Week of July 28-Aug. 3, 2019

Whenever I'm out presenting a sky tour on a clear dark night, I often ask my audience how many stars they can see.

Most reply "millions" or, as the late Carl Sagan might have said, "billions and billions." And my hunch is that if I were to ask you that question, you'd reply much the same.

But, of course, you don't really know this. It's just a guess. So why don't you count them?

Now, before you call the authorities to have me committed, let's think about this for a moment. Scientists count things all the time, and astronomers are certainly no exception: galaxies, asteroids, craters and, yes, even stars. So how do we do this? Do we sit for hours on end peering into the eyepiece of a large telescope, our voices echoing throughout the darkened dome around us: " ... 406, 407, 408 ... "?

If we did that, I can assure you we'd all be locked up by now. No, it's much more sensible to make an estimate rather than an actual count, and it's much easier as well.

Why not try this yourself the next time you're under a clear dark sky? It really isn't all that difficult or time-consuming; the only tools you'll need are a cardboard tube from a roll of bathroom tissue, a pen, notepad and, perhaps, a calculator. And, of course, a nice clear sky.

Place the tube up to your eye and aim it skyward. Holding it still, count the stars you see within the tube and record that number on the notepad. 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 in the first paragraph was indeed "billions and billions," you're in for quite a surprise because, on even the clearest and darkest of nights, the very best eyes can see at most only two or three thousand stars.

It really is quite a remarkable illusion that Mother Nature has performed for us, but it shouldn't be all that surprising. The next time you look upward at night, pay attention to just 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 so that they'd wind up "touching" each other, we'd see just how few and faint they really are. We'd be left with a single "star" that appears only a bit larger or brighter than the planet Jupiter, which now shines in the southern sky at dusk.

To get a sense of just how devastating light pollution from city lights has become to our view of the heavens, try this counting exercise both from a dark rural location and within or near a large city. I suspect you'll be equally surprised!

Estimating the number of stars in the sky is easy with this at-home experiment.

Visit Dennis Mammana at dennismammana.com. To read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.