- Nov 11, 2019

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**What if Earth were a super-Earth? : Read more**

- Nov 11, 2019

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Gravity is not a linear function either since it depends on the mass of a sphere which is not a linear function of radius, as I mentioned above. Your weight will decrease by the square of the distance from the centre of a planet according to the formula F ~ Mm/r², where M = the mass of the planet and m = your mass, divided by the square of the distance from you to the centre of the planet. For your consideration, if you had two planets of equal mass but one was lower density then you would weigh less on the larger planet (the low density one) because you are farther from its centre.

This is not complex math but the article was way too simple and therefore wrong.

This is also quite wrong. First, the problem of size. Again what does 10 x larger mean? If size were radius the core would be 10 times the radius all other things being equal again. But mass is proportional to the cube of radius as I mentioned in my first reply. This means the core would be 10³ = 1000 times more massive not 10! No small difference.

- Feb 9, 2020

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Agreed. When you say two times larger, you have to specify whether you mean diameter or volume. Since the article also says you would be two times heavier, I assume it means twice the diameter. This is the interesting thing about gravity. Other things being equal (like density), the surface gravity of a planet is linear with respect to radius -- it increases in direct proportion to its radius. So even though a so-called "super Earth" that is twice Earth's diameter would have eight times its mass (2^3), it's surface gravity would "only" be twice Earth's.

Gravity is not a linear function either since it depends on the mass of a sphere which is not a linear function of radius, as I mentioned above. Your weight will decrease by the square of the distance from the centre of a planet according to the formula F ~ Mm/r², where M = the mass of the planet and m = your mass, divided by the square of the distance from you to the centre of the planet. For your consideration, if you had two planets of equal mass but one was lower density then you would weigh less on the larger planet (the low density one) because you are farther from its centre.

This is not complex math but the article was way too simple and therefore wrong.

- Feb 10, 2020

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iron coreand liquid mantle would also be 10 times larger, "

This is also quite wrong. First, the problem of size. Again what does 10 x larger mean? If size were radius the core would be 10 times the radius all other things being equal again. But mass is proportional to the cube of radius as I mentioned in my first reply. This means the core would be 10³ = 1000 times more massive not 10! No small difference.

Yes this isn't clear at all in what they wrote. The composition of a planet controls its maximum size but what you will find is that as planets become more massive, the tendency towards gravitational compression increases until eventually, at a mass roughly 1.7 times that of Jupiter or 540 Earth masses, you reach a critical point where the planet stops getting larger. Beyond this critical point, adding more mass to a planet actually makes it smaller because the compression created by the extra mass is greater than the volume of the extra mass.

For rocky planets like the earth the size limit is about 3 earth radii

Galaxies like grains of sand on a beach, random nonintelligent variation in planets is sufficient to explain a rare but present incidence of a planet like Earth. It's perhaps the astonishment of being a Being on such a rarity would create the tendency of a sentient on such an object to hypothecate an intelligence of enormous powers as necessary to it's existence. I too am a sentient impressed by the wonder of it all. This only peripherally skirts G.R.A.P.E.S.

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