Week of Sept. 30-Oct. 6, 2018
I've always felt that we learn best when something intrigues us enough to raise a question. 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 just in this way that I enjoy helping people learn about the heavens, and anyone who has ever been on one of my popular Night Sky Tours knows this quite well. In fact, more than once during a night, people will hear me say, "Turn around!" That's because many stargazers become so fixated on what's in front of them that they miss what's around or above them, and sometimes that's even more amazing or beautiful.
It's not only after dark that I do this. Often when we're watching a beautiful sunset, I'll do something that confuses everyone nearby. Just as the western sky show becomes especially colorful, I place my back to the sunset 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 the sun set, I'm watching night 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 does the shadow appear 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 plains.
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 to the east, so that part of the sky appears a darker blue or purple color. 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 itself.
Depending on the clarity of the air, the Earth's shadow appears most prominent a few minutes after sunset. Eventually, this shadow becomes more diffused as it rises high enough to completely engulf us.
And that is what we call — you guessed it — nighttime!
Visit Dennis Mammana at www.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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