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Orders of Magnitude Fermi Estimates and Understanding Numbers

Orders of Magnitude Fermi Estimates and Understanding Numbers This was my idea of a Fermi Question: Turn every experience into a question. Can you analyze it? If not, you'll learn something. If you can, you'll also learn something. - Philip Morrison , Ph.D. Enrico Fermi (1901-1954).

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Orders of Magnitude Fermi Estimates and Understanding Numbers

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  1. Orders of Magnitude Fermi Estimates and Understanding Numbers This was my idea of a Fermi Question: Turn every experience into a question. Can you analyze it? If not, you'll learn something. If you can, you'll also learn something. - Philip Morrison, Ph.D.

  2. Enrico Fermi (1901-1954) • Born in Italy • Earned Ph.D. in physics at the age of 21. • Received Nobel Prize in 1938, for work on “Artificial Radioactivity Produced by Neutron Bombardment”. • Emigrated to U.S. in 1938, mostly to escape the fascist regime of Mussolini. • Lead work in Chicago which resulted in the first controlled nuclear reaction. • This ultimately lead to the development of the atomic bomb. • In 1944 became an American citizen. • Died in Chicago in 1954. • Today the Fermi National Accelerator Laboratory in Batavia, IL is named after him. Sources: http://nobelprize.org/nobel_prizes/physics/laureates/1938/fermi-bio.html http://www.lanl.gov/history/atomicbomb/pdf/Enrico%20Fermis%20Observations%20at%20Trinity,%20July%2016,%201945.pdf http://larrycalloway.com/trinity-tes

  3. Time and Distance

  4. "How many piano tuners are there in Chicago?" • To start you have to make some reasonable guesses. • Approximately 5,000,000 people living in Chicago. • On average, there are two persons in each household in Chicago. • Roughly one household in twenty has a piano that is tuned regularly. • Pianos that are tuned regularly are tuned on average about once per year. • It takes a piano tuner about two hours to tune a piano, including travel time. • Each piano tuner works eight hours in a day, five days in a week, and 50 weeks in a year. • From these assumptions we can compute that the number of piano tunings in a single year in Chicago is: Source: http://en.wikipedia.org/wiki/Fermi_problem

  5. Sources: N. Angier, The Biggest of Puzzles Brought Down to Size, The New York Times,2009 http://www.nytimes.com/2009/03/31/science/31angi.html Weinstein and Adam, guesstimation, 2008

  6. Need: • Diameter of golf ball. • Circumference of earth. 1 inch ~ 2.5 cm The diameter of golf ball is ~1.5 inches or ~4 cm The circumference of the Earth is a little more tricky. If you can remember it or the Earth’s radius great, but I never do. But I do remember that it is about 3,000 miles from the east coast to the west coast and that is about 1/8 the distance around the earth. So the circumference is ~ 24,000 miles or ~40,000 km 1 mile ~ 1.6 km

  7. ~33 km or ~ 20 mi ~33 km or ~ 20 mi

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