ASTR 151 1nd Edition Lecture 2 Outline of Last Lecture I. Introduction to classII. Hypothesis definedIII. Model definedIV. Scientific Law definedV. Beginning Chapter 1 and 1.1Outline of Current Lecture II. 1.4 Earth`s Orbital MotionIII. 1.5 Motion of the MoonIV. 1.6 Measurement of DistanceCurrent Lectureo Angular Measure Example The distance from the naked eye to the Moon- Theta = 31 arc minutes- 1 Degree = 60 arc minutes- 1 arc minutes = 60 arc minutesII. 1.4 Earth`s Orbital Motiona. Solar Day - Daily cycle is diurnal motionb. Sidereal Day – stars aren`t always in the same place after one Earth rotationc. Earth moves around 12 constellations during the year known as the zodiac, the path is eclipticd. Ecliptic – plane of Earth`s path around Sun; its tilted 23.5 degrees to the celestial equatore. Summer Solstice – Northern point of pathf. Winter Solstice – Southern most point of path- (Both Summer and Winter Solstices points where path crosses celestial equator)g. A combination between a day length and sunlight makes a seasonh. Precession – rotation of Earth`s axis- Earth makes a complete rotation in about 26,000 yearsIII. 1.5 Motion of the Moona. Synodic Month - The moon takes 29. 5 days to go through a cycleThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. Moon phases are created by different amounts of sunlit portions that are visible from Earthb. Sidereal month – time for a full 360 degree rotation around the Earth; its two days shorter than Synodic Month i. Phases:1. Waxing Crescent2. 3rd Quarter3. Waning Gibbons4. Full Moon5. Waxing Gibbons6. 1st Quarter7. Waxing Crescentc. Eclipses happen when the Earth, Moon, and Sun form a perfectly straight linei. Lunar Eclipses1. Earth between Moon and Sun; light reflected from the Earthii. Solar Eclipses1. Moon between Earth and Sun2. Partial when part of Sun is blocked3. Annular when Moon is too far from Earth for totald. Eclipses don`t occur monthly because Earth`s and Moon`s orbit aren`t in the same planeIV. 1.6 Measurement of Distancea. Triangulationi. Measure the baseline and then angles. This calculates distanceii. Use a right triangle for easier useb. Parallaxi. Similar to triangulation but parallax looks at “apparent motion” of an object against distant background from two vantage pointsii. Another way to explain how far apart in angular distance an object seemsto bec. To Measure Earth`s Radius:i. Eratosthenes a Greek mathematician noticed that when the Sun was above in one city, it was at an angle to another 2,300 years ago.ii. Measuring angle and distance between two cities gives us the
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