I recall this Science Fiction story where this guy invents a method of detecting the duration of a organism, he explains it as the body forming a tube through time as it exists, and at birth or death he could detect the kinks in the tube that stopped him measuring the whole history/future of the person and hence could tell people when they where born and when they would die, since he could only tell them when and not how, it was impossible to avoid death.
the story had a lot of releated plots about twists in knowing your exact death (trickery with wills and people trying to dodge death where two), in the end he gets a visit from a young couple who just want to know if they will die together since they couldn`t bear to be parted, he assures them they will be together at the end and they leave his office, then he watches from the window as they are killed crossing the road and getting caught up in a traffic accident, then the story ends as he destroys the machine, I tell it badly, but it wasn`t a bad story (Robert Heinlein iirc)
PS: knowing my luck I will die the day before they invent eternal youth Immortality serum (doctor in old folks home "right! lets try this on patient 35...oh! he died yesterday, well! patient 36 then")
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