Survey of the Universe ASTR 2003 Dr. Julia Kennefick jkennef@uark.edu Office Hours: MWR 10-11am PHYS 213 Course material available on WebCT

ASTR 2003 Course Syllabus Fall 2007 (last revised: March 13, 2006) Course:………… ASTR 2003, Survey of the Universe Classroom:…….. Ozark 025 Time:………….. TuTh 2:00 – 3:20 PM Text:…………… The Essential Cosmic Perspective (4th Edition Web Homework.. Mastering Astronomy – www.masteringastronomy.com Instructor:……… Dr. Julia Kennefick, 575-5916, jkennef@uark.edu Office:…………. Physics Bldg., Room 213 Office Hours:….. MWR 10:00-11:00am, or by appointment WebCT................ Course syllabus, schedules, etc. Welcome to Astronomy 2003. I hope you enjoy the class. This course is designed for non-science majors and contains only a little math (there are a few equations!) Please ask questions and introduce topics for discussion. If you are having trouble with any of the material, please come and see me during my office hours or e-mail me to make an appointment. I will be happy to speak with you. Grades: Your grade will be based on 4 tests/retests and homework. The scale will be 90%=A, 80%=B, 70%=C, 60%=D. Each test/retest will be worth 150 points and the homework/classwork will be worth 400 points for a total of 1000 points possible. The minimum point totals needed to earn a specific grade are as follows: 900=A, 800=B, 700=C, 600=D.

Tests: There will be 4 in-class tests consisting of 50 multiple choice questions each. Each question will be worth 3 points for a total of 150 points per exam. 600 pts (60%). Students will not be allowed to hand in their exams for the first 25 minutes of class time. Once students begin handing in exams, no student entering class late will be able to take the exam. Retests: After each test, you will be required to rework the exam (the “retest”) outside of class using whatever materials you can find and with the help of classmates (please do not ask me or the TA’s for help.) This retest is due at the beginning of the next class meeting (if you cannot attend the next class meeting, then put the retest in my mailbox in PHYS 226 or slip them under my door before class). The retest score will improve your grade on the test - you get one extra point for each additional question you get correct on the retest.) Your grade will not be affected if you do worse on the retest. Make-up Exams: No make-up exams are given, but if you miss an exam, do the retest anyway. You may be able to apply it to the optional final (see below). Note: Photo ID’s and #2 pencils are required for all tests. You will need to purchase “General Purpose NCS Answer Sheet form no. 4521” (they are blue) for each test and retest (9 total). Final: There is an optional final covering the entire course. You can choose to take this exam and substitute the score for your lowest test score, if it is higher. Your grade will not suffer if you choose to take the final. If you miss an exam or choose not to take one, then you can use the final exam as a makeup exam. There is no retest for the final, but a retest from a missed exam may be applied if there was a good, documented reason for missing the exam, such as illness, family emergencies, etc. Students entering the exam hall more than 25 minutes late will not be allowed to take the final.

Homework: I will give approximately 10 web-based homework assignments over the reading material. These will be due before class. See schedule below. The homework will be done on the Mastering Astronomy website associated with your textbook. In order to gain access to the web site, you can either buy the textbook new at the bookstore and use the password that is included, or you can purchase access at (http://session.masteringastronomy.com/myct?productID=bennett_e4). The Course ID for our course is ASTR2003FA07. 400 pts (40%) Bonus Points: I will put a few optional films that you can view in the library for extra points. There will probably also be extra points available for attending public lectures given on topics in astronomy around campus. I will explain this during class throughout the semester. Classroom Environment: If you have a question about the lecture or class material, I strongly encourage you to ask me questions during the lecture. There are probably others in class with the same question who would appreciate you having the courage to speak up. However, please keep extraneous talking during class lectures to a minimum. I do not have a loud voice, and talking during class lectures prevents others from hearing what they have paid money to hear. If this becomes a problem, I will ask offending students to leave the lecture hall. Likewise, please wait until I have dismissed class to begin leaving. I often make announcements in the last few minutes of class that all students need to be able to hear. Thank you.

Weather Policy: Classes will meet unless the University is closed Weather Policy: Classes will meet unless the University is closed. Closure of the University is announced on KUAF Radio, 91.3 FM, or you may call 575-7000. You may also check the UArk Daily Headlines page at http://pigtrail.uark.edu/pubs/university/theuniversity.nclk. If the University remains open, no announcement will be made. Also, check the class website. The lab course, ASTR 2001L is not a co-requisite for this course. It is a separate course and grades in that course are independent of grades in this course. No exceptions will be made to the grading policy above. I will not assign projects for extra credit to improve your grade under any circumstances. Tests will not be given earlier or later than scheduled. I do not give makeup exams. As stated above, always do the retest and come and see me about applying it to the optional final.

