There have been a number of "celebrity" deaths recently, usually people we recall from our childhoods and a pang of nostalgia makes us pause briefly, perhaps dig out an old book or album.
The passing of Stephen Hawking feels different, like something fundamental has just been removed from the universe.
He may have been confined to a wheelchair but it didn't define him, we didn't feel sorry for him, he took his place in our affections in spite of it not because of it. And, unlike those figures from our past whose stars largely faded, his shone ever brighter with the passage of time.
Rest in peace, Professor, you will be sorely missed.