Stars have been paying tribute to Stephen Hawking following his death at his Cambridge home in the early hours of Wednesday morning.
The 76-year-old made remarkable contributions to science in his lifetime but also became quite the pop culture icon, appearing in numerous TV shows and movies as himself over the years, including The Big Bang Theory.
Cast members have been paying tribute to the professor, who featured in the sitcom six times, including the recent season 11 premiere 'The Proposal Proposal'.
Jim Parsons (Sheldon) posted a tribute a message on Instagram saying simply: "Thank you, Stephen Hawking."
While Kaley Cuoco (Penny) posted the below:
Johnny Galecki (Leonard) also posted a tribute on Instagram saying: "RIP #stephenhawking Not only your brilliance, but your sense of humor will be sorely missed by all. 'Life would be tragic if it weren’t funny.' — Stephen Hawking"
And Mayim Bialik (Amy) said: "As we near Pi day (3.14) I join the global community in mourning the loss of the greatest physicist of our era. #StephenHawking is free from the physical constraints of this earthly condition we all exist in and he is soaring above us now marveling at it all. Thank you Dr. Hawking for enlightening us and blessing us with your wisdom and courage."