**PLANETARY ASTROPHYSICS**

**or
**

**Order-of-Magnitude Physics Applied to Planetary Systems and the World Around You**

**Spring 2005**

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Quicklinks
Problem sets
Order-of-magnitude blackboard presentation I
Order-of-magnitude blackboard presentation II
Final exam
**

Physics of planetary systems, both solar and extra-solar. Star and planet formation, radioactive dating, small-body dynamics and interaction of radiation with matter, tides, planetary interiors, atmospheres, and magnetospheres. Emphasis on the ability to
estimate, from first principles, scaling arguments, and
everyday experience, any quantity in the universe to within a factor of 10.
Two high-quality oral presentations and a final exam
will be required in addition to
regular problem sets. |

A. Order-of-magnitude material properties

B. Collision physics, mean free path, optical depth

C. Star formation: Adiabatic vs. isothermal collapse

D. Protoplanetary disks: Structure of minimum-mass solar nebula

E. Planet formation: Gravitational focussing

F. Lead-lead dating and the age of the solar system

G. Aerodynamic drag laws and meteor falls

H. Asteroid physics: thermal diffusion, radiation torques, chaos

I. Seasonal ice caps on Mars: Murray-Leighton model

J. Radiative diffusion in planetary atmospheres: Venusian greenhouse

K. Atmospheric convection: Dry and moist adiabats

L. Brown dwarf luminosity vs. mass vs. time scaling relations

M. Hydrostatic figures of equilibria: Maclaurin/Jacobi ellipsoids

N. Solid-state convection: Rayleigh number and continental drift

O. Tidal dynamics

P. Water waves, earthquakes, and tsunamis

Q. Magnetospheric interactions: Io and the Echo-1 satellite

R. Solar wind: Magnetic braking

(1) Weekly lectures

(2) problem sets (70%)

(3) order-of-magnitude blackboard presentation I (10%)

(3) order-of-magnitude blackboard presentation II (10%)

(5) final exam (10%)

PS 1: Due Thursday Jan 27. Postscript version here. PDF version here

PS SOLUTION PDF SOLUTION

PS 2: Due Thursday Feb 3. Postscript version here. PDF version here

PS SOLUTION PDF SOLUTION

PS 3: Due Thursday Feb 10. Postscript version here. PDF version here

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PS 4: Due Thursday Feb 17. Postscript version here. PDF version here

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PS 5: Due Thursday Feb 24. Postscript version here. PDF version here

PS SOLUTION PDF SOLUTION

PS 6: Due Thursday Mar 3. Postscript version here. PDF version here

PS SOLUTION PDF SOLUTION

PS 7: Due Thursday Mar 10. Postscript version here. PDF version here

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PS 8: Due Thursday Mar 31. Postscript version here. PDF version here

PS SOLUTION PDF SOLUTION

PS 9: Due Thursday Apr 7. Postscript version here. PDF version here

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PS 10: Due Thursday Apr 14. Postscript version here. PDF version here

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PS 11: Due Thursday Apr 21. Postscript version here. PDF version here

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PS 12: Due Thursday Apr 28. Postscript version here. PDF version here

PS SOLUTION PDF SOLUTION

II. Water, Water Everywhere

III. The Kyoto Protocol

IV. Mass Transit

V. Bonnie and Clyde

Each group of 2-3 students should select one of the 5 topics above. Research shows that 3 is the ideal number. More than 1 group can be assigned to each topic. Those of you who don't wish to choose your own groups, please e-mail your top 3 preferences, and I will assemble groups of 2-3 students based on these preferences.

Each group should be independent of other groups working on the same topic.

Members of each group should work together to prepare a unified blackboard oral presentation, not to exceed 25 minutes, during which quantitative answers to all of the questions under their topic are derived from first principles. In-class presentations will be held Tuesday March 15 during the regular class time and Wednesday March 16 from 10-11:30 AM. Credit will be awarded for:

(a) ability to reason from first principles of physics, common sense, and/or material learned in this class

(b) minimum (ideally, zero) reliance on anything else (like Google)

(c) quantitative accuracy of answer

(d) meaningful choice of units in which to express the answer

(e) clarity of presentation

The fewer things you look up, the better. Ask yourself: do I really need to look this up? Looking up things AFTER you have estimated them yourself is, however, encouraged---as a way to check your answer.

During the oral presentation, only use of a blackboard and any in-hand notes will be permitted. Remember, each group will only have a total of 25 minutes, so that each member of the group should present for about 8 minutes. There is absolutely no penalty for taking less than 25 minutes; in fact, points will be awarded for simplicity and elegance in your derivation.

If a question seems ill-defined, it is your responsibility to re-phrase it so that it is quantitatively well-defined. This also happens in real-world research.

Grades will be assigned individually.

Make sure everyone in your group agrees on the answer. Most of all, HAVE FUN.

I. We are the Martians

II. The Sky is Falling

III. The Standard of Living in the Solar System

IV. The Lord of the Rings

V. Raindrops are Falling on My Head

Topic selection due Thursday April 7 (by e-mail or in person). Presentations to be held Thursday May 5 and Tuesday May 10.