Introduction to AstronomyNumbers and Light Travel Time Presented by Robert WagnerNumbers in Astronomy•Astronomy studies both the very large and very small •Numbers need to be expressed in scientific notation•Example – The distance from the Earth to the Sun can be written as:•150,000,000 km or 1.5x108km. The latter is more convenient for the vastly larger distances we will deal with!•Scientific Notation •To convert a number to scientific notation, move the decimal point until there is only 1 number to the left – Count the number of places moved•Move the decimal point to the left – positive exponent ; to the right – negative exponentScientific Notation - Examples•Example 1: •314,000,000•We move the decimal point to the left 8 places•The number becomes 3.14x108 •Example 2: •0.00004563•We move the decimal point to the right 5 places •The number becomes 4.563x10-5SI or Metric Units•All scientific measurements are made in metric units •Meter for length•
