Moon Good Night

moon

For billions of years the moon has been Earth’s ever present companion. It is Earth’s first and only celestial satellite, and it illuminated the night for the first eras of human existence. Debate continues about how it was formed, but most agree that its phases have been integral to the development of life on our planet. Eventually, however, humanity will be saying goodnight to the moon as it leaves Earth’s orbit forever.

Several theories on the creation of the moon exist. Darwin presented the fission theory, the first real attempt to address how the moon formed before life existed on Earth, when the planet was still a spinning lava ball. He believed the moon was once part of our planet, and today’s most widely accepted theory at least partially agrees. Today scientists believe the moon was formed when an object the size of Mars crashed into an early Earth, leaving Earth tilted on its axis. After this major impact, the resulting body (aka the moon) often drew in asteroids that would otherwise impact Earth. Additionally, the orbiting body created a tidal bulge on Earth which slowed the rotation of the planet.

These effects of the newly formed moon were likely good for the evolution of life on Earth: the lengthening of the Earth day to night cycle was integral to the development of the biology behind a variety of animal eye mechanisms. Organisms did not need to hide or be protected from the constant barrage of meteors that may have previously disrupted survival. The axial tilt and moon’s anchorage steadied the Earth’s obliquity and created a range of climates. Third, slower spin also had a steadying effect on the diurnal cycle, allowing for a regularity that was previously absent.

As an aside, the moon is also responsible for the precious metals found on or close to Earth’s surface. Theory has it that the bulk of the mantle core of the Mars-sized planetary body that hit the Earth was thrown into space, where it became the moon. The metallic core, blown apart, fell back to the planet instead of dispersing into space. These metals were mixed into the silicate mantle and were turned into ore via the process of plate tectonics.

The most obvious effect the moon has on Earth is the tides. In some places, organisms that live primarily in water are exposed to air, and vice versa. Some scientists believe that this was integral to the transition of life from sea to land. This tidal pull may have affected more than just the liquid in the traditional sense of what we recognize today. Theories assert that in Earth’s early days, the tidal pull affected the semi-solid surface of the planet to produce an early version of the planet’s crust.

When it formed all those years ago, the moon was much closer to the Earth than it is now. It likely looked huge, but has since been drifting away, growing smaller and smaller in the night sky. The moon began as close as 14,000 miles and now sits about 250,000 miles away. The same tidal action that was such a boon for Earth is the cause of the separation.  The tidal bulge rides slightly ahead of the moon, accelerating it, and pushing out its orbit. The result is that eventually, the moon will drift away into the ether. Without the moon, the Earth may lose its stability, which will have a terrible effect on the seasons. The loss of the moon from Earth’s orbit is an eventuality humanity will likely not need to face, since both celestial bodies will be destroyed when the sun begins its red giant phase. The average person will still bid a good night to the moon before the moon bids a good night to them.

By Aliya Tyus-Barnwell

Sources:
BBC
Cornell
Astrobiology Magazine
Universe Today
Astronomy Today
Science Blogs

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