Total lunar eclipse on its way


By Tom Burns - Stargazing



Sometimes I thank my lucky stars that I get to write this column. If I didn’t, I’d have to go door to door to tell you that a total eclipse of the moon will grace our hemisphere during the night of May 15, stretching into the early hours of May 16.

A total lunar eclipse happens when Earth is positioned directly between the sun and the moon. Earth’s shadow blocks the sunlight that usually illuminates the full moon.

Starting at 10:27 p.m., the moon will pass into the Earth’s shadow and slowly disappear over the next hour. It will look like a giant monster is taking larger and larger nibbles out of a cosmic cookie.

By 11:29 p.m., the entire disk of the moon will be obscured. The full moon will glow some shade of red from orange-red to an ashen red-gray.

It will remain in total eclipse for one hour and 24 minutes. The middle of totality occurs at 12:11 a.m. At that moment, the moon is closest to the center of Earth’s shadow, and we will see it at its darkest.

Luna will begin to reappear at 12:53 a.m. Over the next hour, the moon’s disk will appear to get larger and larger. By 1:55 a.m., the bright disk of the full moon will have returned, and the eclipse will be over.

It is a pleasure to describe an astronomical event that doesn’t require a telescope as big as a corn silo to see and doesn’t demand that you drive to the dark, rural skies of Middle-of-Nowhere, Ohio.

Luna will be low in the sky for most of the eclipse, so make sure that trees or buildings don’t block your view of the moon.

Binoculars are helpful because they help you to see details like craters and lunar “seas” disappear slowly as the face of the moon is obscured. But the binoculars you were born with — your own two eyes — will produce a spectacular view of the eclipse.

Earth’s shadow gets the credit for the event. “The cone of night,” as astronomy writer Chet Raymo called it, is undeniably conical.

Night’s cone stretches away from Earth outward into space in the opposite direction from the sun. At its widest, the cone is the diameter of Earth, about 8,000 miles.

Because we are 93 million miles from the sun, the cone is extraordinarily long and skinny, over 100 times longer than it is wide. It stretches to its conic point about 870,000 miles from Earth’s surface, around three times farther than the Earth-moon distance.

As Raymo so aptly put it, “Earth wears the night like a wizard’s cap.”

We spend about half our lives under it. But we spend much of that time unconscious of its existence because we are sleeping.

Sleeper, awake! Nighttime is more than just a temporal part of a day. The night is a physical presence. English poet Percy Bysshe Shelley puts these words in the mouth of Earth:

“I spin beneath my pyramid of night

Which points to the heavens, dreaming delight.”

As Earth orbits the sun, it carries its shadow with it. Our planet will do so as long as the sun still shines.

Since Earth’s shadow envelopes Luna during a lunar eclipse, you might expect the moon to disappear completely. That would be spectacular, to be sure, but it would contain none of the sublime beauty of a muddy-red moon.

Luckily, Earth’s atmosphere acts like a lens and refracts (i.e., bends) some of the sun’s light around Earth. Our atmosphere loves to absorb and scatter the sun’s blue light. (That’s why the sky is blue.) However, the red light passes much more efficiently through it.

We see the same effect daily when we look at the rising and setting sun. As the sun rises and sets, its light passes through a thicker cross-section of the atmosphere. That’s why the sun and surrounding atmosphere turn red at sunset and sunrise.

Particulate matter in the atmosphere often exacerbates the reddening. Desert dust storms, volcanic eruptions, and even high humidity can redden the sun’s light and make for spectacular sunsets and sunrises.

The moon’s reflected light is far dimmer than the sun’s radiated light. But light is light, so the same thing happens to the moon on a lesser scale.

During my tenure at Perkins Observatory, people often called me asking if an eclipse was happening on a given night because the moon is red. “Nope,” I say. “It’s just that the moon is rising and close to the horizon.”

Lunar eclipses are the ultimate example of atmospheric filtering since the sun’s light is refracted through an extremely large cross-section of the atmosphere.

During an eclipse, our atmosphere filters the moon’s light twice: once as the sun’s light passes through a long stretch of atmosphere and heads toward the moon and a second time as it bounces off the moon and passes through the atmosphere toward your eyes.

Thus, if the lunar eclipse’s totality happens at sunset or sunrise, you might just get a blood-red moon. If there is a lot of particulate matter in the atmosphere, the moon will dim even further to an ashen gray and, in extreme cases, almost disappear completely.

If the level of atmospheric particulate matter is low and the moon is higher up in the sky during the eclipse, the moon can turn a coppery red or a bright yellow-orange.

During the totality, another thing to notice is that the brightness of the red is not uniform over the moon’s entire surface. The part of the moon’s disk closest to the center of Earth’s shadow will be darker than the part of the moon farther away from the shadow’s center.

Many media outlets refer to the May 15/16 lunar eclipse as a “Blood Moon,” a term that I frankly dislike.

First, the phrase is inaccurate. Only under the particular conditions mentioned above will the moon be anything close to a bloody red.

I have seen a dozen or more eclipses in my time. I can’t think of a single time that I would describe the moon as “blood red.”

But there’s a second reason to reject the term “blood moon.” It became popular after the publication of the book “Four Blood Moons” by John Hagee in 2013.

He believes that eclipses portend apocalyptic effects on Earth. His prediction is based in part on the following passage from Acts 2:20 and Joel 2:31: “The sun will be turned to darkness and the moon to blood before the coming of the great and glorious day of the Lord.”

Admittedly, Acts provides a pretty fair description of both solar and lunar eclipses, respectively.

However, just for the record, apocalyptic events did not occur after the Oct. 8, 2014, lunar eclipse, and, odds are, they will not happen after May 16.

So please, media mavens, please spare us the misleading term “blood moon.” Eclipses are inherently beautiful and rare. They don’t need the hype.

They harken back to our prehistoric days. Many ancient cultures honored the moon as a god of fertility. She was a giver of life on whom humans depended for the continuance of the race and the success of their crops. Her disappearance during an eclipse was a truly terrifying event.

It looked to our forebears like a giant, invisible monster had unhinged its jaws and was slowly swallowing the moon whole. When our forebears saw the ruddy totality, they thought it was their goddess shining through the belly of the beast.

Storytellers worldwide depict the beast as a dragon, a snake, a wolf, a jaguar, or some other ravenous cookie monster. Thank goodness the goddess Luna doesn’t taste very good. The beast always regurgitated it.

Some cultures didn’t depend on that. They threw spears, shot arrows, beat on drums, and yelled insults at the monster to encourage the regurgitation process.

And why did humans engage in those rather odd practices for 10,000 years? It always worked. The monster always upchucked their goddess. Why mess with success?

Of course, we know better now. However, there is something eerie, unworldly, about a lunar eclipse. The experience takes you back to your most primal ancestral fears. During the deepest part of the eclipse, if your heart and mind are open, you will be transported to the African savanna or the mountains of India or the forests of Germany 10,000 years ago.

I know the scientific explanation of what happens during an eclipse. But as the moon goes into total eclipse and nothing is left but a glowing red orb, I think I’ll have a spear or two handy, just in case.

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By Tom Burns

Stargazing

Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.