Why is the eclipse longer in some places than in others? [video]

Why is the eclipse longer in some places than in others? [video]

August 21st, 2017 by Aneri Pattani/New York Times News Service in Life Entertainment

This photo provided by Bob Baer and Sarah Kovac, participants in the Citizen CATE Experiment, shows a "diamond ring" shape during the 2016 total solar eclipse in Indonesia. For the 2017 eclipse over the United States, the National Science Foundation-funded movie project nicknamed Citizen CATE will have more than 200 volunteers trained and given special small telescopes and tripods to observe the sun at 68 locations in the exact same way. The thousands of images from the citizen-scientists will be combined for a movie of the usually hard-to-see sun’s edge. (R. Baer, S. Kovac/Citizen CATE Experiment via AP)

Photo by R. Baer, S. Kovac

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The village of Makanda, Ill., is about to experience nearly three minutes of fame.

That's roughly the amount of time the moon will completely block the sun today in this small community in southern Illinois — the longest duration of totality anywhere in the United States during the solar eclipse, according to NASA.

The total solar eclipse is expected to start at about 10:16 a.m. in Oregon and move diagonally across the country until it ends in South Carolina at about 2:48 p.m. (The times are local.) The duration of totality, the period during which the moon completely covers the sun, varies by location.

The difference has to do with the geometry of the Earth and its distance from the moon, says Ernie Wright, a data visualizer at NASA. Totality will be shorter in Oregon because that part of the Earth is tilted away from the moon and farther from it.

The moon's shadow also will move more quickly across Oregon, compared with the middle of the country. "When it hits the edge of the Earth, it has to swoop around the whole curve, so it moves quite a bit faster," Wright says.

Total Solar Eclipse coverage

Eclipse calculators predict the moon's shadow will move about 2,410 mph in western Oregon, 1,462 mph in western Kentucky and 1,502 mph near Charleston, S.C. Totality will last longer in places where the shadow moves slower.

Totality is longest where the Earth is farthest from the sun and closest to the moon. During this solar eclipse, that period will occur above Makanda, which will go dark for two minutes and 41 seconds.

Normally, Makanda is a village of about 600 residents where, locals say, everyone knows their neighbors' names and dogs nap in the road for 10 minutes at a time without being roused. Normally, the village, which has 75 parking spaces, could host about 3,000 without stress.

Today, though, Makanda is bursting at the seams with thousands of visitors who want to drink in the celestial phenomenon for as long as possible. The community has been preparing for the onslaught for three years now, arranging for basic necessities such as portable toilets and ice water.

Joe McFarland, head of the village's eclipse planning effort, compares it to planning the Olympic Games — at least, it has felt like that. This is a town that's not used to more than a handful of visitors per day.

What to look for during the total solar eclipse

With your solar glasses or a special viewer, watch for the partial phases of the eclipse as the moon passes over the sun, a stage that lasts for a few hours. But during those seconds or moments you see the full eclipse, you really want to watch for these highlights.

* Diamond ring: The brief flash of light on the edge of the sun and moon that appears in the seconds before and after totality. Wear your solar glasses during this phase if you are looking directly at it.

* Prominences: A large, bright loop of plasma extending out from the sun's surface. They may appear pink and be near the diamond in the ring.

* Totality: It's safe to take your glasses off now and look up. The diamond ring has disappeared and the moon has completely covered the sun.

* Corona: During the total eclipse, the corona of the sun will be visible. The sun will look like a dark hole in the sky. It's the only time we can see the corona, which is the sun's upper atmosphere. It's usually outshone by the brightness of the sun's surface.

* Planets: In order of brightness, Venus, Jupiter, Mars and Mercury will be visible. Venus will appear to the west of the sun about 15 to 30 minutes before totality. About 30 seconds before and after totality, Mars will appear close to the west side of the sun and will appear orange. At a similar distance on the east side of the sun will be Mercury. Jupiter will be farther to the southeast of the sun.

* The horizon: Look at the horizon during the eclipse, which will be lighted up like a 360-degree sunset. You're seeing the effects of the sun's light 100 or so miles away, where there is only a partial solar eclipse.

* Animals and the environment: Look up at the sky, look at the ground and listen. Animals will change their behavior. Birds and squirrels will return to their nests, and farm animals will return to their barns. Crickets will chirp, and the air temperature will drop several degrees.

* Shadow bands: Immediately before and after the total eclipse, look for shadow bands on the ground and other surfaces. You know how when you look at the bottom of a pool and you see wavy lines? The bands look something like that. How shadow bands appear vary from eclipse to eclipse, and nobody's quite sure what causes them.

* Baily's beads: As totality approaches, watch for Baily's beads around the rim. These are small spots of light created when only low-lying valleys of the moon allow sunlight to shine through. The name comes from Francis Baily, who explained the phenomenon in 1836. Baily's beads appear just before the beginning and end of totality. Wear your solar glasses during this phase if you are looking directly at it.

Source: Earthsky.org, NASA, exploratorium.edu, eclipse2017.org