The professor believes life can survive the extremes of space
A conference is marking the retirement of Prof Chandra Wickramasinghe, a pioneer of the theory that life evolved in outer space before coming to Earth. Christopher Sleight reports.
There is an excited atmosphere in lecture room M040 at the mathematics institute of Cardiff University.
There's a lively discussion about Pluto's recent loss of planet status, but the hot topic of conversation is about life in outer space.
The idea is being discussed earnestly and with scientific references - this is no X-Files-style convention, but a gathering of eminent scientists and academics from around the globe.
They are here for a conference on panspermia and to hear from one of its leading proponents, Prof Wickramasinghe.
The Sri Lankan-born academic, who has just retired from his chair at the university after 33 years, is a passionate believer that we are not alone in the universe.
He freely admits his work is often met with "unabashed hostility".
More diplomatically minded fellow scientists have called his theories "optimistic". Others have described them as a "joke", "ridiculous" - even an "unpardonable heresy".
But the 67-year-old professor takes his ideas very seriously.
"I'm completely convinced that we're right. If one had a wrong theory, then sooner or later you would have a conflict with observations," he says.
"But everything that has happened since 1977 - when we first put forward these ideas - has gone in the direction confirming it, not disproving or falsifying it.
"No evidence has turned up that would make me rethink the idea that life came from space."
Many scientists recently criticised the professor for his claims that the virus causing severe acute respiratory syndrome in 2003 and the flu outbreak in 2000 both came from outer space.
The professor, who remains at Cardiff University as director of astrobiology, claimed that solar activity brought cosmic dust containing the virus into the Earth's atmosphere.
The theory was not universally accepted, to say the least.
It has been much the same for the last 30 years, when Prof Wickramasinghe first unveiled his theories to the wider scientific community.
He says the conference convened to discuss the idea of panspermia in 1981 at the University of Maryland simply tried to debunk the idea.
"It was a group of people who thought they could talk us out of pursuing this crazy idea that life came from space," he says.
Over the past three decades he has also received threatening mail and phone calls because of his ideas "on many occasions".
It is something that irritated him at first, but not now that his theories are becoming a lot more accepted, he says.
"The general idea that life on earth is part of a long chain of connections that extends all the way to the remotest corners of the universe - this idea is beginning to become almost mainstream in science.
"I think the idea is becoming more accepted - so much so that there is huge investment in looking for life from space."
He admits there is still a "huge amount of work" to do in the area, but he remains convinced that conclusive evidence will soon prove that life can exist in the extremes of space.
He says he will continue to ignore his detractors.
"It's essentially a pre-Copernican attitude. Before the middle of the 15th Century the Earth was thought to be the centre of the universe.
"Galileo and Copernicus and others at that time essentially disproved that point of view, but it took a long struggle for people to abandon the Earth-centred view point," he says.
"When you look at the detailed nature of life in terms of molecular complexity it seems extremely unreasonable to suppose that on this tiny speck of dust - which is all that the Earth is - the most complex physical system originated.
"I think the universe must be teeming with sentient life... sooner or later we will make contact with extra-terrestrial intelligence."