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What Would Earth Be Like Without a Moon?

April 4, 2018


I’ve written about where the Moon may have come from, but what if there was no Moon at all? Imagine if we woke up tomorrow and that giant rock four hundred thousand kilometres (250,000 miles) away was just gone.


The truth is that without a Moon, we would probably face some pretty major consequences, but the worst of them wouldn't show up overnight. 


When you think about the Moon's affects on Earth, you probably think about the ocean tides, like I mentioned in my post about black holes. It’s true: tides are produced because the gravitational attraction of the Moon is always exerting its pull on Earth. Without the Moon, the only gravitational pull on our ocean would come from the Sun. But because it's so far away, tides would only be about half as large!


Next, try to picture the night sky without the Moon. Stargazing would be more awesome than ever, because there'd never be any moonlight interference. However, it’d make an even bigger difference to us and other animals. Moonlight obviously helps nocturnal predators, which have evolved to hunt in low-light. Without the Moon, the food web would be really different, really fast.


But the Moon is responsible for more than just tides and night life. Its most important job may actually be stabilizing Earth's axial tilt. Our axial tilt relative to the Sun varies between twenty-two point one and twenty four point five degrees, and it's this tilt that gives Earth its seasons. But much like a spinning top, Earth and other planets are susceptible to wobbling as they spin on that axis. Luckily, we have our Moon to stabilize any potential fluctuations. Its gravitation helps counteract disturbances caused by nearby planets - like Venus, and especially Jupiter - that would otherwise cause Earth to wobble more than we'd like.


Planets without large moons aren't so lucky.



For example Mars, which currently has about twenty four degree axial tilt because Mars only has two small moons. And due to the gravitational forces of its neighbors, scientists believe that its tilt has fluctuated between fifteen and thirty-five degrees overtime, at one point causing its polar ice to drift all the way to the equator. 


Thanks to our Moon, our axial tilt has stayed consistent for hundreds of millions of years. Without it, we'd be subject to fluctuations even worse than what Mars has seen. Sometimes, our tilt would be zero, with Earth standing straight up and down. This would cause an end to the seasons, and at other times, the tilt could be eighty-five degrees, basically rotating on our side like Uranus does. In which case, each hemisphere would experience nighttime for half the year, plunging it into darkness and cold while the other six months of the year would be constant daylight and temperatures that would put the tropics to shame.


And in addition to stabilizing our tilt, the tidal friction caused by the moon also acts as a very slow break on Earth's rotation.


It's not a huge impact - our rotation slows about one second every sixty-seven thousand years. But take the moon away, and things could speed up in a hurry. That's because over a billion years ago, before our Moon existed, many scientists believed the Earth rotated three to four times faster than it does now. This means that back then, a full day on our planet only lasted about eight or nine hours long.


The formation of the Moon slowly applied a gravitational break, as it continues to do today.


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Sources: This story was originally published on SciShow Space. I am republishing a lightly edited version on SkyFeed in light of interest in the subject. Reimers, Reid. "What Would Earth be like Without a Moon?" SciShow Space, YouTube. 23 June 2014. Web video.

Citation: Rovira, Lia N. "What Would Earth be like Without a Moon?" SkyFeed. 4 April 2018. Web article.

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