It’s a sad day in the science world. Today, March 14th, renowned physicist Stephen Hawking passed away at the age of 76. Hawking was famous for being one of the most brilliant minds of his time, and his research helped reinvent the way we see space, time, and the universe as a whole. But Hawking wasn’t just a genius — he often used playful experiments to test his theories, such as the time when he hosted a party for time travelers.

As a segment on his show Into the Universe, the scientist tried to prove his theory that one day, people would be able to travel through time. He threw a party on June 28th, 2009 to test this idea, making invitations that he didn’t send until after the date of the party. The fliers included the coordinates of the party in space and time and clarified that no RSVP was necessary.

On the day of the party, Hawking waited at the party venue, which was decorated with a banner that read “Welcome Time Travellers.” Sadly, no guests from the future made an appearance at Hawking’s soirée.

In a 1999 lecture called “Space and Time Warps,” Hawking wrote that time travel couldn’t be ruled out, although his 2009 experiment seems to suggest otherwise.

Hawking’s theories and accomplishments are too numerous to list in a single article, but the physicist is perhaps most famous for discovering “Hawking radiation,” a phenomenon that demonstrates how black holes decay and vanish over time. And in a recent video published by Popular Science, he explained his theory that nothing existed before the Big Bang.

Hawking may have left us, but his groundbreaking discoveries and his playful sense of humor will live on. On the day of the physicist’s passing, we’ll keep his advice in mind: “Remember to look up at the stars and not down at your feet.”