Total solar eclipses visible in 19th century America sparked scientific expeditions amid growing interest in the astronomical phenomenon, laying the groundwork for the U.S. scientific enterprise to flourish in the 20th century. | Fredriksen/Flickr (CC BY-SA 2.0)
The U.S. Coast Survey Steamer Bibb drew well south of its intended destination on the evening of July 13, 1860, coming upon a shoreline enveloped in mist and dominated by a chain of mountains that exposed no single access route for scientists to claim for a temporary observatory.
Lost to none aboard was that five days remained before a total solar eclipse would own the sky.
The congressionally sanctioned expedition, already delayed by bad weather, had no time to press on without endangering the mission: record each stage of the coming total solar eclipse and the flight of the moon’s shadow over Labrador in the northeastern corner of what is now Canada.
The expedition, led by Princeton astronomer and past American Association for the Advancement of Science President Stephen Alexander, soon located an alternative: an accessible, shielded harbor renamed Eclipse Harbor, according to a report by the Coast Survey, one of the earliest U.S. federal scientific agencies that primarily mapped coastlines.
The eclipse expedition was among a growing number of 19th century research expeditions that helped elevate American science, some through discoveries, and begin to forge ties between science and federal government support.
Scientific institutions also began to emerge in the U.S. during this time, coinciding with a growing interest in all things astronomical — a fascination that further helped put young America on a path to becoming today’s powerhouse of scientific research, according to David Baron, the author of the recently released “American Eclipse,” a compelling story of the July 29, 1878, eclipse.
“It is such a rich time; this was the period and these were the people who laid the infrastructure that enabled the United States to lead the world in science in the 20th century,” said Baron.
Thomas Edison, who founded Science magazine in 1880, Maria Mitchell, America’s first recognized female astronomer who was elected to AAAS in 1850, and James Craig Watson, a leading astronomer of the period and a member of the National Academy of Sciences, are three pivotal astronomers Baron uses to trace the story of the 1878 eclipse.
“The eclipse of 1878 played an important role in infusing science — and astronomy, in particular — with this sense of patriotism. The general American public was really cheering on our home team of scientists and wanting them to show Europe that we were equal when it came to the ability to do science,” said Baron, noting that European counterparts found it hard to envision that an upstart “egalitarian democracy would ever embrace science as a national goal.”
Seven total solar eclipses could be viewed from the United States in the 19th century, each attracting growing scientific interest among American astronomers, physicists, mathematicians and emerging astrophysicists and increasingly capturing the imagination of amateur star gazers, the educated public and people at large, reports and newspaper accounts show.
U.S. Coast Survey Steamer Bibb carried Alexander’s 1860 expedition to the northeastern reaches of Canada to view that year’s total solar eclipse. | NOAA Photo Library
The 1860 expedition to Labrador that Alexander led opens another window onto the foundational role of scientific organizations in establishing structure and expectations and providing scientists with venues for sharing and debating scientific findings, reinforcing core precepts of the scientific process.
Alexander had given each expedition member meticulously detailed assignments for each stage of the eclipse. He briefed his team on their observational tasks and data collection duties the moment the Bibb pulled away from New York Harbor on June 28, 1860, headed to Cape Chidley, the Labrador headland they would not reach.
Three participants, including Alexander, had 32 separate observations to record during the stages of the eclipse: before the beginning, at the start, through and well beyond the “time of total immersion” when the moon fully blocks the sun, leaving visible the glowing crown of its outer atmosphere, the solar corona.
Alexander based his compilation of the necessary observations on earlier experiences witnessing a total solar eclipse on Nov. 30, 1834, from Ebenezer, Georgia, and viewing two annular solar eclipses in 1838 and 1854 during which the orbital position of the moon does not permit it to fully obscure the sun.
He compiled his findings in a paper delivered at the 1854 AAAS Annual Meeting in Washington, a guide that was “deemed a most important document” and published in the May 1854 edition of The Astronomical Journal upon the recommendation of AAAS, reported The New York Times.
The observation guide demonstrates the type of rigor that growing scientific organizations including AAAS and the Smithsonian — whose first secretary, Joseph Henry, was Alexander’s brother in law — began to establish.
“People who were key to studying eclipses were prominent in AAAS and a few of them were presidents of AAAS. It was definitely a place where research on eclipses was presented,” said Baron. Among leading scientists of the era were mathematical astronomer Simon Newcomb, and physicist Samuel Pierpont Langley, both of whom served as AAAS president.
“This was when it all began, when the institutions, the AAAS, the National Academy of Sciences, the Smithsonian were created,” Baron said.
