Unformatted text preview: Clicker Question
Philosophically, from which perspective do you answer the question, What is Life? A) 100% materialist, human beings are nothing more than a complicated arrangement of atoms held together by electromagnetic forces B) leaning toward materialism C) agnostic D) leaning toward vitalism E) 100% vitalist, in addition to atoms, human beings contain a vital force, sprit or soul. Where are we?
Last time I covered: What is Life? Vitalism and Materialism Emergent Properties This time I am going to discuss: What is the nature of the science of nature? The importance of curiosity and luck in making new discoveries The Fermi solution, the power of numbers and dimensional analysis About 10,000 years ago, in the presence of an adequate food supply and leisure time... ...civilization began. The Human Dilemma While people long for the security of civilization, We are also curious about what is yet to be known at its frontiers. This dilemma is ancient... "The longing for a frontier seems to lie deep in the human soul, and people from different parts of the world and with different cultural backgrounds understand it quickly and intuitively." Robert B. Laughlin (2005) The American Frontier
In the late 19th century, Albert Bierstadt captured the imaginations of Americans with his magnificent paintings of the newly accessible western frontier in America. Science is a great frontier where curious adventurers can still explore the unknown. Discoveries at the Frontiers of Knowledge Have Given Us Healthier Lives Through Understanding Sanitation (e.g. Antiseptics) Through a Better Understanding of Nutrition (e.g. Vitamins) Through Preventative Medicine (e.g. Immunization) Through Treatment (e.g. Insulin, Antibiotics) Through Better Surgical Procedures Science: To know (and to know what we don't know) The word science comes from the Latin word scientia, which means "to know". Science is a way of thinking and doing that results in knowing about ourselves and the natural world. Scientific knowledge is presented, in principle, in a language that everyone can understand. When one clearly states the method used to obtain scientific data, one, in principle, states the scope and limitations of the conclusions. Scientific data and the conclusions derived from them are limited and it is just as important "to know what we don't know" as "to know what we know". Where does one find how to do science? How to cross the frontier? How do we discover new scientific ideas? Planned, methodical investigation Accident, Chance, Serendipity Inspiration, Intuition, Imagination Any and all combinations of the above Discovery and Development: Textbook Example Flashlight does not work. Why not? Hypothesize batteries/bulb do not work Predict changing batteries/bulb will make it work Test prediction Test falsifies/does not falsify hypothesis Planned Methodical Research Planned methodical work advances by small incremental steps. While planned research is rational, real discoveries come to prepared minds as a result of luck and/or intuition. Great Discoveries This is not a class on flashlights, but if it were, I would rather cover bigger topics like: What is light? How was electricity discovered? How is electricity converted into light? For bigger topics, and many great discoveries in biology, the most important part of doing science is having a prepared mind to take advantage of accidents. How do you learn to become lucky in your Profession? "The seeds of great discoveries are constantly floating around us, but they only take root in minds well prepared to receive them." - Joseph Henry (1877) "Dans les champs de `l'observation, le hasard ne favorise que les esprits prepares." That is, "Chance Favors a Prepared Mind."
- Louis Pasteur The Creative Approach
In a few minutes I will teach you a method that allows you to use hypotheses to help guide you though the unknown. I call this the Fermi solution. First I want to prepare you to be lucky, by telling you three stories about scientists who were lucky. Oskar Minkowski was Lucky In 1889, Oskar Minkowski did not believe Joseph von Mering's claim that pancreatic enzymes were necessary to break down fatty acids in the digestive tract. To settle the argument, Minkowski performed a pancreatectomy on a dog. Luckily, a laboratory assistant noticed that the "house-trained" dog, whose pancreas had been removed, urinated all over the place and that flies swarmed to its urine. Chemical analysis showed that the urine was loaded with sugar and thus Minkowski had artificially caused diabetes mellitus (which means sugary flow) as a result of removing the pancreas. Oskar Minkowski discovered, by accident, that the pancreas was necessary to control the level of blood sugar and prevent diabetes. Later it was discovered that the pancreas prevents diabetes by producing insulin. Alexander Fleming was Lucky While studying plates of Staphylococcus, a bacterium that causes infections, Fleming noticed that one plate was contaminated by the fungus Penicillium. Instead of throwing the contaminated plate away, he observed it. He found that the bacterial colonies closest to the fungus had lysed and died. This accidental observation lead to the discovery of penicillin, the first antibiotic! In 1928 "...penicillin started as a chance observation." Alexander Fleming was Lucky
"In my first publication I might have claimed that I had come to the conclusion, as a result of serious study of the literature and deep thought, that valuable antibacterial substances were made by moulds and that I set out to investigate the problem. That would have been untrue and I preferred to tell the truth that penicillin started as a chance observation." Walter B. Cannon was Lucky Walter Cannon fed cats food containing contrast agents so he could visualize the mechanical movements of their stomachs with the newly invented x rays. Stomach movements occurred only in the docile female cats and not in the restless male cats so only female cats were used to study the mechanical movement of the stomach. Walter B. Cannon was Lucky A few days later, Cannon noticed that the stomach of a docile female cat stopped moving when she became enraged when someone threatened her kittens. When Cannon stroked the cat reassuringly, she began to purr and her stomach began moving again. Walter B. Cannon was Lucky
That females but not males exhibited movements of the digestive tract led Cannon to study only females and make progress in understanding digestion....but there was a dissonance in the back of his head that had to be resolved. He was prepared to find a new guiding principle that described digestion in males and females. And he did. Walter B. Cannon was Lucky
These experiments led Cannon to realize that the digestive tract is under the influence of strong emotions and that there is a strong relationship between mind and body. This was the first of a series of discoveries that led him to propose the "fight or flight" response (later known as the four F's Fight, Fright, Flight and Sex) in which the body changes its physiology from its normal "rest and digest" pattern to a more active pattern. How do you learn to become a good guesser in your profession?
