This one is for our readers on the other side of the globe from our main office. If you live in the Eastern Hemisphere, look up tonight and you'll notice something strange going on with the Moon. It'll be full, oh yes, and big, but with a pronounced darkness at its upper half. The best time to see it will be 19:05 UTC (3:05 pm EDT). It will be the kind of full moon that looks like it's been through an Instagram filter—maybe Ludwig or X-Pro II. So what in the world is going on up there?


In our light-polluted modern world, the sky can seem pretty boring. Hazy black nights and smoggy white mornings. There are rain clouds, some lightning on occasion, and the Sun and Moon, constant and reliable, up and down, east and west. But don't be fooled. The solar system—our solar system—is a teeming, dynamic system where shadows and light interplay constantly, with beauty and grace.

The Earth casts a pretty large shadow. Sometimes, when orbital dynamics are being generous, the Earth, Sun, and Moon line up just so. When the Moon is between the Sun and the Earth, blotting out our star but for a blinding corona along the rim—a pitch orb ringed in flame—you have a solar eclipse. Next year the United States will be treated to just such an eclipse, its shadow creeping across the North American continent in a line from Washington state to South Carolina.

When the celestial objects are reversed, and the Earth lines up between the Sun and the Moon, you get a total lunar eclipse. What that occurs, the darkest part of our shadow—the umbra—blankets the Moon, blotting it out, denying it sunlight. Sometimes, though, things aren't quite so total. Sometimes the Moon passes into the Earth's shadow, but not its umbra. When the Moon crosses into the outer shadow of the Earth—where the Sun's rays are not blocked entirely—the Moon is darkened but not blackened. This is called a penumbral eclipse, and it's what you're going to see tonight. A good portion of the lunar surface is cast in a grim pall. If you're the kind of person who enjoys creepy sights in the night sky, tonight is going to be your goth Christmas morning.


Because this is the last full moon before autumn equinox, tonight's full moon is called the harvest moon. The name comes from ye olden days, when the light of the full moon gave farmers a little more time with which they might harvest their crops. The autumn equinox is the point in the Earth's orbit in which the Sun shines directly on the Earth's equator, meaning the whole world experiences a day and night of equal length. This year the autumn equinox will fall on September 22. It is the first day of fall.

This is the last eclipse of 2016. This is also the second eclipsed harvest moon in two years. (You might recall last year's super red harvest moon.) Moreover, this is the last eclipsed harvest moon until 2024. (That year will also herald North America's next total solar eclipse, should you miss the one in 2017.) If you live in the Western Hemisphere and want to be part of the penumbral lunar eclipse action, there is hope. Slooh is hosting a livestream of the event, which began at 11:30 a.m. EDT, complete with scientists explaining the mechanics of the event. It won't be as good as the real thing, but you can screenshot it, apply X-Pro II, and post it to Instagram, and no one will be the wiser.