MOST OF THE PLANET HAS NOT seen a total solar eclipse in the last 50-year period, according to Angela Speck, chair of the Department of Physics and Astronomy at the University of Texas at San Antonio.
“We get an eclipse of some sort every six months,” she said on December 8, 2022 — day one of the ASP2022 virtual conference organized by the Astronomical Society of the Pacific. “The chances of it [a solar eclipse] being visible where you are are very slim, and that’s why most people don’t get to see it in their lifetime.”
Two eclipses are coming up for people in North America to view: an annular solar eclipse on October 14, 2023, and a total solar eclipse on April 8, 2024 (also called the Great North American Eclipse). These events will occur when the Moon passes between the Earth and the Sun, either partially or completely blocking out the disk of the Sun for people viewing the event from Earth.
“We get an annular eclipse when the Moon doesn’t quite block out all of the Sun,” said Speck. “Why that happens has to do with the fact that the Moon’s orbit is not circular.”
During the Moon’s orbit, she said, the difference between its closest point (perigee) and its farthest point (apogee) is about 10 per cent. This means that at its closest point the Moon looks about 10 per cent bigger than when it’s farthest away.
When the Moon is near its closest point and full at the same time, “this would be a Supermoon,” said Speck, adding that if a solar eclipse occurs two weeks later, while the Moon is at its farthest distance from Earth, it is too small to block out the entire Sun. As a result, we see a ring of exposed sunlight.
During a total solar eclipse the Moon is large enough to completely cover the Sun when it is passing between the Sun and the Earth.
Speck said most people’s eyes are not sensitive enough to notice the change in light during an eclipse until the Sun is about 80 per cent blocked out. “It’s almost like it’s around sunset and the light is not quite the right strength, but the Sun’s still up there.”
Once this happens, animals will begin to react because the quality of light starts to change (about 80 to 90 per cent eclipsed). Birds will flock, dogs will bark, and cows will go back to their barn.
“One of my favourite [stories] from 2017 was a study done on bees [that] showed that as the light reduces, the bees behave differently. And when it gets dark, the bees stop buzzing,” said Speck. “So there’s all sorts of things that both animals (and plants) will do during the eclipse.”
As the Sun becomes smaller and more crescent-like (the partial phase), Speck said we will begin to see some “really interesting” effects. The space or gap between the leaves of a tree, for example, can act as a pinhole projector, covering the ground with tiny images of the crescent Sun.
For more information about the upcoming 2023 annular eclipse and 2024 total solar eclipse, watch our video interview with Christ Vaughan.