Two New Moons Thought To Be Orbiting Uranus

[YellowSubmarine]

I learned today that the gravity at the gaseous surface of Uranus is actually only about 90 percent Earth's gravity. How neat is that?

I was somewhat shocked when I learned Jupiter's gravity is only 2.5g, as I had foolishly assumed that with 300 times Earth's mass I would be squished by the gravity on the “surface”. I would still be squished by the enormous atmospheric pressure, so same difference. I guess a Cloud City is near-possible because you may create a liveable environment very high in the clouds, and at the same time – the unliveable and hellish crushing environment depicted in Asimov's Victory Unintentional is also kind of realistic for what's down below – except the solid surface doesn't exist, as we'd transition gradually from crushing liquid to solid if there's solid.

 

[Asbo Zaprudder]

I was somewhat shocked when I learned Jupiter's gravity is only 2.5g, as I had foolishly assumed that with 300 times Earth's mass I would be squished by the gravity on the “surface”. I would still be squished by the enormous atmospheric pressure, so same difference. I guess a Cloud City is near-possible because you may create a liveable environment very high in the clouds, and at the same time – the unliveable and hellish crushing environment depicted in Asimov's Victory Unintentional is also kind of realistic for what's down below – except the solid surface doesn't exist, as we'd transition gradually from crushing liquid to solid if there's solid.

The force due to gravity on a mass m at a distance r from the centre of the mass M (outside the body of the mass) is F=G.M.m/r^2. Even though Jupiter is massive, its large radius squared negates that to some extent. In terms of average density, rho, M=(4/3).pi.r^3.rho so F=G.m.(4/3).pi.rho.r.

As Jupiter's radius is nearly 11 times Earth's but its density is roughly 0.24 that of Earth, the relative acceleration due to gravity at the notional "surface' is about 2.6. (G.(4/3).pi is constant so it cancels).

 

[XCV330]

What was size 6?

Uranus?



I
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