Grades 60%: 4 tests and retests (150 points each) 50 questions - 3 points each retest - 1 extra point for each additional correct question 40% homework (web based) and classwork Optional final: substitute for one exam or use as makeup exam if you miss one Scale: 90%=A, 80%=B, 70%=C, 60%=D

What you need: Textbook: The Essential Cosmic Perspective 4th Ed. Internet access for online Homework Account on the Mastering Astronomy site 8 (or 9) NCS Answer Sheets #4521 #2 pencil Photo ID

Parts I and II: Chapters 1-5

Chapter 1 Our Place in the Universe

Light! Astronomers use light to study the Universe. Light travels at a finite speed, c c = 300000 kilometers/second (3x108m/s) = 186000 miles/sec We see distant objects as they appeared in the past because it takes light some time to reach us Light from the Sun takes 8 minutes to reach us; light from the nearest star takes over 4 years to reach us.

d = v t distance = velocity x time If you drive v = 60 miles/hour for t = 1 hour, how far a distance, d, will you go? 60 miles If you drive for t = 30 minutes = 1/2 hour? 30 miles

Definition: Light-Year The distance light can travel in one year. About 10 trillion kilometers (6 trillion miles). Emphasize that a light-year is a unit of distance NOT a unit of time. Remind students of Common Misconception box in text (p. 7). Equation si optional: it is not given in the book, but should be easy for most studnets to follow.

Light-years - it’s a distance! d = v t v = speed of light = c = 300000 km/sec t = 1 year = 365 days/year x 24 hours/day x 3600 sec/hour = 31536000 sec d = 1 ly = c x 1 year 1 ly = 300000 km/sec x 31536000sec 1 ly = 9.460,800,000,000 km = 9.5 trillion km WHEW!

In order to make it easier to write these types of large numbers, we use scientific notation: 9,460,800,000,000 km = 9.4608 x 1012 km 1,000,000,000 LY = 1.0 x 109 LY = 109 LY 0.0000045 sec = 4.5 x 10-6 sec

Let’s Do a Problem Please work these on your own paper and discuss it with your classmates

Express the following numbers in scientific notation: 12345 = 2.5 million = 5 percent = A thousandth = 0.0000345 =

Express the following numbers in scientific notation: 2.5 million = 2.5 x 106 5 percent = 5.0 x 10-2 A thousandth = 1.0 x 10-3 0.0000345 = 3.45 x 10-5

What is our place in the universe? Our “Cosmic Address” Here at the beginning of the semester, our main goal is simply to make sure that students understand the basic hierarchy of structure from planet to solar system to galaxy to universe (clustering is less important at this stage). You might also wish to note that this slide shows a lot about human history. E.g., we first learned that Earth is a sphere some 2,500 years ago; we learned that Earth is a planet going around the Sun only about 400 years ago; and we learned that the Millky Way is only one of many galaxies with the work of Hubble some 80 years ago…

Universe The sum total of all matter and energy; for now, this means everything within and between all galaxies

What are we made of? This slide (Figure 1.2) packs in a lot of basic information. You might go through the frames slowly as follows: • The universe is expanding, from which we infer a beginning in what we call the Big Bang. Note that, based on the observed rate of expansion, we conclude that the universe is about 14 billion years old. (WMAP results from 2003 were 13.7 ± .2 billion years). • The expansion continues to this day except where gravity has “won”: stars, galaxies, clusters. • Galaxies make possible the formation of stars, and recycle material through generations of stars. • Although the universe began with only the chemical elements H & He, stars have created the elements from which rocky planets are made. • Life begins from this “star stuff” on at least one particularly friendly planet.

How can we know what the universe was like in the past? Light travels at a finite speed (300,000 km/s). Thus, we see objects as they were in the past: The farther away we look in distance, the further back we look in time. Destination Light travel time Moon 1 second Sun 8 minutes Sirius 8 years Andromeda Galaxy 2.5 million years Point out how fast the speed of light is: could circle Earth 8 times in one second…. Also note that the speed of light is always the same…

Can we see the entire universe? At great distances, we see objects as they were when the universe was much younger. This slide shows part of Figure 1.4, which you can use to emphasize that we are seeing galaxies as they were in the distant past -- which means when they were YOUNG. (Note: students often equate “past” with “old,” so it’s important to emphasize that galaxies that we see in the past are in fact the ones we are seeing at young ages…) Can we see the entire universe?

