Now, how might this be done without making a bonfire of physics? Consider chronobiology — the science of biological periodicity, which is already well-established and routinely underappreciated. Every organism carries internal clocks tuned to circadian, circannual, and ultradian cycles. My own work on variable stars demonstrated that stellar pulsation follows deep periodicities — Cepheid variables beat with a regularity that encodes their luminosity, and from that regularity we read distance across the cosmos. The human body is no less a pulsating system. If we accept — and I think we must — that the complex interplay of immune function, cortisol rhythm, cardiovascular load, and inflammatory cycles creates a signature periodic vulnerability that peaks annually at a consistent calendar window, then a sufficiently sophisticated longitudinal biomarker analysis could, in principle, identify that window. One law of physics you might strain: strict deterministic unpredictability in complex biological systems. I will grant the opponents that much. But I do not grant them the argument that periodicity is absent — only that we have not yet built the instrument sensitive enough to read it.

The cultural consequences are where I become most insistent, and where I expect the fiercest opposition. My contestable claim is this: knowledge of one's death-day would not produce despair — it would produce the most rational and compassionate society in human history. Consider what birthdays actually celebrate: pure accident, the unremarkable fact of emergence. Death-days, by contrast, would celebrate orientation — the annual return to the threshold, the day one consciously measures how one has spent the preceding year. Every civilization that has produced durable moral architecture — the Stoics, the Zen Buddhists, the Ignatian tradition — has centered itself on memento mori, the deliberate confrontation with finitude. What we are proposing is not morbid; it is structurally honest. The death-day ritual would become what the birthday never quite managed to be: a genuine reckoning. Gifts would be replaced by debts acknowledged. Parties would give way to letters written, wrongs repaired, apprentices taken on.

I am aware that opponents will argue this knowledge would paralyze individuals as each annual death-day approaches — that the uncertainty of the year would compound into annual terror. They are wrong, and I will tell you why with the same confidence with which I told Russell the sun is hydrogen: uncertainty about the year is precisely the liberating variable. The day arrives and passes. You survive it. You are given another orbit. A person who knows their death-day is not a condemned prisoner — they are a Cepheid variable, pulsing through the galaxy with a known period and an unresolved luminosity. They beat. They measure. They illuminate. That is not a diminished life. That, in fact, is the shape of all the lives worth studying.