Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asking the reason alien civilizations might be rare is because most aliens are huge.

To hear it and every episode early and add-free, plus hours of bonus content, check out

go.nebola.tv slash Isaac Arthur and use my code, Isaac Arthur.

Gravity is a fascinating force. It's what holds everything on our planet together, and it might one day help us travel to other planets.

Gravity is a strange thing. On the one hand, it's the oldest and best known of the fundamental

forces, on the other, it's the weakest and least understood. Within that uncertainty may lie the

key as to escaping this world and traveling to countless others, or building structures of

incomprehensible scope and amazing purpose. While we'll cover gravidic technologies beside

Propulsion in February, today we'll focus solely on moving spaceships. We'll explore

everything from mundane uses of gravity for proportion, like slingshining around planets

and the oberth effect, to more hypothetical varieties, such as spacetime warping, gravitational wave proportion,

anti-gravity, dark energy, negative matter, frame-dragging, the diametric, differential,

pitch, and bias drives, and more.

That's a lot to cover, so grab a drink and a snack, hit those like and subscribe buttons,

and let's dive into the topic.

We might as well begin with the best known use of gravity for moving spaceships, preventing

them from moving by giving them a massive gravity well to drag themselves out of, while

also making them drag through a thick atmosphere.

This is where something like anti-gravity could change the game.

It could simply ignore gravity or activate something that counters it, it would be revolutionary.

Anti-gravity is a somewhat vague term, mainly from science fiction, and probably should be

...