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xkcd - Gravity Wells : 重力の井戸

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Gravity wells(重力の井戸)

Scaled to earth surface gravity(地球の地表重力の尺度)

This chart shows the "depth" of various solar system gravity wells.

Each well is scaled such that rising out of a physical well of that depth in constant earth surface gravity would take the same energy as escaping from that planet's gravity in reality.

Each planet is shown cut in half at the bottom of its well, with the depth of the well measured down to the planet's flat surface.

The planet size are to the same scale as the wells.

Interplanetary distances are not to scale.

Depth = ( G x PlanetMass ) / ( g * PlanetRadius )
 (深さ = G x 惑星の重量) / ( g * 惑星の半径 )

G = Newton's constant(ニュートン定数)
g = 9.81 m/s2

You could escape Deimos with a bike and a ramp.
To scale(原寸に比例)

A thrown baseball could escape phobos.

Jupiter is not much larger then Saturn, but much more massive.

At its size, adding more mass just makes it denser due to the extra squeezing of gravity.

If you dropped a few dozen more Jupiters into it, the pressure would ignite fusion and make it a star.

It takes the same amount of energy to launch something on an escape trajectory away from earth as it would to launch it 6,000km upward under constant 9.81m/s2 Earth gravity.

Hence, Earth's well is 6,000km deep.

This is why it took a huge rocket to get to the moon but only a small one to get back.








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