Delaware Public Media

State marks Lewes' role in 18th-century astronomical breakthrough

May 13, 2016

The town of Lewes played an unexpected role in a major scientific discovery about space in the 1700s. Now, the state is honoring that moment in history with a new public archives marker.

 

 


Historian James Morrison has studied the 1769 "transit of Venus," where the planet's path across the Sun was visible from Earth.

"It was the Holy Grail of astronomy in the middle of the 18th century."

Measuring that path would help astronomers chart the entire solar system by giving them a reference to calculate the distance between the Earth and the Sun.

 

"You can use that, then, to calculate the size of the orbit for any of the planets, their distances from each other and from the Sun, the speed of the rotations," Morrison says. "It was the Holy Grail of astronomy in the middle of the 18th century."

 

But to measure it, he says, they needed to observe the transit of Venus from places with known coordinates -- where the planet's movement would also be visible at night.

"And so that put here -- in this case, call it Philadelphia -- at the bleeding edge of transit measurements, because that was the only place it could be seen," Morrison says.

And Lewes was the closest spot that nearby astronomers, including Ben Franklin, could use as a backup observatory.

"It just seems like an unlikely turn of events that little Lewes would be out there playing astronomy with the big boys."

Morrison has charted the hasty expedition that surveyors took to set up that observatory and pinpoint its coordinates. He says astronomers in Philadelphia had six months to set up their two stations, whereas:

 

"The team that went to Lewes had a week," he says, adding that they "did a state-of-the-art survey in primitive, rural Sussex County, did it in four days and did it right."

 

Morrison says the measurements taken in Lewes would stand the test of time in the international astronomical community.

 

"This expedition for the Venus transit in 1769 put Lewes on the map in the history of astronomy forever," he says. "And it just seems like an unlikely turn of events that little Lewes would be out there playing astronomy with the big boys."

 

The new marker is at Bethel Methodist Cemetery on Savannah Road in Lewes. Morrison will give a talk on the whole story after the marker dedication, at the Hotel Rodney on Friday, Nov. 20 at 12:30 p.m.

 

James Morrison is a member of the Lewes Historical Society, "self-appointed Venus transit maven" and author of the book The Astrolabe.