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Lecture

# AS101 Lecture 2

5 Pages
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Department
Astronomy
Course
AS101
Professor
Patrick Mc Graw
Semester
Winter

Description
Lecture 2 1/9/2013 12:26:00 PM A sense of scale Size of the observable universe: 130,000,000,000,000,000,000,000 km. (1.3 x 10 to the power of 23) There are a couple of different ways to avoid writing so many zeros. 1. scientific notation 2. use different units. Powers of 10 and scientific notation: 10, 100, 1000, etc. are all powers of 10: they can be though of as multiplied by itself some number of times:  100=10x10=10 to the power of 2 (1 with 2 zeros)  1000-10x10x10= 10 to the power of 3 (1 with three zeros)  1,000,000= 10x10x10x10x10x10= 10 to the power of 6 (1 with six zeros)  number of 0 = exponent in this way, 6 million can be written as 6x1,000,000 = 6x10 to the power of 6. 6,500,000 = 6.5x10 to the power of 6. Negative powers are fractions: 0.1= 1/10 = 10 to the power of -1 0.001 = 1/1000 = 10 to the power of -3 0.0065 = 6.5 x 1/1000 = 6.5 x 10 to the power of -3 Rules of expressing any number in scientific notation  Place the decimal after the first nonzero digit  Count the number of places that the decimal point moved. This gives the power of 10 (the exponent)  If the decimal moved to the left, the power is positive. If the decimal moved to the right, the power is negative. Size of Jupiter: 143,000 km. =1.43x10^5 km. Size of a large bacterium: 0.000002 m = 2x 10^-6 m. Suppose we need to multiply to numbers: (3x10^5) x (2x10^3) = 3 x 2 x 10^5 x 10^3 = 6 x 10^8 A complication: (6 x 10^5) x (5 x 10^3) = 30 x 10^8 … the number in
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