There are different isotopes of nitrogen, with 2 particularly common: N-14 (~99.6%) and N-15 (~0.4%). Nitrogen molecules N2 have 3 versions with these 2 isotopes. So nitrogen isn't terribly interesting. Carbon is far more interesting, due to its ability to form complex molecules and solids (diamond, nanotubes, etc.). C-12 (~98.9%) and C-13 (~1.1%) are stable isotopes. Benzene, with 6 carbons, can have O(2^6) forms with different carbon isotopes (forget the hydrogen isotopes). Math geeks: exactly how many different benzene rings are there using C-12, C-13, H-1 ? Clearly, in order to retain "identity" for a long period of time, a diamond crystal would seem to be pretty decent for a larger object. One could conceivably "read out" this identity by utilizing some sort of laser configuration that could tweak a single atom in the crystal in order to determine its mass. A question I've asked here before, but never found a satisfying answer to, is "At a given absolute temperature T, what is the half-life before 2 carbon atoms exchange places in a diamond lattice?" Given quantum mechanics, such an exchange is possible, but presumably highly unlikely. Is such a time period longer or shorter than the time for a C-12 or C-13 atom to decay into non-carbon ? At 12:02 PM 4/3/2020, Brent Meeker via math-fun wrote:
That raises the question of how big does something have to be in order to retain its identity over 500yrs?
All nitrogen molecules are identical and their location spreads out per Schroedinger's equation so that one is indistinguishable from others whose wave-functions overlap.
We can refer to a pen or a chair that Leonardo used, but not to an atom he breathed.
Exactly, how objects gain and keep their classical character is part of the interpretation problem of quantum measurement.
Brent
On 4/3/2020 5:07 AM, Ãric Angelini wrote:
... Where did Leonardo (or X) sign the molecule he breathed?