Privileged Planet: Earth densest planet (Introduction)

by David Turell , Thursday, November 11, 2021, 15:26 (897 days ago) @ David Turell

Doesn't fit the solar system pattern:

https://bigthink.com/starts-with-a-bang/earth-densest-planet/

"When solar systems first form, the heaviest elements sink preferentially towards the central protostar, while lighter elements are easily blown away. Based on their atomic composition and ratios alone, Mercury ought to be the densest planet. But Earth is even denser, owing to a combination of its composition and gravitational compression.

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"In the innermost part of the Solar System is the planet Mercury, which has only a negligible atmosphere and is made largely of rocky and metallic material. As we travel farther away from the Sun, atmospheres become common, as do greater proportions of lighter elements. If we were to look at each planet’s composition in terms of the atoms that make it up, Mercury would have the highest percentage of heavier elements, trailed by Venus and Earth, with Mars even farther behind.

"You might think that would make Mercury the densest planet, but that’s not true at all. If you measure each planet’s mass and divide it by its volume, it turns out that Earth, not Mercury, is the densest world in our Solar System.

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"In terms of density, Earth is the record-holder in our Solar System; no other world exceeds our own planet’s density.

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"Inside the Earth’s core, the cumulative gravitational force of everything surrounding it exerts a crushing pressure on the planet’s interior: about 3,600,000 times the pressure we experience at sea level and significantly less than any pressure experienced in Mercury’s interior. At these extreme pressures, atoms themselves start to change, as they become compressed to only a fraction of their normal, zero-pressure size. This factor, known as gravitational compression, is the key piece of the puzzle to understanding Earth’s remarkable density.

"As it turns out — and this was worked out all the way back in the 1950s — a planet can’t be much bigger than Earth and still remain a rocky planet. Beyond a radius of 10,000 kilometers (and Earth is already pushing up against that with a radius exceeding 6,000 kilometers), a planet will actually start to contract as you add more and more mass. As the mass of your planet grows, the sizes of the central atoms shrinks faster than the additionally added atoms grow the overall size of the planet."

Comment: Siegel does not go past this fact of density, but I can. It gives us a liquid nickel-iron core which results in a protective magnetic shield, and floating continents with subduction, all supporting factors for life here. This planet is singularly special. All by God's plan!?