Intergalactic war is probably billions of years away — yet physics can already tell us how it ends. And strangely that conclusion is relevant to decisions people have to make today.

In this video, Rob Wiblin walks through a fascinating analysis from researcher Beren Millidge that uses known physics — no wormholes or faster-than-light travel — to identify the only three weapons that could work at an intergalactic scale.

We then unpack how to best defend against each.

The upshot is that at the intergalactic scale, violence is a losing proposition.

If so, the universe is most likely to settle into a stable patchwork where each galaxy belongs to whoever got to it first. Which would mean that what humanity does over the next few centuries could permanently decide which slice of the cosmos belongs to Earth-originating life — and whether our very existence turns out to be a good thing, or a bad one.

Learn more, video, and full transcript: https://80k.info/war-in-space

This episode was recorded on March 2, 2026.

Chapters:

Let's talk intergalactic war in space (00:00)
The three best weapons for intergalactic warfare (01:43)
How to defend against an attack from space (07:50)
The defender’s surprising advantage (10:00)
What this means for us (11:52)

Video editor: Nick Perlman

Producers: Elizabeth Cox and Nick Stockton

Coordination and support: Katy Moore and Lou Moran

Camera operator: Dominic Armstrong

We can guess what intergalactic war would look like. And strangely, it matters.

80,000 Hours Podcast

We can guess what intergalactic war would look like. And strangely, it matters.