sign in sign up
<<
Home , Planetarium

Study Points • Describe the geocentric and the heliocentric models of the . • The word derives from the Greek "planetes" which means wanderer. Why were the called wanderers? • Explain Aristotle’s main argument against the heliocentric model. • What was Aristotle’s other (and weaker) argument against the heliocentric model? • Who gave the first evidence in favor of the heliocentric model? What was the evidence? • Who added the mathematical calculations to the ? • When a planet undergoes retrograde motion, what does it look like in the sky and what direction does the planet move day to day? • How did the geocentric model explain retrograde motion? • How did the heliocentric model explain retrograde motion? Before the Copernican Revolution

Part 1 of 2 Lectures on the Copernican Revolution Before the Copernican Revolution – Greek • Greeks (influenced by Babylonia, Mesopotamia, Egypt, Rome) • ~700 BC to ~140 AD • Some ideas and people

• Know the starred* items Two Different Solar System Models Everything orbits around what?

Earth

Heliocentric Model* Geocentric Model* - Sun-centered* - -centered* (from Copernicus, 1473-1543AD) (from Aristotle, 384-322BC) Astronomy Before the Copernican Revolution • People all over the world tracked Sun, , and to keep time and seasons quite accurately – Useful for planting & navigating • Many understood the Moon reflected sunlight • Few understood how objects really moved in space Discuss • How do we know the Sun is at the center of our solar system? Can you think of ways to prove the Earth orbits around the Sun? • What is the evidence you could use to prove to a member of the “Flat Earth Society” that our planet is, indeed, round?

• Attendance: Write down your full name and your best reason for the Earth being round. Greeks ~500 BC • What is the sun? Fire? • Tiny lights in the sky? • Why do 7 lights wander among the others?* • 7 Planetes* = wanderers* • The 7 included: Sun, Moon, Mercury, Venus, Mars, Jupiter & Saturn • The 7 moved differently than the stars science.msfc.nasa.gov/ ssl/pad/solar/surface.htm imagine.gsfc.nasa.gov/.../ news/22apr02.html http://artsci.shu.edu/physics/1007/retro2.gif Prior to the Copernican Revolution – Greek Astronomy Pythagoras of Samos ~500 BC • Earth is a sphere • Sphere is perfection in math • Crystal spheres for 7 planetes: Sun, Moon, 5 planets • Already thinking geocentric

http://library.thinkquest.org/C0126626 /fate/geocentric.jpg

Prior to the Copernican Revolution – Greek Astronomy Plato ~360 BC • Heavens are perfect, unchanging (from mathematical perfection) • Heavenly motion must be in circles and uniform – starting with simplest first

Prior to the Copernican Revolution – Greek Astronomy Aristotle ~350 BC • Plato’s student • Earth: corrupt, changeable, imperfect – Separation of perfect heavens and Earth • Arguments for geocentric model* – No parallax of stars** (main argument) • Should see parallax with heliocentric (we do now) – Moon would be left behind if Sun-centered* • Parallax is the apparent change in position of an object due to the change in position of the object or the observer – Parallax thumb demonstration Prior to the Copernican Revolution – Greek Astronomy Aristarchus ~300 BC • First evidence for Heliocentric solar system model • Measured size of Sun based on the Sun being much larger than Earth* • Measured Sun was much farther away than Moon • Eratosthenes, northern Africa, measured size of Earth ~240 BC Prior to the Copernican Revolution – Greek Astronomy Ptolemy ~140 AD • Geocentric model* (often called the Ptolemaic system) • Mathematical model of universe* – Perfect Bodies and orbits: circles, spheres – Uniform motion – Epicycles explain retrograde motion* – Forward motion on half of epicycle*; Backward motion on other half* Prior to the Copernican Revolution – Greek Astronomy From Cycles of the Sky & Moon Lectures Already know this: • Minute to Minute: the Sun, Moon, stars, planets appear to rise in

• Day to Day: Moon moves

• New information: • Day to Day: Planets typically move

• Retrograde Day to Day Motion: Planets move From Cycles of the Sky & Moon Lectures Already know this: • Minute to Minute: the Sun, Moon, stars, planets appear to rise in East and set in West due to Earth’s spin (rotation). (East to West) • Day to Day: Moon moves West to East due to Moon’s orbit (revolution) around Earth. New information: • Day to Day: Planets typically move West to East due to their orbits around the Sun. (similar to Moon) • Retrograde Day to Day Motion: Planets move East to West due to their orbits around the Sun and the difference in speeds of Earth and other planet. Retrograde Motion (Day to Day) Sometimes planets moved backwards against the background of stars.

