Benjamin Franklin and Science

Color image of an exhibit with an image of an older Benjamin Franklin holding up his knuckle to touch a black key on a string.
Franklin was fascinated by electricity and devoted much of his time to studying its properties.

NPS photo


Growing up during the age of Enlightenment, Franklin applied the reason-based scientific method set out by Isaac Newton and others. Above all, he was driven by curiosity. He would research and experiment for the mere purpose of learning, and it was only later that he would seek a practical application for his scientific knowledge.


Nautical Inventions

Early in his life, Franklin’s flair for innovation and youthful love of swimming led him to produce “a method in which a swimmer may pass to greater distances with much facility, by means of a sail.” Centuries before windsurfing, Franklin discovered he could harness the power of the wind with his kite and be pulled effortlessly across a mile-wide pond. At the age of 11, he also created an early version of what we now know as swim fins. “I made two oval palettes… They much resembled a painter’s palette… I also fitted the soles of my feet a kind of sandals.” In 1968, Franklin’s swim fin invention earned him a place in the International Swimming Hall of Fame.

Franklin crossed the Atlantic by ship eight times during his life, voyages that provided him with ample opportunity to observe the ocean and the weather. His charting of the Gulf Stream contributed to an understanding of how the ocean’s currents could affect global trade by helping ship captains sail within the Gulf Stream and thus reduce the lengthy ocean crossing. Because he was interested in improving travel to make it more efficient, comfortable, and convenient, he imagined various ways to streamline vessels for speedier voyages.

Experiments with Electricity

Franklin was fascinated by electricity and devoted much of his time after he retired to studying its properties. Some of his research resulted in “tricks” that he used to amuse others, like a charged metal spider that moved like the real thing and an electrified fence that created sparks. He coined the terms “battery,” “positive charge,” and “negative charge,” and discovered new ways to generate, store, and deploy electricity. His design and promotion of the use of lightning rods helped prevent untold numbers of structural fires throughout the world.

His famous kite experiment occurred in June 1752, and though it is said to have taken place in Philadelphia, the exact location remains unclear. Franklin asked his son William to fly a silk kite, to which he had attached a wire on top and a key at the end of a string. Ultimately, the kite—and therefore the key—amassed an electric charge from a storm cloud. Franklin was then able to collect some of the charge and compare it to the electricity he had created in other experiments. He did not publicly mention the experiment until October, four months after it took place, at which point Franklin did not clarify that he had conducted the experiment himself—an issue that has caused some scholars to doubt Franklin’s story.

Franklin’s electrical experiments launched him into an international network of men (and some women) who worked in fields today known as physics, chemistry, biology, botany, and paleontology. To share and exchange such knowledge, Franklin proposed a society “to be called the American Philosophical Society” which remains today a world-renowned institution headquartered in Philadelphia.


Benjamin Franklin was no stranger to the pleasures of food and drink—he liked good wine, and he liked good food. He also knew that the economic stability for the colonies depended on agriculture, exports, and trade. So he gathered information about which types of crops would thrive in the climates and conditions of the colonies, and he imagined the possibilities of growing plants for medical help, protein, and his own culinary pleasure.

Whether he was in Philadelphia or London, Franklin drew on his network of friends and scientists across the globe and eagerly participated in a whirlwind of botanical exchange. John Bartram, in Philadelphia, sent acorn, magnolia, and honey locust seeds to Franklin in London. Franklin sent naked oats and Swiss barley seeds from London to Deborah in Philadelphia, who gave some to Bartram. Bartram sent seeds to Franklin in London, and Franklin sent seeds back to Bartram. Seeds were sent from East India to London to Savannah, from Philadelphia to Amsterdam and Bordeaux, from London to Turkey to Philadelphia, and on and on until the colonies had been thoroughly pollinated by Franklin and his friends!


The year was 1783. Europe had been wallowing in a dense fog for months. The sun was unable to penetrate the thick cloud layer and there was hardly a summer at all that year. The first snow of the winter, unable to melt, had frozen to the ground, and every snow since had only accumulated.

Franklin, in France at the time, had witnessed the bizarre fog. But for Franklin, the fog had to have a rational explanation. It was a puzzle to be solved. In May of 1784, Franklin suggested a possible cause, theorizing that “It was the vast quantity of smoke, long continuing to issue during the summer from Hecla in Iceland, and that other volcano which arose out of the sea near that island; which smoke might be spread by various winds over the northern part of the world.”

His theory was correct. Iceland’s Laki fissures had been continuously spewing lava since June of that year, one of the largest volcanic eruptions that had ever been recorded. The eruptions released tons of toxic gases into the atmosphere. The change in atmosphere, combined with what had already been an unusually warm summer, caused major weather shifts in the weather throughout Europe and North America for months.


Silk dresses were in vogue throughout Europe and the colonies, and the finest silk came from Asia. But Benjamin Franklin wanted to make silk right here at home. He figured that if the colonists succeeded, they could make money and have inexpensive access to fine silk.

The process of making silk, however, is no easy task. Silk comes from the larvae of a moth called the Bombyx mori. This moth can neither see nor fly, and it lays about 500 eggs in only a few days before dying. These eggs produce about 30,000 worms, which may only be kept alive by a diet of the ever-so-slightly wilted leaves of the White Mulberry Tree, which is only found in Asia.

The American Philosophical Society offered cash prizes for colonists who could succeed in making silk. Sadly, the White Mulberry tree did not flourish in the colonies and the process of making silk was just too laborious for the colonists—not to mention the silkworms.


Never one to miss a lunar eclipse, Franklin set himself up one evening in 1743, ready to watch his favorite nighttime show. His very own almanac had predicted that the eclipse would begin around 9 o’clock that evening. A strong wind began to blow, thick clouds and rain blew in blocking his view… and the eclipse went on without him. Much to his astonishment, he later read about the eclipse as having been seen farther northeast in Boston: “…what surpriz’d me, was to find in the Boston Newspaper an Account … of that Eclipse … for I thought, as the Storm came from the NE. it must have begun sooner at Boston than with us, and consequently have prevented such Observation. I wrote my Brother about it, and he inform’d me, that the Eclipse was over there, an hour before the storm began!”

This led him to study the path of storms, and he deduced that storms which seem to blow from the northeast are actually moving from the southwest as the winds are moving from the northeast, making them especially powerful storms that blow from south to north.

Transit of Venus

In Franklin’s time, the shape and design of our solar system was already well-known, but the actual size was still a mystery. What was missing was a single measurement: the distance between any two heavenly bodies could provide them with the size of the solar system. It was predicted that with the help of relatively simple mathematics, the distance between the Earth and the Sun could be measured during the Transits of Venus in 1761 and 1769, in which Venus passes between the Earth and the Sun.

European nations and North American colonies spent fortunes sending explorers to the far corners of the Earth to witness the rare cosmic event. Scientists risked their lives sneaking past enemy war ships, battling diseases, and journeying the open seas for years at a time to record Venus’ measurements. In Philadelphia, scientists set up an observatory in the Pennsylvania State House Yard (now known as Independence Square) to view the phenomenon. Their measurements, along with calculations from over 170 other observers at over 70 locations around the globe, enabled scientists to figure out the distance between the Earth and the Sun (Astronomical Unit or AU), and begin to understand the size of our solar system.

Once the observations were documented, someone needed to publish and disseminate the findings for the entire world to see—someone well-connected, and well-versed in both science and astronomy. Benjamin Franklin took the lead, making certain that the American Philosophical Society published the Transit of Venus reports and disseminated them far and wide, formally establishing the size of our solar system.

Last updated: December 9, 2017

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