Why was Earth chosen to have living things on it?
Five good reasons! First, Earth has water, the most essential ingredient for life. Earth is the perfect distance from the Sun for water to exist in all three states, solid ice, liquid water, and vapor or gas. Water contains oxygen needed for life, it doesn’t harm the skin, and it’s needed for photosynthesis. Photosynthesis is the process of turning water and carbon dioxide, with the aid of light, into oxygen and sugars used as plant food. Water is drinkable, and permits molecules to move around easily. Mercury and Venus are so close to the Sun that liquid water would boil away. The planet Mars, and Titan, a moon of Saturn, may have water below the surface, but that’s only speculation.
Second, our atmosphere is ideal. It contains breathable oxygen, put there as the byproduct of plant growth. Our atmosphere has some carbon dioxide, which animals and humans give off as part of respiration. The tiny bit of carbon dioxide helps moderate the temperature of Earth. Mars, Mercury, and the Moon are too small to keep an atmosphere. You need enough gravity, and Earth has it. As a bonus, the Earth’s atmosphere is thick enough to filter out many harmful ultraviolet rays. Our magnetic field deflects tons of particles from the Sun that would otherwise kill us in short order.
Third, Earth is blessed with a beautiful climate. The temperature is ideal for life. Mercury and Venus are too close to the Sun, and go from 600 degrees above zero Fahrenheit to 400 degrees below zero Fahrenheit. Those extremes are not conducive to life. Mars is a tad warmer, but at 140 degrees below zero Fahrenheit at times, water and blood would freeze. The outer planets have no solid surface and are way too cold.
Fourth, is something that McDonalds and Walgreens have figured out. It’s location, location, location. Earth gets just the right amount of sunlight. Earth is just the proper distance from the Sun to get sufficient heat and light to permit life to flourish. It is too hot on planets closer to the Sun. It is too cold and dark on planets at a greater distance from the Sun,
Fifth, Earth receives sufficient light for trees and other plants to produce oxygen by the process of photosynthesis. The Earth’s rotation, once every 24 hours, insures that each side of the planet receives sunlight on a regular basis. Venus takes 243 days to spin once on its axis. Any place on Venus is in darkness far too long to support vegetation and life.
Recall the Goldilocks and Three Bears bedtime story. The porridge was too hot, too cold, and just right. The armchairs were too hard, too soft, and just right. The bed was too high, too low, and just right. Goldilocks wisely chose the “just right’ version each time.
Earth is “just right” in terms of location, size, rotation rate, mass, gravity, water, atmosphere, climate, and magnetic field.
So far, we’ve been discussing life our solar system, which is a tiny little corner of the Universe. Is there life on other planets in distant solar systems? Most scientists think the answer is yes, but there is no proof. For now, our Earth is all we know, and we had best take real good care of it.