Weather school: Let’s start with the basics

The majority of the radiation we get from the sun comes in the form of visible light

At this time of the year, unless the weather is particularly bad, there are not a lot of “new” weather topics to discuss. We still have a month or two of winter left, and a lot can happen in that time that will affect our spring. I’ve spent more than enough time looking at long-range weather forecasts, and we have taken our annual look back at the top weather stories from Canada and around the world. So, what should the new weather topic be?

For those of you who have kids in high school, you might know that February is the start of the second semester and students are starting up new classes. With that in mind, I thought it would be a good time for us to go back to school — weather school. Those of you with good memories might remember I did a series of weather school articles awhile back, but I think it is high time we go back to school and recertify our basic weather understanding; after all, it has been 12 years!

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To begin understanding how and why we have weather here on Earth we need to go to the source of almost all of our energy: the sun.

Our sun is an average star, as stars go, and is estimated to be about halfway through its expected life of around 12 billion years. While our sun is on the small size compared to other stars, it comprises about 99 per cent of all the matter in our solar system, the rest being made up of the planets, moons, asteroids, comets and any other debris.

Fusion cuisine

Most of the matter in our sun is hydrogen, the simplest and most abundant element in the universe. Inside the sun, the pressure of all the hydrogen causes the temperature to rise, and when it is hot enough the hydrogen starts to fuse into helium. While this obviously creates helium, it also produces energy in the form of heat. This nuclear fusion reaction has been going on in our sun for billions of years and there is enough hydrogen for it to continue for billions of years more.

Surprisingly, the fusion of hydrogen into helium has been occurring at a remarkably stable rate. While there appear to be some slight changes over time, these changes are extremely tiny when compared to the overall energy output of the sun.

So, as most of us already knew, the sun provides Earth with nearly all of our heat energy. The question is: how does this energy from the sun reach Earth? After all, isn’t space an icy cold vacuum? The answer to this question is radiation — or, more specifically, electromagnetic radiation.

The first thing that comes to most people’s minds when they hear the term radiation is probably nuclear bombs, or some kind of dangerous invisible ray that will give you cancer. So how can all our energy be coming from radiation? Apparently, there are a lot of different kinds of radiation; some of it is harmful to humans (organic life) while other forms are not. To really understand this we need to look at the electromagnetic spectrum.

If you look at an image of the electromagnetic spectrum you would quickly notice that a number of everyday forms of energy are actually part of this spectrum. On the low-energy end of the spectrum we have radio and TV waves and up near the middle we have visible light. That’s right, visible light; the energy that allows us to see things is a form of radiation. At the high-energy end of the spectrum is where we find the really harmful forms of radiation such as X-rays and gamma rays.

All of these different forms of radiation are simply waves of energy, and the size of the wavelength determines how much energy it has. Long wavelengths, such as radio waves, (around one metre in length) have very low energy levels – after all, they are all around us and no one really seems affected by them. As the wavelengths become smaller we move into infrared and then into the visible area of the spectrum. Light waves are around 400 to 700 billionths of a metre in size.

If you think about it, you would assume that most of the electromagnetic radiation coming from the sun would be in the form of high-energy waves such as ultraviolet, X-rays or gamma rays, since our sun is so hot. In actuality, while our sun does emit all of these different forms of electromagnetic radiation, the majority of the radiation comes in the form of visible light.

The most interesting point about electromagnetic energy is that it can travel through the vacuum of space and arrive here on Earth where it is either reflected away or absorbed and turned into a different form of energy. This is what we will look at next “class.” No homework this week!

About the author

Co-operator contributor

Daniel Bezte

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the U of W. He operates a computerized weather station near Birds Hill Park.

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