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I would like to point out this video by minutephysics: https://www.youtube.com/watch?v=R5P6O0pDyMU so far the better and simpler explanation of the color of the sky. It takes into account also color theory (not particle physics of course) and not just scattering.

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Is the only way of calculating altitude to try to guess using the atmospheric pressure? Not at all. One approach is to use GPS. Older GPS receivers indicated altitude above the reference ellipsoid. More modern receivers register altitude above the geoid. The up to 100 meter difference altitude above the reference ellipsoid versus altitude above the ...

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Barometric pressure is a pretty good way to measure altitude when you know the reference pressure (at sea level). This is because the rate of change of pressure is quite high: with the density of air approximately 1.2 $kg/m^3$ at sea level, a 100 m change in altitude gives you a drop of 12 g / cm^2 or 1.2% of atmospheric pressure. The "standard value" used ...

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it likely comes from nitrogen dissolved in the molten iron and nickel in the earth. A large comet would be roughly capable of delivering 1/10000 of the earths atmosphere if it where all nitrogen. They are not all nitrogen, but they have at least a fair amount. The interested reader will note that Mars has an atmosphere very rich in N2. Most likely ...

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From what we know, the Earth's original atmosphere was not made of nitrogen (or oxygen, or carbon dioxide), but of gases such as hydrogen and helium. These would have been lost to space early on, because the Earth's gravity was not strong enough to hold on to them. The present-day oxygen came from organic sources, as you said. Here's what Wikipedia has to ...

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Since gold is much more abundant in the universe than is uranium (by a factor of about 20:1)1, why is the situation reversed in the Earth's crust (by a factor of about 1:600)2? The answer lies in chemistry. Uranium is chemically active. It readily oxidizes (pitchblende) and it readily combines with silicates. Uranium is a lithophile (literally, rock-loving) ...

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I'll be using the tabulated values from a Wikipedia article of abundance of elements in the Earth's crust. Gold has a tabulated value of 0.0031 ppm in mass for crustal abundance. Uranium has a tabulated value for 1.8 ppm in mass for crustal abundance. These figures are interesting in that uranium has an abundance of almost 500 times more ppm than that of ...

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The Earth's magnetic field is caused by eddy currents in the liquid parts of the planet's interior. We believe the field is not due to a permanent magnet because: (1) Its direction and strength change over time, and (2) the planet's interior is hotter than the Curie temperature of its elements, and so a permanent magnet would not retain its magnetism. ...

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