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midterm studyguide - Astronomy Midterm Chapters 1-3 Chapter...

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Astronomy Midterm Chapters 1-3 Chapter 1: Charting the Heavens 1. – Our Place in Space -Earth is average; we don’t occupy any special place in the universe Astronomy – the study of the universe - universe – totality of all space, time matter, and energy w/in -scales of the universe are very large -measure in light-years – the distance light travels in a year – approx. 10 trillion miles -How do we study astronomy? -make measurements explain measurements make predictions -cycle repeats continuously -must test your theories! Does your theory predict what is to come? Four Main Areas of Astronomy: 1) tools – physics and mathematics a. telescopes, etc. 2) a. less massive than stars b. exist forever (stars don’t) 3) stars – make nuclear energy, eventually die 4) a. contain stars, planets, gas, and dark matter – everything that we do not see b. all gravitationally bound 2. – Scientific Theory and the Scientific Method Scientific theories – must be testable -must be continually tested -should be simple yet elegant -can be proven wrong, but they can never be proven to be 100% right -observation leads to theory theory leads to predictions consistent w/ previous observations predictions of new phenomena are observed -if observation agrees w/ the predictions, more predictions can be made -if not, a new theory can be made 3. – The “Obvious” View -simplest observation – look at the night sky -about 3,000 stars visible at any one time -distributed randomly but human brain tends to find patterns -group stars into constellations – figures having meaning to those doing the grouping -useful – Polaris – almost due North
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-not so useful – astrology – makes predictions about individuals based on the star patters at their birth -stars that appear close in the sky may not actually be close in space The Celestial Sphere: -stars seem to be on the inner surface of a sphere surrounding the Earth (they aren’t) -they seem to move from E W where their relative positions stay the same -we can use 2D spherical coordinates (similar to latitude and longitude) to locate objects in the sky -use latitude (declination) and longitude (right ascension) as we do on Earth on celestial sphere - declination – degrees N or S of celestial equator (+90º or -90º) - right ascension – measured in hours, minutes, and seconds Eastward from position of Sun at vernal equinox -astronomers speak in terms of angular positions and separations -full circle contains 360º - Earth rotates once on its axis in 24 hours or 15º/hour -each degree contains 60º (arc-minutes) -in 1 minute, Earth rotates 15’ -each arc-minute contains 60” (arc-seconds) -in 1 second, Earth rotates 15” -angular size of an object depends on actual size and distance away 4. – The Earth’s Orbital Motion Solar and Sidereal Days: -daily progress of Sun and stars across sky is called diurnal motion - sidereal day
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This note was uploaded on 10/14/2008 for the course ASTR 100 taught by Professor Rhodes during the Fall '08 term at USC.

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midterm studyguide - Astronomy Midterm Chapters 1-3 Chapter...

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