It started with a simple question: can I synthesize vitamin D today in London?

I'd been reading about how latitude, season, and skin type determine whether sunlight can actually trigger vitamin D production. The science is clear — below a certain solar elevation angle (~45–50°), UVB radiation is too weak for synthesis regardless of how long you stay outside. But figuring out when that window opens for a given city on a given day? That's a calculation involving solar declination , hour angles, and spherical trigonometry.

So I asked Claude.

The Artifact That Started Everything

Claude didn't just answer the question — it generated an interactive artifact with a solar elevation curve, a day-of-year scrubber, and a threshold line showing when synthesis was possible. It used Spencer's 1971 formula for solar declination and the equation of time, projected onto a clean SVG chart.

I expected a paragraph with some numbers.…