MarsPHY 102 1st EditionOutline of Last LectureI. Yearly Solar Motionsa. Position of the sun in the skyb. North to South motion of the sunII. General Planetary Motiona. Inferior Planetsb. Superior PlanetsIII. ZodiacIV. Theories of Heliocentrism and othersa. Philolaus Cosmologyb. Earthshinec. Homocentric Spheres of Eudoxusd. UnacceptanceOutline of Current Lecture I. Eratosthenes and the Size of the EarthII. Geocentrisma. Eudoxusb. Appoloneusc. Ptolemaic SystemIII. Copernicus, Brahe, KeplerThese 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.a. Copernicusb. Brahec. Kepleri. Elliptical Motionii. Equal Areasiii. Period^2 = Distance^2Current LectureI. Eratosthenes and the Size of the Eartha. “How could Earth move given its great size?”i. In early days, rest was considered the natural stateii. Angels were believed to move the celestial beingsiii. Shows that evidence can be suspectb. Eratosthenes – 200 B.C.i. Traveler and scientistii. In a well in Syene on the first day of summer, sun was right overhead, 1 year later goes to a well in Alexandria and sees the sun was at a different angleiii. Equation he used: angle between the two cities/360 degrees = known distance between the two cities/Circumference of the earthiv. Evidence based on logic and reasoning leads to knowledgeII. Geocentrisma. Homocentric spheres of Eudoxusi. Homocentric spheres did not account for planets appearing brighter opposite the sun (superior planets get brighter when opposite the sun)ii. Homocentric spheres did not accurately predict motion of the planetsb. Example: headlights get closer, lights appear brighterc. Retrograde loops:d. Appolonius introduces epicyclesi. Deferent – a point about which a planet movesii. Epicycle – planet moves around a deferent and epicycle moves around the earthiii. Says when the planet retrogrades that it is brightest because it is closer tothe earthiv. Doesn’t account for irregularityDeferentMarse. Ptolemaic Systemi. Extension of Appollonius’s deferent and epicycle1. Accepts and utilizes circular planetary motionii. Summer is 92 days longiii. Winter is 89 days longSun appears to travel through these 90 degree section equally quicklyEEIII. Copernicus, Brahea. Nicholas Copernicus Marsi. 19 Feb 1473 – 24 May 1543ii. Ptolemaic system is inaccurate and overly complex Earthiii. Simpler sun-centered system that includes perfect circular motioniv. Retains tiny epicyclesv. Mars is moving more slowly so as we view Mars its positionchanges among the background starsvi. Accounts for retrograde motionvii. Year – earth’s revolutionviii. Day – earth’s rotationix. Month – moon’s revolutionx. Copernican system is more simple, less circlesb. Tycho Brahe – Tychonic Systemi. 14 Dec 1546-24 Oct 1601ii. Cannot accept Earth’s motioniii. Sun orbits earth, planets orbit sunPlanetsMoon Suniv. Sky made of “quintessant” essence, not of the earth’s materialsc. Johannes Kepleri. Rejects perfect circular motion studying Marsii. Hven – worked there with an assistant – most meticulous of all observers of astronomyiii. Discovered 3 law:1. Elliptical motion a. Measured the angular distance between the earth and mars after 687 days (1 mars year)b. Different at different times, means it’s an ellipse!2. Equal areasa. As a planet gets closer to the sun it speeds up, as it gets farther it slows downb. Sumer is 93 days because we are farthest from the sun3. Period^2 = Distance^3iv. System used