Transcript Lecture 2

ASTR 1200
Announcements
..
First Observatory Tuesday
(9/2) 8:30pm
..
(telescope dome building west of events center)
AND
Class will be in Fiske Planetarium on Tuesday
(geodesic dome west of events center)
Website
http://casa.colorado.edu/~wcash/APS1200/APS1200.html
Last Time
We generally agreed:
We really don’t know much about the nature of things.
Science has a long way to go.
We don’t understand consciousness and mostly think it is
related to some phenomenon we haven’t yet begun
to describe.
We are probably not alone, but doubt the veracity of UFOs.
Started Drake’s Equation.
Scientific Notation
an atomic nucleus is .000000000000001m
a galaxy is 200000000000000000000 miles away
So awkward we MUST use scientific notation
an atomic nucleus is 10-15m
a galaxy is 2x1019 miles away
Scientific Notation (2)
1 = 100
10 = 101
100 = 102
1000 = 103
2000 = 2x103
.0035 = 3.5x10-3
0.1 = 10-1
.01 = 10-2
.001 = 10-3
etc
(nx10p)x(mx10q) = (nxm)x10p+q
2.5x1019 x 3.0x10-5 = 7.5x1014
2.4 x1019
12
11

0
.
3
x
10

3
x
10
8 x107
Scientific Notation (3)
Errors
2.5(±0.2)x1019
Doesn’t make sense to write 2.500(±0.2)x1019
Does make sense 2.500(±.002)x1019
Question
Two hundred and forty thousand, when
written in scientific notation is:
a) 240,000
b) 240000
c) 240x103
d) 2.4x105
Drake’s Equation
1022 stars in the universe
times
1 suitable planet per star
times
Probability of life
times
Probability of intelligent life given life
We concluded that it is unlikely we are alone.
Size of Things
centimeters
100
101
102
104
105
108
109
1011
1013
1015
1018
1023
1025
1029
thumbtack
baseball
human
football field
kilometer
Texas
World
Moon’s Orbit
Distance to Sun
Solar System
Nearest Stars
Milky Way Galaxy
Nearest Galaxies
Universe
10-2
10-4
10-7
10-8
10-15
sand grain
DNA
water molecule
atom
atomic nucleus