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Physics 107Ideas of Modern Physics www hep wisc edu herndon 107 ... Main emphasis is Modern Physics Post 1900 Physics. Why 1900 Two radical developments Relativity Quantum Mechanics Both changed the way we think as muchas did Galileo and Newton .Physics 107 Fall 2006 1 Goals of the course Learn a process for critical thinking and apply it to evaluate physical theories Use these techniques to understand the.revolutionary ideas that embody modern Implement the ideas in some basic problems Understand where physics is today and where it is going Physics 107 Fall 2006 2. What will we cover Scientific observation and reasoning Motion and energy Relativity Quantum Mechanics . Gravity Particle theory and cosmology Physics 107 Fall 2006 3 Modern Physics From the microscopically.Single atomsand quantum wavesTo the incrediblyEntire galaxies andthe universe.Physics 107 Fall 2006 4 How do we do this Lectures Demonstrations In class interactive questions. Homework Discussion sectionsHW 1 Chap 3 Conceptual 6 28 32Chap 3 Problems 6 10 16Physics 107 Fall 2006 5. What do you need to do Read the textbook Physics Concepts and Connections Come to the lectures 9 55 MWF in 2241 Chamberlin Hall. Participate in discussion section One per week starting Sept 11th Do the homework Assigned most Wednesdays due the following Write the essay. On an approved physics topic of your choice due Dec Take the exams Three in class hour exams one cumulative final examPhysics 107 Fall 2006 6 What do you get . An understanding of the physical A grade 15 HW and Discussion Quizzes 15 essay 20 each for 2 of 3 hour exams lowest. 30 from cumulative final examPhysics 107 Fall 2006 7 Where s the math Math is a toolthat can often help to clarify physics . In this coursewe use algebra and basic geometry We will do calculations but also focuson written explanation and reasoning Physics 107 Fall 2006 8. Observation and Science Look around what yousee is the universe What can you sayabout how it works .Physics 107 Fall 2006 9 Aristotle s ideas about Terrestrial objects move in straight lines Earth moves downward Water downward Air rises up Fire rises above air . Celestial bodies are perfect They move only in exact circles Where did Aristotle concentrate his work Celestial bodies most interesting problem of the dayPhysics 107 Fall 2006 10. Motion of the celestialApparent motion ofRotation about apoint every 24Moon sun and planets.were known to movewith respect to thePhysics 107 Fall 2006 11 Motion of the stars over 6QuickTime and a.Video decompressorare needed to see this picture Physics 107 Fall 2006 12 Daily motion of sun planetsover 1 year.QuickTime and aVideo decompressorare needed to see this picture Movie by R Pogge Ohio.Physics 107 Fall 2006 State 13 Aristotle s crystal spheresEarth Water Air FirePrime mover 24 hrs Cristal sphere 49000 yrs .Firmament 1000 yrs Saturn 30 years Jupiter 12 years Mars 2 years Venus 1 yr .Mercury 1 yr Moon 28 days Already Complex Physics 107 Fall 2006 14 You figure it out .Assuming that the planets and stars aremoving around the earth you wouldA The planets to move faster than the starssince they are closer B The stars to move faster than the planets .C We wouldn t know what to expect I would say it would be helpful to have moreinformation Physics 107 Fall 2006 15 Detailed Observations ofplanetary motion.An instrument Observational notes fromsimilar to Ptolemy s Ptolemy s AlmagestPhysics 107 Fall 2006 16 Retrograde planetaryContinued observation.revealed that the problemwas even more complex thanfirst believed Retrograde motion of Mars Apparent motion not always.in a perfect circle Mars appears brighter duringthe retrograde motion Physics 107 Fall 2006 17 Epicycles deferents and.the legacy of PtolemyEpicycle reproduced planetary retrograde motionPhysics 107 Fall 2006 18 Ptolemy s universe In final form. 40 epicycles and deferents Equants and eccentricsfor sun moon and Provided detailedplanetary positions for.1500 years Very complex However good for whatwas needed navigation Physics 107 Fall 2006 19. More detailed observations some philosophy Copernicus Ptolemy s system worked butseemed a little unwieldy contrived . Required precise coordination ofplanetary paths to reproduceobservations Imperfect circular motionagainst Aristotle . Copernicus revivedheliocentric sun centered universePhysics 107 Fall 2006 20 The heliocentric universe Sun centered. Planets orbiting around Theory didn t perfectlypredict planetarymotion Onlydiscovered later . But the imperfect theory is attractive inseveral ways Physics 107 Fall 2006 21 Advantage Natural .explanation of RetrogradeRetrograde motion observed asplanets pass each other Physics 107 Fall 2006 22 Comparing Ptolemy and.CopernicusPtolemy s Earth Copernicus sun centered centeredWhich is the better theory Physics 107 Fall 2006 23. How can we tell if it is correct Both explained contemporaneous observations But a rotating and revolving Earth seemed absurd Both motions require incredibly large speeds .Speed of rotation 1280 km hourOrbital Speed 107 000 km hr 30 km sec No observational evidence of orbital motion Relative positions of stars did not shift with Earth s motion parallax .Stars weren t brighter when Earth is closer opposition No observational evidence of rotation Daily motions are as easily explained by a fixed earth The motions do not require a rotating earth Physics 107 Fall 2006 24. Advantage A good theory makespredictionshalf illuminatedPlanet Copernicu Actu.Mercury 0 376 0 387Venus 0 719 0 723Earth 1 00 1 00Mars 1 52 1 52Jupiter 5 22 5 20.Saturn 9 17 9 54But at the time these predictions could not be tested Physics 107 Fall 2006 25 20 years of detailedobservations Tycho Brahe. Johannes Kepler Brahe s exactingobservations demandedsome dramatic revisions inplanetary motions .Both Ptolemy s andCopernicus theorieswere hard pressed atthis detailed level 1601 Physics 107 Fall 2006 26. Kepler s elliptical orbits Contribution of Kepler first consideration of non circular orbits inover 1000 yrs of thinking No more epicycles required .Circular Elliptical orbitDetailed observations required a1571 1630 radical new concept for anexplanation Physics 107 Fall 2006 27. Some common threads Philosophical considerations such as complexity and symmetry can lead to revolutionary developments Thoughtful consideration of.possibilities that at first seem outrageous But final evaluation based on comparison withdetailed experimental measurements More detailed observations test and sometimesforce changes to theories .We will see this throughout theIn relativity in quantum mechanics Physics 107 Fall 2006 28 An important difference Ancient theories focused on description of.motion empirical laws without answering why Symmetries were of shape and motion Later developments focus onthe physical laws that govern motion . The actual motion can be quite complex butthe physical laws demonstrateastounding simplicity beauty andPhysics 107 Fall 2006 29.An understanding of the physical universe. A grade 15% HW and Discussion Quizzes 15% essay 20% each for 2 of 3 hour exams (lowest dropped) 30% from cumulative final exam Whereâ€™s the math? Math is a tool that can often help to clarify physics. In this course we use algebra and basic geometry.