The total solar eclipse that will cross North America on April 8, 2024, passing over Mexico, the United States (from Texas to Maine), and Canada, provides us with a wonderful opportunity to display highlights from Cornell's Division of Rare and Manuscript Collections (RMC). The exhibition documents not only the advancement of scientific knowledge in different parts of the world, from ancient times to the present day, but also the ways in which solar eclipses have been a source of both wonder and anxiety. In his De Republica, a book composed around 50 BCE, Cicero mentioned a Roman general who explained to his soldiers that eclipses were not prodigies or miracles but recurring physical events – no cause for alarm. Ever since, new optical technology and new explanatory models have confirmed that there is nothing to fear, but a lot to learn from the observation of solar eclipses!
There are different kinds of solar eclipses. Total solar eclipses are the most stunning of all: the Moon covers the Sun completely, and the world is plunged into near darkness. In order for a total solar eclipse to happen, you need a “New Moon,” when the Moon passes between the Earth and the Sun. However, the Moon isn’t always at the same distance between the Earth and the Sun. Sometimes, even when the Moon passes directly in front of the Sun, it is too far away to obscure the entire solar disk. For more details, see NASA’s explanatory video on the iPad to your right or watch the videos here:
In most pre-modern societies, largely controlled by priests and divinely appointed kings, eclipses were considered to be God's affair; astronomers were allowed to predict their date and magnitude, but not to attempt to explain why they occur. The dominant feeling in the population was fear and anxiety. Wasn't the Sun (the supreme God for the Incas; the main source of light and life on Earth everywhere) “abandoning the Earth”?
In Christendom or Islam, total solar eclipses were the sign that things were going wrong, and possibly a prelude to the end of the world. The Biblical prophet Joel warned that, at the end of times, "the Sun shall be turned into darkness, and the Moon into blood."
Observing eclipses and learning about the universe
Once understood and no longer feared, eclipses have generated a lot of curiosity, not only among professional astronomers, but in the population at large. It is no wonder that eclipses have been popular in Ithaca, New York, a sanctuary for science, since at least 1869, when Ezra Cornell himself took notes about a lunar eclipse in his diary.