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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A couple of things that have not been mentioned: the moon. While planets having moons is common, the size of our moon is NOT common. At about 1/4 of the size of earth, it has the largest ratio of size to its planet than any other moon in the solar system. It is theorized that the moon is likely the result of a collision between earth and a mar sized proto-planet they call Theia. The collision added mass to Earth and the remains formed into the moon. This explains why Earth’s core is also very large for its size. Theia also may be the source of a most of Earth’s water (when Earth initially formed around the sun it probably didn’t come with much water).
The moon (and its origins) are important to life on Earth because
* its origins led to Earth’s large core which is vital for generating the magnetic field that protects the earth from solar wind which would destroy life
* its origins brought water to earth, essential for life
* the moon moderates Earth’s wobble on its axis, leading to a stable climate
* the moon causes tides, affecting ocean currents and climate
* the moon impacts tectonic plate activity, without the moon there would probably be less tectonic activity
* And more…
Another cool thing we take for granted: as children we look at the Sun and the Moon and think they are the same size because they appear the same size in the sky. We learn later than actually the Sun is much much larger, but further away, and the moon is much smaller but closer. IT JUST SO HAPPENS that the sun is about 400 times as wide as the moon, but also 400 times further away. Therefore the two look the same size in the sky, which is completely unique in our solar system. Although we do not know the odds of this happening in our galaxy, this seems like a very unusual coincidence. Because of the sizes and distances of the Sun and the Moon we are able to experience solar eclipses.
This was important for science in a really interesting way. in 1905 and 1915 Einstein published his theories of relativity and they were met with skepticism. But on May 29, 1919 Sir Arthur Eddington used two solar eclipses to prove Einstein’s general theory of relativity as correct. Direct evidence of “space-time” didn’t come until 2015 with the detection of gravitational waves.
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