microsoft surface

Matt Parker of Stand-up Maths asks whether a country's reported land area accounts for hills and mountains, working through how surface area depends on the resolution of elevation data. It follows up on a question from a viewer and work by researchers who measured it.

Sabine Hossenfelder explains how the greenhouse effect actually works, given that infrared is mostly absorbed low in the atmosphere already. She walks through why more CO2 still warms the surface.

PBS Space Time episode on the black hole information paradox, covering how black holes seem to destroy information, the no-hair conjecture and the proposed role of the event horizon. It is part of a series on black holes.