“—so now that we’ve established that planets are abundant in the galaxy, the next question is how many of them might be habitable. But since we can’t land a shuttle on any of these planets and open the door and sniff the air, like in Galaxy Quest, we need to devise a series of questions that we can apply to the data we collect from these incredibly distant objects. I want to elaborate a little on some of the excellent points Kasting makes on this subject—”
While he talks, he glances at the box in the corner of his laptop screen which shows him how many students have clicked in: 96 today, out of a total enrollment of 109, so 13 absent. He allows students to miss three of the semester’s twenty-seven lectures without penalty, which means if no student exceeded the limit, an average of 12 students would be missing every class. Of course some students do exceed the limit—on average, about 9 percent—and their grades suffer. He announces at the first lecture that laptops cannot be used in the first eight rows because there are still about a quarter of the students who take notes by hand—these also tend to be the more studious ones—and having someone else’s laptop screen in your field of view can be distracting, especially when that person is chatting on Facebook. Mark isn’t naive, some healthy fraction of the approximately seventy students with open laptops are not paying attention. He doesn’t let himself worry about it. Anyone who can spend all that money on college tuition, or have someone else do it for them, and then ignore what’s taught in their classes is a lost soul, as far as he’s concerned. Merely to satisfy his own curiosity, he sometimes asks a multiple-choice question based on something he has said in the past ten minutes, and after the students hit their iClickers, he throws the results up on the screen as a bar graph. Occasionally there might be a genuine misunderstanding, but usually the 15 percent or so who are laughably off-base—for example, the ones guessing today that the current estimate for the number of planets in the Milky Way is around one million—are right now shopping for spring sweaters or playing Angry Birds or hoping to learn what happened between Audrey and Brendan at the rad party last night. (He is under no illusion that his lingo is up to date. “Rad” probably went out years ago. Maybe Angry Birds, too. And come to think of it, these kids were probably ten when Galaxy Quest was made.)
“—Ward and Brownlee caution us that there may be reasons why Earth is not ‘average’ at all. And what we’re learning right now about other stellar systems suggests that the arrangement of our solar system may also be unusual, perhaps even quite rare. We have to be careful about overusing the Copernican Principle, which assumes that we, as observers, are not in some privileged position. For example, it’s often said, even by astronomers, that our Sun is an average star, but that’s not true. Most stars are part of binary or trinary systems, in which stable planetary orbits are either extremely unlikely or impossible. Sol is more massive than 95 percent of the stars in the Milky Way. Planets in the habitable zones around smaller stars, such as red dwarfs, are tidally locked, which is likely unconducive to life. Stars more massive than Sol, because of the luminosity-mass relationship, have exponentially shorter lifetimes, and also emit a larger fraction of their light as ultraviolet and x-ray radiation. Both of these facts probably make the development of complex life unlikely.”
And on he goes—or maybe, on and on and on he goes—tossing up images on the screen, tossing out iClicker questions, checking his timer against his place in the outline. Sure enough, he falls behind and has to skip over a fascinating bit about the dinosaurs, and another about interstellar travel and planetary resource depletion, which he very much regrets. In the last ten minutes he hurriedly dismantles the Drake Equation, invokes the Fermi paradox and ends with a foreboding speculation about the Great Filter.
If he can find the idea moving that three Jersey barriers might hope to be pretty, it’s probably no surprise that he struggles against being audibly emotional in the lecture’s last minute, which concerns whether humans are alone in the universe, and the chances of their survival as a species. Like his aphasia, this troublesome excess emotionalism plagues him more each year. It is profoundly embarrassing to think that he can move himself to tears with his own words. He steadies himself by focusing on the faces in front of him, many of which seem bored or distracted. Is he being unfair to them? Just as he doesn’t want to become a weepy old man, he doesn’t want to become an old fart, continually comparing the younger generations invidiously to his own.
“—I’m sorry, I see that I’ve gone over five minutes, so I’ll stop there. Remember my office hours are tomorrow,
