Sky watch: Counting the stars in the sky

Anyone who has ever gazed up at a clear, dark sky far from the blinding lights of a city is stunned by the number of stars he can see. But did you ever wonder just how many that is?

If you're like most stargazers, your response to that question might be to paraphrase the late Carl Sagan and say that there are "billions and billions." But that's just a guess; you really don't know. So why not count them? easier as well.

, a pen, a notepad, a calculator and a nice clear, dark sky.

Place the tube up to your eye and aim it skyward. Holding it still, count the stars you see and record that number. Now do the same for seven other spots randomly scattered around the entire sky. When you're finished, add all eight numbers together, and multiply that sum by 10.

That's it. That's the approximate number of stars you can see with your eye from that location on that night.

Now if your answer to my question was, indeed, "billions and billions," you're in for a shock, because, on even the clearest and darkest of nights, the best eyes can see at most only two or three thousand stars.

It is a remarkable illusion that Mother Nature has performed for us, but it shouldn't be that surprising. The next time you look up at night, pay attention to how little of the sky is taken up by those points of light we call stars. The sky consists mostly of darkness rather than stars.

In fact, if we could remove the dark portions of the sky and squeeze all the stars together, we'd see just how few and faint they really are. We'd be left with a single "star" not much larger or brighter than the planet Venus.And to get a real sense of just how devastating light pollution from cities has been on our view of the heavens, try this counting exercise both from a dark rural location and from within or near a city. I suspect you'll be equally shocked!