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Posted March 24, 2002

Hello, you're listening to Mostly Mozart on CJLY in Nelson 93.5fm, Kootenay Coop Radio. My name is Tom Clegg. Mostly Mozart is sponsored by Tom Clegg, soon to be selling some sort of product or service.

I'm feeling especially lazy today, as is often the case. So I'm going to tell you a bit about the law of conservation of energy.

If you were planning on doing some work today, instead of conserving energy like me, that's OK too; as it turns out, this particular law can be broken. But I'll get to that later.

For now, I've got some more of the Magic Flute, which was cut off mid-sentence at the end of last week's show.

You're listening to Mostly Mozart, sponsored by Tom Clegg. My name is Tom Clegg and I'm here to tell you about the law of conservation of energy, its implications, and its shortcomings.

There are many forms of energy -- such as momentum, gravitational potential, heat, and electricity. Of course, it is pretty common to convert one form of energy into another. A device whose purpose is to convert one form of energy into another is generally called a machine or an engine. For example, your car converts chemical potential energy into heat by a chemical process, and then converts heat into momentum by a mechanical process.

The law of conservation of energy states that energy can not be created or destroyed.

It's easy enough to convert one form of energy to another, and to another form, and another, but you always end up with the same total amount of energy as you started with. No more, no less.

In practice, when you convert energy from one form to another, you find that some is lost along the way. When an engine has 40% efficiency, that means that the energy output is only 40% of the energy input. This so-called "lost" energy is not really lost, though; it just comes out in a different form than what the engine is trying to put out.

For example, in a car, a fair amount of energy is converted into heat instead of momentum. This heat energy is considered "lost" or "wasted" in a practical sense, because having a lot of heat doesn't help you get where you're going.

But if you consider this so-called "wasted" heat energy to be part of the output of the engine, all engines are exactly 100% efficient.

So the law of conservation of energy is that the total amount of all the different forms of energy never changes. This applies to chemical reactions like rusting, burning, exploding, and producing electricity from a battery. It also applies to physical processes like pushing a car, lifting weights, and rolling down hill. It applies to organic processes too, like digesting food, growing, shouting, and rotting.

There's another law, the law of conservation of mass, which says something very similar to the law of conservation of energy. If you measure the total mass, or amount of matter, before and after any chemical or physical reaction, you'll get the same result. Again, this includes growing, burning, rotting, and generating electricity from a battery. Like energy, matter can be rearranged, and converted from one form to another; that's what the field of chemistry is all about. In case you didn't know, the first big push in the field of chemistry was the attempt to make gold.

Of course, gold is an atom, not a molecule. Chemical reactions can cause molecules to break up, and their constituent atoms to rearrange into different molecules. But chemical reactions don't break atoms. For example, water is a molecule; you can consume water in a chemical reaction, so you end up with less than you started with. But each water molecule is made of exactly one oxygen atom and two hydrogen atoms. Even if some of your water molecules are missing, the hydrogen and oxygen atoms will still be there.

The touble with all this, of course, is that E=mc2. The "E" stands for energy and the "m" stands for mass. According to Einstein, a certain amount of energy is equal to a certain amount of mass. The "c" is the speed of light, which is rather large; so the implication is that even a small amount of mass is equal to a huge amount of energy.

There's one kind of process that I left out when I talked about the laws of conservation of mass and energy. That process is a nuclear reaction. Nuclear reactions break up atoms and form new ones.

There are three places where nuclear reactions are common: nuclear bombs, nuclear power plants, and stars.

All of these are fairly new inventions, which is why the laws of conservation of mass and energy were accepted as laws until recently. Except stars, of course, which have been around for ages -- but so far it's been impossible to study even our own Sun up close. It turns out that the reason the Sun is able to emit so much energy, without absorbing energy from anywhere else, is that it is a nuclear device.

Most of a star's life is spent converting hydrogen into helium. This process is called fusion, and it also happens to be the same nuclear process as the second stage of a modern nuclear bomb. It turns out that helium is slightly less than 4 times as heavy as hydrogen. When you fuse four hydrogen atoms into one helium atom, you get a tiny bit less mass than you started with, and a huge amount of energy that wasn't there when you started.

So, even if we get rid of all of our nuclear weapons and nuclear power plants -- which might not be such a bad idea given the health and safety risks -- as long as there are stars in the sky, the laws of conservation of mass and energy are both false.

In fact, this makes them false in much the same way that Newton's laws of motion are false. If you're dealing with everyday things like driving, falling, burning, and looting, even using nerve gas, or having someone else use nerve gas on you, or travelling to Jupiter to escape whichever government happens to be gassing you, then Newton's laws of motion will do just fine. And you won't gain or lose any mass, and you won't gain or lose any energy. You'll convert energy from one form to another, and you'll rearrange atoms to form different molecules, but the total amount you're left with will be the same as what you started with.

On the other hand, if you move to the Sun, your entire body may well be converted into energy. Whether you're converted into ordinary energy, or the more literary "pure energy," is an entirely different matter.