We take the word “myth” to mean something this isn’t true. “Is he Man or Myth?” “Unicorns are Mythological.” This is a very superficial and inadequate understanding of the word. Myths are stories we tell to explain very complicated and nuanced things that are nevertheless very important. “Where do we come from?” “Why are we here?” “What is Justice?” “What makes Greeks different from Persians?” “What does it mean that we have one God and the Egyptians have many gods?”
These stories have to be true, even if they’re not factual. Truth and fact are not the same thing. Factually it is not true that a great fish swallowed Jonah. In truth, there are great and grave consequences for not following God’s plan for your life. Hera may not have factually assigned twelve impossible labors for Heracles, but in truth, some men spend their entire lives and perform incredible feats to redeem themselves. It’s unlikely there was ever a man like Heracles, but the myth of Heracles is true of all men.
From the beginning, the Greeks had a burning, passionate curiosity about the world. They also were blessed with a very descriptive language which they used to create the most remarkable myths to tell the truths of the world, even if they lacked the scientific knowledge to discover the facts of the world. To explain how the world began, the Greeks created the myth of Gaea and Uranus. They had 12 children called Titans: Oceanus, Coeus, Crius, Hyperion, Iapetus, Cronus, Theia, Rhea, Themis, Mnemosyne, Phoebe, and Tethys.
The titan Theia was the mother of Selene, the goddess of the moon, and it’s here that our story begins.
As the universe began to slow from creation and cool from the event that began it, pools of matter, mostly hydrogen, began forming in the new fabric of what we call space. This matter, all matter causes a warp in the fabric of space; this warp draws bits of matter to other bits of matter.
Imagine the surface of a trampoline. In one spot on the trampoline, you place a heavy watermelon. The mass of the watermelon warps the surface of the trampoline. Now place an egg on another part of the trampoline and a cantaloupe on another. The egg distorts the surface of the trampoline too, but not very much; so does the cantaloupe, which warps it much more. Because the egg deforms the trampoline's surface less, it is drawn to the warp of the cantaloupe. Once the egg and the cantaloupe are together, they are both drawn to the deformation in space caused by the watermelon. Soon, the egg, the cantaloup, and the watermelon all occupy the same deformation in the trampoline's surface.
This is what happened at the beginning of the universe. As matter began to come together, it created a deformation in space and time. As more matter comes together, the deformation becomes larger, attracting even more matter to it. Eventually, enough hydrogen is trying to press itself into the same instance of time and space that the matter begins to compress. The space between atoms gets smaller and smaller as the compression gets greater and greater, and eventually, the mass reaches a critical point. This ball of hydrogen ignites and explodes, creating a star, in this case, a star we call Sol, our sun.
In the explosion that created Sol, some of the matter from the original mass is ejected out with great force but is held in the gravitational pull of the new star, so the forces trying to fling this matter out into space work against the pull of gravity, and all this matter begins to spin around the new star.
At first, this matter was a flat disk, but lumps began forming in it over time. The largest lumps become the planets Jupiter, Saturn, and Uranus. Smaller lumps contain less gas and more compressed rocky matter, and they form the other planets and the rocky inner planets, including Earth.
In the third orbit around the sun were two masses, one called Earth and one called Theia, because of her future role. Both planets were still white hot from creation. They burned across the sky, expelling their energy out into the coldness of space. Theia was much smaller than Earth, about the size of Mars, and for millions of years, it held a stable spot in orbit around the sun, but eventually, the gravitational attraction of Jupiter and Saturn caused Theia’s orbit to spiral, and once it spiraled enough to escape its Lagrange point of stability and put it on a collision course with earth.
Earth and Theia were molten and unformed at this point, but their rocky core had already formed. Theia didn’t collide with Earth head-on, but more of a glancing blow. The force of the collision made most of the molten rocky core of Theia join with the Earth's molten rocky core, which is why the Earth has a core much larger than the other rocky planets.
Some of Theia’s matter was flung out into space and became part of what we now call the asteroid belt. Parts of Theia and parts of Earth were pushed to the side of Earth, far enough away to collapse into their own body rather than fly out into space or collapse back into Earth.
Within hours gravitational forces formed this molten matter into a globe, much smaller than the Earth, and forever locked in orbit around it. The planet Theia gave birth to our moon in much the same way that the Titan Theia gave birth to Selene.
Ancient Greeks didn’t have access to the type of physics or the computers necessary to calculate how the collision of Earth with a previously unknown sister planet might form the moon, but they understood the causality of things and created a myth to tell the truth of the moon’s origin, even if they had no way to know the facts. Even my essay is more myth than science because I skipped over huge volumes of physics and computational mathematics, but it doesn’t make what I wrote any less true.