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(The following piece reminds one of Ship of Theseus or Theseus’ Paradox. There is a beautiful thought provoking Indian film based on that paradox. Watch it here on You Tube. Ed.)
DEBBIE ELLIOTT, host:
From NPR News, this is ALL THINGS CONSIDERED. I’m Debbie Elliott.
Time now for our look at some of the elemental questions of life in our segment, Science Out of the Box.
(Soundbite of music)
ELLIOTT: Many have heard someone say, I’m not the person I was. Well, that may be more true than you know.
NPR science correspondent David Kestenbaum has this tale.
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DAVID KESTENBAUM: Okay, we all get haircuts. But have you ever thought that when we do we lose atoms. That hair that was once part of us goes its own way. So at the end of the day, what happens to my hair on the floor here?
Unidentified Woman: Well, they get swept up and put in the trash.
KESTENBAUM: Those are my atoms.
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KESTENBAUM: How much of me is really with me throughout my life? I mean, my skin rubs off, I trim my fingernails, part of me is eroding and presumably being rebuilt. But how much is it, 1 percent? Is it 10 percent?
I called around to biologists and chemists, and no one seemed to know the answer.
Mr. LOGAN McCARTHY (Chemistry, Harvard University): I’m Logan McCarthy. I teach chemistry at Harvard University.
KESTENBAUM: Had you ever thought about to what extent we’re just spare parts being replaced all the time?
Mr. McCARTHY: I guess it never really occurred to me. You know, who I was is not – the atoms that I have now are not the same atoms that I had, you know, yesterday or the week before.
KESTENBAUM: McCarthy did some research and he found this article from a Smithsonian Institution publication from 1953. So this is the beginning of the Atomic Age. And the article described these experiments where researchers fed to people radioactive atoms. Or they injected them with radioactive atoms. And then using radiation detectors, they could watch the atoms as they moved around. So they’d watch them go up one arm, into the heart and down the other arm.
Mr. McCARTHY: You can follow it through their body. Does it get excreted through urine, or is it excreted through their sweat or through feces or, you know, what happens to it? Does it end up in their fingers or in their eyeballs, or you know? So you can follow where these atoms go.
KESTENBAUM: Where do they by doing that?
Mr. McCARTHY: Well, they end up in all of your tissues.
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