bolís

Greek bolís (βολίς) meant a missile or a thrown javelin, from bállein, 'to throw.' The word was applied to bright meteors by astronomers who saw the streak of light as something hurled across the sky. Pliny the Elder, writing in Latin, used the Greek term to describe fireballs that outshone the moon. The object was not falling — it was thrown.

The distinction between a meteor and a bolide is brightness. A meteor is any visible streak caused by a particle burning in the atmosphere. A bolide is a meteor so bright it causes shadows on the ground. The International Astronomical Union does not formally define bolide, but working astronomers use it for any fireball brighter than Venus — roughly apparent magnitude minus four or brighter.

The Chelyabinsk event of February 15, 2013, was a bolide. A twenty-meter asteroid entered Earth's atmosphere over Russia at 19 kilometers per second and exploded at an altitude of about 30 kilometers. The airburst released energy equivalent to 500 kilotons of TNT — thirty times the Hiroshima bomb. Over 1,500 people were injured, mostly by glass from shattered windows. No one died.

Bolides are recorded throughout history. Chinese court astronomers logged them meticulously. Medieval European chronicles describe 'fire from heaven.' The Tunguska event of 1908 — which flattened 2,000 square kilometers of Siberian forest — was almost certainly a bolide, though no fragments have been recovered. The Greek javelin keeps being thrown.