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Unformatted text preview: Wednesday, August 30, 2006 9:46 AM • 1 Au is defined as the average distance between the earth and the sun • An arcsec is a fraction of a degree o 1 degree has 60 acrminutes o 1 arcminute has 60 arcseconds o 1 degree has 3600 arcseconds • 1 Parsec is defined as 3.26 lightyears o At a distance of 1 parsec, a length of 1 AU subtends an angle of 1 arcsec • A lightyear is defined as the distance light travels in one year. Wednesday, September 06, 2006 9:41 AM • Two reasons for seasons o The tilt is the sole reason for different seasons • Has two effects 1. The concentrations of lights are different a. Accounts for about 30% of temperature difference in seasons 2. Longer exposure to sunlight during the summer and less exposure in the winter a. Accounts for about 70% of the temperature difference in season 1. The distance from the sun has absolutely nothing to do with the seasons o In fact, during summer, we are farthest from the sun 2. Polaris will not always be the north star 3. When the sun crosses the Meridian it is noon o The Meridian is an imaginary line from north to south, which cuts West and East in half 4. Every 15th longitude is a center of a time zone 5. The clock is set on that longitude for noon on vertical equinox 6. Solar day o During one day the earth rotates 361 degrees • This causes another four minutes to be factored ine 7. Siberial day o A true 360 degree turn Friday, September 01, 2006 10:13 AM • Declination o How far north or south you are from the equator • Vertical Equinox o Used to set plots Friday, September 08, 2006 9:42 AM • The source for the solar system is the sun • Since the earth and the sun are spherical o At the very most, only half of each are lit • If the right of the moon is lit its waxing • If the left side of the moon is lit then its waning • When we can see the moon during the day its because the earth is reflecting the suns light upon it. • The moons rotational period equals it orbital period o Means that the same side of the moon will always face the earth • Everyone on earth has seen the same side of the moon • Geosynchronous-an object in orbit which stays above the same spot on the earth constantly • What percent of the lit side can you see The Cause of Moon Phases activity 1. d 2. 3. 4. F 5. C-Half of the moon is illuminated by the sun 6. A-None of the moon is visible to the earth 7. No because even though half of the moon is lit by the sun, we can only see a quarter of that side and a quarter of the unlit side Ranking Moon Phases activity 1. A,F,E,B...
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This note was uploaded on 04/28/2008 for the course ASTR 1101 taught by Professor Campbell during the Spring '08 term at LSU.
- Spring '08