Epidemiology: Everything Turns on One Number Crossing One
If each case produces more than one further case, an outbreak grows; below one, it fades. That threshold is simple — and almost everything else about the subject is context-dependent.
Topic
Longevity & Health
Neuroscience: The Brain Rearranges Itself Around What You Do
The computer analogy breaks down at the most important point — the hardware physically changes with use. That single property explains most of what is practically known about learning.
Longevity and Health: The Big Effects Are the Ones Nobody Sells
The interventions with the largest effects have been known for decades and are unglamorous. Attention flows almost inversely to effect size, for a simple reason — the big ones cannot be sold.
Half-Life: Why the Last Bit Takes So Long to Go
An afternoon coffee still has an eighth of its caffeine in you the next morning. Anything that loses a constant proportion per period behaves this way — including skills and knowledge.
Antifragility: The Things That Get Better When You Drop Them
We label parcels 'fragile' but have no word for the opposite — not strong, which survives shocks unchanged, but something that improves because of them. Your muscles are the everyday example.
Hormesis: The Dose Decides Whether It Helps
Lifting weights tears muscle, and the tearing is the point. A small dose of something harmful can trigger a repair response that leaves you stronger — but only under two specific conditions.
The Aging Biomarkers That Actually Predict Outcomes
Chronological age tells you almost nothing useful. A handful of measurable fitness markers tell you a great deal more.