The time has come for "Hey, Science," our relentlessly scientific weekly feature in which we have your most provocative and/ or dumb scientific questions answered by real live scientists (or related experts). No question is too smart for us to tackle, quite unfortunately. This week, scientists ponder the question: Are there atoms of Abe Lincoln in my body right now??

THE QUESTION: Body image-obsessed reader Aaron asks, "Are there any atoms in my body that used to belong to Abe Lincoln? What about Hitler?" In other words, do particles of matter on earth get mixed so well by natural processes that when we die, our particles are evenly distributed over the whole world, a little bit everywhere? Are we made of everyone?

Greg Fiete, professor of physics, University of Texas:

Probably stuff (dead skin, breathed air) that ends up in air is well-mixed over the Earth, but stuff under the ground less so (at least on a 100 year time-scale).

Leo Kadanoff, professor of physics and math, University of Chicago:

It depends. If you get cremated and the ashes get spread around, pretty soon you are everywhere. If you are in a stout coffin in a solid mausoleum you won't start to get around 'til the coffin and mausoleum begin to leak. [Ed.: Well... yes.]

Leonard Brand, professor of biology and paleontology, Loma Linda University:

I suspect that many atoms get distributed around quite thoroughly. But the real answer to the question is that it is a matter of probability. It is possible that our bodies have atoms from many different animals and persons from Adam to Mother Teresa, but what is the probability of it? How many atoms are in our earth compared with how many atoms are in a person? How many persons have lived during earth history? With figures like that a statistician could calculate the probability that I have some atoms that were a part of Queen Victoria.

The American Chemical Society posted our question to their internal message board, and it drew this reply from the chemist Bryan Balazs: "I remember doing an exercise in undergraduate P-Chem in the early 1980s in which we were asked to calculate the chances that a breath that we took would contain a molecule (oxygen, nitrogen, carbon dioxide, it didn't matter) of "Caesar's last breath". The answer turned out to be about 50%, so for every few breaths you take, you have a reasonable chance of breathing in a part of "Caesar's last breath". We were asked to ignore effects of material transport, atmospheric convection, chemical reactions, etc., which would be a big part of the answer to the original question posed."

Another scientist referred us to this piece from Marquette Magazine (which seems to contradict the above answer somewhat, but which also seems more statistically well grounded) in which biology professor Martin St. Maurice speculated that these things are possible, but unlikely: "What are the chances that an atom of oxygen you just breathed was once a small part of Julius Caesar? We can estimate approximately 67,500,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 atoms of oxygen on earth and 6,350,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000 atoms of carbon (that's a lot of zeros). A quick calculation, loaded with assumptions, reveals that even if we sample completely different atoms of oxygen with every breath of life, we sample at most 0.0000000001 percent of all the oxygen atoms on earth over an 80-year lifespan." (He says the chances of sharing a carbon atom are better, but still "extremely slim.")

THE VERDICT: Are there any atoms of Abraham Lincoln in your body right now? Possibly, but the probability seems low (lower if the person was buried, or died recently). Are there any atoms that once belonged to some real interesting people and probably also some dinosaurs in your body right now? You bet!

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[Do you have a question for "Hey, Science?" Email me. Image by Jim Cooke.]