Welcome to NSCI 111 Introduction to Astronomy

1. Instructor: Dr. Johnny B. Holmes Office: AH 004 phone: 321-3448 E-mail: jholmes@cbu.edu Course web page (which serves as the text): http://facstaff.cbu.edu/~jholmes/N111/introN111.html Purpose of the course: (to satisfy the general education requirement for science to)show you what science is and what it isn’t by working in the specific area of our universe. Welcome to NSCI 111Introduction to Astronomy

2. Grading: (explained on syllabus) • 5tests, each counts as one grade • final exam, which counts as 3 grades (no papers are required since there will be three written lab reports in the lab course) Total: 8 grades (each based on 100 points) Final course grade will be based on the average of these 8 grades: 100 – A – 93 – B – 82 – C – 70 – D – 65 – F – 0

3. Test Format 1. There are Study Guides (available on the course web page) for each part that contain study questions. Those marked with a ** WILL be on the test, those with * probably will be on the test, those without an asterisk may be on the test. 2. A copy of the test I gave last time for each part and for the final exam is on the course web page. 3. On each test there will be True/False questions usually worth about 10 points (out of 100 total). The grading of the true/false questions is a bit different than usual: if you get a T/F question correct you earn 1 point; if you get it wrong you lose 1 point; if you don’t answer you get 0 points. This is usually how I distinguish A’s from B’s. To help you with this, there is a computer program for each of the five sections (which runs on Windows) that asks true/false questions, and after you answer it lets you know if you are correct, and if the answer is false it lets you know what is false about the statement. Warning: in determining whether I make the statement true or false on the test I flip a coin, so don’t try to see any pattern in the T/F answers.

4. Absence policy If you miss 3 or fewer classes, your lowest single score will be dropped. If the final is lowest, it will count only 2 instead of 3 times. Thus, if you have 3 or fewer class absences, the total will be based on the remaining 7 grades.

5. In-class Presentations Opportunities(not a requirement) for an in-class presentation on either an ancient civilization’s use of astronomy (Part 1) or on one of the planets (Part 3) will be available for up to 10 bonus points – one presentation per student on a first come first served basis (both topic and time) with requests made via e-mail to me. Each presentation should contain 5 to 7 slides and last about 10 minutes. Check with me about the date for a presentation. The date of the presentation on an ancient civilization must be before the 1st test. The date of the presentation on one of the planets must be before the 3rd test.

6. OFFICE HOURS I would enjoy seeing you outside of class – whether to talk about upcoming tests, or just talk about astronomy – whatever you are interested in. So please feel that you are welcome to stop by my office anytime you see me in my office! My office is in the basement of AH on the West end in AH 004 – right next to our classroom! No formal appointment is necessary. My availability is marked right beside my office. By the way, I won’t think that you are “dumb” for doing this! On the contrary, it shows me you are interested in learning!

7. Astronomy This picture was taken by the Hubble Space Telescope and is provided courtesy of the Space Telescope Science Institute. What is out there? How big is the universe? Does the universe have an “edge”? When did the universe begin, and will it end? Is anybody else out there?

8. More questions related to Astronomy In addition to the big questions on the previous slide, there are lots of other questions related to astronomy, such as: Will the sun keep shining, or will it “die”? Are there other dangers from our active, changing sun (such as damage to our electrical grid from solar flares or major climate change like ice ages)? Are there other places we could go if the sun does change drastically or even dies? What caused the extinction of the dinosaurs, and could it happen again if we don’t protect ourselves?

9. Questions! Notice that we start the course by asking a bunch of questions. This lies at the heart of science: asking questions based on what we have observed so far. In this course we will be asking a LOT of questions, and trying to answer them as best we can – based on our initial observations and then on other observations prompted by our theories. This course is more about trying to answer questions than learning “facts”.

10. Astronomy Astronomy is one of the sciences. This class is designed to fulfill the science requirement and so needs to emphasize what science is (and isn’t) and how science works, using astronomy as the example. Thus, the first question to ask is: What is a Science? (and what is NOT science?) Which of these are science subjects? Astronomy, Biology, Chemistry, Economics, Engineering, English, History, Marketing, Philosophy, Physics, Political Science, Psychology

11. Science Which of these are science subjects? Astronomy, Biology, Chemistry, Economics, Engineering, English, History, Marketing, Philosophy, Physics, Political Science, Psychology How do we decide? Another question we need to consider while we consider the first question is: Can Science discover “the truth” ?

