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I published the Sidereus Nuncius — the Sidereal Messenger — in March 1610. Sixty pages. It sold out immediately. It contained four discoveries: the moon is not a perfect sphere but mountainous and cratered; there are far more stars in the Milky Way than the eye can detect; Jupiter has four moons that orbit it; Venus has phases that can only be explained if it orbits the sun.

The last point was the dangerous one. If Venus orbits the sun, and Jupiter's moons orbit Jupiter, then not everything in the heavens orbits the Earth. The Ptolemaic system — the Earth at the centre, everything circling it — was contradicted by direct observation through the instrument in my hands.

I sent telescopes to princes and cardinals. I knew the surest protection was to make the powerful complicit in the discovery. It worked for twenty years. Then it stopped working.