James Woodward

A leading astronomer yesterday dismissed theories that aliens from other planets have been visiting Earth, claiming the distance was too vast for a spaceship to fly.

Dr Christian Kaiser, of the University of Southampton, said while it was possible life existed on other planets the "enormous" gap between us and the next Earth-like body would prevent the journey.

A spate of reported sightings of UFOs has led to renewed speculation that aliens were surveying the planet.

Speaking ahead of a public lecture later this month, Dr Kaiser, of the School of Physics and Astronomy, said: "There has been breathtaking progress in finding planets.

"Proof of life on another planet would be a huge scientific discovery and would also severely challenge our social, political and religious thinking.

"Until recently, most detected planets have masses much larger than that of Earth, but new discoveries push that limit down to only a few Earth masses. Planets comparable to Earth should have solid surfaces and may harbour life.

"However, the distances between stars in our galaxy are enormous. Therefore, there is no way that life forms from another planet, if such exist, could have already visited us on Earth."

The upsurge in interest in UFOs was also highlighted by South Wales Police, who received a report from an anxious caller, concerned about a bright stationary object in the sky.

The mystery was soon solved, as the exchange between control and a police officer sent to the scene makes clear.

Control: "Alpha Zulu 20, this object in the sky, did anyone have a look at it?"

Officer: "Yes. It's the moon. Over."