7

There is an internet trope that every atom in your body is replaced every seven years, and I looked it up to see if it is true.

The short answers is, as I expected, "No," but they are rotated fairly frequently.  Atoms in your skin and hair are replaced fairly quickly, atoms in your muscle and organs can sit there for a decade or so, atoms in your brain and teeth remain stagnant for your whole life. (source)(source)

What made me think of that was the recent death of my father.  We took his body and put it in a box with his name on it, but that was really only his final form.  Seven-year-old Lloyd, forty-year-old Lloyd, even eighty-year-old Lloyd, had mostly already moved on.

If you think about it, your body changes with every breath.  Atoms that had been a part of you-- carbon, water vapor, perhaps alcohol if you had a fun night-- are all swapped out for something new with each inhale and exhale.

And this is a bit of a tangent here, but since the human body is mostly water,  when a body is cremated most of it is released upwards into the clouds, where it then it rains down everywhere.  My parents are now part of the grass, part of the trees, part of the rivers and streams, and part of all the life within them.

That comforts me.