On April 8, a total solar eclipse will travel across the Americas, moving from Mazatlan, Mexico to Houlton, Maine. The 2024 eclipse represents a rare opportunity to view a total solar eclipse within the US. In Ithaca, only a partial eclipse will be visible — meaning that it will never be safe to remove specialized eclipse glasses during viewing. However, a total eclipse will be visible to the northwest in cities like Rochester, Seneca Falls, NY and Canandaigua, NY.
A solar eclipse occurs when the moon is directly between the sun and earth, casting a shadow on the earth’s surface. This alignment — when the moon’s shadow hits the earth — is possible only when the moon is in the same plane as the earth’s rotation around the sun.
Because the moon is smaller than the earth, its shadow falls on only a small section of the planet. As the earth and moon continue their typical motions, the shadow traces a path across the earth.
Viewers watching the solar eclipse from the shadow’s center will experience totality — when the moon covers the sun completely. The path of totality refers to the trajectory of this central, dark part of the shadow as it moves across the earth. You must be within the path of totality to witness a total eclipse. Outside the path of totality, there are regions where observers can still see the sun peek out from behind the moon — known as a partial solar eclipse. A partial eclipse will be visible in Ithaca beginning at 2:08 p.m. and ending at 4:34 p.m. on April 8. The partial eclipse will reach its maximum at 3:23 p.m.
A total solar eclipse is a coincidence of nature — the sun happens to be 400 times larger than the moon and 400 times farther away from the earth than the moon. Therefore, the sun and moon appear the same size to us, and the moon can block the sun completely. One way to think of this is if you were to hold your thumb in front of your face and see that it blocks larger objects in the distance.
Cornell Astronomical Society President Gillis Lowry ’24 witnessed the last total solar eclipse in 2017 as it passed through St. Louis, Missouri.
“It was one of the most amazing astronomical experiences you could ever see with just your eyes,” Lowry said. “It was a 360-degree sunset around you. If you look up, there’s just a black spot in the sky as if there’s a hole in the sky, and the sun’s swirling atmosphere is just coming out of what looks like a hole in the sky.”
Statistically, witnessing a total solar eclipse is a once-in-a-lifetime experience. Solar eclipses occur multiple times a year, but because viewing a total eclipse is restricted to the thin path of totality, it is only visible in a small portion of the planet. For example, the 2024 solar eclipse’s path of totality will range between 108 and 122 miles wide and is approximately 9190 miles long. On average, this means that just 0.5 percent of the earth’s surface area will experience totality.
Additionally, not every solar eclipse is total. The moon’s orbit around the earth is not perfectly circular, so the moon is closer and farther from the earth at different points in its orbit. When the moon is farthest from the earth, it no longer appears big enough to entirely block the sun. This type of eclipse is called an annular eclipse and is characterized by the “ring of fire” — a band of sun still visible around the moon.
The next total solar eclipse that will be visible near the U.S. will occur in 2044, and the next to be visible in New York State will not occur until 2079.
When watching a solar eclipse, observers will first see the moon move slowly across the sun over a span of hours, creating a partial eclipse — which will look like a bite has been taken out of the sun. But if observing within the path of totality, viewers will watch the eclipse become total as the moon completely obscures the sun, turning day into night.
Several safety measures must be followed to view a solar eclipse. At no point other than totality — when the sun is completely obscured — is it safe to directly view the eclipse. Until the moon completely moves in front of the sun, it appears as a partial eclipse, and observers must either wear eclipse glasses or view the eclipse indirectly.
Eclipse glasses are specially designed to block out extreme amounts of light to protect your eyes. No light other than the sun and very bright lights should be visible through functioning eclipse glasses.
As president of the Cornell Astronomical Society, Lowry has been leading outreach efforts to educate the Cornell community and general public about eclipse safety.
“Don’t use sunglasses, don’t use x-ray or film strips or anything [besides certified eclipse glasses or solar viewers],” Lowry said. “Even if it looks dark, it’s not blocking enough of the light for it to be safe.”
