Caesar loses a fleet to a spring tide

Caesar had been in Britain a few days when a gale and an unfamiliar tide got in among his beached ships and wrecked most of them, and he wrote down why: it was a full moon.

Mediterranean tides are small, and a Roman army had no reason to expect the Atlantic ones. Caesar's own line — that the same night happened to be a full moon, "which usually produces the highest tides in the Ocean" — is the earliest surviving connection anyone made in writing between the Moon's phase and the size of a tide, and it is the reason the invasion can be dated astronomically at all.