Tag Archives: science

A Fermi Problem About Pharmaceuticals

Rebecca Skloot tweets the following question, which she asks on behalf of Melinda Wenner (@lindy2350):

Anyone know how I can find the # of people worldwide taking a particular class of drug?

This is an interesting problem, and as well it’s a nice example of what has come to be known as a “Fermi problem.” The physicist Enrico Fermi famously posed the question “How many piano tuners are there in Chicago?” to his students, to be answered without consulting any reference sources: the answer to the question must come entirely from “back of the envelope” calculations. A similar situation faces a scientist approaching a new problem. How much voltage will be required for a new apparatus, made for an experiment never performed before? What is the most critical quantity in a new, never-before-tested theory? How large an effect should be expected if our theory is correct? Even an estimate of the order of magnitude of the quantity of interest would be useful, since nothing is known about it. Fermi problems are intended to train a student to think about quantities whose values can be discovered and what their relationships are, so that the answer to the Fermi problem can be deduced.

I’d like to consider Melinda’s question, but first, I’d like to work through the piano tuners problem, direct readers to some more sites with Fermi problems, and describe an experiment conducted by Fermi with nothing more than scraps of paper and “back of the envelope” calculations—to measure the power of the first atomic bomb.

Click here to keep reading…

Chance and Explanation in Evolutionary Biology

The page on this site at Philosophy > Chance and Explanation has been updated with the following:

  1. A brief essay describing my work in history and philosophy of science concerning chance and explanation in evolutionary biology.
  2. My PhD thesis. The abstract: The central claim for which I argue in this dissertation is that there are important phenomena that occur by random drift that evolutionary biologists explain using a strategy I term “process explanation.” This claim puts me at odds with an influential view about the nature of explanation that I term “Hempelianism.” Hempelianism is the view that the scientific explanation of a particular event E requires (a) showing that E was to be expected, or indicating the degree to which it would have been rational to expect E’s occurrence; and (b) laws of nature. My central claim entails that both (a) and (b) are false. A process explanation consists of a narrative describing events causally relevant to the event to be explained. These narratives need not contain laws, show that the event to explained ought to have been expected, or indicate the degree to which it would have been rational to expect the event. My position about random drift also puts me at odds with evolutionists who, influenced by Hempelianism, claim that only natural selection can explain evolution. In my argument, I articulate the strategy of process explanation and defend it against Hempelian critics; describe a mechanism of random drift known as “indiscriminate sampling;” and describe process explanations of phenomena of drift that occur by indiscriminate sampling.

Modern Science Writing: A List of Works

Hypoglycemiagirl‘s reflections on an early holiday gift she bought for herself, published online under the title “Anthology of Science Writing: Now almost 4% with ovaries,” have led to a discussion of Richard Dawkins’ selection of works for inclusion in The Oxford Book of Modern Science Writing. The central issue (as the blog post title suggests) is that women authors account for 3.6% of the selections. Sheril Kirshenbaum at The Intersection picked up the thread, and Tara C. Smith at Aetiology continued the discussion. Should women writers be more broadly represented in the anthology? Does it matter? Is the fault with Dawkins himself, or with the culture of scientific research, in which women find success harder to come by than men?

Without resolving these issues, it’s possible to make up for the weaknesses of Dawkins’ suggestions by offering alternatives. The alternative list should include works by authors excluded from Dawkins’ selection, not just because of gender—if indeed it is because of gender that some are excluded—but because their works concern areas of study not represented by any works on Dawkins’ list. The alternative list may include popular books, that is, works not published primarily for an audience of scientists; Dawkins’ list includes such works. Of course, the list should name works of the highest quality, judging by the science they report, their prose style, and whether they use particularly engaging examples and offer particularly clear explanations. They must also be “modern,” which, judging by Dawkins’ selections, requires that they be written in the 20th Century; the 21st should be allowed, also.

The idea here is not to suggest works which Dawkins might have included (some are probably too technical) but to recognize accomplishments of prose style and intellectual achievement which someone reading the Oxford Book would not be aware of, if he or she had only that work as a guide. Examples of works by women are important. They provide evidence that women are capable of doing important work in science, something which might not seem to be the case to a student or young researcher, who, simply by the numbers, will not be exposed as often by scientific works by women. Everyone should draw the conclusion that one’s gender ought not be a barrier to making a contribution in science.

