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MIT AST 100 - Astronomy 100

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Astronomy 100 Tuesday, Thursday 2:30 - 3:45 pm Tom Burbine [email protected] MaterialGoals of the Class for MeCourse is divided into 4 SectionsStar TrekBattlestar GalacticaThemeGradingGradesExamsMakeup ExamsHomework1st HW assignmentPRSStudent ContractIf you are not enrolled in the class and want to beNow some AstronomyThings you need to know because we will use the metric systemSo how far have we travelled?So how far have we travelled?Scientific NotationHow do you write numbers?How do you do multiply?How do you divide?Terms for large distancesLight YearWhen we are looking at stars or galaxiesMilky Way GalaxyStars in the UniverseAnswerTimeSpaceship EarthEarth is rotatingWe are rotating around the SunStars near us are also movingDoppler ShiftStars in the Milky Way are rotatingThe Universe is also expandingAstronomy 100Tuesday, Thursday 2:30 - 3:45 pmTom [email protected] Material• Course Website: www.xanga.com/astronomy100• Textbook: Stars, Galaxies, and Cosmology, The Cosmic Perspective, 3rd Edition by Bennett, Donahue, Schneider, and Voit•PRS:You need to have an InterWrite PRS transmitter.Goals of the Class for Me• The class should be interesting• You should learn some fundamental concepts in Astronomy• Motivate a few people to be Astronomy majorsCourse is divided into 4 Sections• The Night Sky • Gravity, Light, and Spacetime• The Nature of Stars • Galaxies and the UniverseStar Trek• Antimatter• Faster than Light Travel• Alien RacesBattlestar Galactica• Interstellar TravelTheme• Does life exist elsewhere in the solar system?• Does life exist elsewhere in the Universe?Grading• 4 in-class exams and a cumulative final• I will drop the lowest test score• The average of the 4 highest scores will be 80% of your grade• 10% of your grade will be your homework score• 10% of your grade will be from PRSGrades• 90-100 You get some type of A• 80-90 You get some type of B• 70-80 You get some type of C• 60-70 You get some type of D• If the average is not reasonable, I will curve upExams• #1 Feb 15 Tuesday• #2 March 10 Thursday• # 3April 7 Thursday• #4 May 10 Tuesday• Final May 14-20Makeup Exams• If you miss an exam, I need a doctor’s excuse or documented family emergency to give a makeup exam• If you are going to miss an exam for a religious observance or university-sponsored activity, I need to be contacted in advance• I will be very strict since I am dropping one examHomework• You need to get a maximum of 20 homework points out of ~30 possible points• If you get 20 points, you get 100% homework score• I will divide your homework score by 20 to calculate your percentage with a maximum total of 100% • Primarily the assignments will be on OWL1stHW assignment• You need to find an article on astronomy (web, newspaper, magazine)• Print it, copy it, or cut it out• Read it• Write one paragraph on why it is important or why you found it interesting• Staple them together• Write your name and ID number on front page• Write the first three letters of your last name in big letters on front page• Hand it in during next class• You will then get 1 Homework credit!!PRS• 10% of your grade will be from using PRS• You need to get a maximum of 20 PRS points out of ~30 possible points• I will divide your PRS score by 20 to calculate your percentage with a maximum total of 100%Student Contract• I need you to turn it in by the 2ndclass• If I do not get it, I will assume you have dropped the classIf you are not enrolled in the class and want to be• Talk to me afterwards• I will try to get everybody in the class who wants to be in itNow some Astronomy• The first thing we will talk about is distance• The huge distances that occur in the universeThings you need to know because we will use the metric system• one kilometer is 5/8 of a mile• one kilometer is 1000 meters• one meter is approximately a yard or 3 feet• We will use the metric system in this class• Do you all remember the Mars Climate Orbiter?590 meters5,900 million km = 5,900,000 million metersThe distances are one ten-billionth of their actual valuesSo how far have we travelled?• What is the only planetary body that humans have walked on?• How many planets have spacecraft visited?• What spacecraft has travelled the farthest from Earth?• How far away is the closest star system?So how far have we travelled?• What is the only planetary body that humans have walked on?• Moon (385,000 km away)• How many planets have spacecraft visited?• All planets except Pluto• What spacecraft has travelled the farthest from Earth?• Voyager 1 (14 billion km away)• How far away is the closest star system?• ~40 trillion kilometers away (Alpha Centauri)Scientific Notation• 10000 = 104• 100000000 = 108• 10000000000 = 1010• 100000000000000000000 = 1020• 0.001 = 10-3• 0.0000001 = 10-7How do you write numbers?• 31700000 = 3.17 x 107• 2770000 = 2.77 x 106• 0.00056 = 5.6 x 10-4• 0.0000078 = 7.8 x 10-6How do you do multiply?•106 x 108 = 10(6+8)= 1014•10-5 x 103= 10(-5+3) = 10-2• (3 x 104 ) x (4 x 105) = 12 x 10(4+5) = 12 x 109 = 1.2 x 1010How do you divide?•108/106 = 10(8-6)= 102•10-6/10-4 = 10(-6-(-4))= 10-2• (3 x 108)/(4 x 103) = ¾ x 10(8-3) = 0.75 x 105 = 7.5 x 104Terms for large distances• In the Solar System• astronomical unit (AU) = distance between Earth and Sun (1.5 x 108 km)• Mercury is at 0.4 AU from the Sun• Jupiter is at 5.2 AU from the SunLight Year• A light year is the distance light travels in a year• The speed of light is the fastest anything can travel in the universe• How far is a light year: (3 x 108 m/s) x (1 yr) x (365 days/yr) x (24 hr/day) x (60 min/hr) x (60 s/min) = 9.46 x 1015m• Alpha Centauri is 4.4 light years away from EarthWhen we are looking at stars or galaxies• We are looking into the pastMilky Way Galaxy• Milky Way is 100,000 light years in diameter• There are ~100 billion stars in the Milky WayStars in the Universe• Say there are 100 billion galaxies• Each galaxy has 100 billion stars• So how many stars in the universeAnswer• Number of stars in universe • = (100 x 109) x (100 x 109) = 10000 x 1018 = 1 x 1022• This is about the same number of grains of sand in every beach in the worldTimeSpaceship Earth• We are travelling through the Universe• Velocity =


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