Have you ever played part of a movie on a DVD in reverse? It’s delightful to watch a person shoot out of a pool with a splash and land perfectly on a diving board; or to see a dog masterfully throw a Frisbee to his human companion, his dog’s best friend, again and again, while running and jumping backwards at high speed.
The sky brightens at dawn from dark to light, culminating in a sunrise in the east instead of fading to black, following a sunset in the west as it does at dusk.
The sky at dawn always seems more crisp to me than at dusk, and a sunrise always seems more impressive and promising than a sunset. One reason for this may be the way our eyes adapt to the changing environment.
At dusk, our eyes slowly grow dark, adapting in the ever-diminishing light, playing catch-up with the surroundings to allow us to see what we want. At dawn, our eyes begin from their fully dark-adapted state (presuming we have been out for awhile) and are always at full power as they slowly adapt to the ever-brightening ambiance.
We see more clearly into the darkness in the morning.
• At dawn we catch a glimpse of the future.
The sky at dawn near the beginning of autumn is the same as the sky at dusk near the beginning of winter.
As I have noted previously, the stars rise and set four minutes earlier each day, compared to the day before.
As winter sets, the stars rise earlier and earlier, and dusk rushes at us with earlier and earlier sunsets, making the sky appear the same at dusk in mid-winter as it does at dawn near the first day of autumn.
The winter constellations are most impressive; and, if you get up and out early, you can see them without standing in the cold and slipping on ice in the driveway.
• Jupiter is presently high overhead at dawn.
After spending the summer lost in the glare of the sun, Jupiter is again gaining prominence in the sky. Rising high overhead near sunrise, easily the brightest “star” in the sky, Jupiter is a sight to see.
And, if you watch day after day, you will be able to see for yourself that planets — Jupiter, in this case — drift against the background stars.
Jupiter is presently drifting slowly eastward; but in early January, he will come to a standstill, then backtrack to the west into the spring. This looping motion is a challenge to understand, and confounded astronomer’s attempts to determine the layout and scale of the solar system well into the 17th century.
All this, and more, is yours for the taking if you get up and out before the sun rises.
— By Doug Furton, a member of the physics faculty at GVSU. Send questions and suggestions to firstname.lastname@example.org.