Insight is provided into some of these issues in MIT’s 1999 “Study on the Status of Women Faculty in Science at MIT“. I note that this study does not conclude that there is any reason women should not succeed at the same level that men have because women have intrinsic cognitive limitations or differ in their capacity for analytic thought or reasoning. The Study reports that institutional changes are required so that women are more highly visible and actively recruited and supported. Surely an institution such as MIT would not recommend such changes if its researchers had found that there really were cognitive deficiencies in women. If it were believed that women are as nearly well-represented as they will ever be because of the scarcity of intellectually adequate women in science, the recommendations would not include attempting to expand the cohort of female science faculty at MIT.

Readers are invited to offer suggestions in the comment thread in response to this posting, and to explain, in a few sentences, why the work should be included in this “alternative” list. If there are enough contributions, perhaps the list will be published here as a small bibliographic database or list of bibliographic references.

The works are listed below in no particular order. As the list grows, it will be organized alphabetically and by subject.

It is noted that many of the works listed below are “alternative” only in the sense that they do not appear on Dawkins’ list. Many are foundational works in their disciplines, and many are widely recognized for excellence as works for general readers.

A List of Works

  1. Motoo Kimura. “Evolutionary rate at the molecular level.” Nature 217 (1968): 624 – 626. In this paper, Kimura argues that facts about the rate of evolution at the molecular level are best explained by random drift, not natural selection. This theory as well as the “nearly neutral theory” (see below) have become the “theories to beat” in molecular population genetics, that is, there is a presumption in favor of them.
  2. Jack Lester King & Thomas H. Jukes. “Non-darwinian evolution.” Science 164 (1969): 788 – 798. King and Jukes reach a conclusion similar to Kimura’s, using different arguments. This paper and Kimura’s make excellent reading—concise, forceful, and clear.
  3. Sewall Wright. “The roles of mutation, inbreeding, crossbreeding and selection in evolution.” In Evolution, ed. William Provine. Chicago: University of Chicago Press, 1986. Originally published 1932. In this paper, Wright introduces the idea of a surface of selective values, more commonly known as an adaptive landscape. Wright’s impressionistic prose and sketches of the landscapes dominate his generally impenetrable mathematics. Other works by Wright in the Provine collection, for instance, his work on F-statistics, and his contributions to a controversy with Fisher and Ford about the shifting balance theory, develop what have become classic ideas in population genetics.
  4. Tomoko Ohta. “Slightly deleterious mutant substitutions in evolution,” Nature 246 (1973): 96-98. Ohta proposes the “nearly neutral theory” of molecular evolution. An MIT History of Recent Science and Technology article provides a brief overview of Ohta’s work on the nearly-neutral theory, with key references and a link to a web page with her biography.
  5. Olivia Judson. Dr. Tatiana’s sex advice to all creation. New York: Henry Holt and Company, 2006. Crisp prose; concise explanations; engaging subject matter and choice of examples. Dr. Tatiana accepts questions about sexual reproduction from different animals, explaining what’s known about their mating habits, and how and why they are most likely to have evolved by natural selection. Each vignette is a few pages long, so this book is well-suited for the commuter. Judson writes the Wild Side blog for the New York Times.
  6. Janna Levin. How the universe got its spots: Diary of a finite time in a finite space. Princeton: Princeton University Press, 2002. “Is the universe infinite or just really big?” Cosmologist Janna Levin explains her view that the universe is finite in extent in the styles of memoir and correspondence. At once intimately personal and objective, she describes her struggle with ideas and with the nomadic life of a scientist looking for a permanent home in research and teaching.
  7. Jennifer A. Clack. Gaining ground: The origin and evolution of tetrapods. Bloomington: Indiana University Press, 2002. Looking at her credentials, Jenny Clack (she clearly prefers “Jenny,” judging from her web site) could hardly be considered alternative: she is  Professor and Curator of Vertebrate Paleontology at the University Museum of Zoology at Cambridge University, and a fellow of the Royal Society. Her work concerns early tetrapods, i.e., those animals which, among other things, made the move from water to land. Gaining Ground concerns the kinds of changes that animals adapted for aquatic life had to undergo in order to succeed in a new environment.  Clack advances our knowledge of this important transition, synthesizing insights from her own work with what’s already known. The book is a technical monograph, but the subject is so intriguing, and Clack’s exposition so straightforward, that a non-specialist can profit from reading it. Most people will immediately recognize the distinctive body plan of Acanthostega and Icthyostega. Readers of recent popular books about early tetropod research may be familiar with the kind of research it requires by having come across Neil Shubin’s recent book Your Inner Fish (recently reviewed in Evolution: Education & Outreach).