Study Examples Practice on Your Own Love (like an amateur) and Find Delight (like a dilettante) in your Professional Work The Fermi Solution
In order to train his students to estimate things that they did not know, Enrico Fermi would ask them "How many piano tuners are there in Los Angeles?" After they looked befuddled, he would say: Fermi Solution "You can estimate the number of piano tuners from first principles! For example how many people are there in Los Angeles? 1 million? What percentage has pianos? Five percent? Then there are 50,000 pianos in Los Angeles. How often does a piano need to be tuned? About once a year? Then 50,000 pianos need to be tuned in a year. How many pianos can a piano tuner tune in a day? Three? Then one tuner would have to spend 16,667 days a year tuning pianos. But since there are not that many days in a year, and he or she probably only works 250 days a year, then there must be around 67 piano tuners in Los Angeles." William Harvey was a Good Guesser Before Harvey's work, the standard theory of blood was that the liver converted the food we eat into blood. Then the heart sucked the blood from the liver to deliver it to the rest of the body. Harvey used "the Fermi solution" to propose that the heart was a pump and the blood circulated. William Harvey (1628) was a Good Guesser Harvey realized that the heart was a muscle that contracted like our voluntary muscles. when the heart contracted, its volume diminished and consequently, the blood was pumped out into the arteries. the food we ate could not provide enough liquid to replenish the blood that left the heart. Harvey guessed that the blood must circulate throughout the body even though he could see the capillaries that connected the arteries to the veins since he did not have a microscope. Harvey estimated the flow rate of blood. How would you estimate the rate (in liters/minute) that the heart pumps blood? Guess: What is the volume of the heart? (Hint: It is about the size of a clenched fist) Guess: What is the pulse rate? Assume blood is not created or destroyed. Assume the heart empties 1 volume/beat Model mathematically using dimensional analysis:
(Volume of heart) (1 emptying volume/beat)(pulse rate)(conversion factors) (____ml)(1 liter/1000ml)(____beats/min)(60min/h)(24h/day)=___ liters/day Harvey estimated the flow rate of blood. How would you estimate the rate (in liters/minute) that the heart pumps blood? Guess: The volume of the heart is about 75 ml. Guess: The pulse rate is about 70 beats/min. Assume blood is not created or destroyed. Assume the heart empties 1 volume/beat Mathematical model using dimensional analysis:
(Volume of heart) (1 emptying volume/beat) (pulse rate) (conversion factors) (75 ml) (1 liter/1000ml) (70 beats/min) (60min/h) (24h/day) = 7560 liters/day Harvey guessed that the blood was not created in the liver by the food we eat, but must circulate though the body since a person did not and could not eat or drink over 7000 liters/day. He was right. Thanks to many prepared minds and good guessers, scientific research has produced many valuable results that allow us to lead healthy lives and to know ourselves. And because there will be more prepared minds and good guessers in the future, "...recent findings and present concepts are only the last approximation in a long series of similar attempts...." One last thing... "The greatest value of science is "the freedom to doubt". Richard Feynman (1955) ...
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This note was uploaded on 09/24/2007 for the course BIO G 110 taught by Professor Wayne,r. during the Spring '07 term at Cornell.
- Spring '07
- William Harvey, Walter B. Cannon, fermi solution