What makes Earth so gosh darn livable? How is it different from the other planets in our solar system, or viewable planets in our galaxy?
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Earth has a combination of factors that made life much more likely to form here, vs anywhere else we know of.
First off, Earth’s orbit is at just the right distance from the sun to allow liquid water. Too close, and the oceans would boil. Too far, and they freeze. The region in between is called the habitable zone.
Having liquid water is important because it is a near-perfect environment for a lot of chemistry, *especially* organic chemistry.
Secondly, the sun itself is actually pretty important. It’s fairly calm as stars go, and will live quite a while. Stars that are much smaller or much bigger each have different problems.
Red and Orange Dwarfs, which are smaller than our sun, will sometimes flare violently. This can increase their brightness by as much as *eight* times! Imagine if the sun regularly became eight times brighter in the sky.
White and Blue stars, which are bigger than our sun, are much shorter lived. This likely doesn’t give any planets orbiting those stars enough time to develop complex life. Around the largest, shortest lived stars, planets won’t get enough time for *any* life, or even prebiotic chemistry.
Thirdly, Earth has a pretty strong magnetic field. This is important because, while our sun may be calm for a star, it still puts out ridiculous amounts of energy. This is mostly light, but there’s also a constant barrage of charged particles from the sun’s atmosphere. This is called solar wind, and over millions of years it will slowly blast away a planet’s atmosphere (and oceans if it has them). Fortunately, Earth’s magnetic field deflects most of the solar wind, protecting our atmosphere and oceans.
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