ASTRONOMY 103 The Evolving Universe Professor: Andy Sheinis sheinis@wisc.edu Office: 5520 Sterling Hall Phone: 262-0492 Office Hours: Tu 2pm-3pm, Wed 3pm-4pm TA: Ella Braden ebraden@wisc.edu Office: 4514 Sterling Hall Phone: (608) 265-2554 Office Hours: Monday: 11:45-1:15 Wednesday: 11:00-12:30 Thursday: 1:45-3:15 Friday: 11:00-12:30 Sunday 8:00-9:00pm online office hour ASTRONOMY 103 The Evolving Universe Text: "Pathways to Astronomy" Schneider and Arny, McGraw-Hill (with the clickers and Starrynight observing program). Clickers: We will use the clickers for this class. Clickers are available with the text or separately at the UW Bookstore. They must be registered online at www.einstruction.com before you can use them in class. The registration code for the class is Class Key: F37866N695. Directions for registering the clickers are attached as well as a tutorial. Website: http://www.astro.wisc.edu/~sheinis/103course.htm See the website for HW assignments, solutions and interesting astronomy 1
ASTRONOMY 103 The Evolving Universe Grading: 2 midterms 20%+20% Homework 15% Labs 5% Quizzes (in Lecture) 10% Participation (clickers + section) 5% Final: 25% ASTRONOMY 103 The Evolving Universe EXAMS: Two (2) mid-terms and one (1) final exam will be given. All exams consist of multiple-choice questions based on material covered in lectures and readings. Some questions may be based on the assigned web-based reading reviewed in discussion sections. NO EXAMS CAN BE DROPPED. NO MAKEUP TESTS are given for exams except in the case of arrangements made at least 2 weeks in advance of the exam, or for medical emergencies documented by a physician's note. Focus of Exams: concepts not memorizing - like in-class quiz questions. - focus on lecture material and DEMOS!! 2
ASTRONOMY 103 The Evolving Universe Honors: Honors credit for this course will be awarded on the basis of the successful completion of the following: 1. Written notification from the student to the instructor indicating the student will be taking the course for honors credit. This notification must be provided before the end of 2nd week of classes. 2. A final grade of AB or better in the course. 3. A project or research paper to be defined by the student in consultation with the instructor. The student will contact the instructor to set up appointment(s), nominally during the instructor's office hours. Homework: Please -- Goal is to solve on your own. Work together when stuck, but please don't copy, or allow others to copy. Feel free to see/contact me for help. Goal is to show understanding: Show your work, explain specifically how you would get the answer if stuck. Any work: Give credit to sources of info where due (don't need to cite the text) 3
Also -- Due dates: Please hand in work in class when due. (10%)=1 grade penalty/day of lateness without prior arrangements Exam and lab dates: Make prior arrangements for scheduling problems! Lecture outline 1) 10-15 minute lecture on textbook unit 2) Pose a question/answer via clickers 3) Small group discussion 4) Repose question 5) Discuss answer(s) 6) Repeat 1-5 4
Introductions Astrophysics Universe is the Xtreme physics lab: Gravity General relativity Atomic physics Amazing things: black holes, neutron stars supernova explosions gravitational lenses nebulae accretion disks, relativistic jets (and planets) 5
Ask Questions When did the Universe begin? Do black holes really exist? What makes stars shine? Do stars ever die? What is at the edge of the universe? Is there an edge? Why are the most distant objects in the universe so different from objects nearby? How do we know they are different? How do we know they are far away? Course outline will use the book but skip around Part 1: Astronomical Framework (8 Lectures) Part 2: Stars and Stellar Evolution (9 Lectures) Part 3: Milkyway and Galaxies (8 Lectures) Part 4: Cosmology and Life in the U. (4 Lect) 6
What is SCIENCE?? The Scientific Method The Scientific Method is the procedure scientists use to construct their ideas about how the Universe works. Start with a hypothesis a testable idea of how something works Test the hypothesis! If the test fails, modify or abandon the hypothesis, and retest. Hypotheses that pass many years of testing become Laws (mathematical) or Theories (described using words). A Model is a complex description of physical phenomena incorporating many laws and/or theories Ex: The Celestial Sphere Ex: Universal Gravitation 7
Theory or Law Tests/observations Models/predictions Facts/observables Hypothothesis Why is it impossible to prove a theory? A theory is not a fact. Only facts can be proven. * A theory is only supported by observations, a single contrary observation can disprove it. Theories can be proven! Once it is proven it is called a fact. It is not possible for humans to observe evrything about the universe, if they could they could prove a theory. (this one can also be argued as true) 8
Astrology vs Astronomy vs Astrophysics?? The Earth The Earth is a planet, a body in orbit around a star (The Sun) Radius: 6371 km (3909 miles) Mass: around 6 billion trillion tons Actual value: 5,970,000,000,000,000,000,00 0,000 kg Too many zeros! Use 5.97 1027 kg, instead! Metric System Easier to use (everything is a factor of 10!) More in Unit 3 9
The Moon The Moon is a satellite, a body orbiting a planet Rocky world, littered with craters Bombarded by meteors Where are the Earth s craters? Smaller than the Earth Less than 1/80 the mass ¼ the diameter of Earth Small, so cooled quickly! Cold, airless and lifeless Why is the moon so cratered, while the Earth is not? The Moon is older and hence hasn t been impacted as much. The Moon protects the Earth from meteors since it s orbit surrounds the Earth. The Earth has an atmosphere which protects it against smaller meteors. The Earth has erosion which hides the evidence of impacts. The Earth does have as many craters, we just don t see them due to oceans and plants. 10
The scale of things (reduced 1:10 billion) Pluto 0.2mm 590m Neptune 4.8mm 450m Uranus 5.2mm 287m Saturn 12mm 143m Jupiter 14.3mm 78m Mars 0.7mm 23m Earth 1.3mm 15m Venus 1.2mm 11m Mercury 0.5mm 6m Asteroid Belt 140mm (14 cm) Scale Models of the Universe Scale model #1 11
Scale Models of the Universe Scale model #1 Sun - a basketball in my hand Earth - at the back of the room Pluto - at the State Capital Building (edge of solar system) Nearest star - Hawaii -- now, even smaller -- Scale model #2 Sun - a speck of dust in my hand 12
-- now, even smaller -- Scale model #2 Sun - a speck of dust in my hand Nearest star - at the back of the room Center of Milky Way - Chicago Nearest galaxy - opposite side of the Earth The Nature of Matter Protons (positively charged) and neutrons (uncharged) make up the nucleus at the center of an atom. Electrons (negatively charged particles) are found relatively far from the nucleus If we enlarged the nucleus to be the size of a grape, the electrons would orbit at a distance of slightly less than a football field! Most solid matter, then, is made up of mostly empty space! 13
Fundamental Forces in Nature Gravitational Force Force between massive bodies Infinite in range, but weakens with distance Electromagnetic Force Force between charged bodies Infinite in range, but weakens with distance Strong Force Force that holds atomic nuclei together Very short range 10-15 meters! Weak Force Force responsible for radioactive decay Very short range 10-18 meters! Please read: Units 2,4,12 14