Thousands will be on the watch

  • In this May 20, 2012, file photo, the annular solar eclipse produces flare through a lens in Alameda, Calif. Destinations are hosting festivals, hotels are selling out and travelers are planning trips for the total solar eclipse that will be visible coast to coast on Monday. A narrow path of the United States 60 to 70 miles wide from Oregon to South Carolina will experience total darkness, also known as totality. AP PHOTO

For The Recorder
Published: 8/17/2017 1:09:26 PM

On Monday, people across the country will stand outside in the middle of the day to watch the sun go out.

Monday’s total solar eclipse will be visible in the continental United States for the first time in 38 years. The U.S. is the only country in which it will be seen — the first time that has happened since 1776.

When Meg Thacher announced those facts to a crowd of about 40 people recently at Forbes Library, the whole room gasped. Thacher, an astronomer and a Smith College lab instructor, is spending the days before the eclipse presenting talks to tell people what they’ll be able to see.

“A total solar eclipse is very rare and very beautiful,” Thacher said. “So when it happens, we have to get excited about it.”

A very particular series of astronomical events must happen perfectly for a total solar eclipse, Thacher explained.

As it orbits the Earth, the moon passes between our planet and the sun. The moon’s elliptical orbit is tilted, compared to the Earth’s elliptical orbit around the sun. Were it not so, were the moon’s orbit on the same plane as the Earth’s, a solar eclipse would occur somewhere with every circuit of the Earth the moon makes.

But, with its tilted orbit, the moon must be at exactly the right angle so that when sunlight hits it, the moon’s shadow falls on the Earth. And because the orbits of both moon and Earth are elliptical rather than perfectly circular, the moon must be at just the right distance to perfectly block out the sun.

Even then, the moon’s shadow might only fall onto the oceans, and would only be visible to those at sea.

But the sun and moon have aligned this time, and people in the “path of totality” — the darkest part of the moon’s shadow as it travels across the country — will be able to see the total eclipse for up to 2 minutes and 40 seconds.

The path of totality for this eclipse stretches diagonally, northwest to southeast, across the U.S., from Oregon to South Carolina. People in that band will be able to see the sun’s corona — the bright ring of gases flaring around the sun — surrounding the black disc of the moon in front.

“The sun just goes out — the sun, one of the main constants in life on Earth,” Thacher said. It used to frighten people when it happened in ancient times. Strange things happen in nature during an eclipse.”

The sky will go dark. Planets and stars will be visible during the day, Thacher said. Birds and bats will think it is night — the birds will go to sleep and the bats will wake up.

The Pioneer Valley is not in the path of totality, so a full eclipse will not be visible here. But from 1:25 p.m. to 3:58 p.m. on Monday, Aug. 21, Area residents will be able to watch as most of the sun is obscured by the moon, Thacher said.

At 2:45 p.m., the height of the eclipse for this area, 66 percent of the sun will be covered. Its light will be only one-third as bright as normal. It’s what sunlight would look like if we lived in the asteroid belt, Thacher said.

To watch the eclipse, whether in part or in full, it’s important to remember to protect your eyes, Thacher said. Eclipse glasses, which block all but a tiny fraction of the sun’s light, can be bought from NASA-approved sources, but many online sellers offer unsafe glasses.

“Don’t use sunglasses — and double-check where you’re buying eclipse glasses from,” Thacher said. “It’s tempting to just stare at the sun during an eclipse. It’s not worth going blind.”

Some people will travel to the path of totality to see the full eclipse for themselves. Thacher will be in Oregon. Barbara Johnson, from Florence, plans to drive to South Carolina to see it.

“It is just such a rare occasion to watch the light change like that,” Johnson, 68, said. “I remember watching a solar eclipse when I was a child — probably not a total eclipse, but a partial one. It’s exciting to watch something happen on such a large scale.”

Thacher said one of her favorite parts of an eclipse is how it can bring people together. It is rare that the public is interested in what scientists and astronomers are interested in, she said.

“People everywhere are sharing an experience at the same time,” Thacher said. “It takes something really big for that happen.”


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