Because the oxygen we breathe in gets converted and leaves our bodies as carbon dioxide, one would assume that we are always drawing in a “fresh breath.”  However, there is 1% of our breath that doesn’t renew as we inhale and exhale. This part of our breath is made up of atoms that are chemically inactive or inert, so they are simply released back into the atmosphere.

Argon atoms. We breathe them in and breathe them out without absorbing them. So, when you exhale, those argon atoms re-enter the air to be inhaled by others. According to astronomer Harlow Shapley, a year from now, those same argon atoms will have circulated around the entire planet, and fifteen of them will have made their way back to you to be breathed in again. This means that there is a good chance that your next breath may contain argon atoms that were inhaled and exhaled many, many times by many, many others over many many years …

…this is certainly a topic for Throwback Thursday.