[split] Radiometric Dating

[Alex K]

2) When you measure decay rates of short lived isotopes, you get an exponential, not a constant. It is what the theory predicts, at least in first approximation. There's no actual reason why long lived isotopes would behave differently, seeing as they follow the same law, just with a different time constant.

There is maybe a slight misunderstanding of nomenclature, the decay rate per nucleus is indeed constant, but since the total rate depends on the amount of nuclei of a given type which is lowered, we get an exponential. We have

totalrate = rate * numberofnuclei
and d/dt numberofnuclei = -totalrate.

The solution to that differential equation for rate=constant is

numberofnuclei(t)= Exp[-rate * t]*numerofnuclei(0).

I'm just typing that out for the benefit of our creationist friend here.

While you are absolutely correct that there is no reason why long lived isotopes would behave differently, we can do much better than that: if you take enough material, you can measure the constant decay rate per nucleus (i.e. the inverse life time) directly, even if the individual lifetimes are much longer than the duration of the experiement. This is for example how we know that the proton lifetime is larger than 10^40 seconds or so.

The question then becomes: has this decay rate changed over the past millions of years. The theory predicts a constant rate (per nucleus) as a complicated function of fundamental constants.

Now here, the Creationists (I'll avoid to use the ableist term creatard) shoot themselves in the foot with their argument from fine tuning: the decay rates are of course not independent magical quantities, but are a result of the dynamics of the strong and weak force, the quark masses, the W boson mass, the Higgs field. Change that around, and physics changes *a lot*, as in the vacuum explodes, random particles decay, everything ends in a firestorm. Of course you can never prove that God didn't magically manipulate the decay rates, but we don't need to argue against unfalsifiable unjustified assertions. Direct evidence against changes in nuclear properties since 1.7 billion years ago has been provided by analysis of the oklo natural nuclear reactor in Africa.