Astronomy- Copernican Revolution, Newtonian Gravity, Solar System – Flashcards
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Geocentric model with epicycles to explain planets' retrograde motion
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Ptolemy (I got tolled in May because I was selfish and did donuts)
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Heliocentric model -still used epicycles so wasn't any more accurate than Ptolemy (but simpler) -retrograde motion is an apparent motion when one planet passes another planet in orbit
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Copernicus
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Accurately measured planets positions and charted their motion -"Greatest naked eye astronomer" -observed a comet and supernova (showed the heavens are changing) -failed to measure parallax of any stars
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Tycho
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Used Tycho's data to fit mathematical motion model to data. Came up with three laws to explain planetary motion.
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Kepler
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First used telescope to observe sky. Made observations that verified the heliocentric model. -also studies how things moved. laid groundwork for Newton's work
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Galileo
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-sunspots (celestial objects imperfect and sun rotates on its own axis) -craters on moon (imperfect) -moons of jupiter (objects were orbiting around something other than the earth) -phases of venus (can't be explained by geocentric model) -rings of saturn (celestial object not a perfect sphere) -stars in milky way (millions of individuals stars, universe larger than thought) -object's natural state not at rest -Sun's rotational period
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Galileo's telescope observations
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Measuring the size of the earth -noon on summer solstice, no shadow in Alexandria -noon on s.s., yes shadow in Syene -sun in Syene 7 degrees from overhead -7 degrees is 1/50 of a circle, so distance between those two places must be 1/50 of the circumference of the earth
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Eratosthenes
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-what they called planets because they moved across the sky at different rate than stars
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wandering stars
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a planet would appear to stop, go backwards, and start moving forward again -all 5 of the planets visible with the naked eye exhibited retrograde motion
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retrograde motion
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circular orbits on orbits -explained by Ptolemy -added "epicycle upon epicycle" to make theory agree with observation
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epicycles
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-renaissance brought new ideas -copernicus introduced new heliocentric model -beginning of rebirth and revolution of science and the methods of science -published book (the year he died)
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Copernicum revolution
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-contradicted intuition (earth doesn't feel like it's moving) and long held religious beliefs (earth at center and immovable) -wasn't any more accurate than Ptolemaic model
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Why Copernicus was hesitant to publish ideas
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effect where position or direction of nearby object appears to shift when viewed from a different position -nearby object has larger parallax
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Parallax
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1. planets orbit in ellipses (not circles) 2. planet sweeps out equal area in equal time 3. relationship between planet's distance from the sun and its period (p^2= a^3) P=orbital period in years A=average distance from sun in AU
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Kepler's Three Laws of Motion
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1. Earth could not be moving because objects in the air would be left behind 2. Non-circular orbits are not "perfect" as heavens should be 3. If earth were really orbiting sun, we would detect stellar parallax
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Objections to Heliocentric Model
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any change in velocity
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acceleration
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magnitude and direction
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velocity
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-first to come up with mathematical model to describe gravity and forces
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Isaac Newton
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1. body remains at rest or moves in a straight line at constant speed unless acted upon by an outside force 2. (net) force= mass x acceleration 3. whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body
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Newton's 3 Laws of Motion
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an object's tendency to resist a change in motion
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Inertia
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Newton's laws prove all of Kepler's
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Relationship between Newton and Kepler
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-independent of mass -a=9.8 m/s^2 -if elevator were accelerating down at -9.8 m/s^2, you would register on a scale as weightless -there is gravity in space....weightlessness due to constant freefall
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Free Fall Acceleration
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-rocky, small, close to the sun, few moons, no rings -Mercury, Venus, Earth, Mars
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Inner (Terrestrial Planets)
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-much smaller than earth -cratered
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Mercury
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-closest to Earth's size -"sister planet" -permanent cloud cover -"see" surface by sending radio waves through the clouds, bounce off surface -gently rolling hills and volcanoes
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Venus
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-only surface liquid in solar system -surprisingly large moon -geologically active
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Earth
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-a bit smaller than earth -big shield volcanoes -Valles Marineris as big as US and 3 times as deep as Grand Canyon -Olympus Mons: largest volcano is solar system, 3 times as tall as Everest, so large because of Mars' lack of tectonic plates -river channels suggest water may have been there once
