In February 2013 an entirely undetected asteroid entered the Earth’s atmosphere above Chelyabinsk, Russia at roughly 60 times the speed of sound and at a very shallow entry angle. The object, which was ‘only’ 17-20 metres across, exploded as it entered the atmosphere producing a bright flash, many small meteorites and a powerful shock wave damaging 7,200 buildings and injuring 1,500 people.
The light produced was brighter than the Sun, the heat from the fireball was felt by people on the ground and it released 20-30 times more energy than the atomic bomb detonated at Hiroshima. It also caused significant panic as the lack of detection meant no warning and no explanation!
So what if something 500 metres across was to come our way? Have you ever wondered if there were secret international committees discussing this?