Week of April 16-22, 2023
I've always felt that astronomy is best learned when something occurs to make us question our eyes or, in some cases, even our sanity. If we're curious and dedicated enough to follow through on what we've experienced, we will most likely make a wonderful discovery.
It's in just this way that I enjoy helping people learn about the heavens, and anyone who has ever been on one of my popular Borrego Night Sky Tours knows this well. In fact, more than once during the night, people will hear me say: "Turn around!" That's because stargazers often become so fixated on what's in front of them that they miss what's around them, and sometimes that's even more amazing or beautiful.
It's not only after dark that I do this. Often while watching a beautiful sunset, I'll do something that befuddles everyone nearby. Just as the western sky show becomes especially colorful, I turn around and face east.
The reaction I get is usually a puzzled look, followed by a gentle reminder: "Uh, what are you doing? Sunset's the other way."
Perhaps even more perplexing to people is my response: "While you're watching our daytime star set, I'm watching nighttime rise."
It's usually at this point that folks get a nervous look in their eye and step slowly away from me. But I'm quite serious about what I'm doing; I'm watching night rise. The fact is that nearly everyone has noticed the phenomenon, but few have ever realized what it is they were seeing.
The next time you have a cloudless sky, try it yourself. Face east just after the sun sets in the west. Low against the eastern horizon, you'll see an immense purple arc, bordered by a fringe of pink just above it. Many people think it's just haze or pollution. Not true. This is the shadow of our Earth.
Early risers can see the same phenomenon around sunrise, only then it appears low in the west. Just before sunrise, face west and you'll see the arc as it sets behind the terrain. Your best chance to spot it is when you've got a cloudless sky with a low horizon, such as the ocean or desert.
This occurs because our planet is a solid body that casts its shadow in the direction away from the sun. When the sun sets, for example, we find ourselves on the boundary between daytime and nighttime. Sunlight continues to illuminate the atmosphere in the west — that's what gives the sky a light blue color — but our solid planet blocks the sunlight from reaching the air in the east so that part of the sky appears a darker blue or purple color. And between the darker and brighter parts of the atmosphere lies a fringe of pink — also known as the "Belt of Venus" or the "anti-twilight arc" — illuminated by the reddened sunset light that's passing through the atmosphere.
Depending on the clarity of the air, the Earth's shadow usually appears most prominent 10 minutes or so after sunset. Eventually, this shadow rises high enough that it completely engulfs us.
And that is what we call ... you guessed it: nighttime!
Visit Dennis Mammana at dennismammana.com. To read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.
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