For starters, transits help us to determine our place in the cosmos.

Consider this brief history:  In 1716 astronomer Edmond Halley calculated that you can quantify the distance from the sun to the earth by having observers across the globe time the passage of Venus across the sun.  Knowing he would not live to see the next transit, Halley predicted global sites that would be suitable for viewing a transit and called upon future generations to pursue his plan.  For the 1761 transit and every transit opportunity since then, explorers sailed to distant lands to time the transit.  The quest to time the transit of Venus in 1761, during the Seven Years War, marked one of the first times the international community cooperated to answer one of the leading scientific questions of the day.

By quantifying the distance from the sun to the earth, a simple application of Kepler’s Third Law gives you the distances of all the planets from the sun, and thus the scale of the solar system.  Knowing the size of the solar system gives more accurate parallax measurements of distant stars.  Today, the transit of Venus as a means to measure the sun-earth distance is largely of historical interest, for tools such as radar have measured distances to planets much more accurately.

A transit is a great opportunity for the public concurrently to study the sun, which influences life on earth on both a planetary and a personal scale.  A dynamic between the sun and earth sustains life here, while our personal lives--which are becoming more technology dependent--are impacted by the sun's shenanigans.