SCIENCE INTERVIEW : Gregory Sloan, Cornell astronomer on Tuesday morning's lunar eclipse

Tim Kelley/via Flickr
April 14, 2014

If any of you night owls out there are outside late tonight, have a look up up at the nighttime sky for a glimpse of a lunar eclipse. For those of us who don’t remember high school astronomy, a lunar eclipse occurs when the sun, earth and moon are all in a straight line. The sun shines onto the earth, and the earth casts a shadow onto the moon. It happens about every six months. Morning Edition host, Monica Sandreczki, talked with Dr. Gregory Sloan, an astronomer at Cornell University, about tonight’s eclipse.

Morning Edition : What do we need to do to see the lunar eclipse?

Gregory Sloan : First of all, we want to aim for clear skies. I’ll take partly cloudy and you want to be awake. So if anyone is looking for an excuse to not do their taxes until the night before they’re due, this is perfect because they can even have a study break in the middle of the wee hours of the morning to go out and watch the eclipse.

ME : It’s not like a solar eclipse where they say, “don’t stare at the sun!”

GS : (laughs) No, there won’t be a sun to look at and the moon is perfectly safe to look at. Actually, I was looking at the sky a couple of nights ago to sort of see what’s up and then also looking at the star charts for next Tuesday and the moon will be very close to Mars when it goes into eclipse. And so that’ll be really pretty to look at because Mars will be right beside the moon. It’ll be a little to the right. Then to the left there’ll be, a little bit further away, there’ll be Saturn. So, it’ll be nice. It’ll be a very nice evening. You’ll have this blood red moon, Mars to one side and Saturn a little further away on the left. And right below the moon will be the star Spica, so if anybody’s a Virgo, maybe there’s some extra significance for them because Spica is the brightest star in the constellation Virgo.

ME: What’ll be the sequence of when it first touches the earth’s shadow and then continues on?

GS: So the earth has two shadows : the deep shadow and then the bigger, shallow shadow. The moon will start to touch the bigger at about 12:54 in the morning. The very edge of it will start to change, but it’s really hard to see that. The lunar eclipse doesn’t start to get to be a lot of fun until the moon starts to touch that deeper, darker shadow. That central shadow. And that starts at 2:00 in the morning. Then by 3:00, it’ll be almost completely inside the earth’s shadow. Then at 4:30 it’ll start to come out the other side. If anybody’s really determined to watch the whole thing from beginning to end, all 5.5 hours of it, unfortunately, the sun comes up and the moon sets, so they won’t be able to see the whole thing.

ME : What will that end up looking like in the sky?

GS : You know, except for the fact that this time the moon will be deep in the heart of the earth’s shadow and very very red, every month when there’s a full moon, that happens.

ME : The moon is going to look red. Why is that?

GS : Well, because the earth has an atmosphere, which is a good thing because I don’t know about you, but I really like to breathe, because there’s this atmosphere around the edge of the earth, some light from the atmosphere will actually get refracted into the shadow region.  And so there’ll be a little bit of this light into the darkest part of the shadow. And for the very same reason sunsets are red, that shadow will be red.

ME : Dr. Gregory Sloan, thank you so much for talking with me today.

GS : You are certainly welcome.