Retrograde motion is East to West and observed day to day. Minute to minute motion across sky is still East to West due to Earth’s rotation. Ptolemy • Geocentric Model • Perfect circles, spheres, uniform motion • Added epicycles to explain retrograde motion*

Earth Mars’ Epicycle Mars Both models explain observations…

Retrograde motion of planets

Copernican Revolution Retrograde motion – Geocentric Explanation

• Planets ride on epicycles • Sometimes appear to move backwards

Prior to the Copernican Revolution – Greek Astronomy Retrograde motion – Heliocentric Explanation • One planet overtakes another planet. • Slower planet appears to move backwards. • Retrograde motion is due to a difference in speeds of the planets.*

Copernican Revolution Retrograde motion – Heliocentric New (and correct) explanation of retrograde motion of the planets: due to speed difference* •Retrograde (westward) motion of a planet occurs when the Earth passes the planet. •Ptolemy’s epicylces unnecessary Copernican Revolution Retrograde Motion of Mars

Copernican Revolution https://upload.wikimedia.org/wikipedia/commons/7/70/Apparent_retrograde_motion_of_Mars_in_2003.gif Retrograde Motion of Mars

Copernican Revolution

Watch: https://www.youtube.com/watch?v=2lDcBwkeeuU Big Gap Before Copernican Revolution • Dark Ages in Europe, ~400-1400 AD – Roman libraries sacked, famine, wars, & plague – Europe sees very little progress • Islamic Golden Age of Science, ~500-1200 AD

Long time between Ptolemy ~140 AD to Copernicus ~1500 AD

Prior to the Copernican Revolution Big Gap Before Copernican Revolution • Dark Ages in Europe, ~400-1400 AD • Islamic Golden Age of Science, ~500-1200 AD – Al Mamon starts Baghdad school of astronomy ~800AD – Islamic criticized & improved Ptolemy’s model – Native Americans & Chinese document supernova in Taurus , now Crab , 1054 AD – built in Asia, Middle East, & northern Africa

Long time from Ptolemy ~140 AD to Copernicus ~1500 AD Prior to the Copernican Revolution Summary

• Before Copernicus ~700BC to 140 AD • Geocentric Model Dominated – Pythagoras of Samos – Plato – Aristotle* – Aristarchus* – Ptolemy* Observation • Planetarium Start Jan. 28; Due May 5 (10 points) Go to a planetarium show • Best Option: Como Planetarium Class Field Trip on Tuesday, Feb. 4. (FREE!) at Como Elementary School – Bus from Minneapolis College at 8:15am from the corner of Spruce Place & Harmon Place on the south side of Science bldg., by T bldg. Bus returns by 10:30am. – Free show at 9am this day only. – You can drive on your own but you need to be early because the door will be locked. Address: 780 West Wheelock Parkway, St. Paul, MN • If you do not go to the Como Planetarium with the class, then you can go any time on your own at your own cost – you pay. See the link at the top for options: – Como Planetarium Tuesdays at 7pm usually – see their calendar – Bell throughout the week – Jackson Middle School classroom planetarium – Make a Shoebox Planetarium You only need to do this once. If you go to Como on Feb. 4, then there is no need to do any more for this. Observation Projects

OBSERVATION PROJECTS: 135 points available, 100 pts max All Observations due by midnight (11:59pm) on their due date. You can hand in the observation during class, email a picture by midnight, or submit on D2L Assignment Submissions. ✓ Earth-Sun Scale Model Due Jan. 28 (10 points) Make scaled model & take picture ❑ Sunset – Part 1 Due Feb. 18 (10 points) Take 1st picture of sunset (same location) ❑ Moon Phases Due Mar. 5 (10 points) Observe 4 phases & record in table ❑ Planetarium (Plan) Due May 5 (10 points) See a show Feb. 4 ❑ Stargazing (SG) Due May 12 (20 points) Go stargazing & write report ❑ NEW: Telescope (Tel) Due May 12 (20 points) Look through a telescope ❑ NEW: Moon Craters (MC) Due May 12 (10 points) Look at moon craters

FUTURE: (don’t start yet) ❑ Student Conference Start Feb. 25; Due Feb. 27 (occurs on Feb. 25) (5 points) ❑ Astrophysics Lecture or Report Start Mar. 19; Due Apr. 21 (10 points) Attend lecture Apr. 14 or write report ❑ Sunset – Part 2 Start Apr. 7; Due Apr. 28 (10 pts) 2nd sunset picture, same location ❑ Astronomy News Evaluation Start Mar. 31; Due May 5 (20 pts) New report Earth – Sun Scale Model Observation • Scale 1 mm = 2000 mi (equivalently 1 cm = 20,000 mi and 1 m = 2,000,000 mi) • Given data Sun is 900,000 mi in diameter Earth is 8000 mi in diameter distance from Earth to Sun is 100,000,000 mi

New: Moon is 2000 mi in diameter distance from Earth to Moon is 240,000 mi • What does this look like? Homework • Continue flashcards of STUDY POINTS • Do D2L Brightspace Quizzes 1 – 3 • Come prepared to Lab this week • Test 1 in 1 & 1/2 week, Tuesday, Feb. 11 – To prepare: study points & 4 D2L Brightspace quizzes – About 60 multiple choice questions. Bring a pencil. – Optional: bring calculator (not graphing); some available here • Grades updated weekly (check for mistakes) • Planetarium Field Trip Tuesday, Feb. 4 – be early: 8:15am! • See Observations on previous slide