Meteors (“shooting stars”) and meteorites
A meteoroid is a small body in space (from dust up to a few metres). When it enters the Earth’s atmosphere at 11–72 km/s it heats up through friction with the air at ≈ 80–120 km and makes a bright streak – a meteor (“shooting star”); a very bright one is a fireball (bolide). A remnant that reaches the ground is a meteorite. Meteorites are stony (≈ 94 %), iron or stony-iron; they help date the Solar System (≈ 4.57 billion years). Meteor showers occur when the Earth crosses the dust trail left by a comet: the Perseids (≈ 12–13 August, comet Swift–Tuttle), the Leonids (≈ 17–18 November) and the Geminids (≈ 14 December, asteroid Phaethon). Big events: the Tunguska explosion of 1908 (a body ≈ 50–60 m wide exploded in the air and flattened ≈ 2000 km² of forest) and Chelyabinsk on 15 February 2013 (≈ 20 m, ≈ 440 kilotonnes of TNT energy, more than a thousand people injured mostly by broken glass). Meteors can be watched without any instruments from a dark place, with an adult, warmly dressed.
On the night of the Perseid maximum (August), with an adult, lie for 30 minutes away from city lights and count the meteors you see. Allow 15–20 minutes for your eyes to adapt; use a red light.