1. Review of Scientific Notation
102 = 100, 101=10, 100 = 1, 10-1=0.1, 10-2=0.01
1012=1,000,000,000,000=trillion (Tera-)
109 =1,000,000,000 = billion (Giga-)
106 = ,000,000 = million (Mega-)
103 = ,000 = thousand (kilo-)
10-2= 0.01=one-hundredth (centi-)
10-3= 0.001=one-thousandth (milli-)
10-6= =one-millionth (micro-)
10-9= =one-billionth (nano-)
5.4x103=5, x10-3=
4,700=4.7x = 1.7x10-2
Start here on 1/9

2. Powers of Ten Arithmetic
Multiplication:
(5.3x103) x (6x10-5) = 31.8x103+(-5)
=31.8x = 3.18x10-1
= = 0.3
One significant figure! Keep only the minimum number of significant figures going into the calculation in the answer.
Division:
(9.3 x10-4)/(3.10x10-6) = 3.0 x10-4-(-6)
= 3.0 x102
= 300
BUT, 3.0x102 is the better answer, as it CLEARLY has two significant figures; scientific notation is PRECISE.

4. The Scales of the Universe
We deal with the largest possible things -- the whole universe -- and with the smallest -- nuclei of atoms.
This requires us to use a wide range of PHYSICAL UNITS and we USE THE METRIC SYSTEM.
Length: m or cm Mass: kg or g
Time: s or yr Temperature: K(elvins)
ON 1/18/05 START w/ SLIDE 8 SEASONAL VARIATIONS
Radius of Sun = 6.96x10^10cm = 7x10^5 km
Mass of Sun = 1.989x10^33g = 2x10^33g = 2x10^30 kg
One year = 31.5x10^7 s
1 pc = 3.26 light-yr = x 1018cm=3.1x1013km
1AU = 1.496x1013cm = 150,000,000 km (astronomical unit = mean distance between earth and sun)

5. Sizes of Everything
Universe: open or flat -- infinite; closed cm
Galaxies: no of stars ; size ~ 1023cm~3x104pc
Stars: cm (most radii)
Typical separations: 1018cm ~ 1 pc
Planets: RE=6.4x103km = 6.4x108cm
Separations: ~ 1 AU
Mountain: Tallest ~ 10 km, more typical ~6 km Hm/RE=6.4km/6.4x103km=1.0x10-3
People: 1.5m = 1.5x102cm (~5 feet)
Visible light: wavelength=500nm=5x10-5cm
Atom: 0.1nm=10-8cm=10-10m (X-ray wavelength)
Nucleus: 1 Fermi = 10-13cm = 10-15m
Write math symbols for >, >=, equivalent, approx equal, proportional, roughly equal

6. Time Scales of the Universe
Time since the Big Bang: ~1.4x1010 yr
Galaxies formed: ~1.3x1010 yr ago
Solar system formed: 4.55x109 yr ago
Oldest rocks on Earth: 3.8x109 yr BP
Earliest life forms: ~3.5x109 yr BP
Earliest hominids:~2x106 yr BP
Mountains: Appalachians:~2.5x108yr BP; Rockies: 7x107 yr BP
Human lifespan: ~75 yr
Oscillation time for visible light: ~2x10-15 s
Time for light to pass the nucleus of an atom: ~3x10-24s

7. Astronomy 1020 Lab Requirements Bring to lab next week
Astronomy: A Laboratory Textbook, 3rd Ed., by John W. Wilson
Metric ruler ~ 30 cm long
Protractor
Drawing compass
Scientific calculator (not a cell phone)