Letters to a Young Scientist Read Online Free PDF

think it’s a hylid frog,” his companion replies. “No, no, wait, I’ve never seen anything like it. It’s got to be something new. What the hell is it? Listen, get close, and be careful, don’t lose it. There, got it. We’re not going to preserve it yet. You never know, it might be an endangered species. Let’s take it back alive to camp and see what we can find on the Encyclopedia of Life website. There’s that guy at Cornell, he knows all the amphibians like this one pretty well, I think. We might check in with him. First, though, we ought to look around for more specimens, get all the information we can.” The pair arrive back at camp and start pulling up information. What they find is astonishing. The frog appears to be a new genus, unrelated to any other previously known. Scarcely believing, the pair go online to spread news of the discovery to other specialists around the world.
    The potential paths you can follow with a scientific career are vast in number. Your choice may take you into one of the scenarios I’ve described, or not. The subject for you, as in any true love, is one in which you are interested and that stirs passion and promises pleasure from a lifetime of devotion.

Charles Darwin at 31 years of age. Modified from painting by George Richmond.

Four

    W HAT I S S CIENCE?

    W HAT IS THIS grand enterprise called science that has lit up heaven and earth and empowered humanity? It is organized, testable knowledge of the real world, of everything around us as well as ourselves, as opposed to the endlessly varied beliefs people hold from myth and superstition. It is the combination of physical and mental operations that have become increasingly the habit of educated peoples, a culture of illuminations dedicated to the most effective way ever conceived of acquiring factual knowledge.
    You will have heard the words “fact,” “hypothesis,” and “theory” used constantly in the conduct of scientific research. When separated from experience and spoken of as abstract ideas they are easily misunderstood and misapplied. Only in case histories of research, by others and soon by you, will their full meaning become clear.
    I’ll give you an example of my own to show you what I mean. I started with a simple observation: ants remove their dead from the nests. Those of some species just dump the corpses at random outside, while those of other species place them on piles of refuse that might be called “cemeteries.” The problem I saw in this behavior was simple but interesting: How does an ant know when another ant is dead? It was obvious to me that the recognition was not by sight. Ants recognize a corpse even in the complete darkness of the underground nest chambers. Furthermore, when the body is fresh and in a lighted area, and even when it is lying on its back with its legs in the air, others ignore it. Only after a day or two of decomposition does a body become a corpse to another ant. I guessed (made a hypothesis) that the undertaker ants were using the odor of decomposition to recognize death. I further thought it likely (second hypothesis) that their response was triggered by only a few of the substances exuded from the body of the corpse. The inspiration for the second hypothesis was an established principle of evolution: animals with small brains, which are the vast majority of animals on Earth, tend to use the simplest set of available cues to guide them through life. A dead body offers dozens or hundreds of chemical cues from which to choose. Human beings can sort out these components. But ants, with brains one-millionth the size of our own, cannot.
    So if the hypotheses are true, which of these substances might trigger the undertaker response—all of them, a few of them, or none? From chemical suppliers I obtained pure synthetic samples of various decomposition substances, including skatole, the essence of feces; trimethylamine, the dominant odor of rotting fish; and various fatty acids