Eclipse glasses should always be worn over prescription glasses — not under — according to Lowry. Otherwise, the glasses may magnify light onto the eclipse glasses, causing them to not function properly.
If you cannot obtain certified eclipse glasses in time for the April 8 eclipse, do not worry. There are many methods to view an eclipse indirectly. One method is to create a pinhole camera by poking a hole in a piece of paper. Holding the paper in the sunlight and letting light pass through the hole projects an image of the sun on the ground. Through the pinhole method, you can see the moon’s progression in front of the sun.
“It’s not so obvious if you just look at the sun through the pinhole normally. It makes a round image so it’s not immediately obvious to you — ‘is that actually an image of the sun, or is it just because the hole is round?’” said Prof. Philip Nicholson, astronomy. “But when you see the little crescent [of a partial eclipse], you say, ‘okay, that really is an image of the sun.’”
For Nicholson, the best ways to view a solar eclipse without eclipse glasses involve many different pinhole images. If you stand under a tree, the overlapping leaves create many pinholes and project hundreds to thousands of images of the sun on the ground. However, with April’s lack of many leafy trees, both Nicholson and Lowry recommend using a colander to create a similar effect.
While a colander is a fun way to view the eclipse, Nicholson stressed that it is extremely dangerous to view the eclipse directly through a telescope, binoculars or camera without specialized equipment.
Viewers in Ithaca must use eclipse glasses to safely look at the sun. If you do not have eclipse glasses, you must use an indirect viewing method to witness the eclipse.
However, Lowry recommends traveling to the path of totality. Only during totality is it safe to look directly at the eclipse without eclipse glasses. It is only safe to remove the glasses at the moment when the moon completely covers the sun, and the view through eclipse glasses becomes dark.
When viewing a solar eclipse with the naked eye during totality, the sun’s corona — its upper atmosphere — is visible. With the moon blocking the light from the sun’s surface, it is possible to see the streaks of plasma — hot charged gas — that extend thousands of miles into space.
Just before totality is over, you must put your glasses back on or avoid looking at the eclipse to avoid damaging your vision. Lowry recommends knowing exactly how long totality will last in your viewing location to know when to stop viewing the eclipse directly.
“I would say do take a few tens of seconds [during totality for] looking around you as well in addition to looking directly at totality,” Lowry said. “It’s really interesting to see the effects on the sky, the environment and the animals that might be around you.”
For those hoping to travel, maps depicting the path of totality are available online. Some maps, like that of the National Solar Observatory, are interactive. Ithaca is about a 40-minute drive from the very edge of the path of totality, where the moon will block the sun for around 30 seconds. However, the closer you drive to the centerline of totality, the longer totality lasts — in Seneca Falls, at the north end of Cayuga Lake, totality will last for two minutes and 12 seconds.
Experts warn of a significant increase in traffic for those traveling to see the eclipse. One analysis found a heightened risk for traffic accidents in the hours following the 2017 solar eclipse. To ensure safe travel, it is recommended to arrive early, plan to stay in one place, avoid distracted driving, avoid parking near traffic and remain in place after totality.
Outside of their appeal as an observational wonder, solar eclipses offer modern scientists an opportunity to study the sun from earth. Even ancient understandings of solar eclipses are still relevant today, as scientists still use records dating back thousands of years to answer scientific questions about changes in the earth’s rotation, the gradual drift of the moon away from the earth and other solar system dynamics.
“[Eclipses] draw enough attention that people have observed them for literally thousands of years, and they’ve recorded what they’ve seen,” Nicholson said. “They clearly observed these things, they made an attempt to predict them, they had their own kind of theory.”
For Lowry, the eclipse is about more than just science.
“I think that [the solar eclipse] connects us to all of human history because people have been watching these sights long before they ever knew anything about what was going on,” Lowry said. “I think it’s a really neat way of connecting ourselves to all of human history and experiencing the wonders of the universe for ourselves.”