A famous Australian meteorite fall occurred on 28 September 1969 at Murchison, near Shepparton, Victoria. Meteorites which are found after their fireball was witnessed are called 'falls', but if found accidentally long after their arrival they are called 'finds'. Meteorites range in size from pea-sized pieces up to large masses many tonnes in weight. Most are heated for less than 10 seconds while they fall. They can travel at very high speeds, typically from about 5 km - 70 km per second, the fastest ones (over 30 km per second) can be destroyed on impact with the atmosphere. Large meteoroids can form brightly glowing fireballs (bolides) seen clearly in daylight, accompanied by spectacular light and sound effects. They sometimes break up into several pieces while still in flight or when they hit the Earth. Meteoroids that survive their journey through our atmosphere land on the Earth's surface as meteorites. These constellations are much further away than the showers themselves. They are given the name of the constellation which forms their backdrop (e.g. Meteors tend to arrive in 'showers' of many individual meteors at definite times throughout the year. These brief, bright streaks of light are sometimes called 'shooting stars'. The trail of glowing, electrically-charged gases that surrounds and streams away from the meteoroid is called a meteor. When heated to incandescence by friction with air in our atmosphere, they burn up completely at heights of about 80 km - 130 km. The small particles which become meteors typically range from the size of a grain of sand up to the size of a pea. Tiny dust particles get rid of heat as quickly as it is applied, so do not burn up and fall gently on the Earth's surface. Very small meteoroids may remain intact or melt to form glassy droplets which rain down on Earth's surface as micrometeorites. meteorites: larger meteoroids survive their fiery ordeal and land on the Earth's surface.
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