科学美国人60秒:Viewing This Weekend's Lunar Eclipse

This weekend, many parts of the world—including North America—will be treated to a total lunar eclipse. So here with your viewing guide—how it happens, what to expect, and when to head outside—is Michelle Nichols, Director of Public Observing at the Adler Planetarium in Chicago. 

"There is a total eclipse of the moon on Sunday evening, January 20. A total lunar eclipse occurs when the moon passes through the shadow cast by the Earth into space. When this happens, sunlight shines onto the Earth and passes through the atmosphere that is all the way around the edge of the Earth. The blue light from the sun is scattered away by our air, leaving the red colors of light. So many times, a lunar eclipse turns the moon a dark dusky red, as we are seeing the collective light from sunrises and sunsets around the entire edge of the Earth at once. The moon can appear coppery orange, red, gray, or it may seem to almost disappear completely during a lunar eclipse. 

This eclipse will be visible from all of North and South America, and Hawaii will see it in progress when the moon rises. The main part of the eclipse starts at 10:33 P.M. Eastern / 7:33 P.M. Pacific on Sunday evening, when the moon starts to pass into the darker part of the Earth’s shadow. This is the partial phase of the eclipse. Go outside and face east or southeast and look for the moon in the sky. As the eclipse progresses, you will see more and more of the Earth’s curved dark shadow. At 11:41 P.M. Eastern/8:33 P.M.  Pacific, the moon is fully within the earth’s shadow. We call this “totality,” and the hour or so of totality that we will see is when you want to pay attention to the color of the eclipse. The moon exits totality at 12:43 P.M. Eastern/ 9:43 P.M. Pacific, and the partial eclipse is finished at 1:50 P.M. Eastern/10:50 P.M. Pacific.

My favorite tidbit about lunar eclipses is that we don’t know what color the moon will appear during a lunar eclipse until a lunar eclipse happens. The difference in the color has to do with how cloudy, dusty, sooty, or clear the Earth’s atmosphere is at the time of the eclipse, so the color of the eclipse can tell us a bit about what is going on with Earth’s air at that time."

So, despite the popular names you may have heard about the eclipse this weekend, like "blood moon," just go out and enjoy it—regardless of what color it is. Because the next one won't come around til May 26, 2021. 

—Christopher Intagliata