Here are today's general risks from asteroids or comets both tiny and very large. Importantly, even relatively small rocks can still be threatening, as the surprise 56-foot (17-meter) rock that exploded over Russia and blew out people's windows in 2013 proved.

Over the next several weeks, astronomers will be looking closely at an asteroid called 2024 YR4 that could be as big as a football field as they try to determine how likely it is to strike Earth in 2032.