2024 YR4 flyby geometry, or 1.8% of What?

The experts in ESA’s Planetary Defence Office have determined that, as of 6 February, the risk of 2024 YR4 impacting Earth on 22 December 2032 is 1.8% — a small increase from the 1.2% estimate published in the ESA website on 29 January due to new observational data. This numerical value is expected to evolve in the coming weeks as additional observations are reported, first rising and then falling, if this asteroid follows the pattern of past such discoveries. Basically, the more observations...