Thought Question Assume the universe is 14 billion years old. Why can’t we see a galaxy 15 billion light-years away? Because no galaxies exist at such a great distance. Galaxies may exist at that distance, but their light would be too faint for our telescopes to see. Because looking 15 billion light-years away means looking to a time before the universe existed. This is an optional question to ask your students, to see if they have grasped the idea of the observable universe.

Thought Question Assume the universe is 14 billion years old. Why can’t we see a galaxy 15 billion light-years away? Because no galaxies exist at such a great distance. Galaxies may exist at that distance, but their light would be too faint for our telescopes to see. Because looking 15 billion light-years away means looking to a time before the universe existed. This is an optional question to ask your students, to see if they have grasped the idea of the observable universe.

The Cosmic Horizon

The Scale of the Universe How big is the Earth compared to our solar system? On a scale of 1-to-10 billion, the Sun is about the size of a grapefruit. The Earth is the size of a tip of a ball point pen about 15 m away. The distances between planets are huge compared to their sizes. How far away are the stars? On the same scale, the stars are thousands of kilometers away. How big is the Milky Way Galaxy? It would take more than 3,000 years to count the stars in the Milky Way Galaxy at a rate of one per second. The Milky Way Galaxy is about 100,000 light-years across.

How big is the Universe? The Milky Way is one of about 100 billion galaxies. 1011 stars/galaxy  1011 galaxies = 1022 stars This slide gives our favorite way of giving students a sense of the size of the observable universe; be sure to note we are talking about the OBSERVABLE universe, since we do not know the extent of the ENTIRE universe. It has as many stars as grains of (dry) sand on all Earth’s beaches.

The Scale of the Universe How big is the universe? 100 billion galaxies in the observable universe 14 billion light-years in radius As many stars as grains of sand on Earth’s beaches How do our lifetimes compare to the age of the universe? On a cosmic calendar that compresses the history of the universe into one year, human civilization is just a few seconds old, and a human lifetime is a fraction of a second.

Everything moves… Contrary to our perception, we are not “sitting still.” We are moving with the Earth in several ways, and at surprisingly fast speeds. The Earth rotates with respect to the Sun once per DAY, or every 24 hours. Since the Earth is 6400 km in radius, this means people at the equator travel 1650 km/hr (1000 miles/hr). Our first motion is ROTATION. Point out that most of us are moving in circles around the axis at speeds far faster than commercial jets travel, which is why jets cannot keep up with the Sun when going opposite Earth’s rotation… 40000 km 6400 km

Earth orbits the Sun (revolves) once every year… at an average distance of 1 AU ≈ 150 million km. with Earth’s axis tilted by 23.5º (pointing to Polaris). and rotates in the same direction it orbits, counter- clockwise as viewed from above the North Pole. Our second motion is ORBIT. Point out the surprisingly high speed of over 100,000 km/hr. Astronomical Unit: 1 AU = 1.496 x 108 km

… And it orbits the galaxy every 230 million years. Our Sun moves randomly relative to the other stars in the local Solar neighborhood… at typical relative speeds of more than 70,000 km/hr. but stars are so far away that we cannot easily notice their motion. … And it orbits the galaxy every 230 million years. Our third and fourth motions are MOTION WITH THE LOCAL SOLAR NEIGHBORHOOD and ROTATION OF THE MILKY WAY GALAXY.

Hubble discovered that… all galaxies outside our Local Group are moving away from us. the more distant the galaxy, the faster it is racing away. Conclusion: We live in an expanding universe. Now relate the raisin cake analogy to the real universe…

If we didn’t move, gravity would pull objects together Earth rotates on axis: > 1,000 km/hr Earth orbits Sun: > 100,000 km/hr Solar system moves among stars: ~ 70,000 km/hr Milky Way rotates: ~ 800,000 km/hr Milky Way moves in Local Group This slide summarizes our motion with spaceship Earth… Universe expands

Review of Concepts: Astronomers use light to study the Universe Light travels at a finite speed: c = 3 x 105 km/sec Light year: 1 ly = 9.5 trillion km Astronomical Unit: 1AU = 150 million km Rotation - spin (day) Revolution - orbit (year) We live on the planet Earth, in our Solar System dominated by the Sun, in our galaxy the Milky Way, in our Local Group of galaxies, in our Local Supercluster, in an expanding Universe. Distances in the Universe are vast; we haven’t been around very long compared to the age of the Universe; we move at enormous speeds.