theories. One of them is that electrons are not free to orbit as they wish but instead are confined to specific distances from the nucleus. These distances are like steps in a staircase. You can be on the bottom step, or on the second or third step, but you can’t be on the second-and-a-half step; there isn’t any such place. If you are on the bottom step and try to get to the second, either you have enough energy to get there or you stay put.

So it goes for electrons. They stick to their specific orbit unless they get enough energy to jump to the next one. If even 99 percent of the energy needed to jump comes their way, they cannot do it. They need exactly the right amount to move to that next step, that next level. This jump became known as a quantum leap.

In reality, a quantum leap is a teeny-tiny jump. The distances are fantastically small, measured as billionths of a centimeter or less.

So you might conclude that an ad bragging about a product being a quantum leap over other products is silly, since it means it’s ahead by only 0.00000000001 centimeters!

You might be surprised to find out that I have no problem with this phrase. I don’t think it’s bad at all! The actual distance jumped may be small, but only on our scale. To an electron it truly is a quantum leap, a sudden jump from one stage to the next. The phrase itself has nothing to do with the absolute distance the electron moved, but everything to do with its being a major leap forward, skipping the intervening space and landing in a new spot far ahead of where it was.

Sometimes people say that when something is easy, it isn’t exactly rocket science. But in this case, maybe it is!

Part II

From the Earth to the Moon

The Earth is a big place. There are 511,209,977 square kilometers of it, give or take a kilometer or two, which might seem like room enough for everything. But even that much surface area isn’t enough to contain all the bad astronomy out there. Not by a long shot. I wish it were at least true that it could be restricted to near-Earth space, but even then we run out of room pretty quickly. Still, there’s a lot to be seen in our extended neighborhood. You need not even wait for nightfall. Most people might associate astronomy with nighttime, but we can scrounge up some during the day, too. As I write this the sky is a deep, rich blue, and the warm sunshine is blanketing my backyard. Just a few steps outside my house I can feel the warm embrace of an environment fraught with myths, misconceptions, judgment errors.

That cerulean-blue sky is a good place to start. True to the cliche, one day my five-year-old daughter asked me why the sky was blue, and I had to figure out how to answer her. I explained to her about molecules and sunlight, and the cosmic pachinko game played as the light from the sun makes its way to our eyes. When I was done, she thought about it for a second, and said, “All that stuff you just said doesn’t make any sense.”

I hope I’ve done better writing it all down in the next chapter.

But why stop with our air? We can move out of the atmosphere and peer back down on the Earth, seeing our frigid poles and tropical equator. Why are those two locales different, and why does everything in between change from season to season? That’s a fair question, too, and the cause is rooted in astronomy.

Moving a bit farther out, we encounter the Moon, our closest neighbor in the universe. I cannot think of any other object so loaded down with grossly inaccurate theories. The Moon only shows one face to us, but it does spin; it goes through phases that look like miniature eclipses, but they are nothing of the sort; it looks unchanging and unchangeable, but that, too, is an illusion. In the past, in the future, and even right now as you read these words, the Moon is being sculpted by unseen forces, just as it is profoundly changing the Earth. These same forces are at work throughout the universe, shaking mighty volcanoes, tearing apart stars, devouring entire galaxies.

If we can put a man on the Moon, you’d think we could stamp out most of the bad astronomy floating in the Earth’s immediate vicinity.

4.

Blue Skies Smiling at Me: Why the Sky Is Blue

In the course of every parent’s life there comes the inevitable question from their child: “Why is the sky blue?” As we grow to adulthood we sometimes learn not to ask such questions, or we just forget how. The vast majority of adults in the world have seen a clear-blue sky tens of thousands of times, yet only a few know just why it’s blue. If you don’t know, don’t fret: the question baffled scientists for hundreds of years. Nowadays we are pretty confident that we know the real reasons, but I’ve never heard of them being taught in schools. Even worse, a lot of web sites I’ve seen give an incorrect answer to the question. College textbooks on optics and atmospheric physics cover the topic correctly, but who wants those lying around the house?

Well, I do, but then I’m a huge geek. I’m operating on the principle that you are a normal human. And, lucky for you, the reason behind the blue sky isn’t all that complicated, and it can be easily explained, even to a five-year-old. Let’s start with some of the incorrect reasons given for the sky’s cerulean hue.

Probably the most common idea is that the sky is blue because it reflects the blue color of the ocean. However, a moment’s reflection (ha-ha) reveals that this can’t be right: if it were true, the sky would look bluer when you are sailing on the ocean than when you are on land. But that’s not the way it happens. It still looks just as blue from say, Kansas — a healthy hike from the nearest significant body of water — as it would from an ocean liner steaming its way from the United States to England.

Another commonly given incorrect answer is that blue light from the Sun scatters off dust in the air. As we’ll see, this answer is close, and certainly better than the one about reflections off water, but dust is not the cause.

The correct answer, if you want details, is a little more involved. In the end we can simplify it for our hypothetical five-year old, but first let’s look at the whole problem.

When you examine most problems in astronomy, or for that matter in any other field of science, you’ll commonly find that to get to the solution you need two separate lines of attack. The color of the sky is no exception. To understand the blueness we actually have to understand three things: just what sunlight is, how it travels through our atmosphere, and how our eyes work.

You may be surprised to learn that when it leaves the Sun’s surface, sunlight is white. By this scientists mean it is actually a balanced combination of many colors. The individual colors like red, green, and blue are all produced by the complex physics near the sun’s surface. The roiling, writhing gas making up the Sun’s outermost layers produces light of all different colors. But when this light gets mixed together, it produces what looks to our eyes like white light. You can prove this for yourself: Hold a glass prism up to a beam of sunlight. When the sunbeam passes through the prism, the light gets “broken up” into its constituent colors. This pattern of colors is called a spectrum.

This same thing happens after a rainstorm. The raindrops suspended in the air act like little prisms, breaking up the white sunlight into a spectrum. That’s how we get rainbows. The order of the colors in a rainbow is the same every time: red on the outside, then orange, yellow, green, blue, indigo, and finally violet, which makes up the innermost curve of the arc. This pattern may be tough to remember, so it’s usually taught to students using the acronym ROY G BIV, like that’s a common name or something. Still, that’s how I remember it, so it must work.

Those colors are coming from the Sun all at the same time, but a funny thing happens on the way to the ground. Molecules of nitrogen and oxygen (N2 and O2) in the air can intercept that light. Almost like little billiard balls, photons — the fancy name for particles of light — bounce off these molecules and head off in a different direction every time they hit one. In other words, nitrogen and

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