Are there something out there? Or are we the only living creature in the Universe. So far scientists have found no evidence of alien life forms.
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.
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.
The chance of finding other life is calculated by using the Drake equation. There are billions of Earth-like planets and many people believe that there are many planets which have intelligent life. Scientists do not know how likely it is that life emerges, and it is possible that life on Earth is unique. It is also difficult to know how likely it is that intelligent life develops.
In order for aliens to send a signal they have to develop some sort of intelligence. Scientists believe that it is unlikely to find intelligent life in our solar system. But there might be life on other planets in our solar systems, and this life might look completely different from life on Earth.
After years of searching for a radio signal, no message from another planet has been received. Scientists have found planets beyond our solar system, and many scientists believe that given a suitable environment and sufficient time, it is possible that life will develop on other planets.
Humans have sent messages to try to contact aliens. Photos, drawings, and text messages have been sent at the planet Gleise. This active SETI is also called METI (Messaging to Extraterrestrial Intelligence) and some scientists have criticised this active way of looking for other life since the location of Earth could be revealed to aliens.