Before I came to Harvard, my sister--a member of the class of 1995--tried to give me some pointers on collegiate life. One of her more shocking revelations was that she had, on few occasions, fallen asleep during class.

At the time, this concept was as foreign to me as a Yugo. I had never even considered sleeping during one of my high school classes, and assumed that I would be listening attentively to everything every professor ever said to me.

Boy, was I wrong.

In my three plus years at Harvard, I have majored in sleep. REM. Snoozeville. I have zonked out in so many classes, I can't even remember all of them. Big classes, small classes, sections. Lecture halls with chairs so comfy that it's even better than your own bed, or classrooms with benches so wooden that I wake up with three fewer vertebrae in my back. Good professors, boring professors, weird professors.

Put it this way: I can count the classes I haven't dozed off in on one hand.

Most of my friends think this is bad. They say that if I'm going to fall asleep, why go to class? Or, if you already dragged your butt to class, why not stay conscious?

Incidentally, these are the same people that get all excited when they fall asleep during CS 50, like it's some big deal. They're like a kid that think he's Rambo if he sneaks into the garage and looks at presents before Christmas.

Anyway, my response to their argument goes like so: Sometimes lectures are pointless, but sometimes they're useful--even within a single class. That is, professors have an uncanny ability to fade between the relevant and the irrelevant, so why should I not fade in and out as well?

The keys, of course, are the ability to wake up when lecture gets interesting and to be able to fall asleep whenever the situation permits it. The first skill isn't that difficult to learn--you just have to train yourself to wake up when you hear a change. If the professor drones on, stay on cloud nine; but if he or she stops talking to write on the blackboard, or if you hear notebooks being opened or pens clicking as the poor awake listeners begin to take notes again--now it's time to rouse yourself. Also, this can prevent the embarrassing situation of remaining asleep after everyone has left the classroom.

The second ability is a bit more difficult to get a handle on. You need to have a knowledge of where and when sleep is safe. And that is the focus of the rest of this article.

First, an axiom: You don't want the professor to know that you're asleep. I find this pretty self-evident. To konk out in the first row is a bit rude, and that tenured person is the one that's writing your recommendation.

Therefore, prospective snoozers should always go to the back row to be as safe as possible. But even then, it can sometimes be difficult to know if it's safe or not.

However, it is possible to do a rough estimate given the known factors, which are the lighting, the professor's age, the relative level of the podium to the seats and the number of rows in the auditorium.

First, when I say lighting, I don't just mean how bright it is in the lecture hall; experienced sleepers can doze on the surface of the sun. What I mean is the ratio of the lighting level on the stage/podium as compared to the seating area. It's hard to look from a well-lit place to a dark place; the converse is quite easy. So if the room is dark and a bunch of stage lights are pointing at the professor, it's beddy-bye time.

The professor's age, meanwhile, takes two factors into account: the eyesight and the probability of tenure. Older profs can't see as well as younger ones; moreover, they are more likely to be jaded and tenured and thus less likely to care about a trivial 20-year-old snoozing. Hey, their research grants are still coming in, so it's no skin off their backs.