At any given moment on any given evening, the stars and planets seem motionless up there. If you watch for a little while, they all together shift position westerly because the Earth is rotating, but none of them seems to move independently of the others.

This is a trick of the eye, though. Everything is in motion even though it doesn’t look like it. If you watch carefully over weeks, you’ll notice the moon and planets (“wanderers”) occupy different spots. The motion seems gradual because they’re so far away. In fact, the stars are moving, too, but their distances are so immense that even after thousands of years they still appear fixed in relation to each other.

Occasionally something bright streaks out of the firmament and takes you by surprise, even when you’re watching for it. Sometimes it’s just a glint in the corner of your eye, and sometimes by luck you’re looking right at it. This motion is noticeable because the objects are, comparatively, so close.

The quick, short-lived streaks are “shooting stars,” or meteors – not actually stars but pieces of grit smaller than your thumbnail. They fall into the Earth’s atmosphere and heat up until they burst into flame for a second or so, sending down flares of light. Two prominent meteor showers occur in August and November.

Sometimes larger rocks tumble in and burn brighter and longer. These are called fireballs, and they can be scary to see because some leave trails of smoke and fire in different colors. Some are so big they don’t burn completely and hit the ground, and then they’re called meteorites. A meteorite about 5 inches wide crashed through a guy’s ceiling in Park Forest, Ill., a few years ago and demolished his computer printer. No one was hurt.

Not all moving objects are easily identified, although I’ve never seen a UFO that wasn’t man-made. I thought I had, once. Peering from the back seat of my father’s Piper Cub one summer evening decades ago, I watched a tiny, dull pinprick of light slip steadily through the stars. It must be a flying saucer, I thought.

It turned out to be a satellite. You can see them passing overhead if you’re lucky or know where to look just after sunset and just before sunrise. The roughly 3,000 of them now orbiting the Earth hundreds of miles above us bounce sunlight off their antennas and silvery coverings, and many can be seen fairly readily. Some scoot through the stars very fast, others more slowly.

Like everything else in the sky, it’s possible to predict when they’ll wander overhead, and to watch for them. Some of the brighter ones are the International Space Station, the Hubble Space Telescope, and Iridium telecommunications satellites, which sometimes flash.

The fact they’re man-made and temporary doesn’t nullify their strange beauty. They still strike the eye like the blazes of meteors and the permanent scintillations of planets. Artificiality is a trick of your mind. Everything up there is part of the firmament.

Two handy computer programs that predict satellite passes are available online at these Web addresses:

science.nasa.gov/Realtime/jpass/20 and www.heavens-above.com. A lot of reliable information on satellite spotting is available at the Visual Satellite Observer’s Home Page, www.satobs.org.

Dana Wilde can be contacted at dwilde@bangordailynews.net.