HISTORY
In 1716 astronomer Edmond Halley calculated that you can quantify the distance from the sun to the earth (solar parallax) 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. …. The quest to time the transit of Venus in 1761, during the Seven Years War, marked the first time the international community cooperated to answer one of the leading scientific questions of the day.”
— NASA website