2018-03-15Theoretical Physicist Stephen Hawking Dies at 76

World-renowned British physicist Stephen Hawking, who sought to understand a range of cosmic topics from the beginning of the universe to the intricacies of black holes, died Wednesday at age 76.

A family spokesman said he died peacefully at his home in the city of Cambridge where he worked for decades as the Lucasian Professor of Mathematics at the University of Cambridge.

"He was a great scientist and an extraordinary man whose work and legacy will live on for many years," Hawking's children, Lucy, Robert and Tim, said in a statement.

He was diagnosed with amyotrophic lateral sclerosis at the age of 21, a disease that eventually confined him to a wheelchair and took away this ability to speak, leaving Hawking to communicate through a voice synthesizer.

Doctors predicted he would only live a few years, but he instead thrived, focusing on his work that included seeking to bridge the gap between Albert Einstein's General Theory of Relativity that describes the motion of large objects and the Theory of Quantum Mechanics dealing with subatomic particles.

"My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all," Hawking said.

WATCH: Theoretical Physicist Stephen Hawking Dead at 76

His 1988 book "A Brief History of Time" became an international bestseller and brought him widespread fame.

One of his most famous accomplishments came in his research on black holes, showing that small amounts of radiation could escape their gravitational pull. The phenomenon is now commonly known as Hawking radiation.

A sign of his popularity came in October when Cambridge put Hawking's 1966 thesis online for the first time, and demand for the document was so high the university's website crashed.

Hawking was also a proponent of human space travel to the Moon and Mars, an endeavor he said would help unite humanity in the shared purpose of spreading beyond Earth.

Hawking said making the first moves into space would “elevate humanity” because it would have to involve many countries.

"We are running out of space and the only places to go to are other worlds. It is time to explore other solar systems. Spreading out may be the only thing that saves us from ourselves. I am convinced that humans need to leave Earth," he said last year. "If humanity is to continue for another million years, our future lies in boldly going where no one else has gone before."