Stephen Alexander was a Princeton professor, active in the early days of AAAS and the National Academy of Sciences and a life-long astronomer who led expeditions to view eclipses. | AAAS
With Eclipse Harbor selected, Alexander and his team wasted no time setting up an observatory on a plateau facing the harbor. By July 16, 1860, the table was set, the expedition having prepared achromatic refractor telescopes to correct for light distortions, laid base lines to align measurements, set tidal gauges, arranged chronometers to keep precise time and secured for a second time meteorological equipment in a tent after a storm had flattened the initial setup. Positions for the telescopes and a camera obscura were selected and marked, tents pitched and provisions organized along with other tools needed to catalogue the coming astronomical phenomenon.
Just as the astronomical show was getting underway, Alexander and his team, one of whom was directed to count seconds while another the minutes, used photography to record the exact moment of the moon’s first incursion “proving the belt of light nearest the moon was much brighter than the rest,” reported an Aug. 8, 1860, account in The New York Times.
“The phenomenon was a most beautiful sight and it was with difficulty that the beholders could restrain their ecstasy,” Alexander told a scientific gathering in Newport, R.I., on Aug. 8, 1860, according to a Boston Daily Advertiser report. “It looked like an intensely brilliant, incandescent fragment of metal exposed to the intensest heat, the sharp points falling away until the sun was gone.”
The expedition was declared “entirely successful” despite clouds preventing some of Alexander’s intended observations from being fully recorded, said astronomer Charles A. Young in a memoir read to the National Academy on April 17, 1884, following Alexander’s death on June 25, 1883.
The National Academy of Sciences — an organization for which Alexander served as one of 50 founding members — also tapped Alexander to lead an expedition to view the total solar eclipse of on Aug. 7, 1869, from Ottumwa, Iowa. The event drew other leading astronomers, including Young, Watson, Mitchell and Newcomb, many of whom used spectroscopes — optical devices used to observe the light spectrum to — hunt for elements in the solar corona. Later, related devices would be used to view the atmosphere closer to the sun’s disc known as the chromosphere.
Young and William Harkness of the U.S. Naval Observatory, for instance, made a discovery during the 1869 total eclipse that was only fully understood decades later when their identification of a new, bright, greenish line in the spectrum of the solar corona, which they named coronium, would turn out to be highly-ionized iron.
Weeks after the discovery, Young delivered two papers at the 1869 AAAS Annual Meeting in Salem, Mass., about his spectroscopic observations of the moon’s first contact with the sun and another on his spectrum observations from Iowa during the 1869 total eclipse.
“We on Earth are living in the outer atmosphere of the sun, an extension of the solar corona, and we had better understand it as well as we can.”
Jay Pasachoff, Williams College professor of astronomy
The finding is still perplexing today: why is the sun’s outer atmosphere as much as 3.6 million degrees Fahrenheit, millions of degrees hotter than the surface of the sun, its heat source?
The solar corona draws as much of an interest today as it did then. Scientists now know the bright halo belongs to the sun, not the moon as originally thought, and that the sun’s outermost atmosphere is made up of 90% hydrogen, 9% helium and a mixture of other highly heated elements, said Jay Pasachoff, a professor of astronomy at Williams College. The highly-ionized iron in the sun’s outer atmosphere, Pasachoff noted, is so hot that it has shed half of its normal 26 electrons.
Pasachoff was a featured speaker at the 2017 AAAS Annual Meeting in Boston on the science behind the coming total solar eclipse on Aug. 21: the first to spread coast-to-coast across the United States since 1918. Scientists expect the event to be one of the biggest public displays of science in a generation, with planning for observation sites and events underway for years.
“The sun is just a fantastic laboratory that we are lucky enough to have only 93 million miles away instead of hundreds of light years away.”
Jay Pasachoff, Williams College professor of astronomy
From Willamette University in Salem, Oregon, a premiere viewing site, Pasachoff and his team of scientists will conduct detailed observations “to study the solar corona in every conceivable way that we are able,” he said, as well as the configuration of the sun’s magnetic fields and their stored energy that gets triggered during a solar flare — a massive burst of radiation that can disrupt Earth’s atmosphere and damage communications systems — or during coronal mass ejections — huge magnetic field and plasma explosions from the sun’s corona.
“We on Earth are living in the outer atmosphere of the sun, an extension of the solar corona, and we had better understand it as well as we can,” said Pasachoff, ticking off the dangers posed by solar flares or coronal mass ejections: “hitting the Earth could cause trillions of dollars of damage.”
Researchers will pay particular attention to how the sun’s corona is heated, something that could provide information relevant to “billions and trillions of stars” with coronas, noted Pasachoff, adding that the solar corona is vital to study and understand. “The sun is just a fantastic laboratory that we are lucky enough to have only 93 million miles away instead of hundreds of light years away.”
Norma Rosado-Blake, AAAS’ archivist and records manager, provided research assistance for this article.
[Associated image credit: NASA/JAXA/Flickr (CC BY-NC-ND 2.0)]