On Wednesday, world-renowned astrophysicist Stephen Hawking died at age 76 in his home in Cambridge, England. He lived for 55 years with the neurological disease amyotrophic lateral sclerosis (ALS), and as a result, he spent most of his life using a wheelchair, which, for the last decade, also included hands-free communication capability that gave him the computerized voice with which so many people now associate him.

As a working physicist and prolific public figure, Hawking helped revolutionize the field of astrophysics. His scholarship helped elucidate our modern understanding of the universe and its origins, and he was quick to share his views on humanity and society. While his achievements are many, there are five in particular worth noting.


5. Stephen Hawking Theorized How Black Holes Emit Information

Black holes are notoriously hungry phenomena, distorting spacetime and sucking in any matter that passes within their event horizon. But Hawking theorized that black holes actually radiate energy as a result of quantum effects near the event horizon. We could only observe this theoretical energy, which is referred to as “Hawking radiation,” in smaller black holes that are about the same mass as our sun. In larger black holes, it would be overwhelmed by the gas falling into the black hole. Hawkin’s hypothesized phenomenon hasn’t been directly observed, but as Inverse previously reported, physicists are working on it.

'Big Bang Theory' loved its nerdy celeb cameos, and Stephen Hawking's was an absolute treasure.

4. Stephen Hawking Proposed That the Singularity Was an Essential Element of the Big Bang Theory

The Big Bang Theory — the physics one, not the television one — proposes the universe began with a powerful expansion that started with one point, the singularity. Before Hawking’s time, physicists tried to reconcile the apparent paradox of the singularity. The idea of a single point of infinite density simply didn’t mesh with the conventional views of physics in the middle of the 20th century. In 1970, though, Hawking co-authored a paper with Roger Penrose that began to reconcile this notion.

This paper, titled “The singularities of gravitational collapse and cosmology,” countered the widely discussed notion that the Big Bang was preceded by the universe contracting. Physicists generally accept this version of the Big Bang Theory, in which there was nothing before the beginning of the universe.

Ripples in spacetime.

3. Stephen Hawking Proposed There Was No Meaningful Distinction Between Space and Time in the Early Universe

In his 1988 best-selling book, A Brief History of Time, Hawking proposed that at the very beginning of the universe, space existed, but time as we know it did not yet exist. Astrophysicists continue to describe space and time as being intrinsically tied to one another, but Hawking hypothesized that at the very beginning of everything there was no meaningful distinction. The curious public digested this hypothesis in Hawking’s book, but physicists continue to debate his idea.

Stephen Hawking, Big Bang

2. Stephen Hawking Provided Evidence That Time Travel Is Impossible

Back in 2009, Hawking hosted a time traveler party, inviting time travelers to join him for a reception to celebrate their achievements. Here’s the catch, though: He didn’t send out the invitations until the next day. The idea was that anyone who actually showed up would clearly be legit since nobody knew about the party before it happened. On Hawking’s 75th birthday in 2017, he announced that nobody had shown up to his party. While this isn’t definitive proof that time travel doesn’t exist, it’s pretty strong evidence. After all, if you discovered how to travel through time, wouldn’t Hawking’s time travel party be one of your first destinations?

Stephen Hawking on 'The Simpsons'

1. Stephen Hawking Played Himself Four Times on The Simpsons

Sure, revolutionizing astrophysics is great, but what about having your cartoon avatar immortalized for posterity? In addition to playing himself on Star Trek, Hawking appeared on The Simpsons four times between 1999 and 2010. Sure, this achievement wasn’t scientific, strictly speaking, but it does embody the character and public image of one of the best-known scientists in modern history. As a physicist, Hawking didn’t create much original work in his later years. But as a science popularizer, he continued to inspire people to learn about the world around them. And as far as monumental achievements go, that one’s hard to overstate.

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