12. Science To answer the first two questions, what is science and what subjects are science subjects, we can say that any subject that follows the Scientific Method is a science. So to really answer this question and the follow-on question about truth, we need to ask: What is the Scientific Method? (What are the STEPS in the Scientific Method?)

13. Scientific Method 1. Define the problem: what are we trying to figure out? 2. Gather data: experiment to see what happens. 3. Hypothesize: try to “explain” what we see; a good theory should a) organize what we know, and b) predict new things to look for. 4. Test the hypothesis: Go back to step 2 (gather data) to see if the predictions work.

14. Requirements for Scientific Theories For a theory to be classified as scientific, it must be testable (and hence falsifiable). For data to be considered scientific, the data must be repeatable. As we go through this course, we will see theories that were quite useful in their time but were later proved inadequate and were replaced by better theories. This process is continuing today.

15. Science Now we can address this question: Which of these are science subjects? Remember that the theories must be testable and the data repeatable. Astronomy, Biology, Chemistry, Economics, Engineering, English, History, Marketing, Philosophy, Physics, Political Science, Psychology Like most things, there is often not a definite yes or no to some of these areas. Some theories in some areas are only good statistically, and some data is not repeatable.

16. Scientific Truth The scientific method looks like an infinite loop - it keeps going back to step 2 – gather data! Do we ever get out of this loop – do we ever discover the real “truth” ?

17. Scientific Truth A related question is: can we perform “perfect” experiments - can we make “perfect” measurements? No! If we cannot measure perfectly, there is always room for a little doubt! Does this mean that we really don’t know anything?

18. Scientific Truth In some cases, we have tested theories, and they agree with experiment to a high degree of accuracy: these theories agree with measurements to the best that we can perform the measurements. For example, we know that gravity attracts, and that Newton’s Law of Gravity works extremely well! However, even though it works extremely well, it was replaced by Einstein’s theory of general relativity. We still use Newton’s Law of Gravity in many cases since it is much easier to work with and doesn’t lead to significant errors. But in GPS systems, we need the more accurate relativity theory.

19. Scientific Uncertainty However, other theories (like weather prediction and global warming) are still somewhat uncertain and do not always make accurate predictions. However, we are making good progress in these difficult areas. Since science is based on experiment, even “untrue” theories can still be useful in organizing our information and in making predictions and hence in developing technologies. However, we must always be careful in “believing” theories until they have been thoroughly tested.

20. Science and Philosophy In some cases we have theories which cannot yet be tested. In Astronomy, one example is speculation about parallel universes. In these cases, choosing between competing theories is more a matter of philosophy than of science. Later, when the technology allows for tests to be made, the theories can then become scientific.

21. Beliefs I will not ask you what you believe – for the purposes of this course I don’t care. I do require that you know what the current generally accepted theories are, and why they are generally accepted. In the past, many philosophical and/or religious beliefs shaped the physical & astronomical theories, and in some cases physical & astronomical theories shaped philosophical and/or religious belief – in both cases often for the worse. Remember that our scientific theories may not be totally true, but they should help us organize the data and guide us in making new discoveries.

22. Astronomy The first step in the scientific method is: Define the situation: what are we trying to explain? The “situation” is different for the different scientific disciplines. So what are we looking at in astronomy?

23. Astronomy course overview Astronomy is the science which describes the celestial bodies according to their locations, sizes, motions, constitutions and evolutions. By evolutions we mean changes in time. For example, do stars get old and die, and are there new stars being born? In part 1 of the course we consider what we can find out by using only our unaided eyes. We will consider how different people and different civilizations “made sense” of these observations.

24. Astronomy course overview In part 2 we will look at our modern tools(mainly the telescope and spectrograph) for extending our data gathering. In the remaining parts of the course we consider our current best theories about astronomy: in part 3 we consider the objects in our astronomical neighborhood: the solar system; in part 4 we consider stars; and in part 5 we consider how stars are grouped and how big and how old the universe appears to be.

