The distinction between the theories—and the distortions that distinction might produce—was minor, Horrocks knew. But scaled against the solar system, at distances that could be cadenced in thousands of Earth radii, it was just large enough to turn a non-event into a full-blown transit of Venus. Kepler's Rudolphine Tables had Venus passing just above the sun on November 24, 1639. Horrocks predicted that Venus would pass in front of the sun, just as it had eight years earlier.
And this was not all. Horrocks believed that this, the second Venus transit of the decade, was no fluke. Yes, he agreed, Kepler was right about the frequency of Venus transits. They recurred at intervals 105.5 and 121.5 years. But Horrocks now claimed that they recurred in pairs. After 105.5 years, two Venus transits would occur, eight years apart. Then, after 121.5 years, two more Venus transits would follow, again eight years apart. Horrocks believed that Venus transits would no longer be isolated events—nor had they ever been.