Earth meets space rock constantly, and almost all of it is harmless. Tiny meter-scale objects enter the atmosphere regularly and burn up as fireballs, occasionally dropping small meteorites; this is a normal, ongoing process, not a threat. The frequency of arrivals drops steeply as size rises — the bigger the object, the rarer the event.
City-threatening impacts, from objects in the tens-to-hundreds-of-metres range, are rare on human timescales, spanning centuries to many thousands of years between events. Civilization-scale impacts from kilometre-class objects are extremely rare, separated by millions of years, and surveys have already found the great majority of the largest near-Earth asteroids — none of which threaten Earth in the foreseeable future.
Discovery is led by dedicated sky surveys that sweep the night sky for moving points of light: the Catalina Sky Survey, Pan-STARRS and ATLAS find most new NEOs today, and NASA’s planned NEO Surveyor space telescope will sharpen the search for smaller, harder-to-spot objects. The catalogue grows every clear night, which steadily shrinks the population of unknown objects.
Planetary defense has moved from watching to acting. In 2022, NASA’s DART mission deliberately struck the small moonlet Dimorphos and measurably changed its orbit — the first demonstration that a threatening asteroid could, with enough warning, be nudged off course. Combined with years-to-decades of advance notice from the surveys, this is why the realistic picture is one of steady, manageable monitoring rather than imminent danger.