Stephen Hawking during a lecture in September 2014. (Desiree Martin/AFP/Getty Images)

Theoretical physicist Stephen Hawking, who observed that black holes are not truly inescapable, died Wednesday at the age of 76. His scientific curiosity was matched by a delightful sense of humor. He put this combination to use in an experiment to determine if time travelers exist. Hawking threw a party at noon on June 28, 2009, at latitude and longitude specified in the invitations.

There was one wrinkle: He did not publicize it until after the event. “You are cordially invited to a reception for time travelers hosted by Professor Stephen Hawking,” the post-party invitation read. “To be held in the past, at the University of Cambridge Gonville & Caius College, Trinity Street, Cambridge.” Attendees, for the obvious reasons, did not have to RSVP.

Footage from the poorly-attended party on YouTube shows Hawking alone among balloons, popped champagne bottles, hors d'oeuvres and a banner that read “Welcome Time Travelers.” No one materialized from the future. A shame, he said — he'd been “was hoping a future Miss Universe was going to step through the door.”

Not one to let data go to waste, Hawking cited the event several times, such as in 2012, when a reporter at the Seattle Science Festival asked him about the possibility of time travel. “I sat there a long time,” he said, “but no one came.”

— Ben Guarino