Thursday marks the first death anniversary of Stephen Hawking, the world-renowned theoretical physicist and author of "A Brief History of Time."

Hawking was diagnosed with ALS, also known as Lou Gehrig's disease, at the age of 21 in 1963. Although doctors expected him to live for only a few more years after the diagnosis, Hawking lived for over 50 years more. He died in 2018 at the age of 76.

"He was a great scientist and an extraordinary man whose work and legacy will live on for many years. His courage and persistence with his brilliance and humor inspired people across the world,” Hawking’s children said in a statement on his passing. "He once said, 'It would not be much of a universe if it wasn't home to the people you love.'"

Here are a few quotes by him to celebrate one of the most brilliant minds in the field of science, courtesy Brainy Quote

“While physics and mathematics may tell us how the universe began, they are not much use in predicting human behavior because there are far too many equations to solve. I'm no better than anyone else at understanding what makes people tick, particularly women.”

“Look up at the stars and not down at your feet. Try to make sense of what you see, and wonder about what makes the universe exist. Be curious.”

“Scientists have become the bearers of the torch of discovery in our quest for knowledge.”

“With genetic engineering, we will be able to increase the complexity of our DNA, and improve the human race. But it will be a slow process, because one will have to wait about 18 years to see the effect of changes to the genetic code.”

“Science is beautiful when it makes simple explanations of phenomena or connections between different observations. Examples include the double helix in biology and the fundamental equations of physics.”

“I believe alien life is quite common in the universe, although intelligent life is less so. Some say it has yet to appear on planet Earth.”

“My advice to other disabled people would be, concentrate on things your disability doesn't prevent you doing well, and don't regret the things it interferes with. Don't be disabled in spirit as well as physically.”

“No one undertakes research in physics with the intention of winning a prize. It is the joy of discovering something no one knew before.”

“Our population and our use of the finite resources of planet Earth are growing exponentially, along with our technical ability to change the environment for good or ill.”

“Time travel used to be thought of as just science fiction, but Einstein's general theory of relativity allows for the possibility that we could warp space-time so much that you could go off in a rocket and return before you set out.”

“If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans.”

“The past, like the future, is indefinite and exists only as a spectrum of possibilities.”

“We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the Universe. That makes us something very special.”

“God may exist, but science can explain the universe without the need for a creator.”

“People who boast about their I.Q. are losers.”

“Life on Earth is at the ever-increasing risk of being wiped out by a disaster, such as sudden global nuclear war, a genetically engineered virus or other dangers we have not yet thought of.”

“I think computer viruses should count as life. I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image.”