Bad Astronomy. Misconceptions and Misuses Revealed, from Astrology to the Moon Landing 'Hoax'

narrow opening of the chimney blocks the glare of most of the sky. We’ve done this by looking at all the advantages of viewing the sky from the bottom of a long, dark shaft. But we must be fair and look at the disadvantages as well.

There is one big one, and it’s a deal-killer. Ironically, we looked at it as an advantage before: the narrow opening of the chimney. Before, it was good because it cut out glow from the sky, increasing contrast, making it easier to see stars. However, the small opening means there’s less of a chance of a bright star passing into your field of view.

Most people think of the sky as being filled with stars. That’s an illusion. You can see roughly 10,000 stars with the unaided eye, and they’re spread out over the entire sky. We can estimate the average number of stars you might see through the opening at the top of a chimney. The answer may surprise you: even with a big opening, you will usually see only about 10 to 20 stars on the very darkest and clearest of nights. On a more typical night you might only see one or two stars. So, actually, looking through a chimney makes it a lot harder to see stars even at night. You are cutting out so much of the sky that only a few stars can be seen through the narrow aperture. During the day the odds are far, far worse. There are only six objects that you can see during the day to start with, not 10,000. The odds of one of these being in the chimney opening are remote indeed.

Scientists, of course, don’t usually just calculate a number and assume it’s correct. They actually go out and test it. An astronomer named J. Allen Hynek did just that and published his results in an issue of Sky and Telescope (no. 10 [1951]: 61). One day he took a few members of his astronomy class to an abandoned smokestack near Ohio University, where he taught. The bright star Vega — the fourth brightest in the sky — passes very close to directly overhead at that latitude, and they timed their experiment so that it would be in their field of view from the bottom of the smokestack. Vega is about half as bright as should be possible to see according to our calculations, but it is still one of the brightest stars in the sky. If it cannot be seen during the day, then certainly the vast majority of stars cannot be seen then, either.

At the appointed time Hynek and his students peered upwards, straining to see a glimmer from the star, but they all failed to observe it. Two students even used binoculars, which should have helped by increasing the contrast even more. They failed to see Vega as well. This is not surprising, really. Vega is too faint. Still, they showed by direct proof that stars are at least extraordinarily difficult to see through a chimney.

Another legend bites the dust, or in this case, the soot. While looking through a narrow opening does increase your ability to see faint objects, it simply doesn’t increase it significantly enough to see stars during the day, and that same narrow opening makes it highly unlikely that a bright star will be in a viewable position.

Still, I have no doubts the legend will persist, as they all do. Even a friend of mine, an astronomer of no small status, swears the legend is true. He claims he saw it himself: he once looked up a long chimney during the day and saw a star. David Hughes, in his excellent paper entitled “Seeing Stars (Especially up Chimneys),” notes that a good chimney will have an updraft, even when there is no fire (Quarterly Journal of the Royal Astronomical Society 24 [1983]: 246–257). It’s possible that my friend saw bits of debris caught in the draft and briefly lit by the Sun. At a great distance the debris will look tiny, unresolved, and not appear to move very quickly. This could be mistaken for a momentary glimpse of a star. I explained this to my friend, and I explained the idea of a star’s brightness versus the sky’s surface brightness, and I even talked about the odds of a bright star just happening to be in that extremely tiny line of sight, but he would have none of it. He stands by his story. I guess even the staunchest of scientific minds can have superstitions they don’t want to drop. It’s an interesting cautionary tale for all of us, I think.

Now, having said all that, I must confess that it is possible to easily see one starlike object during the day: Venus. Venus is roughly 15 times brighter than Sirius, so not only is it possible to see during the day, it’s also relatively easy. You need to know just where to look, but it can be done. I’ve seen it myself on several occasions, in broad daylight. However, extrapolating from seeing Venus during the day to seeing stars from a chimney is a pretty big stretch. In the end, the legend turns out to be just that: a legend.

A final note on this topic: I know for a fact that I would fall for that old boy scout tube trick. Why? Because a variation got me when I was about seven or eight years old, except I was told it was a coordination test. I was supposed to roll up a paper plate, put it in the front of my pants so that it stuck out a few centimeters, balance a rock on my nose, and then tilt my head forward so that the rock fell into the rolled-up paper plate.

As soon as I tilted my head back one of the other kids poured a glass of ice cold water into the paper-plate tube. This incident may have mentally scarred me for life; I still shrink away from picnics featuring paper plates. For all I know, the stunt gave me a core of vehemence against such things, which in turn led to the book you are holding in your hands right now. So, I say to those older kids who played such a mean trick on a naive young kid: thanks!

12. The Brightest Star: Polaris — Just Another Face in the Crowd

A few years ago I was chatting with a friend of mine. The night before, he claimed to have seen a bright, slowly moving object in the sky. I realized immediately that he had seen a man-made satellite, but his description confused me. The problem was the way he described where it was in the sky. He said the object was in the west, near the horizon, but he also said it was near Polaris.

“But Polaris isn’t in the west,” I told him. “It’s in the north. And it’s well above the horizon.”

“Oh, well, the thing I saw was near this really bright star just after sunset,” he replied.

Aha! I thought. The bright “star” must have been the planet Venus, which was low in the western sky at dusk at that time of year. Venus was almost painfully bright, far brighter than any other star in the sky, brighter even than most airplanes. He thought it was Polaris; and when I finally figured all this out I realized I had stumbled onto some more bad astronomy.

A lot of people think Polaris is the brightest star in the sky. Let’s get this right off the bat: it isn’t. Polaris just barely makes it onto the list of the top 50 brightest stars, and, as a matter of fact, it is hard to see if you live in even moderately light-polluted skies. Growing up in suburban Washington, D.C., I could barely see it. If the sky was even a little hazy, which it often is on the east coast of the United States, I couldn’t see it at all.

Okay, so Polaris is a bit of a dim bulb. Why, then, is it often mistaken for a powerhouse? I have a theory: people confuse brightness with importance.

Polaris isn’t a bright star, but it is an important one. The reason it’s important is that it sits very close to the sky’s north pole. And to see just why the sky has a north pole at all, we need to do something we’ve already done a few times in this book: start with the Earth beneath our feet.

The Earth is basically a giant ball. It’s also a spinning ball. A sphere sitting all by itself has no real up or down. Nothing on its surface is any different than any other part. But when you spin it, it automatically gets two points that are easily defined: the points where the spin axis intersects the surface. On the Earth, we call these the north and south poles. By definition, the north pole is the point at which, if you are above it looking down, the planet appears to spin counterclockwise. Another interesting place is the line that goes around the Earth halfway between the poles; this is the equator.

Of course you’ve heard this before, but now comes the fun part. We observe the sky from the Earth, and even though the sky itself isn’t spinning, to us it looks like it does because we are spinning.

We think of the Sun and the stars as rising and setting during the day and night, but really we are the ones turning around on our giant spinning ball, not the sky. Still, it’s convenient to think of the sky as spinning. Ancient astronomers thought the stars were holes in a giant sphere through which shone the light of heaven. Nowadays we know better, but it’s still a useful model.

Imagine the sky really is a ball spinning around us. Just like the Earth, then, it has a north pole and a south pole, which we call the north celestial pole, or NCP for short, and the south celestial