Is seeing believing?

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1 Is seeing believing? a mini-course designed by Manolis Papastergis Astronomy Department Cornell University Spring 2010 Graduate Student School Outreach Project Public Service Center, Cornell University

2 Table of Contents Abstract 3 Course Description 4 Introduction 4 Mini-Course Goals 5 General Suggestions 5 Graduate Student Biography 7 Individual Session Descriptions Session 1: What is that light in the sky? I 8 Session 2: What is that light in the sky? II 10 Session 3: Is seeing believing? I 12 Session 4: Is seeing believing? II 14 Session 5: Dark Matter, Dark energy I 16 Session 5: Dark Matter, Dark energy II 18 Resource Materials 19 Appendix 20

3 Abstract This mini-course aims at presenting how technology and physics can help us discover and study objects and phenomena in the universe that we cannot see with our eyes. For thousands of years humans had been studying the heavens using only one instrument: the naked eye. Even though all ancient civilizations did their best to figure out what the universe was like based on what they saw, they got the big picture wrong This is simply because most of the universe is invisible to our eyes! Most celestial objects are just too faint to see (like galaxies, nebulae, Jupiter s moons etc), other objects are bright but not in the optical spectrum (like pulsars, black holes, the early universe etc.). In fact, astronomers very recently realized that most of the contents of our universe are fundamentally invisible! (96% of our universe is made up of Dark Matter and Dark Energy). In this course I will try to present in a simple way, involving fun demos, how technology and physics have helped astronomers over the last few hundred years discover objects and phenomena that are invisible to our eyes, yet are fundamental to understanding what our universe is like!

4 Course Description Introduction This mini-course is designed to cover 3 distinct (but related) topics. Each of them can be presented in one or more sessions, depending on the pace that the instructor and teacher want to maintain. The first unit introduces students to the night sky as we see it. It consists of the stars, the Sun, the Moon and the 5 planets visible to the naked eye. Ancient civilizations observed the motions of all these celestial objects and came to the conclusion that the best way to explain what they saw was to assume that the earth sits at the center of the universe, with the Sun, Moon, planets and stars revolving around it. Only after about 1000 years, when Galileo used the telescope to study the heavens, it became apparent that this old, geocentric idea about the universe had to be abandoned. The discovery of new objects (like the moons of Jupiter) and phenomena (like the phases of Venus) that are invisible to the naked eye is what revolutionized our understanding of the universe! The second unit is about the discovery of light we cannot see (electromagnetic waves outside of the visible spectrum). The unit starts with a brief historical overview of how these new forms of light were discovered (presenting the ingenious experiments of William Herschel and Johann Ritter that discovered infrared and ultraviolet light respectively). Next, beautiful astronomical pictures taken in many different wavelengths (ranging from the radio to the X-rays) are used to illustrate why studying the universe in wavelengths other than optical is extremely important! The third and last unit attempts to present some very recent scientific results regarding the contents of our Universe (namely Dark Matter and Dark Energy) in a simple and engaging way. Even though Dark matter and Dark Energy make up about 96% of our universe they are fundamentally invisible! This unit focuses on how, through the understanding of the laws of nature you can discover and study these exotic types of matter, that make up most of our universe!

5 Mini-Course Goals First Unit: Students should realize that most of what we know about the universe and most of what is taught in science classes today (and taken for granted by people to be right) is actually impossible to prove by just using our eyes to study the heavens. Only through the invention of the telescope and other astronomical instruments, were people able to discover the correct picture of what our solar system is like. This first unit is also ideal for interactive demos to illustrate some simple phenomena like the seasons, the phases of the moon, parallax and retrograde motion of planets. Second Unit: The goal for this unit is to show how creativity and original thinking can lead to revolutionary discoveries in science. It should also make clear that often times in modern science we research phenomena that are imperceptible by our senses. The second unit is ideal for some very interesting and fun demos that need time, preparation and materials, however. Replicating Herschel s or Ritter s experiments can be very fun and gratifying for the students (instructions for them are available online, see for example here). Also, bringing an infrared camera to class (if available) is guaranteed to give students a fun time. Third Unit: The third unit aims at presenting some more advanced topics that students might never have heard before. It is important to keep this unit as simple as possible, but the instructor should not worry if not everything is immediately clear to the students! General Suggestions The mini-course above was taught to an elective Astronomy class, at the Spencer-Van Etten High School, in Spencer, NY in May The class was composed of 11 students total (half of them seniors and the other half juniors), and was taught by Mrs. Jessica Browne. This mini-course requires only a basic astronomy and physics background (knowing Newton s laws motion is more than enough!), and in fact most of it should be clear even to students with no physics background. However, since the concepts

6 presented during this mini-course are rather subtle, I think it is best suited for high school students (and their teachers!). The mini-course can be taught in any number of sessions between 4 and 7 depending on the pace desired and depending on whether the instructor intends to include interactive demos. A slow pace is always advisable, and giving time to students for questions is also important.

