[PapaBear3625]

Yes, except that nobody can directly observe the past to know the age of the universe, it is all circumstantial, and radioisotope dating is not strictly physics (it was covered in chemistry); and once you apply it to rock ages because you must presume initial conditions to know the age, and once again nobody was around taking measurements at the beginning to know what the original composition of the rocks were.

Nobody can directly observe an electron, either. The circumstantial evidence of it's existance is sufficient for me.

Regarding radioisotope dating, it IS physics rather than chemistry. Where you have an isotope with a known half life, and can measure the proportion of the isotope and its decay products, you can have a pretty good idea of how long that isotope has been sitting there.

[CharlesWayneCT]

Type in "Chemistry Radiosotopic dating" on Google and you will see that people in CHemistry classes are covering the topic and asking for help.

However, I see that there are physics hits for the same search (Physcs radioisotropic dating), which means that it has bled over into physics from it's natural home in Chemistry. Can't say why.

Physics - (used with a sing. verb) The science of matter and energy and of interactions between the two, grouped in traditional fields such as acoustics, optics, mechanics, thermodynamics, and electromagnetism, as well as in modern extensions including atomic and nuclear physics, cryogenics, solid-state physics, particle physics, and plasma physics.

I guess the "modern extension" of nuclear physics would cover radioactive decay, and by extension dating methods, even though we covered atoms and decay in chemistry when I went to school.

Chemistry - The science of the composition, structure, properties, and reactions of matter, especially of atomic and molecular systems.

I guess at some point they decided that radioactive decays wasn't an "atomic system" so much as a "nuclear physics" question.

Radioactive decay is a relatively simple process, and was easily understood in a basic Chemistry class when I went to school.

[Fichori]

Yes, except that nobody can directly observe the past to know the age of the universe, it is all circumstantial, and radioisotope dating is not strictly physics (it was covered in chemistry); and once you apply it to rock ages because you must presume initial conditions to know the age, and once again nobody was around taking measurements at the beginning to know what the original composition of the rocks were.

“Nobody can directly observe an electron, either.” [excerpt]

This is a strawman because an electron can be indirectly observed in the here and now.

History cannot be directly or indirectly observed in the present.