How Come?

Why does the moon change color in the fall? asks Alex Dickinson, a student in Holtsville, NY.

It just wouldn’t be fall without a huge Halloween moon glowing orange at the horizon, rising above a spooky landscape of black tree limbs and piled-up leaves.

We call the moons of autumn harvest moons, but the official Harvest Moon rose on September 26th. The Harvest Moon is the full moon closest to the autumnal equinox, which fell on September 23rd this year. The Hravest Moon was probably named by farmers. Long before there were huge, gas-powered harvesters with blinding headlights, there was the bright fall moon, lighting the fields as the work of crop-gathering stretched into the night.

The romantic image of the autumn moon even inspired a famous song: “Shine On Harvest Moon,” written more than 100 years ago, remained popular for much of the 20th century. (For a clip of comedic actors Laurel and Hardy performing the song, visit
www.hamienet.com/midi12542_Shine-on-Harvest-Moon.html. )

The moon is a rocky gray-and-brown ball, lit up by brilliant sunlight. But the color we on Earth see depends on where the moon is located in the sky. No matter what the time of year, as the moon first peeks over the horizon, it may appear yellow, orange, or nearly red. Gradually, as the Earth turns eastward and the moon rises higher in the sky, the color pales to white.

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How come you can still see a star that disappeared many years ago? asks Rebecca Herskovits, a student in Yeshiva Har Torah, Bayside, NY.

Human beings are fascinated with the idea of a time machine–a way to shake off the bonds of the present and travel into the past or the future. No one has ever made a time machine, and scientists say it may be impossible–the very nature of the universe may prevent such “travel.”

But the sheer size of the universe means that light carries information from the distant past into our present, showing us what the cosmos looked like long, long ago and far, far away. When we look into the night sky–or even at our own Sun–we are seeing the past, not the present.

Here’s how it works. Light, the speediest thing we know of, zips along at 186,000 miles a second in the vacuum of space. Light leaves the surface of a star or planet, travels a great distance, and finally enters our eyes. We see the star or planet as it was–not as it is.

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Why does the moon look gigantic rising on the horizon but not nearly so large overhead? asks Jerry Hostetler, of Phoenix, AZ.

Have you ever been riding in a car in the evening and noticed something huge and yellow behind the trees and buildings in the east–and then realized it was the Moon? Especially in the fall, a pumpkin-colored harvest moon, looming up over the horizon, looks enormous and even spooky. It’s not hard to imagine a broomstick-riding witch flying across.

But picture this Halloween scene when the moon is high in the sky, small and white, and it’s just not the same.

Scientists say that the horizon Moon appears up to twice as big as the overhead Moon to most of us. People have been arguing over why for more than a thousand years. Astronomers, psychologists, and nonscientists all have their theories. In 1989, researchers even published a book of such explanations, called “The Moon Illusion.”

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How come it is still light for an hour after the sun sets? asks P. Ramana Mohan, of India.Twilight time: a time of purple clouds, deepening shadows, a fading glow in the sky. Still light enough to play outside, but getting harder and harder to read without a lamp. As a song made popular by the group The Platters in 1958 goes, “Heavenly shades of night are falling; it’s twilight time.”

Twilight usually refers to the time just after the sun sets in the evening. But it also can mean the time just before the sun rises in the morning. During twilight, although the sun is hidden below the horizon, the sky is still aglow with light, gradually dimming (after sunset) or intensifying (before sunrise).

During twilight, the light for our evening activities comes courtesy of the upper atmosphere.

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Why does the Moon seem to follow us when we drive? asks a 4th-grade class in Lancaster, OH.

Feel like you’re being followed? While it seems like the Moon is always just over your shoulder on a moonlit night, the Sun is also shadowing you as you drive on a sunny afternoon. And then there are those distant mountains to worry about…

According to astronomers, the reason why the Moon and the Sun seem to be following us is because they are so far away. The Moon, for example, is about 240,000 miles away; the Sun about 93 million miles. And no matter how fast we drive, we just can’t pass them.

When you drive by a stand of trees or a series of telephone poles near the road, you pass them very quickly. So you see roadside objects first ahead of you, then next to you, and finally behind you, receding into the rear-view mirror.

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