If you’ve seen our show, ‘Earth Millions of Years Ago’, you’ll know that 4.54 billion years ago, an exploding star, or supernova, led to the creation of our solar system. The Sun formed, and with the leftover clumps that cooled down, the planets formed, too. Earth became the third big rock from the sun, as the planets arranged themselves in orbit. During this time – many millions of years – another thing happened.

One of the chunks from all the debris, a planetisimal, hit the Earth, throwing some of the Earth’s crust into space. This impact tilted the planet to 23.5 degrees, and so we have seasons. We also have what was left of this bit of Earth, the moon, and that’s what we’ll talk about today, in this episode of The Infographics Show, What if the moon had a moon?

First we’ll give you some moon facts, while staying away from the fashionable conspiracy theory of whether we actually landed on the thing… or if it’s really made out of cheese…

Depending on where the moon is in orbit, it is anywhere from 221,500 miles (356,500 km) at the perigee and 252,700 miles (406,700 km) at the apogee. It takes 27.3 days to orbit Earth, and depending on its position, and how it reflects the sun, is how much of it we will see in the sky. It’s thought that it travels at a speed of 2,287 mph (3,680.5 km/h). The moon has a diameter of 2,159 miles (3,475 km), making it bigger than Pluto, and also making it the fifth largest moon in our solar system.

Its size, in terms of its diameter, is roughly about one quarter the size of Earth. This is quite big in terms of planets and their moons in this solar system, which makes our moon quite influential on our planet. The moon has a small core, which is thought to be about 420 miles (680 km) wide. That core is thought to be mostly made of iron. Its surface is rocky, and it is also pockmarked by all the asteroid hits it’s taken over millions and millions of years.

There isn’t much atmosphere on the moon, so it’s not a place we can stand for long. If an astronaut took off his or her helmet up there, the experience would be the same as being in a near vacuum. No, eyeballs would not pop, but the experience would be uncomfortable, a little like experiencing the bends. They would pass out and die of oxygen deprivation.

The temperatures aren’t very suitable for humans up there, with the sunny side of the moon reaching up to 273 degrees F (134 C); and the dark side going down to minus 243 F (minus 153 C). While we may not be able to live on the moon, it affects the Earth in big ways. Because its gravity pulls at the Earth, it causes changes to our sea levels. This is why we have tides. Does the moon affect people when it’s full, aka, the lunar effect? Well, studies have shown that it might affect our sleep patterns, reproduction, or even result in spikes of crime. Perhaps the word lunatic might have some credence? Other studies, however, have debunked this.

The question is, as REM lead singer Michael Stipe once asked: “What if there were two, side by side in orbit?” He was singing about the moon of course.

Firstly, we know that a planet can have two moons because Mars has two moons, Phobos and Deimos. Jupiter has 67 moons, Saturn 62, Uranus 27, and Neptune 14. But can our moon have a moon? The question was put to an astronomer at Cornell University. He answered in the positive, explaining, “The region of space around a satellite where a sub-satellite can exist is called the Hill sphere. Outside the Hill sphere, a sub-satellite would be lost from its orbit about the satellite.” The Earth has a Hill Sphere of about 37,200 miles (60,000 km), where a sub-satellite can orbit. The moon also has a Hill Sphere, so a sub-satellite can orbit it.

But according to the astronomer, the distance between rocks will keep shrinking until the sub-satellite eventually crashes into the moon. She further explained that if the moon does have something orbiting it, that generally only lasts a couple of years. As for why our moon doesn’t crash into us, that’s because the moon is at a certain distance, and has a number of astronomical survival advantages in place. This favorable positioning is what astrophysicist and author Ethan Siegel has called a “sweet spot.” In conclusion, the moon could have a small moon, or sub-satellite, but it wouldn’t really mean anything would change.

Could the Earth have a second moon, though? The closest thing we’ve had is what is referred to as a large quasi-satellite. This was sometimes called a second moon, but it was really an asteroid that went by the name of 3753 Cruithne. The 3 mile wide (5 km) object was discovered in 1986 crossing the Earth’s orbit. It wasn’t principally orbiting the Earth, though, just passing by, and looking as if it was orbiting Earth. It’s actually orbiting the sun. Astronomers at Cornell University published research in 2012 indeed saying for a time the Earth has mini-moons. They come into Earth’s orbit, but after time break from our planet’s gravity. These are tiny, though, compared to 3753 Cruithne.

So, let’s ask a more hypothetical question in what would have happened if two big moons had formed around Earth?

Well, life on Earth would have been very different. One scientist asks what would have happened if a giant moon had formed after life had already formed on Earth. He says the appearance of such a moon would cause massive tsunamis, earthquakes, and lots of increased volcanic activity. The downside to that would be mass extinction on Earth.

The two-mooned Earth would be brighter he says, leading to different kinds of animal species that have adjusted to the new Earth. High and low tides would measure differences of thousands of feet, so any humans left would not live near the coast. In fact, we’d have little of Earth to live on. We’d no longer have months as they’d be irrelevant, but in the end he says the two moons would collide, we’d have another mass extinction due to moon debris, and only one moon would survive. This was taken from the book, ‘What If the Earth Had Two Moons’, written by Neil Comins, a physics professor at the University of Maine.

Lastly, what would happen if we had no dear moon? Let’s say it was somehow obliterated. Well, firstly all the debris would litter down on Earth from whatever caused the obliteration. This would wipe out areas of the Earth. Whole cities would be destroyed. We’d also be a lot more vulnerable to other objects that used to hit our moon; that would now hit us.

There would be solar tides, but the water would be rather still. Much of water-based life would die because it would not receive the nutrients it received when the moon was moving the water around. According to another scientist, we would have shorter days because without the moon the Earth would spin faster. This is because the ebb and flow of the tides slows down the Earth’s rotation. It’s also thought because of this fast spin, we would have many more storms and much faster winds.

So, there you go, the moon’s moon, Earth’s two moons and no moon at all. Let us know your thoughts about the subject in the comments! Also, be sure to check out our other video called What If You Drank Coke and Nothing Else?! Thanks for watching, and, as always, don’t forget to like, share, and subscribe. See you next time!



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