There is a huge freak­ing aster­oid 2,000 feet long out there in the cos­mos called 99942 Apophis. In cos­mic terms, 2,000 feet is very small. But what’s so spe­cial about this aster­oid? It may hit the planet in 2036.

The con­cern: Within the object’s range of pos­si­ble fly-by dis­tances lie a hand­ful of grav­i­ta­tional “sweet spots,” areas some 2,000 feet across that are also known as keyholes.

The physics may sound com­plex, but the poten­tial ram­i­fi­ca­tions are plain enough. If the aster­oid passes through the most prob­a­ble key­hole, its new orbit would send it slam­ming into Earth in 2036. It’s unclear to some experts whether ground-based obser­va­to­ries alone will be able to pro­vide enough accu­rate infor­ma­tion in time to mount a mis­sion to divert the aster­oid, if that becomes necessary.

Tim­ing is every­thing, astronomers say. If offi­cials attempt to divert the aster­oid before 2029, they need to nudge the space rock’s posi­tion by roughly half a mile – some­thing well within the range of exist­ing tech­nol­ogy. After 2029, they would need to shove the aster­oid by a dis­tance as least as large as Earth’s diam­e­ter. That feat would tax humanity’s cur­rent capabilities.

Great.