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Light Years Ahead
Posted October 28, 2001

You're listening to CJLY 93.5fm in Nelson, Kootenay Coop Radio. My name is Tom Clegg and Mostly Mozart is sponsored by Tom Clegg. That's me.

It occurred to me today that I haven't done nearly enough complaining lately. At least, not on my radio show. Then I walked past someone who was working outside with the radio on, and the radio said something about "the best soft rock." So I started thinking about oxymorons and mixed metaphors, and eventually I came up with a few scientific terms that are commonly used in ways that don't make sense if you know their scientific meaning.

Critical mass, for example. In nuclear bomb technology, critical mass is the amount of matter that has to be converted into energy in order for the energy output to exceed the energy input. At that point, the excess output is used to start more nuclear reactions, and the amount of matter being converted grows exponentially. In a split second, all available matter is converted into energy, and the bomb has gone off.

So, when you manage to interest a critical mass of people to participate in your special project, I guess that means your project will start consuming people at an exponential rate. Either that, or your project will blow up.

Another favourite expression from physics is the quantum leap. Non-physicists almost always use that term to mean a large sudden change. Which is odd, because physicists have only ever encountered extremely tiny quantum leaps. In fact, the reason nobody talked about quantum leaps until the 20th century was that they were small enough that nobody noticed them until then.

A quantum is an indivisible amount of energy. The exact amount depends on the situation, but the principle is that subatomic particles have a finite number of possible energy levels. You'll never catch a particle anywhere between level 1 and level 2; it's one or the other. The quantum is the distance between 1 and 2. Or between 2 and 1, of course; a quantum leap is just as likely to represent a loss of energy as it is to be a gain.

I'll deal with light years in a few minutes, and if you're lucky, I will also remember what inertia really means. If you're really lucky, I'll even talk about how this show has evolved since last November. Or maybe not.


You're listening to Mostly Mozart on Kootenay Coop Radio, CJLY 93.5fm in Nelson. My name is Tom Clegg, and I sponsor Mostly Mozart.

You've probably heard about someone who was light years ahead of his time. You might have even heard that Einstein was light years ahead of his time, which would be especially ironic.

I will be the first to admit that the term "light years" contains the word "years." But that doesn't mean it's a measure of time. People casually refer to light years as if they were really long years. Like millenia, or eons, perhaps. But of course they're not. They're not even really short years, which is probably how the soft drink industry would use the term.

A light year is a measure of distance. One light year is the distance covered by a light wave in one year. Which is quite a long distance, as it turns out. Light travels at 300,000 km per second. There are about a hundred thousand seconds every day, and about 300 days in a year. So a light year is about 9 thousand billion kilometres -- Also known as 10^16 metres.

What's the point of having a special word for 9 thousand billion kilometres? Well, not surprisingly, it has to do with light. There are lots of stars in the sky that are a few light years away from us, and much more. Or at least, they were that far away from us, a few years ago. When you look at a star that's 1000 light years away, you're seeing what it looked like 1000 years ago. It might not even be there right now; for example, if it's a really old heavy star, then in the last 1000 years it might have even experienced death by supernova. Thus making a brilliant colourful scene, which future astronomers will surely take pictures of, and sell as placemats.

Oh, I'm sorry! You're not very lucky today. I can't remember what inertia is. So I'll just keep doing whatever I was doing before.