How do you get into space without a rocket? Just use a very, very big gun.

It's an idea with a surprisingly long history, laid out in detail by Duncan Geere on Medium. It starts with a thought experiment by Isaac Newton in 1728, imagining a cannon so powerful that its payload escaped the Earth's gravitational pull. For centuries afterwards, there have been aerospace engineers obsessed with making it work. In practice, that meant building enormous cannons — sometimes more than 100 meters long — which often occupied an uneasy place in international diplomacy. The full story weaves through World War II, Saddam Hussein and contemporary plans for a methane-powered cannon submerged under the ocean.