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Mars
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-all 4 have rings -rings are dark and smaller particles (other than saturn)
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Outer (Jovian) Planets
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-largest planet -horizontal bands which are clouds -big red spot=hurricane
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Jupiter
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-second biggest planet -most extensive ring system -rings are fragments of ice and ice-coated rock, large and far apart
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Saturn
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-rocky core, liquid metallic hydrogen shell, molecular hydrogen mantle
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Saturn and Jupiter structure
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-not as big as Jupiter or Saturn -has 27 moons -rings and satellites -hazy atmosphere with few clouds -tilt gives it exaggerated seasons
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Uranus
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-13 moons -giant storm spot
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Neptune
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rocky core, highly compressed water, liquid hydrogen and helium
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Neptune and Uranus structure
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-all Jovians have rings because they all have small moons close-in -impacts on these moons are random -impacts cause small particles to blast off
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Ring formation
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-Ganymede -Titan -Callisto -Io -Moon -Europa -Triton
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7 largest moons (in order) Great Trees Crash Into Movies Everyone Tripped
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-sculpted by volcanic activity -most geologically active body in the solar system
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Io's surface
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-may harbor water under its icy surface
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Europa
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-largest moon in system -larger than mercury
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Ganymede
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-wears scar of asteroid impact
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Callisto
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-has thick, opaque atmosphere rich in nitrogen, methane, and other hydrocarbons
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Titan
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all show evidence of past volcanism or tectonics
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Saturn's medium size moons
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Phobos Deimos -most likely are captured asteroids
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Mars' moons
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-far more numerous -not enough gravity to make them round
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small moons
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-rocky, closer in -most orbit sun in between Mars and Jupiter -orbits of near-earth asteroids cross earth's orbit -cratered and not usually round
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asteroids
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-icy and rocky and are in orderly orbits 30-100 AU from sun (outside Neptune)
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Kuiper Belt objects
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-icy and rocky and are in random orbits extending to 50,000 AU from sun (spherical)
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Oort Cloud objects
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asteroids, Kuiper belt, Oort Cloud
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leftover debris from formation of solar system
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-may come when object in Kuiper belt of Oort cloud gets gravitational kick, can enter an orbit that takes it into the inner solar system -comets have two tails, but don't get them until enter inner solar system -tails always point away from sun
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comet
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-occur when Earth passes through dusty tail debris lefty by a passing comet -dusty particles burn up when enter Earth's atmosphere
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meteor shower
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-pluto and moon charon about same size and are tidally locked which means the same side of charon always faces pluto and charon orbits pluto in one pluto day -for a long time was known as largest object in Kuiper belt -far from sun but unlike the Jovian planets -in 2003 Eris, an object larger than pluto was found
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Pluto
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1. Orbits the sun 2. Massive enough for its own gravity to give it a (nearly) spherical shape 3. clears its orbital neighborhood Objects that don't meet the last are "dwarf planets"
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Definition of a planet
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Pluto, Eris, Ceres, Makemake, Haumea
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Dwarf planets
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-all large bodies in solar system in same direction and same plane -division of two types of planets -swarms of smaller objects
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Clues to solar system formation
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-came from a hug gas cloud of recycled "star dust" -big bang produced H and He -heavier elements created by massive stars, dispersed when stars die -solar system formed from cold cloud of dust and gas called solar nebula 4.6 billion years ago -dust gathers into planetisimals, which gather into protoplanets, which gather up leftover debris and become planets
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Raw Materials of our solar system
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direct- observations of planets themselves (difficult and rare) indirect- measurements of stellar properties revealing the effects of orbiting planets (gravitational tugs, transits)
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Planet detection
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-star and planet orbit around their common center of gravity -star wobbles around that center of mass with same period as planet -we can measure this wobble -most exoplanets found this way
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Gravitational Tugs
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-when a planet crosses in from a star -resulting eclipse reduces star's apparent brightness
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Transit
