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REVIEW SHEET: ASTRON 103, PART I. Apparent Motions in the Heavens; (actual motions responsible) Daily Motion (Earth’s rotation on its axis) Annual Motion of the Sun (Earth’s revolution around the Sun) Precession of the Equinoxes (wobble of Earth’s axis – 26,000 years) Seasons Tilt of earth’s axis (23.5°) How angle of sunlight, number of hours of daylight, vary during year Vernal, Autumnal Equinoxes; Summer, Winter Solstices Moon Phases Waxing (New Moon to Full Moon) Waning (Full Moon to New Moon) Difference between Moon’s sidereal, synodic periods Eclipses Solar eclipses (mode of occurrence; kinds) Lunar eclipses (mode of occurrence; kinds) Why eclipses aren’t seen every month Tides Reason for twin bulges (action of Moon’s gravity on Earth, oceans) Celestial Sphere North, South Celestial Poles Altitude of North Celestial Pole [Polaris] (how varies as function of latitude) Celestial Equator; Ecliptic Horizon Coordinate System: Altitude, Azimuth Equatorial Coordinate System: Right Ascension, Declination Ptolemy’s geocentric model of Universe Explanation for retrograde motion Copernicus’s heliocentric model of Universe Explanation for retrograde motion Kepler’s Three [empirical] Laws of Planetary Motion Elliptical orbits Area Law Harmonic Law: P2 = a3 Newton’s Three Laws of Motion Law of Inertia Force Law Law of Action-Reaction Newton’s Law of Gravity (obeys inverse-square law) Analogy between apple, moon (argument for universal gravitation) Newton’s version of Kepler’s Third Law Escape Velocity Einstein, Relativity Theories Special Theory (1905) – length contraction, time dilation, mass increase General Theory (1916) – equivalence principle Electromagnetic Spectrum Relation between speed (c), frequency (f), and wavelength (λ) Relative energies, frequencies, wavelengths. Light; Color-Temperature relations Wien’s Law; Stefan-Boltzman Law Spectra Continuous Emission (bright) line Absorption (dark) line Doppler Effect Optical Telescopes Refractors, Reflectors Magnification Light Grasp Angular Resolution Ground-based vs. space-based Sample Questions – Exam I 1. The Sun’s apparent position against the background stars changes throughout the year because of the ________. a. b. c. d. Earth’s daily rotation Earth’s revolution around the Sun tilt of the Earth’s axis precession of the equinoxes 2. When the Moon reaches its Full phase, it ________. a. b. c. d. rises at midnight rises and sets with the Sun sets at midnight rises at sunset and sets at sunrise. 3. Newton’s Second Law of Motion states that ________. a. force is the product of mass and acceleration b. for every action, there is an equal and opposite reaction c. objects at rest, or in uniform motion, will remain in that state if no outside forces act upon them d. the force of gravity between any two masses decreases with the square of the distance between them 4. What approximate range in wavelengths is the human eye sensitive to? a. b. c. d. 100-300 300-400 400-700 700-900 nm nm nm nm 5. A telescope that collects and focuses light with one or more lenses is called a ________. a. b. c. d. reflector Newtonian Cassegrain refractor 6. Match the astronomers’ names with their contributions below. a. Ptolemy ____ Made the most precise observations of the planets b. Newton ____ Explained retrograde motion with epicycles & deferents c. Tycho Brahe ____ Invented a reflecting telescope ANSWERS: 1:b 2:d 3:a 4:c 5:d 6: c a b