Next Thursday night, March 13, we’ll see a total eclipse of the Moon.
The strange word “penumbra” often makes television anchors mess up their eclipse announcements. It’s incorrect on a lot of social media too. Consulting a reference book, writers think the action starts with the penumbral phase at around midnight. So the first important tip is that the real «start» time, when anything happens that you can actually see, is when the Full Moon first touches the dark visible edge of our planet’s shadow. That will occur at 1:09 a.m. EDT, meaning early, early Friday morning.
So 1:09 a.m. is when the action begins. If you like technical accuracy, it’s the start of the umbral eclipse. The Moon is the only body whose speed carries it through space its own width each hour. So it then takes that long, around one hour, to fully enter Earth’s shadow. During this time, from 1:09 until 2:26 a.m. EDT, the Moon goes through a bizarre series of odd shapes. Some resemble lunar phases, but most are much stranger than that.
Earth’s shadow tapers like a chopstick to roughly half its original width at the Moon’s distance, making a lunar eclipse a geometric wonderland involving different size curves, which produce their weirdest dreamlike effect when Earth’s shadow falls near the Moon’s outer edge, at roughly 2 in the morning. So that’s the don’t-miss period Thursday night, the time of Maximum Strangeness. If you’re setting an alarm and only care to invest five minutes in this spectacle, look about halfway up the southern sky at around 2 a.m.
But if you’re cool with staying awake a bit longer, totality starts at 2:26 a.m. Friday morning. But unlike a solar eclipse, whose totality displays all the marvelous spectacles that shouldn’t be missed, nothing much happens during lunar totality except the Full Moon is coppery red. And the countless faint stars that were masked by the Full Moon’s brilliance during the night’s first half now fill the sky. So although a total lunar eclipse is nowhere near as mind blowing as a total solar eclipse, it’s still very worth going out to see.
That’s next Thursday night.
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