October 10, 2026 · 7 min
Dark lines in the Sun's light
Spread sunlight wide enough and thin dark lines appear in it. Nobody knew what they were for forty years.
Free
Because
A short letter every Sunday: one discovery about the sky, and the steps that led to it.
2,800 readers
Free, and you can leave any time
More posts
What the stars are made of
Once the dark lines in sunlight were matched to flames in a lab, the stars could be read like a label.
Kepler and the shape of an orbit
Years of numbers about Mars, and the moment a circle gave way to a stretched one.