He has grappled with some of the biggest questions about the universe but Professor Stephen Hawking has revealed one mystery still baffles him - women.

Making the comments during a Reddit Ask Me Anything (AMA) session, the eminent physicist said the opposite sex is 'life's most intriguing mystery,' but admitted it is a mystery that should remain unsolved.

Although the questions were posted back in July, the scientist has only just responded, discussing topics as diverse as artificial intelligence to his favourite song.

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During an Ask Me Anything session on Reddit, Professor Stephen Hawking has said that despite unravelling some of the secrets of the universe, women are the biggest mystery he has faced. The eminent theoretical physicist has been married and divorced twice. He is pictured above with this second wife Elaine in 2005

Asked what the one mystery in life he found most intriguing was, he replied: 'Women. My PA reminds me that although I have a PhD in physics, women should remain a mystery.'

Elsewhere, he reiterated claims he has made previously about the threat of artificial intelligence adding that the greatest risk from AI will be its ability to disregard humans rather than deliberately destroy them.

PROFESSOR STEPHEN HAWKING'S OTHER RESPONSES Do you believe AI is evil? 'The real risk with AI isn't malice but competence. 'A superintelligent AI will be extremely good at accomplishing its goals and if those goals aren't aligned with ours, we're in trouble. 'You're probably not an evil ant-hater who steps on ants out of malice, but if you're in charge of a hydroelectric green energy project and there's an anthill in the region to be flooded, too bad for the ants. 'Let's not place humanity in the position of those ants.' What is your favourite song? 'Have I Told You Lately' by Rod Stewart. What is your favourite movie? Jules et Jim, 1962 What was the last thing you saw online that you found hilarious? The Big Bang Theory Advertisement

He said artificial intelligence is unlikely to hold a grudge against mankind, but may ultimately harm us as a result of trying to achieve its goals.

He said: 'The real risk with AI isn't malice but competence.

'A superintelligent AI will be extremely good at accomplishing its goals and if those goals aren't aligned with ours, we're in trouble.

'You're probably not an evil ant-hater who steps on ants out of malice, but if you're in charge of a hydroelectric green energy project and there's an anthill in the region to be flooded, too bad for the ants.

'Let's not place humanity in the position of those ants.'

Professor Hawking, who is the director of research at the department of applied mathematics and theoretical physics at the University of Cambridge, added an AI computer could eventually evolve to have a desire to survive.

He said: 'An extremely intelligent future AI will probably develop a drive to survive and acquire more resources as a step toward accomplishing whatever goal it has, because surviving and having more resources will increase its chances of accomplishing that other goal.

'This can cause problems for humans whose resources get taken away.'

During the Reddit AMA, Professor Hawking admitted the funniest thing he had seen on the internet recently was the hit comedy TV series The Big Bang Theory. He appeared in the show in 2013 (pictured above with actor Jim Parsons who plays Sheldon Cooper)

Stephen Hawking has said in the past he spends most of the day thinking about women and finds them a 'complete mystery'. He is pictured above with his first wife Jane

BLACK HOLES ARE NOT PRISONS The widely-held assumption is that anything sucked into a black hole is gone forever. But in his latest work, Professor Stephen Hawking has called this assumption into question. The theoretical physicist claims to have discovered a mechanism 'by which information is returned out of the black hole,' - meaning they may not be as black as first thought. In fact, his new theory suggests information lost in black holes could be stored in alternative universes. Speaking to a group of scientists at KTH Royal Institute of Technology in Stockholm, Professor Hawking talked about finding a solution to one of science's most difficult questions - what happens to the information about the physical state of things swallowed up by black holes, and is it retrievable? The laws of quantum mechanics demand that it should be, but that presents a paradox for our current understanding of black holes, known as the 'information paradox.' 'I propose that the information is stored not in the interior of the black hole as one might expect, but on its boundary - the event horizon,' he said. Advertisement

He continued that if AI machines develop the ability to improve themselves without human help, it could result in an 'intelligence explosion' that will result in computers becoming as superior to us as we are to snails.

However, he added that researchers were a long way from being able to produce computers with artificial intelligence equivalent or beyond the human brain.

'When it eventually does occur, it's likely to be either the best or worst thing ever to happen to humanity, so there's huge value in getting it right.

'It might take decades to figure out how to do this, so let's start researching this today rather than the night before the first strong AI is switched on.'

The Reddit AMA with Professor Hawking attracted more than 9,000 questions and comments, making it the third most popular of the events that the website has hosted.

It took nearly four months before Professor Hawking was able to reply and he responded to just 11 questions.

Most of the questions he chose to answer focused on the topic of artificial intelligence – something he has spoken about extensively recently.

Earlier this year he signed a letter, along with several other leading scientists and computing entrepreneur Elon Musk, warning about the threat posed by artificial intelligence.

He has also warned that robots may eventually take over human capability in the next century and so it was essential scientists ensured their goals are aligned to those of humanity.

The Reddit discussion is also not the first time Professor Hawking, who has been married and divorced twice, has confessed to being baffled by the opposite sex.

In an interview in 2012 to mark his 70th birthday, he admitted he spent most of the day thinking about women. He said: 'They are a complete mystery.'