The Origin of the Moon

Our solar system was nothing but a mist of dust and gases, what is known as a solar nebula.

SourceBut then, about 4.6 billion years ago something majestic happened.

We don't know exactly what caused it, but some scientists believe that the shockwave of a nearby supernova hit our nebula,

Sourcecausing it to start spinning and contracting.

Now, as things collected together, their overall gravity got stronger and they pulled more stuff in it. And boom, we've got a Sun.

SourceA half billion years later, and the disk of junk circling around the Sun starts coming together in its own way, into what we now call the planets.

One of these planets I've actually visited and it's called Earth.

But before we get ahead of ourselves, what the heck is the Moon doing there? I mean, here's the problem.

When you look at all the terrestrial planets, all the planets near us, near the Sun, they all have very similar structure and they'll have the same big metal core and they all have very similar densities.

SourceBut the Moon is very not dense.

And it doesn't have a similar structure, it doesn't have a huge dense metal core.

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In fact when we visited them and brought back dust and rocks to analyze what the Moon was made out of, we found that the Moon was made out of the same stuff that you find in Earth's crust and mantle but not Earth's core.

This discovery gave rise to a pretty awesome idea that the moon is actually made out of what used to be on Earth.

SourceAbout 4.52 billion years ago there used to be another planet called Theia. It was a little bit smaller than Mars but it had an unfortunate orbit.

It was fine for millions of years but eventually and what did happen to it was that it collided with Earth. Now, it's believed that the collision happened quite slowly and the centers, the cores of both Theia and Earth fused into one. And material from the mantle and crust of Earth wasn't just scattered but it was forcefully ejected, literally launched into outer space.

SourceIt circled around Earth and scientists believe that it took only about a week for all that Earth material out in space to coalesce into what we now call the Moon.

SourceBy the way, if that's how the Moon formed, it was such a strong collision the actual axis that the Earth spun on was tilted 23.5 degrees, which to this day is why we have seasons.

SourceSo four billion years ago the continents as we know them began to emerge. You know, these pieces of the Earth's crust that have cooled down

Sourceand are floating around on Earth's molten liquid insides.

Now, they move and they've been in constant motion since they began but they move very, very slowly. Every 300 to 500 million years, the continents all converge into what's called one big supercontinent.

SourceAll the land in the entire Earth altogether and the rest of it covered in ocean. The most recent super continent is kind of a famous, it's called Pangaea.

SourceBut scientists believe that there may have been four, five, six or even more super-continents that existed before Pangaea.

What's really mind-blowing is the fact that eventually there's going to be another Pangaea, another supercontinent. And based on calculations, the Earth at that time will look like this.

SourceBut like I said, these land masses are moving very very slowly and so for that reason it is worth learning their names as they are now. Which brings us back to the question of England, United Kingdom, Great Britain, British Isles and what all these terms mean.

Let's begin. The British Isles and Ireland are a collection of 6 thousand islands off the coast of Europe.

SourceThe term Great Britain refers to the largest of these islands.

SourceNow, Great Britain contains three separate countries: England, Wales and Scotland. If we add Northern Ireland into the mix, we're now looking at what is known as the United Kingdom or the UK.

SourceThe Republic of Ireland is a separate country that is not part of the United Kingdom.

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Thanks for reading.