Before this I'd never heard of Hoagland or his insane theories. I'd also never heard of Planet X or that guy who things comets gain mass as they approach the sun and then they become planets. I'd heard the UFO nuts and the Moon-Landing-Were-Faked nuts, but I was surprised by some of these other ones.
What other big conspiracy theories am I missing? I'm sure there are a TON, but I'm just asking for your favorites or some of the biggest ones. I'm especially asking about the science based ones as every historical event surely has one