# Chapter 01 - Lecture 2 - Numbers and Light Travel Time.pdf...

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Introduction to AstronomyNumbers and Light Travel Time Presented by Robert WagnerNumbers in AstronomyAstronomy studies both the very large and very small Numbers need to be expressed in scientific notationExample – 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 movedMove the decimal point to the left – positive exponent ; to the right – negative exponentScientific Notation - ExamplesExample 1: 314,000,000We move the decimal point to the left 8 placesThe number becomes 3.14x108 Example 2: 0.00004563We move the decimal point to the right 5 places The number becomes 4.563x10-5SI or Metric UnitsAll scientific measurements are made in metric units Meter for length

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