PHY 102, Week 2 notes
PHY 102, Week 2 notes PHY 102
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This 4 page Class Notes was uploaded by Sarah Misurac on Friday January 22, 2016. The Class Notes belongs to PHY 102 at Illinois State University taught by Dr. Justin Bergfield in Summer 2015. Since its upload, it has received 32 views. For similar materials see Atoms to Galaxies in Physics 2 at Illinois State University.
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Date Created: 01/22/16
From Atoms to Galaxies: Lecture 4 (1-20-16) From last time: -Scientific method -Pseudoscience (How can we tell?) -Structure of science (Chemistry, Biology, Physics, etc) -The first science is Astronomy Today: Astronomy The Night Sky (one of the first places scientific inquiry came into play) -The movement of the stars, planets, our sun, were critical for survival for our ancestors -Because of the necessity to predict seasons, astronomy is considered the first science -Ancient observers (i.e., Myans): physical events are quantifiable and therefore predictable Stonehenge: -Started 2400-2200 BC, but they were built by many people (i.e. druids and others) -Current understanding of Stonehenge: Marks the passage of time (seasons) -Also burial site, religious site, etc. -Stones are 50,000 kg each (1 kg= 2.2 lbs) -Largest stone around 150,000 lbs and came from around 20 miles away -Aliens? Prob not. The Birth of Modern Astronomy: Ptolemy and Copernicus nd -Ptolemy: 2 century AD -First planetary models/theories -Earth is at the middle and everything goes around us -Perfect celestial spheres -Accounted for observations (moon’s phase, eclipse of the sun by the moon) -THE theory for 1500 years -Along comes Copernicus (1543) -Hypothesis: Still have spheres, but the sun is in the middle -Simplified lots of observations -Contested humanity’s special place but also made unique predictions -No telescopes yet, so differences couldn’t be measured What to do? We wait for Tycho Brahe and Johannes Kepler -Tycho: Famous for observing supernova (violent and bright rare death of a star) which suggested that the heavens change -Developed a device to measure planet positions with high accuracy -Kepler (student): Used math to find patterns in Tycho’s data -Kepler’s Law #1: Mathematical analysis proves that some stars don’t have circular orbits -Kepler’s Law #2: Speed of stars change Lecture 5 (1-22-16) From Last Time: The first science: Astronomy Today: Chapter 2 Galileo (1564- 1642) and Mechanics (moons around other planets, planets aren’t perfect circles, etc) Mechanics: Branch of science- deals with the motion of materials -“Classical mechanics”- This lecture and next few -“Quantum Mechanics”- A little later Background info: In 1615 a cardinal of the Catholic Church said “a true physical demonstration that the sun doesn’t circle the Earth but the Earth circles the sun” was necessary to prove the Copernican model. Problem for scientists of the time: -Heliocentric (sun in the middle) model should show a shifting star pattern (parallax) as the Earth moves through the year -Parallax- Far away = move slowly Close= moves more quickly -Using this method we can determine how far away a star is -But in 1600’s the shift couldn’t be measured – this suggests to Copernicus that the universe is very large (this is not accepted as truth) Galileo Galilei (1564-1642) – Math professor that invented thermometer, improved the telescope, and invented a pendulum for time keeping -Telescope: First (we know of) to have used it for astronomical observations -Before this is was used by the military to spot the enemy When Galileo looked through his telescope: 1.) Saw lots of stars and could map their motions better than before (Bruno [1548- 1600] had a theory that our sun was just like the stars) -Galileo was able to record data supporting Bruno’s argument 2.) Was able to view the moon’s craters and observe the phase 3.) Was also able to observe spots on the sun -Big picture: Earth is not the only place of change and decay 4.) Discovers 4 moons of Jupiter -Called this a mini heliocentric system -Jupiter acts like a sun to the moons 5.) Venus also goes through phases like our moon Mechanics (aka Kinematics): -Speed: How far you go divided by how long it takes (5 miles in 1 hour = 5 mph) -Velocity: Speed with direction (5 miles west in 1 hour = 5 mph west) AND distance divided by the time including a direction [Equation: V= d/t] V= velocity(m/s) d= distance(m) t= time(s) -Acceleration: change in velocity divided by the change in time [Equation: (m/s)/s = Velocity change/time change] *slope = rise/run = change in position/ change in time
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