A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth.
A total solar eclipse occurs when the Moon’s apparent diameter is larger than the Sun’s, blocking all direct sunlight, turning day into darkness.
Totality occurs in a narrow path across Earth’s surface, with the partial solar eclipse visible over a surrounding region thousands of kilometers wide.
Total Solar eclipse of June 24, 1778
This was the first total solar eclipse recorded in the United States. The total solar eclipse of 1778 began in the middle of the Pacific Ocean and swept eastward, passing close to Philadelphia. There, it was observed by prominent astronomer David Rittenhouse, whose comments on the eclipse were published in one of the first volumes of the American Philosophical Society’s memoirs.
Thomas Jefferson, who was in Virginia at the time of the eclipse, wrote in a letter to Rittenhouse that “[we] were much disappointed in Virginia generally on the day of the great eclipse, which proved to be cloudy. In [Williamsburg], where it was total, I understand only the beginning was seen.” Jefferson went on to humbly request that Rittenhouse send him a more accurate timepiece—one designed to be “for astronomical purposes only.”
Total Solar eclipse of October 27, 1780
In 1780, Harvard College commissioned the Reverend Samuel Williams, Hollis Professor of Mathematics and Natural Philosophy, to observe the total solar eclipse predicted for October 27, 1780, although the Colonies were still at war with Great Britain. Professor Williams traveled to what is now Penobscot Bay in Maine, where the British naval officer in charge of the area allowed him to land long enough to make his observations. The Harvard expedition, after all their efforts, missed the eclipse because they chose a site outside the path of totality.
Total Solar eclipse of July 18, 1860
Accurate observations of solar eclipses in the 19th century were sparse until the solar eclipse of July 18, 1860. The Moon’s shadow came in from the Pacific Ocean near where Portland, Oregon, is now located, then moved northeastward across Washington Territory into Canada. This eclipse is remarkable chiefly for the fact that it put an end to the mystery of the red flames seen around the dark disk of the Moon during totality. Early observers believed the flames were caused by “exhalations” or by volcanoes on the Moon.
Drawings from across the path of the 1860 eclipse show large, white finger-like projections in the Sun’s atmosphere—called the corona—as well as a distinctive, bubble-shaped structure.
One hundred years later, with the onset of space-based satellite imagery, scientists understood what these structures were. Those illustrations from the 1860 eclipse looked very similar to satellite imagery showing Coronal mass ejections, or CMEs – meaning 1860 may have been humanity’s first glimpse at solar storms that are a result of combustion of the hydrogen that envelopes the entire globe of the Sun.
Total Solar eclipse of August 7, 1869
The total solar eclipse of August 7, 1869, crossed America diagonally from Alaska to North Carolina. The Moon’s shadow entered the United States from Canada, near Simpson, Montana, and then sped southeasterly across the Midwest to the North Carolina coast and out over the Atlantic Ocean. The eclipse path was almost one continuous observatory, lined from beginning to end with astronomical expeditions. The astronomer and explorer George Davidson made a scientific trip to the Chilkat Valley of Alaska. He told the Chilkat Indians that he was especially anxious to observe a total eclipse of the sun that was predicted to occur the following day. This prediction was considered to have saved Davidson’s expedition from an attack.
Total Solar eclipse of July 29, 1878
On July 29, 1878, over 100 astronomers observed an eclipse along the shadow path from Montana to Texas.
James Watson was among the astronomers and scientists who traveled to America’s West to observe a total solar eclipse in 1878, shortly before he was named the first director of the Washburn Observatory on the University of Wisconsin-Madison campus.
During the 1878 total solar eclipse, Watson, who by then had discovered comets and 22 asteroids, became convinced he glimpsed a new planet called Vulcan closer to the sun than Mercury. This body, whose existence had never been scientifically established, had been predicted by the French astronomer L.J.J. Leverrier in 1859, but had never been seen. Watson’s announcement that he had observed the object caused a half-century’s fruitless search by leading astronomers. Today, we know there is no planet Vulcan, at least none that could have been seen through Watson’s four-inch telescope.
Maria Mitchell was an astronomer, librarian, naturalist, and above all, educator. In 1847 she discovered a comet through a telescope, for which she was awarded a gold medal by the King of Denmark. In 1865, she became Professor of Astronomy at the newly-founded Vassar College. As dozens of male scientists, who dominated the field of study were heading West for the 1878 eclipse and getting government support for their expeditions Mitchell found herself excluded. So she put together a successful all-female expedition to the path of the eclipse in Denver Colorado.
Total Solar eclipse of March 7, 1970
During the eclipse of March 7, 1970, the Moon’s shadow, traveling at more than 1500 miles an hour and darkening a 100-mile-wide path of totality, crossed the Gulf of Mexico, entered Florida near Tallahassee, and then sped up the Atlantic coast before heading out over the ocean. The event passed directly over NASA’s Wallops Station, where researchers launched 32 sounding rockets, also known as suborbital rockets, to “conduct meteorology, ionospheric and solar physics experiments surrounding the solar eclipse event”. The maximum duration of totality was almost four minutes!
Total Solar eclipse of February 26, 1979
On February 26, 1979, a total solar eclipse—the last such event to be seen in the United States in the 20th century—was visible from the Pacific Northwest through northern Canada. The total phase began at sunrise in the North Pacific, with the path of totality sweeping through Oregon (where the skies were, unfortunately, completely overcast), Washington, Idaho, and Montana, as well as most of central Canada and Greenland. Maximum duration along the central line was over two minutes.