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Scientists do not know whether there are any aliens but they have been searching for life on other planets for thousands of years. From the beginning ideas about aliens were linked to religious myths, and people regarded gods, angels, spirits, and demons as real. Democritus, a Greek philosopher, argued that all forms of matter consists of atoms and these tiny particle could be linked together to form plants and animals not only on Earth but also on other planets. The German mathematician and astronomer Johannes Kepler described in his book Somnium (The Dream, written around 1611) a type of reptilian creatures living on the Moon. Sunvolvans lived on the side facing the sun, and Privolvans lived on the dark side.Two
Today, scientists are searching for life on other planets by trying to catch radio signals. In 1960, Francis Drake, steered a giant 26-metre dish towards a star Epsilon Eridani, and the antenna picked up an artificial signal. The signal turned out to be produced by secret military radar but this was the beginning of the search for radio signals sent by aliens.
The word SETI stands for Search for Extraterrestrial Intelligence, and it is an international research programme that seeks evidence of life in the universe.