EART265 Order of Magnitude Estimation

Instructors: Prof. Patrick Chuang
A254 Earth & Marine Sciences Bldg.
tel. +1-831-459-1501

Prof. Francis Nimmo
A219 Earth & Marine Sciences Bldg.
tel. +1-831-459-1783

Classes are Tues/Thurs 1:30-3:05pm D236, E&MS.

Office hours Weds 12:30-1:30pm and Thurs 3:05-4:05pm A219 (FN) and Mon/Tues 12-1pm A254 (PC).

An important skill for graduate students is the ability to make "quick and dirty" calculations, to see whether a problem is worth investigating properly. Such "back of the envelope" techniques are a vital part of any working scientist's intellectual toolbox. This class is designed to teach some of these techniques.

Classes will consist of a mixture of lectures, discussions and in-class problems. Problem sets will consist of both solving, and suggesting, suitable problems. There will be a final exam (oral).

We will discuss problems relating to: Planets, Oceans and Atmospheres, Energy and the Environment, and Real Life. Typical examples: How long does it take the Moon to cool? Do beaver dams affect global warming? How dense is a neutron star? What controls how tall trees (or mountains) grow? How small is the smallest mammal? How many piano tuners in New York City? (Aficionados will recognize the last question as the archetypcal Fermi Problem).

Very few textbooks are available on this kind of material, but two reasonable ones are Back of the Envelope Physics , C. Swartz, Johns Hopkins Univ. Press, 1993, and Guesstimation , L. Weinstein and J.A. Adam, Princeton Univ. Press, 2008. An outstanding guide to order of magnitude problems as applied to energy and the environment is Sustainable energy - without the hot air by D.J.C. McKay (UIT Press, 2009). By far the most entertaining ``textbook'' is What If? , R. Monroe, Houghton Mifflin, 2014.

There are also several useful websites. By far the best is an excellent (if incomplete) textbook from Sanjoy Mahajan at MIT. Sanjoy has also published a related book, Street-Fighting Mathematics (MIT Press 2010) which is, however, not as useful. Eugene Chiang at Berkeley has a very useful home page for a course similar to this one; Sterl Phinney at Caltech has another. The University of Maryland has a good Fermi Problem site. And here are some astrophysical examples from Ohio State.

Here is the syllabus. This will only be approximate - we prefer covering a few topics in depth (lots of examples!) to more topics less carefully.

You can download the lecture handouts and problem sets (PDF format) below.
Week 1 (8 Jan) Basic concepts and more on basic concepts; Getting our feet wet
Week 2 (15 Jan) Material properties Binding energies Sanjoy's chapter Problem Set 1 Answers
Week 3 (22 Jan) Heat transfer and mass transfer Problem Set 2 Answers
Weeks 4-5 (29 Jan) Fluid mechanics Viscous flows Problem Set 3
Week 6 (12 Feb) Turbulence, more turbulence, and boundary layers
Week 7 (19 Feb) Waves and Oscillators
Week 8 (26 Feb) Energy and the environment
Week 9 (5 Mar) Disasters More disasters

Over the course of the term we will be compiling a list of useful numbers; there will also be a list of basic equations and some useful formulae to know.
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