The moon is just so familiar. It’s been hanging out in the sky for as long as any of us can remember, going through its phases, waxing and waning like the tides. But really, it’s a pretty strange object. Take some time to think about it, and you start to appreciate what a weirdly intriguing place our closest cosmic neighbor is.

The moon is about 238,855 miles away from Earth, which is roughly a three-day drive if you’re an Apollo astronaut. It’s about 4.5 billion years old, basically a coeval twin with Earth itself. And it was born in violence: The prevailing theory is that a Mars-sized object called Theia collided with the young Earth and the moon formed out of the rubble. That’s not some esoteric myth. That’s what the geochemistry of the moon rocks tell us.

One of the more underrated things about the moon is its size. Relative to its parent planet, the moon is enormous. Most moons are tiny compared with the planets they orbit. Our moon, though, is about one-quarter the diameter of Earth. Some scientists even consider Earth and the moon to be a double planet. That’s a different way to think about home.

It’s not just a matter of perspective, either. The moon’s size means that its gravitational pull helps stabilize Earth’s tilt, holding it steady at about 23.5 degrees over long time scales. Without the moon, Earth’s axis might wobble wildly, leading to massive, life-altering climate fluctuations. The moon is not just a pretty face in the sky. It has been, in a very real sense, a guardian of Earth’s climate.

And then there are the tides. The moon’s gravity pulls on Earth’s oceans, setting the tidal rhythms that have sculpted coastlines and dictated the lives of sailors and marine organisms for millennia. The sun has something to do with it, too, but the moon is the dominant force. When moon, Earth, and sun all line up, you get those extra-high spring tides. When they make a right angle, you get the less dramatic neap tides.

The moon’s surface itself is a landscape of violence. The dark splotches you can see from Earth are maria, which are vast, lava-filled basins that hardened into rock billions of years ago. The craters on the rest of the moon’s surface are a record of impacts over billions of years. Because the moon has no atmosphere and almost no geology, there’s nothing to erase those craters. They remain, a testament to history.

There’s water on the moon, too. Ice, actually, locked up in permanently shadowed craters near the moon’s poles. Sunlight never reaches them. We only confirmed the reality of this water within the past couple decades, but it’s been a game-changer for scientists and space agencies thinking about the moon. You could mine that ice for drinking water or even rocket fuel.

Humans have sent 12 people to walk on the moon’s surface, all of them between 1969 and 1972. Nobody has been back since. That is one of the more inexplicable facts in the history of exploration, and with several space agencies now planning a return to the moon, it shouldn’t remain a fact for long.