While Steven Spielberg has created some of the best aliens in cinema, the 79–year–old director now claims he also knows a thing or two about real–life extraterrestrials.

In an interview promoting his latest sci–fi blockbuster, Disclosure Day, Mr Spielberg says he is certain that aliens have already visited our planet.

Speaking to CBS News, he said: ‘I absolutely think that they have been here, and they are here. And who knows, maybe they’ve always been here.’

The director of Close Encounters of the Third Kind added that this view is ‘based on the circumstantial evidence of everything that I’ve gathered throughout my whole life, everybody I’ve listened to and every documentary I’ve ever watched and all the testimonies in Congress that I’ve heard.’

Now, some scientists say there could be a kernel of truth behind Mr Spielberg’s wacky claims.

Dr Jacco van Loon, an astrophysicist from Keele University, told the Daily Mail: ‘It is a possibility.’

He added: ‘If they visited a billion years ago, they would have encountered seas with microbial life, and bare land.

‘While they may not have left artefacts on Earth, one interesting possibility that has been considered is that they may have left artefacts on the Moon or elsewhere in the Solar System, to monitor Earth or simply as waste.’

While it is widely considered likely that life exists somewhere in the universe, the biggest barrier to any advanced civilisation visiting Earth is the enormous distances between stars.

For many scientists, this is an insurmountable barrier to any chance of an alien civilisation travelling to Earth.

Dr Thomas Haworth, an astrophysicist from Queen Mary University, told the Daily Mail: ‘We have a feeling that the term “astronomical” means large, but it’s quite hard to convey just how large distances are in space.

‘To get to the nearest known star with planets, Proxima Centauri, would take the Parker Solar Probe – the fastest spacecraft humans have launched – 6,500 years.

‘Although I am sure that life is out there, the odds of life being on the planets next door are low. When we look to other planets, the distances and timescales just get larger and larger, making it harder and harder to travel.’

Read More: Steven Spielberg claims aliens have already visited Earth – now scientists say he might be right