7 Graduate Student Biography My name is Manolis Papastergis and as you can probably tell from my name I come from Greece, and more precisely from the island of Rhodes (have you ever heard of the colossus of Rhodes?). What you can t tell from my name is that I m also half Italian since my mother is Italian, and I was actually born in Italy. I considered myself very lucky to have this mixed origin because: i) I speak both Greek and Italian as mother languages and ii) I got to travel very often as a kid, visiting family in Italy once or twice a year. Since middle school I have been fascinated by Astronomy I remember myself looking at the night sky without knowing what anything of the objects I saw was. Living in a badly lit, small village in Rhodes, it was just natural to turn my head up and look at the stars! Even though enjoying the view of the stars at night is all it takes to become an Astronomer, it is not enough if you want to become a professional Astronomer Luckily, I really enjoyed studying math and physics at school, and even more luckily I was good at them. So after I got my undergrad degree in Electrical & Computer Engineering (don t ask me why) in the beautiful Greek city of Thessaloniki, I decided to apply for a PhD program in Astronomy in the US. I got accepted at Cornell University 3 years ago and since then I have been able to do what I always wanted to do: research in Astronomy!

8 Session 1: What is that light in the sky? part 1 Learning Outcomes Upon completion of this session, students will: Duration Know how ancient civilizations thought the universe was like, and why. Understand that it is impossible to prove that the ancients idea of how the universe is like (earth is at center of universe, etc.) is wrong, if we are to use our eyes only to study the heavens. About 50 minutes. Activities This session is very suitable for some simple demos. For example, simple demos explaining the seasons or the phases of the moon can be instructive and at the same time they give the presenter a chance to get to know the students. Materials A light bulb and a couple of tennis balls (or globes of the earth and moon if available). A celestial sphere to demonstrate the geocentric universe, if available. Background Information All of the material in this first session should already be familiar (more or less) to the students. What will be novel is the perspective. Students will spend all of the first session figuring out that the best explanation for all the phenomena that we see in the sky is that the earth is at the center of the universe and does not move, while the Moon, Sun, the

9 planets and stars revolve around it. The same conclusion (not surprisingly) was reached by ancient and medieval civilizations around the globe. Suggestions Usually we take for granted that a high school student (or college student) knows the answer to questions like: What causes the seasons on Earth? and Why does the moon have phases? They can even recite the correct answer when asked. However, never underestimate the power of very simple demos explaining phenomena like these!

10 Session 2: What is that light in the sky? part 2 Learning Outcomes Upon completion of this session, students will: Duration Know that Galileo discovered the telescope. Find out how Galileo s discoveries ultimately led to the rejection of the idea that the earth is at the center of the solar system. Understand how the heliocentric model can explain some weird phenomena (especially the retrograde motion of planets). About 50 minutes. Activities A demonstration of how a simple telescope works would be ideal. All that is required is a pair of convex lenses. Alternatively, a galileoscope can be used (see Suggestions on how to get one). Also, a demonstration of how the phases of Venus arise is (almost) mandatory! Materials A light bulb and a tennis ball. A pair of convex lenses or a galileoscope (if available). Background Information This is also material that most students will have heard before. However, many times students are not aware of how Galileo s use of the telescope lead to signs, first, and a proof, at last (Venus phases), that the geocentric universe could not be right.

11 Suggestions A galileoscope can be ordered online at It is really inexpensive (about $15-20) and just assembling can be a very instructive activity. Of course, you will then have a telescope for life with which you can see the Moon, the planets and even clusters of stars. (Warning: delivery of the galileoscope can take several weeks. Try to order it in advance!)

