First, when their body stops functioning. Second, when their body is buried (or cremated). And the third and final death is when their name is uttered for the very last time in human history.
I am fairly confident Stephen Hawking will have only died two deaths.
I guess that a man that was self-declared atheist would not appreciate the religious concept of "all good people go to heaven when die". I can understand that is a comforting social convention in any case.
In before or instead of Sagan possibly? I was not particularly aware of Sagan before the internet, whereas I imagine Hawking has been a household name in much of the world for decades?
Sagan is a special case. Will be remembered (mainly) as a very good science communicator. Not so many people connect it with a famous and top-class scientist woman. The work of his first wife, Lynn Margulis, changed forever the concept of evolution.
If we put Sagan with Darwin we should not forget to add Margulis to this list also.
Aside: My first encounter with Margulis’s Serial Endosymbiosis Theory blew my mind.
I’d go so far as to say that SET changed my worldview. I’d always looked at evolution solely through the cold, brütal lens of selective pressure and competition.
SET showed us, however, that symbiosis (i.e. fundamental cooperation) is right up there with competition... kind of a countervailing force within the story of evolution.
I don’t know why, but I take great emotional comfort in that. Perhaps, being non-religious, it allows me to see something humane(?) encoded in the rulesets that govern change.
He is one of the very rare human beings whose names will never be forgotten.