5 basic questions about eclipses answered
We are just a few weeks away from the August 21st eclipse, but how much do you really know about the rare phenomenon. Well, how about some questions answered by Angela Speck, Director of Astronomy at the University of Missouri.
-Why does the eclipse go from west to east?
"The moon moves faster than the earth spins. Everything rotates and orbits counterclockwise as viewed from above the north pole – but we perceive the sun and moon to move east to west because of earth's rotation," Speck said. "Over the course of a day, the sun actually moves eastward by 1 deg because of our orbit around the sun; the moon moves 12 degrees because of its orbit around us. So the moon is moving fastest of the motions involved."
-How often to total solar eclipses occur?
"There is a total solar eclipse somewhere on earth almost every year. However, only about 0.1 percent of the earth’s surface will see each eclipse. So actually for any given location on earth, eclipses are much rarer – with an average time between eclipses of about 375 yrs – although the range of intervals is big (from a few years to over a millennium)," she said. "The last eclipse on Mainland US was in 1979, but that was in the NW US. The last one in MO was in 1869 – visible only in the northeastern part of the state. For Kansas City the last eclipse was 1806, for Columbia, Missouri and St Louis it was 1442, and for Jefferson City, it was even longer ago."
-Why can't you look directly at an eclipse?
"You can look at the total eclipse – when the sun is completely blocked out. The total eclipse is only as bright as the full moon and not dangerous. However – if any part of the sun remains uncovered (like during the partial eclipses before and after “totality”) it is not safe," Speck said. "There is simply too much light coming from the sun – so much energy entering your eye can cause damage and burn the retina. Even with only 0.1% of the sun showing, the light from the sun is still 1000 times brighter than the full moon – that’s too bright!"
-What causes an eclipse to occur?
"Eclipses occur because the moon gets between the earth and the sun – but the trick is to figure out WHEN will the moon get in the way. The moon orbits the earth every 27.3 days and is in new moon position every 29.5days – but don’t get an eclipse with every new moon," she said. "This is because the moon’s orbit is tilted with respect the earth’s orbit around the sun. So most months, at new moon, the moon is above or below the plane of the earths orbit and doesn’t get directly in between the sun and the earth. Twice a year, new moon will coincide with the moon’s orbit crossing that of earth. Then we get an eclipse."
-Where is the best location to see a total eclipse?
"Anywhere you can see it! Seriously – the sun is going to the just west of directly south (182-186 degree) for the time the total eclipse hits Missouri. It will also be almost at its highest point (the sun is high in the sky when it is directly south, 180 deg)," Speck said. "It will be more than 60 degrees above the horizon. So as long as you have a clear view south and you don’t have tall buildings or trees directly in front of you – the view will be great."
Copyright 2017 (Meredith Corporation). All rights reserved.