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 0.1 = 10-1 .01 = 10-2 .001 = 10-3 etc 2000 = 2x103 .0035 = 3.5x10-3 (nx10p)x(mx10q) = (nxm)x10p+q 2.5x1019 x 3.0x10-5 = 7.5x1014

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: 240,000 240000 240x103 2.4x105

Drake’s Equation 1022 stars in the universe times 1 suitable planet per star Probability of life Probability of intelligent life given life We concluded that it is unlikely we are alone.

Size of Things centimeters 10-2 sand grain 100 thumbtack 10-4 DNA 10-7 water molecule 10-8 atom 10-15 atomic nucleus 100 thumbtack 101 baseball 102 human 104 football field 105 kilometer 108 Texas 109 World 1011 Moon’s Orbit 1013 Distance to Sun 1015 Solar System 1018 Nearest Stars 1023 Milky Way Galaxy 1025 Nearest Galaxies 1029 Universe