Science & Technology

The Longest Lunar Eclipse of the Century Is Happening This Week

2018 is really shaping up to be a year of incredible lunar phenomena. Seriously. January started with a supermoon and ended with a super blood moon. We just had another super-moon a couple of weeks ago, but this Friday, most of the world is going to get the chance to see the most incredible sight yet: the longest lunar eclipse of the century.

Red Moon Rising

If you're a loyal Curiosity reader, you don't need to be reminded that a blood moon and a lunar eclipse are one and the same. But if you need a refresher, here it is: Lunar eclipses happen every time the moon passes into the Earth's shadow. That means that they can only happen during a full moon when the sun is on the opposite side of the Earth since that's when the Earth hogs all the sunlight that hits the moon. Because the light waves have to battle our atmosphere to make it to the moon during a lunar eclipse, only long wavelengths of red light manage to make the journey. That's why it makes the moon reflect a deep crimson. If you're wondering why every full moon isn't a lunar eclipse, the answer is simple: The moon orbits the Earth at an angle, so it only lines up with the Earth's shadow every once in a while.

This week, the lunar eclipse is going to be something extra special, however. It's a "mini-moon," which is the opposite of a supermoon. A supermoon and a mini-moon always occur in pairs a couple of weeks apart. The supermoon happens at the lunar perigee when the moon is closest to the planet, and the mini-moon at the lunar apogee when it's farthest away. Because the moon will be crossing the Earth's shadow from so far away, it has a longer path to travel to get out into the light again. That makes this particular eclipse longer than usual. A lot longer, actually: All told, the moon will be bathed in red for one hour and 43 minutes.

Moon Under Miami

Remember the Great American solar eclipse from 2017? You might recall that it wasn't visible from everywhere on the planet — you had to be standing along a specific path to see the moon and sun line up together. That's not exactly the case with a lunar eclipse. A solar eclipse casts only part of the Earth in shadow, but during a lunar eclipse, the entire moon is cast in shadow. That means it doesn't matter so much where you are on the planet — if you can see the moon during the eclipse, you'll see it in full, red bloom.

That's a bigger "if" than you might think, though. Remember, the moon doesn't rise at the same time the whole world over. And while the USA got a front-row seat to last year's solar eclipse, North America is going to miss this historic lunar event entirely. South America will spot the beginning of it, Australia the end, and almost the entire rest of the world will see the whole shebang. Oh, well. There's always next century.

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If you're stuck in the States when the lunar eclipse goes down, that's just too bad. At least you can get a mini-moon nightlight for your house. We handpick recommendations we think you may like. If you choose to make a purchase through that link, Curiosity will get a share of the sale.

Time-Lapse of a Total Lunar Eclipse

Written by Reuben Westmaas July 23, 2018

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