Moment of Science: Eclipses

“An eclipse is one phenomenon that is actually more impressive from the ground.” -Leroy Chiao, astronaut
On April 8th, 2024, millions of Americans will look skyward to a total solar eclipse. Dan Smith has the how, why and when -- including a weekend test run! ☀️➡️⚫
Published: Oct. 10, 2023 at 1:53 PM EDT|Updated: Oct. 12, 2023 at 8:51 AM EDT
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Every now and then, the Sun and Moon align to create a spectacular sight... sounds romantic, but it’s just scientific. This week, we’re quite literally covering the topic of eclipses, and trying not to get a certain Bonnie Tyler song stuck in our head.

* You’ve probably heard about the next big one for North America coming up in April, but we’re going to start with the basics. A solar eclipse happens when the Moon passes between the Earth and the sun, blocking the light from the latter and casting a shadow on the former. They can only happen during the New Moon phase, and the Moon’s orbit is tilted five degrees off from the Sun’s, making this a pretty rare occasion.

* Eclipses might all look the same if the Moon went around the Earth in a perfect circle -- which it doesn’t. The “ellipse” (not eclipse) it takes, means there’s about 31,000 miles between its farthest and closest point from the planet -- the “apogee” and “perigee,” respectively. That means the Moon can appear 14% larger at perigee, and that apparent size difference makes all the difference. A “total solar eclipse” happens when the Moon is closest, and gives that signature halo from the blocked sunlight. Those can have a fascinating temporary reaction at ground level, from flower petals closing up as if it were nighttime, to spooked horses and silenced cicadas. An “annular eclipse” means the fully-concentrated shadow the Moon casts isn’t long enough to reach us on Earth. It still creates a big solar ring in the sky, but it’s far from safe to view with the naked eye, even in totality. There are also partial solar eclipses, where the Sun and Moon barely misalign, making for the world’s hottest croissant... and lunar eclipses switch it up by having the Earth get in the way of sunlight reaching the Moon instead.

* Overall, eclipses (either solar or lunar) happen four to seven times a year worldwide... and here are the next two events to watch for North America. You may have already heard of the annular eclipse on Oct. 14, heading southeast from Oregon through west Texas, and the Lone Star State will get a double dose of the action six months later. The total eclipse on April 8, 2024, may be the celestial event of a lifetime for some of us, with the sun fully blocked for up to five minutes in places like Dallas, Indianapolis, and Buffalo.

* Saying “don’t stare directly at the sun” seems obvious, but I’m sure at least a few of us know of someone who did it for the 2017 eclipse -- maybe it was even you. That path cut from Oregon through South Carolina, so some west coast residents might still have their special eclipse glasses. If you really want the full experience along the line, remember to get your pair... it’s not like the event will be postponed due to weather conditions... which reminds me, you should hope and pray for clear skies the day of.

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