Why do some planets have moons? A physics expert explains why Earth has only one moon while other planets have hundreds

An illustration of an orange-and-red planet surrounded by four large moons.

On Earth, you can look up at night and see the moon shining bright from hundreds of thousands of miles away. But if you went to Venus, that wouldn't be the case. Not every planet has a moon – so why do some planets have several moons, while others have none?

I'm a physics instructor who has followed the current theories that describe why some planets have moons and some don't.