Renowned physicist and self-proclaimed atheist, Stephen Hawking, had a personal encounter with Pope Francis at the conference for the members of the Pontifical Academy of Sciences at the Vatican in Rome.

Pope Francis warmly welcomed Hawking, who was confined in his wheelchair and who has been in a battle with a slow-progressing form of amyotrophic lateral sclerosis (ALS) since he was 22, by approaching him and touching him gently on the shoulder. This is not the first time the British theoretical physicist met a reigning pope. A member of the academy since 1986, Hawking has also met Popes Paul VI, John Paul II and Benedict XVI.

Hawking was one of the many scientists honored by the Holy See at the five-day conference entitled "Science and Sustainability: Impacts of Scientific Knowledge and Technology on Human Society and its Environment."

At the event, Hawking gave a 20-minute speech explaining his theory on the origin of the universe as he stated in the No-Boundary Proposal, which he co-authored with another notable physicist, James Hartle.

"With James Hartle from the University of California, I worked out what physical conditions the early universe must have, if space time had no boundaries in the past. Our model became known as the No-Boundary Proposal. It says that when we go back toward the beginning of our universe, space and time become fuzzy and cap off, somewhat like the South Pole and the surface of the Earth. Asking about came before the Big Bang is meaningless according to the No-Boundary proposal, because there is no notion of time available to refer to. It would be like asking what lies south of the South Pole," explained Hawking, an article by Rome Reports stated.

In 2014, Hawking publicly announced during an exclusive interview that he was in fact an atheist.

"Before we understand science, it is natural to believe that God created the universe. But now science offers a more convincing explanation. What I meant by 'we would know the mind of God' is, we would know everything that God would know, if there were a God, which there isn't. I'm an atheist," the Daily Mail wrote.