25. Gathering Data What are the objects that we see when we look up? For each, we need to consider the following questions: • how big does it appear in the sky? (how big an angle does it make with the eye?) • how bright does it appear to be? (how do we measure brightness?) • where is it located? (how do we indicate location?) • how does it appear to move? (is it moving, are we moving, or both?)

26. Gathering Data What are the objects that we see when we look up? 1. Sun 2. Moon 3. Stars • Planets (how are planets and stars different?) • Other stuff (e.g., comets and shooting stars) and events (e.g., solar eclipses) that don’t appear to be permanent like the first four objects – we’ll save these for later in Part 3.

27. 1. Sun • How big? what shape is it? how do we measure size for this shape? how do we measure size for objects that are far away? This image was taken by SOHO's EIT (Extreme-Ultraviolet Imaging Telescope) and is courtesy of the EIT Consortium.

28. Sun • How big? A circle (or ball?) in the sky with a diameter that forms an angle with the eye of about ½ degree.There are 360 degrees in a full circle. Who decided that we break a circle into 360 equal parts instead of, say, 100? From horizon to horizon covers 180 degrees Angle the sun makes is about ½ degree

29. Sun Who decided that we break a circle into 360 equal parts instead of, say, 100? The 360 degrees in a circle comes from the observed fact that there are 365 days in a year (solar cycle). But 365 is an inconvenient number since it is odd. The 360 is much better since it is divisible by 1, 2, 3, 4, 5, 6, 8, 9, and 10! However, 360 is not divisible by 7. Neither is 365 – which allows for our birthdays to fall on different days in different years. We’re not always stuck having our birthday on the same day of the week. b) How bright is the sun?

30. Sun • How bright is the sun? Very! It overwhelms almost everything else in the sky when it is visible. (We’ll set up a scale later.) c) Where is the sun located?

31. Sun • Where is the sun located? At different places in the sky at different times of the day; and at different places in the sky at the same time when viewed from different locations on the earth. (For instance, the sun may still be up on the West Coast when it has already set on the East Coast, and as you move South towards the equator, the sun at noon is higher in the sky.)This will be further analyzed as we answer the next question: d) How does the sun move?

32. Sun d) How does the sun move? d1: a DAY is the time from noon on one day to noon on the next day. Noon is the time of day when the sun is highest in the sky (and shadows are the smallest). d2: The sun rises in the East (more or less) and sets in the West (more or less). Does the sun always rise exactly due East and set exactly due West?

33. Sun d2: Does the sunalways rise exactly due East and set exactly due West? No! The sun rises North of due East and sets North of due West in the spring and summer, and it rises South of due East and Sets South of due West in the fall and winter. It only rises due East and sets due West on the first day of spring and first day of fall.These two days when the sun does rise due East and set Due West are called the spring and fallequinoxes, and they happen near March 21 and September 23. This change in the rising and setting positions of the sun can be (and has been) used to mark a yearly calendar.

34. Sun d2 – cont.: Does the sunalways rise exactly due East and set exactly due West? Since the rising and setting of the sun moves throughout the year, sometimes North and sometimes South of due East and due West, there is a time when the sun goes from rising more and more North and then turns and starts rising more South. This time has a name called the summer solstice. This happens around June 21. When the sun stops rising further South and turns to start rising further North, this time has the name of the winter solstice. It happens around December 21.

35. Sun In the first lab meeting, we will use a star chart to investigate the motions of the sun:a) how it rises and sets throughout the year;b) how high in the sky it is at noon on different days throughout the year;c) how the sun moves relative to the stars. There is a separate powerpoint set on the Star Charts which you can use to familiarize yourself with this useful tool.

36. 2. Moon a: How big is the moon , e.g., what angle does it make with the eye? What shape is it? How does the moon’s size (angle) compare to the sun’s size (angle)? Will a penny held atarm’s length totally block the moon? The Galileo spacecraft sent back this image of the Moon as it headed into the outer solar system. The distinct bright ray crater at the bottom of the image is the Tycho impact basin.

37. Moon • How big is the moon? Will a penny held at arms length be able to completely block the moon? A circle (or ball?) that makesabout ½ degree with the eye.This is about the same size (in angle) as the sun. This will be important when we talk about eclipses in Part III. Try the penny experiment yourself! The moon appears to change shape: from a new moon (which is dark) to a crescent shape to a half circle to a gibbous shape to a full circle and then back through these shapes to a new moon. This cycle takes about a month (a moonth). b) How bright is the moon?

