Transcript 14 full-time tuners in Chicago - Pomona College Astronomy Program

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?
11
10
11
10
= Average Stars per galaxy
= number of galaxies (estimated)
2.3 = average number of planets per star
(based on current research)
Best Guess:
a). 1011
11
b). 2x10
22
c). 10
22
d) 2x10
23
e). 4x10
Fermi Problem
How many planets are in the universe?
11
10
11
10
= Average Stars per galaxy
= number of galaxies (estimated)
2.3 = average number of planets per star
(based on current research)
Best Guess:
a). 1011
11
b). 2x10
22
c). 10
22
d) 2x10
23
e). 4x10
The Size of
Things
Moving Through Space to the Edge of the Universe
by Dr. Bryan E.
Penprase
Limit of Human Travel
(1.25 light seconds)
Geosynchronous
Orbit
Near Earth Environment
unexplored
Limit of Human Spacecraft
(Voyager 1: 125 AU;
Voyager 2: 102 AU)
1 AU = 8 light minutes
Solar System
Next Spiral Arm
(500 pc)
Nearest star (3
light years)
Nearby Stars (with parallax)
Virgo Cluster of Galaxies
(10 Mpc)
Andromeda Galaxy
(0.9 Mpc)
LMC and SMC (50kpc)
Galactic Center
(8.5 kpc)
Nearby Galaxies
Edge of the Universe
First “free” photons
(13.7 billion lyrs-300klyrs)
“Dark Ages” (unexplored)
Most distant quasars
Half way back to origin
of time and space (z=1)
Distant Galaxies
Large Scale Structure
(100 Mpc)
Our Place in the
Universe
Our Place in the Universe (continued)
This part will include history of transit expeditions; especially poor French dude Vo
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 mo
Ask David Haley to be sure “Digital Universe” is installed on laptops; can do 3D
imageing and proper motions both.
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 some interesting information on early radar studies;
some calculations for distances to different planets.
Try to find some good footage of lunar ranging (email 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).
Flying through the Big Dipper
Flying through Orion