One of the most radical ideas in the Codex Leicester is about fossils. In Leonardo’s day, most people believed that seashells found on mountaintops were carried there by Noah’s flood.
But he didn't stop at hydrology. While studying water, he leaped to the moon. He theorized that the moon is covered in water, and that the "dark spots" we see are oceans reflecting the Earth’s light. He was wrong about the oceans, but right about the concept of —the faint glow on the dark side of a crescent moon caused by sunlight reflecting off Earth.
Despite the fancy name, this isn't a dusty medieval poem. It is a 72-page scientific notebook written entirely by Leonardo between 1506 and 1510. It is a firehose of genius, covering geology, astronomy, optics, hydrodynamics, and paleontology. the codex leicester
In one paragraph, he jumps from the flow of a river to the cratering of the moon to the growth of a tree. He saw no barrier between art, science, and nature. To him, the curl of water in a fountain followed the same mathematical rules as the curl of hair on a human head.
If you ever get the chance to see the Codex in person (it travels occasionally), you’ll notice something odd. The text is written in Italian, but it’s backwards—from right to left. One of the most radical ideas in the
That Leonardo lives in the Codex Leicester .
Leonardo wrote the Codex Leicester because he couldn't not know. He wasn't trying to publish a book; he was trying to talk to himself about the universe. While studying water, he leaped to the moon
He argued that the fossils were proof that the mountains had once been the beds of ancient seas, lifted up over incredibly long periods of time. He realized the Earth was ancient, shaped by slow, relentless processes like water erosion—not a single catastrophe. This put him centuries ahead of modern geology.