I offered the Lord Ludovico ten engines of war and only then a painting. Here is what I promised, what I drew, what was never built, and what I refused to write down.
Leonardo's letter to Ludovico Sforza, the giant crossbow of 42 braccia, the armoured car and its gearing, and why he called war a most bestial madness.
Leonardo da Vinci
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November 8, 2026
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30 min
Double the weight, double the rubbing, and the face it lies on makes no difference. I found it with blocks, a cord and a pan of lead, and wrote a quarter into every machine.
Leonardo's friction rules two centuries before Amontons: load not area, a quarter of the weight, rollers and bearings, and the Madrid Codex elements of machines.
Leonardo da Vinci
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November 8, 2026
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28 min
Discs that drink the steam, a channel with no moving part that refuses to flow backward, the Hotel New Yorker years, and the last page of the notebook.
Tesla's disc turbine and valve worked by hand, tested against 2021 measurements, and the end of his story: 1943, John G. Trump and Belgrade.
Nikola Tesla
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November 5, 2026
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27 min
Tesla builds a dynamo with 384 poles to reach ten thousand alternations a second, silences the arc lamp, and finds the current hiding in the skin of the copper.
Tesla works out how many poles make 10,000 alternations a second, why the iron must be wire, and why copper carries current only in its skin.
Nikola Tesla
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November 5, 2026
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30 min
New York, 1884 to 1887: I work for Edison, dig ditches, and prove on paper that copper grows as the square of the distance and falls as the square of the pressure.
Tesla's New York notebook: why 110 V direct current reached about a mile, the I²R arithmetic of copper, Edison's three-wire saving, and the $50,000 story.
Nikola Tesla
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November 5, 2026
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24 min
by Marie Curie 