Week of August 31 - September 6, 2025
If you've stood outdoors on any clear night, you've likely seen a "star" drifting lazily across the sky. If you're like many stargazers, you watched it for a few minutes ... and were surprised to see it gradually fade from view. What you saw, of course, was a satellite, one of the thousands now orbiting our planet.
What puzzles many is why they disappear. One may wonder if the satellite's light has burned out ... but of course, satellites don't carry lights. They are so high above us that they're still in sunlight while we are in darkness, and that's what illuminates them. So when one appears to fade from view, we know it has drifted into the Earth's shadow. In other words, it just drifted from the daylight side of our planet into the nighttime side.
We can see the Earth's shadow at other times too. One is during a lunar eclipse, when the full moon (also the Earth's natural satellite) drifts into this shadow, causing the lunar surface to darken for a few hours. The next lunar eclipse we'll see from North America will occur on March 3 of next year.
Another way to see the Earth's shadow happens every day, and I'd be willing to bet that you've seen it but didn't know what it was.
The next time you're outdoors during late afternoon with clear sky and a fairly low eastern horizon, face east as the sun sets in the west. Low over the eastern horizon, you'll begin to notice an immense purple arc stretching from south to north, bordered on top by a beautiful fringe of pink.
Early morning skywatchers can see it too, but in the opposite direction. Not long before sunrise, face west and you'll notice this purple arc as it slowly sets behind the western horizon.
Most of us have seen this phenomenon in the evening but dismissed it as simply haze or pollution. Not true. This is the shadow of the Earth being cast through our atmosphere. As the sun sets in the west, this shadow rises higher in the east.
It shouldn't surprise anyone that the Earth has a shadow. It's a solid body that blocks sunlight, just like every other solid object in our environment. The difference is that this shadow is big. Really big!
As the sun sets, we're standing on the boundary between daytime and nighttime. Sunlight continues to illuminate the atmosphere above us to the west and produces the sky's light blue color. Our opaque world blocks sunlight from reaching the air to our 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.
If the evening air is particularly clear, this phenomenon will appear most prominently for a few minutes after sunset. Within the next half hour, though, it will become more diffuse as it ascends higher in the sky.
And there it is: You've just watched nighttime rise!
Visit Dennis Mammana at dennismammana.com. To read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at creators.com.
Photo courtesy of Dennis Mammana
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