Fermi Problems and Scale of the Universe Advanced Introduction to Astronomy Spring 2014 Pomona College by Dr. Bryan E. Penprase An Example of a “Flipped” Class!!

Fermi Problems Enrico Fermi, U. of Chicago Physics professor (and pioneer of nuclear physics) at the chalkboard

Fermi Problem How many cars are in Claremont? 35,000 = Population of Claremont 2.28 = average cars / household in the US 2.5 = average household size in US Best Guess: a). 15,000 b). 20,000 c). 35,000 d) 50,000 e). 60,000

Fermi Problem How many cars are in Claremont? Best Guess: a). 15,000 b). 20,000 c). 35,000 d) 50,000 e). 60,000

Classic Fermi Problem How Many Piano Tuners are there in Chicago? Population of Chicago = 2.7 million (2013) Number of families - 1 million (using 2.7 = avg family size) Number of pianos? ~7% would be at income level with kids -> 75,000 pianos

Fermi Calculations each piano tuned every 3 years -> 25,000 tuned per year tuner can do about 5 per day -> 5*360 days = 1800 per year need 25,000 / 1800 = 14 full-time tuners in Chicago

Fermi Problem How many planets are in the universe? = Average Stars per galaxy = number of galaxies (estimated) 2.3 = average number of planets per star (based on current research) a) b). 2x10 11 c) d) 2x10 22 e). 4x10 23 Best Guess:

Fermi Problem How many planets are in the universe? = Average Stars per galaxy = number of galaxies (estimated) 2.3 = average number of planets per star (based on current research) a) b). 2x10 11 c) d) 2x10 22 e). 4x10 23 Best Guess:

The Size of Things Moving Through Space to the Edge of the Universe by Dr. Bryan E. Penprase

Near Earth Environment Geosynchronous Orbit Limit of Human Travel (1.25 light seconds)

Solar System 1 AU = 8 light minutes Limit of Human Spacecraft (Voyager 1: 125 AU; Voyager 2: 102 AU) unexplored

Nearby Stars (with parallax) Nearest star (3 light years) Next Spiral Arm (500 pc)

Nearby Galaxies LMC and SMC (50kpc) Andromeda Galaxy (0.9 Mpc) Galactic Center (8.5 kpc) Virgo Cluster of Galaxies (10 Mpc)

Edge of the Universe Distant Galaxies Large Scale Structure (100 Mpc) First “free” photons (13.7 billion lyrs-300klyrs) Half way back to origin of time and space (z=1) Most distant quasars “Dark Ages” (unexplored)

Our Place in the Universe

Our Place in the Universe (continued)

The Cosmic Distance Ladder - The first rungs (to Milky Way Center) Parallax ✤ Venus Transit - measure of AU ✤ Stellar Parallax ✤ Early studies ✤ Modern techniques (Hipparcos + SIM) Distance Ranging Radar studies of planets Laser lunar ranging Timing of Spacecraft signals Secondary Techniques Standard Candles Cepheids + Spectroscopic Parallax This part will include history of transit expeditions; especially poor French dude Voyager exercise to recreate parallax; Retrograde loops and order of mag calculations; definition of parsec; intro to proper motion History of telescopes and first proper motion and parallax measurements Modern techniques -- Hipparcos sattelite and upcoming Kepler and SIM missions If time allows -- do simulation with the Partiview program where one sees stars moving. Ask David Haley to be sure “Digital Universe” is installed on laptops; can do 3D imageing and proper motions both. This part will include history of transit expeditions; especially poor French dude Voyager exercise to recreate parallax; Retrograde loops and order of mag calculations; definition of parsec; intro to proper motion History of telescopes and first proper motion and parallax measurements Modern techniques -- Hipparcos sattelite and upcoming Kepler and SIM missions If time allows -- do simulation with the Partiview program where one sees stars moving. Ask David Haley to be sure “Digital Universe” is installed on laptops; can do 3D imageing and proper motions both. This part will include some interesting information on early radar studies; some calculations for distances to different planets. Try to find some good footage of lunar ranging ( our friend teaching with us - ask for talk slides or movie) Include information on spacecraft and alternate theories of gravity This part will include some interesting information on early radar studies; some calculations for distances to different planets. Try to find some good footage of lunar ranging ( our friend teaching with us - ask for talk slides or movie) Include information on spacecraft and alternate theories of gravity Include basic concept of standard candle. Give some information on number of photons from different sources. Sun for example - kw + photons per square cm per second. Then scale for sun at distance of 1 pc. Include idea of flux units and basis for inverse square law This will set us up for discussion of light on next class (Tuesday). Include basic concept of standard candle. Give some information on number of photons from different sources. Sun for example - kw + photons per square cm per second. Then scale for sun at distance of 1 pc. Include idea of flux units and basis for inverse square law This will set us up for discussion of light on next class (Tuesday).

Flying through the Big Dipper

Flying through Orion