Eclipses
What is a Total Solar Eclipse?
A total solar eclipse (TSE) occurs when the Moon passes between the Earth and the Sun covering the solar disk and casting a shadow over Earth. Specifically, the Sun’s diameter, which is 400 times bigger than the Moon’s and 400 times farther from Earth than the Moon, combined with planetary motion, results in the alignment of the Sun, the Moon and the Earth every 12 to 18 months.
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Totality occurs when the Sun’s disk is completely covered by the Moon. This occurs because the Moon is at the correct distance from the Earth to appear to be the same size as the Sun’s disk. It is only during totality that we are able to see the Sun’s atmosphere, or corona. The brightness of the solar disk hides the dimmer atmosphere on a regular basis.
Predicting Eclipses:
From Ancient Cycles to Modern Calculations
For thousands of years, solar eclipses have stirred awe, fear, and fascination. In ancient times, they were often seen as divine omens or celestial warnings. And yet, long before humanity fully understood the mechanics of the heavens, some civilizations were already predicting eclipses with impressive accuracy.
Babylonian astronomers, for instance, discovered that eclipses follow recurring patterns. One of the most famous is the Saros cycle, which lasts approximately 18 years, 11 days, and 8 hours. By carefully observing the skies and keeping detailed records, they could forecast future eclipses—even if they didn’t know exactly why they occurred. Similar knowledge emerged independently in other advanced cultures, such as the Mayans and the Chinese, who also identified repeating cycles of solar and lunar eclipses.
The turning point came with the Scientific Revolution. In the 17th century, the work of Copernicus, Kepler, and Newton transformed our understanding of the cosmos. Kepler described how the planets and the Moon move in elliptical orbits, while Newton’s laws of motion and universal gravitation explained the forces behind these motions. With these tools, astronomers could begin to calculate precisely when and where eclipses would occur, based on the relative positions of the Sun, Moon, and Earth.
Today, eclipse prediction is a highly refined science. Astronomers use sophisticated mathematical models to track the exact paths of celestial bodies, accounting for even subtle variations such as irregularities in Earth’s rotation. Satellite missions like the Lunar Reconnaissance Orbiter provide high-resolution data on the Moon’s surface and solar activity. These are combined with advanced astronomical reference systems—like those developed at NASA’s Jet Propulsion Laboratory—to simulate the Moon’s shadow as it moves across the Earth with extraordinary accuracy.
As a result, we can now predict eclipses centuries in advance. We know exactly where they’ll be visible, how long the total phase will last, and the precise moment of maximum eclipse at any given location. This level of precision enables scientists, photographers, and eclipse chasers to plan expeditions around the world—like the upcoming total solar eclipse in Egypt in 2027—to witness the full spectacle.
The ability to predict eclipses is a powerful example of how humanity has moved from interpreting nature through myth to understanding it through science. What was once a terrifying mystery is now a reason for wonder, exploration, and global collaboration. That spirit is at the heart of Solar Wind Sherpas.
Eclipse Sunglasses: Why and When?
Eclipse sunglasses are a safe way to view the Sun at any time other than during totality. In particular, as the Moon starts to cover the Sun (this is called first contact), look through the glasses in order to see the crescent shape forming. For about an hour, as the Moon continues to cover the Sun, the crescent will continue to get smaller and smaller until it disappears and the Sun is completely covered by the Moon (this is called second contact).
At second contact, it is safe to remove the sunglasses as totality has been reached. At this point, when the corona is visible to the naked eye, the structure of the corona, white rays and streamers radiating around the lunar disk can be seen. The intensity of the corona is much like that of a full Moon. Once the Moon begins to uncover the Sun (this is called third contact) and continues to move across the sky, the eclipse can be viewed in reverse order. Once again, eclipse sunglasses must be worn.