12 Session 3: Is seeing believing? part 1 Learning Outcomes Upon completion of this session, students will: Duration Find out that there is more light in nature than our eyes can see. See how some of these other kinds of light were discovered. (Get to see what the first ever X-ray looked like! ) About 50 minutes. Activities This session can be fully interactive if desired, but it takes time, planning, materials and student participation. Both the Ritter and Herschel experiments can be a fun and rewarding activity for students. These experiments can either be performed during the session or be assigned as homework to the students (see Suggestions on how to perform these experiments). Materials See Suggestions. Background Information The history of the discovery of other forms of light is usually not taught in school (or in college). So the students will hear new things, and will get a chance to appreciate original thinking that, when matched by hard work and patience, can lead to exciting discoveries. Suggestions If people in the beginning of the 19 th century were able to perform the experiments with minimal equipment, then any class should be able to replicate them! Visit

13 for instructions on how to perform the Ritter and Herschel experiments. Be aware that these experiments need time, materials and organization and need to be performed in advance by the instructor so that he/she knows what problems may arise and how to make the experiment work.

14 Session 4: Is seeing believing? part 2 Learning Outcomes Upon completion of this session, students will: Have seen some cool multi-wavelength astronomical pictures. May have played with an infrared camera. Duration About 50 minutes. Activities This session is ideal for a demo using an infrared camera (if available). Students are guaranteed to enjoy it and will also understand how different the images of an object look like when viewed in different wavelength. Materials An infrared camera and a projector. Any of the following items can make the experience more fun: hot and cold beverages, ice cubes, Plexiglas, black plastic bags, blowtorch, liquid nitrogen etc. Background Information If an infrared camera is available, this can be the fun part of the mini-course. Mostly concentrate on having a fun time. If not, then this session can be a showcase of beautiful multi-wavelength astronomical images, and will help students realize why it is so important to study the universe in these other wavelengths.

15 Suggestions Tons of Multiwavelength astronomy pictures can be found on wavelength_astronomy/ or or simply by searching on the web for UV Andromeda or radio galaxy. There are many fun activities that can be done with an IR camera. Remember that IR radiation tracks heat, so that a hot object looks bright and a cold object looks dark. You can use this fact to devise games such as guessing which mug in the room contains hot coffee and which mug contains iced tea, having students paint their faces with ice cubes. You can also see the trace of your footprint or your handprint (if your feet and hands are warm!), by the heat they have deposited on the floor/desk Also, it is always fun to play with the notion of some material being transparent or not. Students will discover that Plexiglas is transparent to visible light but completely opaque to infrared light and that most black plastic bags are completely transparent to IR radiation.

16 Session 5: Dark matter, Dark Energy part 1 Learning Outcomes Upon completion of this session, students will: Duration Will know how to weigh an astronomical object. Find out that something funny happens when you weigh a galaxy. About 50 minutes. Activities A few calculations can be carried out on the board, if the class shows interest for that. For example students may be asked to calculate the mass of the Sun from the earth s distance from the Sun and the length of a year, or the mass of the Earth from the properties of the orbit of the Moon. Background Information It is challenging for the presenter to keep this session on a simple level and make it interesting for the students. It is also challenging for the students to understand some of the concepts involved. So don t worry if students do not grasp everything you say right away! However, it is a great way to see how scientists deal with a problem in their current understanding of nature. Examining all the alternatives, challenge previous knowledge and experimental testing are key ingredients in scientific crises like the one that lead to the realization of the existence of Dark Matter. Give the students the opportunity to list the possible explanations for the problem themselves and let them draw the conclusions. This will make them think like real scientists!

17 Suggestions Feel free to derive some simple relations on the board if the class seems interested in math, but be careful, because the easiest way of losing a student s attention is by writing math on the board!

18 Session 6: Dark matter, Dark Energy part 2 Learning Outcomes Upon completion of this session, students will: Duration Know that the universe expands, and that is expanding ever faster. Understand that this accelerated expansion of the universe cannot be accomplished by any kind of matter. About 50 minutes. Background Information This is also a challenging session. Try to keep it as simple as possible, and give to the students the opportunity to draw the conclusions themselves. Be sure to thank the kids for their attention! Suggestions This last session can be replaced by a Q&A session, where kids can ask you questions about aliens, black holes, galaxies, the universe etc. or even simply about studying, college and school in general. This option will give a relaxing and relatively low key last session for the students to remember!

19 Resource Materials Order a small and really inexpensive telescope: Instructions for the Ritter and Herschel experiments: ex.html Multi-wavelength Astronomy pictures: omy/multiwavelength_astronomy/ or

20 Appendix Together with this word document I have submitted the power-point presentations for the 2 first units (What is that light in the sky? and Is seeing believing?). The power-point presentation for the third unit (Dark Matter, Dark Energy ) is also available but is not finished, because I chose a slow pace for the first two units and I chose to have a student Q&A session during the last session. However it gives a good starting point and illustrates the overall spirit!

ASTR : Stars & Galaxies (Spring 2019)... Study Guide for Midterm 1

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