Scope: clock vs. sample accuracy

This paper addresses sample-level dating accuracy, not whether decay clocks are correct. Laboratory-measured decay constants (A = λN) are environment-independent — Oklo and SN 1987A bound fine-structure drift below 10⁻⁷ over two billion years. Accuracy is therefore set by event attribution and open-system exchange, not by the decay physics.

Two different claims are routinely conflated: that a decay clock is wrong, and that a given sample is dated wrong. This paper addresses only the second. The laboratory-measured decay constant (A = λN) and its environment-independence are taken as given; accuracy is set by event attribution and open-system exchange, not by the decay physics.

Two claims must be separated at the outset, because conflating them is the most common error in critiques of geochronology. The first is that a decay clock is unreliable. The second is that a particular sample has been dated inaccurately. This paper concerns only the second.

The decay rates underlying both methods are measured directly in the laboratory, without any geological input. A pure uranium source emits a definite number of alpha particles per second; counting that activity over an hour fixes the decay constant through A = λN, and hence the half-life, with no clock “running” over geological time and no circular reference to a rock’s age^[5]. [F] Decay constants are environment-independent over the relevant range: natural-reactor (Oklo) and astrophysical (SN 1987A) constraints bound any drift in the fine-structure constant to below 10⁻⁷ over two billion years^[8]. [F] We therefore take the clocks as given and do not re-litigate them.

What remains genuinely uncertain, and what controls accuracy in practice, is whether the material analysed actually records the event of interest, and whether it has exchanged matter with its surroundings. This is the domain of the present work, and it is the same domain the companion radiocarbon paper addresses for biogenic carbon^[1]. The aim here is to show that radiocarbon and zircon U–Pb fail in the same way, to make that shared failure explicit and quantitative, and to handle it with a single, transparent protocol.