temporarily. You see that change as a wave.

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this post was submitted on 20 Aug 2023
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