An exhibition in Greenwich looks at our fascination with aliens through history.
Are we alone in space? Could aliens exist? People have asked these questions for hundreds of years and there are countless stories and films about space ships, UFOs and extra-terrestrials. A new exhibition at the Royal Observatory in Greenwich looks at our fascination with aliens through history.
Would aliens come in peace? War Of The Worlds is one of the most famous fictional stories about aliens. It was written in 1898 by HG Wells and tells of aliens from Mars attacking Earth with enormous fighting machines called Tripods. Don't worry though - the Tripods don't exist and Nasa's rovers have yet to find any aliens on Mars.
Have humans been abducted by aliens? This photograph shows Betty and Barney Hill who claimed they were captured by aliens in 1961. The couple said they were driving home from a holiday by the Niagara Falls when strange beings that were 'not human' took them onboard a UFO. Their story was made into a book in 1966.
Have aliens been to Earth? Aliens are often blamed for mysterious crop circles appearing in fields - although some have been revealed as man-made hoaxes. Lucy Pringle took this photo of a crop circle in Avebury, Wiltshire. She has studied crop circles for 25 years and told Newsround she doesn't think aliens are responsible - she thinks the crop circles are caused by an 'unknown intelligence using all the forces of nature' to make the patterns on Earth.
What would aliens look like? In 1835 an American newspaper said respected astronomer Sir John Herschel had seen bat-winged apes living on the moon using his telescope. The stories were widely believed to be true - until Sir John himself read them and said they were nonsense. The stories became known as the Great Moon Hoax.
Will we ever visit other stars? This spacecraft was designed in the 1970s to travel to other solar systems. It was based on technology that existed at the time but it was never built. After man walked on the moon in 1969, one TV series predicted that people would live there by 1999. It didn't happen of course - and we've yet to send humans to any other planet. The pictures are on display at the Royal Observatory in Greenwich.