QUESTION: Why don't we rot, even though we are exposed to the air and are basically large chunks of raw meat?

ANSWER: Our sponsor for this item is the deodorant-soap industry. We give the answer, you start taking more showers, the soap industry makes huge profits. This is the genius of the Info-Industrial Complex.See, we do rot. We rot constantly. No doubt you have noticed some people seem to be a little more rotten than others. The polite thing to do is walk up to them and say, "Pardon me, but I believe that you have `gone bad,' so to speak."

"Rot" is not a scientific word, but it connotes a scientific concept. We put a piece of meat on the table, leave it for a few days and something very obvious happens to it, and we call this "rotting."

"What that really means," says Greg Francis, microbiologist at the University of Maryland, "is that microorganisms from the air have landed on the piece of meat and have begun to digest it. What you smell are the byproducts of the microorganisms. There are things like butyric acid, and butyric acid has a very overpowering rotten smell to it."

The key thing to realize is that these little bacteria can digest something whether it's alive or dead. They aren't discriminating.

"We have a certain number of bacteria that live in our bodies, so theoretically we are subject to the same digestive processes that this piece of meat on the table is. However we also have an immune system that is keeping the bacteria in our bodies in check," Francis says.

There are still zillions of the little beasts inside us, and so to help prevent rotting, our bodies slough off dead cells and bacterial byproducts. Over the years, our bodily renewal works less and less efficiently. More dramatically, we get sick sometimes and the rot takes hold; when we get strep throat our tonsils sort of rot away until the immune system can deal with it.

"A lot of time if you smell the breath of someone who is very ill you will get an aroma that is tantamount to rotting meat," Francis says.

Well, gosh, that brightens our morning. As long as we are delving into these gummy, goopy details we should note that people who don't ventilate their skin or shower very often will also suffer the fate of dead meat. Soap destroys the cell walls of bacteria and the water rinses the crud away.

Now then: Aren't you glad you use Dial?QUESTION: Why is "light" visible but not other brands of electromagnetism?

ANSWER: Admit it, we have an amazing knack for knowing exactly what our reading public is most interested in: INCOMPREHENSIBLE PHYSICS.

("No, no," someone is shrieking, "I said BUD Light.")

With the naked eye, a human being is able to "see" only a narrow portion of the electromagnetic spectrum. This kind of electromagnetism is called "light." What you can't see are things like microwaves or radio waves. This is why no one is all that amazed by the workings of a light bulb, but we all are totally astonished that "Can't Buy Me Love" can travel invisibly through the air from a radio station to our car antenna. Light is mundane, radio is magic.

But it's the same stuff! The key difference is the wavelength. We see light because our eyeballs are designed to see electromagnetism at those wavelengths. The design, we are happy to report, is not at all arbitrary.

The sun produces a lot of its energy at the visible wavelengths. For our eyes to see less energetic waves - like radio waves - we'd need much more sensitive eyeballs.

And not just sensitive - bigger, too. As it is, our eyes are large enough to pick up lots of light waves at once, which helps with resolution and focus. Light has a narrow wavelength of between 40 and 80 millionths of a centimeter. Radio waves, by contrast, are about a meter apart. Microwaves, contrary to the name, are also fairly large, a few centimeters from crest to crest. For our eyeballs to see microwaves or radio waves with any resolution they'd have to be the size of the New Orleans Superdome.The Mailbag:

We got a letter a while back from someone (we'd be more precise but the entire "Why Things Are" mailroom staff has been laid off due to the recession) who wanted to know why lightning isn't STRAIGHT. The answer is common-sensical: Lightning doesn't just go ZOT! in one big motion, but rather it moves in steps. These steps average about 50 meters, though there are actually mini-steps that are much shorter. You see, the leading edge of the bolt has no idea where it's going. It just skips along crazily, a chaotic process.

And by the way, we should mention that there really is such a thing as a "bolt from the blue." Lightning can travel horizontally for 10 to 15 miles before coming down to earth. You can get hit by a bolt from a storm that's low on the horizon and out of view.

Just in case you wanted something else to worry about.