1.13 Astro 1

1.13 Astro 1 - Astro 1 Section 1 Professor Brandt Wednesday...

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Astro 1, Section 1, Professor Brandt Wednesday January 13th 1999 Announcements: Lecture notes: How big is the Universe? How small are we? Demonstration of how to find the Big Dipper Title of class We will cover atoms (5x10 -9 cm) to galaxies (1x10 23 cm) 100 000 000 000 000 000 000 000 cm in a big galaxy want a way to write down very large numbers without all the zeroes --called scientific notation To use scientific notation count the zeroes Examples: 10cm = 1 x 10 1 cm 100 cm = 1 x 10 2 cm 1000cm = 1 x 10 3 cm Million stars in glob cluster = 1000000 stars = 1x10 6 stars for 2 billion stars = 2x10 9 for 2.5 billion stars = 2.5x10 9 Now we also want to be able to do simple math with scientific notation to get relative sizes radius of earth is 6x10 8 cm radius of solar system is 6x10 14 How many times bigger is radius of solar system than the radius of the earth? =1x10 6 Simple rule is 10 a /10 b = 10 (a-b) in the above example 14-8 = 6 so 1x10 6 solar system radius is about a million times larger than the

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Unformatted text preview: earth's radius A few more useful numbers • distance to nearest star = 4x10 18 cm • size of a galaxy = 3x10 22 cm • distance to nearest galaxy = 2x10 23 cm So how much bigger is the distance to the nearest galaxy as the size of our galaxy 2x10 23 / 3x10 22 = 2/3 x10 1 = 6.6 Scale model of solar system Earth is 1/10 of a cm in size The solar system is the size of campus Where is the nearest star? about the distance to Los Angeles Discuss Video Lots of distances in that video In this course you will learn how people actually measure those giant distances Today we'll start with a well known method to astronomers called parallax Parallax = a method for finding the distances to fairly nearby objects like planets and some stars. Far away objects move less. Astronomers use the same effect with 2 telescopes to determine distances...
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• Spring '99
• Brandt

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