THE RECORD
What changed
Galileo published observations of lunar relief, Jupiter's moons and Venus's phases, challenging perfect heavens.
EVIDENCE
What remains
Surviving telescopes, Sidereus Nuncius, sketches and repeated observations allow the claims to be tested.
WHY IT MATTERS
Why it matters
Instrumentation extended human senses and made mediated vision part of scientific argument.
OPEN QUESTION
Where interpretation begins
Galileo did not invent the telescope, and observations did not instantly decide among every cosmological model.