Shadows and Silhouettes: Looking for Transits Map shows where on
Earth the Mercury Transit will be visible and not visible. Image
On November 8, Mercury will transit the Sun. From Earth, we'll
see the silhouette of Mercury travel across the disk of the Sun.
Transits are uncommon but predictable events. The geometry of
Mercury (or Venus), the Earth and the Sun has to be aligned
precisely for a transit to occur. Most of the time, these inner
planets cross above or below the disk of the Sun. Historically,
transits of Mercury and Venus promised a method to better
measure the distance to the Sun. Johannes Kepler predicted and
then endeavored to see a transit of Mercury in 1607. Likely, he
observed a sunspot with his camera obscura--two years before
Galileo discovered sunspots with his primitive telescope in
1609. Later, telescopes aided transit observers in estimating
the scale of the solar system. This is a difficult method,
fraught with problems of timing, optical effects caused by
Earth's atmosphere, poor weath