On 27 December 2024, astronomers spotted an asteroid that was potentially heading towards earth. Named 2024 YR4, it was estimated to be between 40m and 90m across, with the potential to cause massive damage if it hit a populated area of the planet.

The chances of that happening, however, seemed to fluctuate significantly - ranging from 1% to a peak of 3%, before falling to virtually zero.

Tim Harford investigates what was going on, with the help of Davide Farnocchia, a navigation engineer at NASA’s Jet Propulsion Laboratory.

Presenter: Tim Harford Producer: Lizzy McNeill Series producer: Tom Colls Production co-ordinator: Brenda Brown Sound Mix: Hal Haines Editor: Richard Vadon