Renowned theoretical physicist and best-selling author Stephen Hawking died Wednesday at the age of 76. Heralded for his cosmic discoveries, profound influence on modern science and determination in the face of the crippling Lou Gehrig's disease, the late physicist was admired by leaders both in and out of the scientific community.
"Stephen Hawking's integrity and scientific dedication place him above pure brilliance," Apple co-founder Steve Wozniak told the BBC.
Shortly after the announcement of Hawking's death, tech execs, celebrities and world leaders alike, flooded social media with their condolences and shared memories.
Here's what they had to say:
1. Tim Cook, Apple CEO
The Apple CEO paid tribute to Hawking by sharing his favorite quote from the late physicist. "We will always be inspired by his life and ideas," wrote Cook.
Hawking's work overlapped with Apple's interface over the years, according to Apple Insider, and he used an iOS app called Swiftkey software to communicate during his later years.
2. Satya Nadella, Microsoft CEO
"We lost a great one today," Nadella wrote on his LinkedIn. "Stephen Hawking will be remembered for his incredible contributions to science – making complex theories and concepts more accessible to the masses."
The Microsoft CEO also praised Hawking's sense of wonder and dogged pursuit to understand the universe. "May he rest peacefully as his legacy and brilliance live on," he wrote.
3. Sundar Pichai, Google CEO
Pichai expressed his sorrow via Twitter on Tuesday. "The world has lost a beautiful mind and a brilliant scientist," the Google CEO tweeted. "RIP Stephen Hawking."
4. Neil deGrasse Tyson, astrophysicist
A fellow physicist, Tyson shared a photo with Hawking on his Twitter, where he expressed his condolences and looked to the future.
"His passing has left an intellectual vacuum in his wake," wrote Tyson. "But it's not empty. Think of it as a kind of vacuum energy permeating the fabric of spacetime that defies measure."
In a follow-up tweet, Tyson shared a video clip of an interview he recently held with Hawking, which first aired on National Geographic.
5. Barack Obama, former U.S. president
Obama chimed in on Twitter with a simple message and photo of the late physicist at the White House. "Have fun out there among the stars," he wrote.
6. NASA
The aerospace research agency paid tribute to Hawking with a touching video showing the late scientist without his wheelchair floating in zero gravity during a 2007 demonstration.
"Remembering Stephen Hawking, a renowned physicist and ambassador of science," NASA tweeted. "His theories unlocked a universe of possibilities that we & the world are exploring. "
7. The cast of 'Big Bang Theory'
Cast members of the award-winning sitcom, which features four physicists, shared their individual memories with Hawking who was often featured on the show.
The official "Big Bang Theory" Twitter page released a photo of Hawking with the cast. "Thank you for inspiring us and the world," said the tweet.
8. Bill Gates, Microsoft co-founder
Gates reminisced about his shared past with Hawking, who he met on a visit to Cambridge University in 1997.
"I feel lucky to have known Stephen Hawking. His work is an inspiring reminder of what human minds are capable of," Gates tweeted.
9. Richard Branson, Virgin Group founder
The billionaire sent a series of tweets expressing his sadness and shared memories with Hawking. In 2015, Branson offered the physicist a free ticket, which goes for $250,000, aboard his Virgin Galactic spaceflight. Last year, Hawking told Good Morning Britain that he never dreamed he'd be able to go to space and had immediately accepted Branson's offer.
Branson explained his reasoning behind the offer on his Virgin blog: "Professor Stephen Hawking is one of the people I admire most in the world," he wrote at the time. "He is the only person I have given a free ticket with Virgin Galactic, and he is signed up to fly as a Future Astronaut with us if his health permits it."
In October of last year, Branson told CNBC's Squawk Box that he expects to be in space by April of this year. Unfortunately, the late physicist will miss seeing this dream come to pass.
"Proud Stephen Hawking was a member of our @virgingalactic family," Branson wrote on his Twitter. "Sorry we didn't get him to space, but honoured he played such a meaningful role in our development."
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