Lecture 2: Overview of the solar system: Background for discussion of Mars and Saturn Mathematics in astronomy: the essence of physical sciences like astronomy is the mathematical structure of the universe. This is a Hellenistic idea. A useful tool: scientific notation in expressing very large and very small numbers

Scientific Notation: A shorthand for expressing very large or very small numbers 1640 = 1.64 X 1000; 1000=10X10X10 = 103; 1640 = 1.64 X 103 , OR 1.64E+03. 6,280,000 = 6.28X1,000,000; 1,000,000=10X10X10X10X10X10 =106 ; 6,280,000 = 6.28X106 = 6.28E+06 Little numbers too; 0.0015 = 1.5/1000 = 1.5X(1/1000) = 1.5X(1/(10X10X10)) = 1.5X(1/103) = 1.5X10-3 =1.5E-03

An Overview of the Solar System

Size scales in the solar system Basic unit: 1 meter 1 kilometer = 1000 meters = 0.6214 miles Diameter of Earth: 12756 kilometers (~ LA to Sydney) Closest object in space: Moon, 384,000 km average distance Most prominent object is astronomy: Sun, 149.6 million kilometers; 1 Astronomical Unit demo

The Sun

Facts about the Sun Distance: 149.6 million kilometers = 1.496E+11 meters = 1 astronomical unit Radius = 695,990 kilometers = 6.960E+08 meters (109 times radius of Earth) If Earth were scaled to 1 foot globe size, the Sun would extend from goal line to 30 yard line at Kinnick stadium The Sun, not the planets (including Earth) is the dominant object in the solar system

The Terrestrial Planets Distance (au) Size Mercury 0.387 0.38 Venus 0.723 0.95 Earth 1.00 Mars 1.523 0.53

The Jovian Planets Planet Distance (au) Diameter Jupiter 5.2 11.2 Saturn 9.5 Uranus 19.2 4.0 Neptune 30.1 3.9

The Earth and Mars

But… the Earth and Saturn