He said: “I still can’t rule out that possibility, and I’d love it to be true: the world would be far more interesting with aliens than without them.
“However, while I’ve seen some intriguing evidence, I’ve yet to see any definitive ‘you can take it to the bank’ proof.
“So the bottom line is that while I’m sure there’s life elsewhere in the universe, I don’t know whether or not we’re being visited.
“If we are, I suspect we’re dealing with automated probes, or craft operated by some sort of artificial intelligence.
“Even if there are flesh and blood aliens out there somewhere, the cosmic radiation and the immense time required to travel interstellar distances probably rules out biological lifeforms making such journeys – unless there’s a way around what seems to be the absolute barrier of light speed.”
Mr Pope said for the time being, concepts such as warping spacetime or using wormholes “are science fiction and not science fact, so if we’re being visited by extraterrestrials, we’re probably dealing with machine intelligence and not biological entities”.
Mr Pope added: “I don’t believe any of the conspiracy theories that say aliens are already here on Earth, and that they’re secretly working with various governments.”