The age of the Earth

[Ferrocyanide]

depending on the dirt.  some dirt contain zircon which could be 95% as old as the earth.   some dirt may contain fragments of meteorites that somewhat older than earth.

Fun fact: An empty plastic bottle of water contains hydrogen atoms that were synthesized in the first few minutes of the Big Bang.

Not exactly. Things aren’t as static as they seem to be.
Even when you have a hydrogen molecule, H2, the hydrogen atoms exchange electrons. When you have a H2O molecule, again, there is an exchange of electrons between the hydrogen and oxygen atoms (at least for the last orbital).
H2O in the liquid state is not stable either. Once in a while, they dissociate and recombine.
I think water has a pH of 7.0 at 20 C.

Also, when you have some pure H2O and D2O and you mix them, because of all the exchange going on, you end up with 25% H2O, 25% of D2O and 50% DHO.

[Anomalocaris]

Fun fact: An empty plastic bottle of water contains hydrogen atoms that were synthesized in the first few minutes of the Big Bang.

Not exactly. Things aren’t as static as they seem to be.
Even when you have a hydrogen molecule, H2, the hydrogen atoms exchange electrons. When you have a H2O molecule, again, there is an exchange of electrons between the hydrogen and oxygen atoms (at least for the last orbital).
H2O in the liquid state is not stable either. Once in a while, they dissociate and recombine.
I think water has a pH of 7.0 at 20 C.

Also, when you have some pure H2O and D2O and you mix them, because of all the exchange going on, you end up with 25% H2O, 25% of D2O and 50% DHO.

that may be,  but it’s the solitary proton in the nucleus which is at least 2000 times more massive than its electron that define hydrogen, and that is a far more durable identity that anything marked by its electron.   Most of those nuclei that contain only a solitary proton, including those in any water bottle, have had that same solitary proton and no others since moments after the big bang.

[no one]

A gentleman never inquires a lady's age.


That being said, she's old enough to have a good time, legally.