38. Moon • How bright is the moon? A full moon is quite bright - enough to make it hard to see the dimmer stars, but not nearly as bright as the sun. The new moon is so dim it is hard to see (also because it appears to be so close to the very bright sun). c) Where is the moon located?

39. Moon • Where is the moon located? At different places in the sky at different times of the day; the phases (shapes) of the moon are related to its position during the day. New moons are always near the sun, and full moons are always opposite the sun. • How does the moon move?

40. Moon • How does the moon move? It follows a path similar to that of the sun: rising somewhere in the East and setting somewhere in the West. It’s time of rising and setting changes during the month. When the moon is new, it rises and sets with the sun; when the moon is full, it rises and sets opposite the sun.

41. 3. Stars • How big do the stars appear to be? Betelgeuse is the bright star on the upper left side in the picture below. Note: the brighter stars appear larger in the photographs only because of the way the light affects the film. In Part 4 of the course we’ll see how we can determine the actual sizes of the nearer starts as indicated on the left side of the picture. Betelgeuse, the brightest star in the constellation Orion. (Produced with ESA's Faint Object Camera (FOC), Hubble Space Telescope.)

42. Stars • How big do the stars appear to be? Each star appears to be a point, that is, it makes too small an angle to be measured.Later in the course we’ll see how to determine a star’s diameter – as implied in the previous picture. b) How bright are the stars?

43. Stars • How bright are the stars? The stars vary in brightness - some are so dim that they can only be viewed by the most powerful telescopes while others are bright enough to be seen in faint early dawn or late evening twilight. (We’ll set up a scale later.) c)Where are the stars located?

44. Stars • Where are the stars located? Like the sun and the moon, stars move across the sky; however, the stars do not move relative to one another - that is, we can group them into constellations (like the big dipper). d) How do the stars move?

45. Stars • How do the stars move? Except for the North Star, all stars move across the sky. In the Northern hemisphere they move around the North Star and so most seem to rise in the East and set in the West just like the sun and moon. In this connection, the sun and the moon do change their relative positions with the stars. The sun seems to move along a path through the stars called the ecliptic. The moon follows a path very close to the ecliptic.

46. Sun and Stars The constellations that are found on the path of the sun (the ecliptic) are called the constellations of the zodiac. During the year the sun moves along the ecliptic spending approximately one month in each of the 12 constellations of the zodiac. The sun moves from West to East through these constellations(although it moves from East to West across the sky), and this causes the sun to rise a little later than a particular constellation or star each day, and conversely the constellation and its stars rise a little earlier (about 4 minutes earlier) each day.

47. Constellations of the Zodiac The months below refer to when the sun appears to be in the constellation ConstellationMonthConstellationMonth Aquarius March Leo September Pisces April Virgo October Aries May Libra November Taurus June Scorpius December Gemini July Sagittarius January Cancer August Capricornus February Note: The months are approximate You will need to know these twelve constellations of the zodiac for the test since they serve as nice markers in the sky.

48. Heliacal Rising Since the stars appear to rise a little earlier each day than the sun, for each star there is one day each year that the star can first be seen before sunrise (assuming clear skies). After that, the star can be seen earlier and earlier. This first day is called the “heliacal rising” of that star. Some cultures based their calendars on such heliacal risings of certain bright stars.

49. Moon, Sun and Stars The moon also moves along a path very close to the one the sun moves on (the ecliptic). It makes a complete cycle around the path through the constellations of the zodiac (the ecliptic) once a month(rather than once a year like the sun). It also moves East along its path through the stars (but moves West through the sky as we see it), so it also rises a little later each day than the stars, and the moon rises a little later relative to the sun each day. For example, the full moon rises as the sun sets; the next day the (not quite full) moon will rise about 50 minutes after the sun sets.

50. 4. Planets Although the stars do notappear to move relativeto one another (and hence we can make constellations out of them),there are five visible exceptions to this(besides the sun and moon which makes the total seven which is equal to the number of days in a week; by the way, what are the days of the week named?)These the Greeks named wandering stars which today we call planets. The five planets visible to the naked eye are: Mercury, Venus, Mars, Jupiter and Saturn. Voyager 2 captured this image of Neptune in 1989.