History of Astronomy
History of Astronomy AST1002
Popular in Planets, Stars, and Galaxies
Popular in Astronomy
verified elite notetaker
This 3 page Class Notes was uploaded by Margaux Stickney on Wednesday September 14, 2016. The Class Notes belongs to AST1002 at Florida State University taught by Professor Vladimir Dobrosavljevic in Fall 2016. Since its upload, it has received 4 views. For similar materials see Planets, Stars, and Galaxies in Astronomy at Florida State University.
Reviews for History of Astronomy
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 09/14/16
9/12 • people thought the Earth was flat like a pancake • BUT we figured out the Earth is round bc things go UNDER the horizon line • also, at higher altitudes we can see farther into the horizon • Erastothenes (200 BC): Alexandrian astronomer and mathematician who measured the Earth’s diameter • he used an obelisk in Alexandria and an obelisk in Syene and their shadows (which were different at the same time of day), used trig to find the radius of the Earth (and then the diameter) • Plato (400 BC): heavens are perfect • Aristotle (350 BC): crystal spheres with stars, planets, and moons attached to them that are rotating around the Earth at different rates • almost right, but he used a geocentric model • Ptolemy (140 AD): retrograde motion • put forward the theory of epicycles to explain the weird loop (went against the crystal sphere theory): • nobody knew what was in the center of the epicycle???? but if u questioned it u would be burned at the stake • Copernicus (1500): heliocentric model • explained retrograde motion bc as the Earth overtakes Mars in orbit, it appears that Mars is going backwards bc Earth is fast • Galileo (1600): used the telescope, observed the phases of venus • planets don’t twinkle, stars do (jimminy cricket didn't sing twinkle twinkle little planet) 9/14 • Kepler was a student of a prince Tycho De Brache • 20 years of planetary observation • Kepler’s Laws of Planetary Motion: • the orbit of the planets are ellipses, with the sun located at one of the focus of the ellipse • ellipse: (x/a)^2 + (y/b)^2 = 1 • eccentricity is deviation from circle • most planets have a weak eccentricity • Mercury’s orbit is more eccentric • comets have a very large eccentricity, motion is faster as it goes around the sun • The Law of Equal Areas: A line from the planet to the sun sweeps over equal areas in equal intervals of time. Hence, the planet moves faster when closer to the Sun • “rollercoaster law” • a planet’s orbital period squared is proportional to its average distance from the sun cubed 2 3 • P = a • P = orbital period in years, a = distance from the sun in AU • 1 AU = 150,000,000 km = distance between the Earth and the sun 2 • Newton discovered the universal law of gravity: F = G(m g /r ) 1 2 • Law of Inertia: a body continues at rest or in uniform motion in a straight line unless acted upon by some external force • Second Law of Mechanical Motion: a body’s change of motion is proportional to the force acting on it and is in the direction of the force • F = ma • Force = (mass)(acceleration) • Law of Action and Reaction: when a body exert a force on a second body, the second body must exert an equal and opposite force back on the first body
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'