PHYSICS 160: Cosmos Spring 2015 Homework #1 MODEL SOLAR SYSTEM. To get an intuitive feeling for the size of the solar system.

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1 Name Date PHYSICS 160: Cosmos Spring 2015 Homework #1 MODEL SOLAR SYSTEM Purpose: To get an intuitive feeling for the size of the solar system. Perhaps you ve heard the phrase to disappear into empty space. One of the results of this assignment will be to show you just how much empty space there is in space. The other result of this assignment will be that you should have a better understanding of what terms like solar system, galaxy, and universe really mean. These terms are constantly mixed up in the minds of many, not to mention the media; yet they mean radically different things. So in this assignment, as an introduction to the topic of astronomy, we are going to map out our solar system as a stepping stone to understanding the distances between the hundreds of billions of stars that make up our galaxy, which is just one of hundreds of billions of galaxies in our Universe. Introduction PART 1: YOUR PERSONAL PLANET WALK Have you ever looked at a road map while on a long car trip? On the map the dot marking LA and the dot marking New York City are 27 inches apart. In reality we know that the two cities are not actually 27 inches apart. But we do know that the map is to scale. What this means is that we can trust that every inch shown on the map corresponds to some number of miles in real life. This is the map s scale and is usually shown by a bar in the corner somewhere. For the map I ve described above, the scale says that 1 inch = 100 miles (scale = 100 miles/inch). If the two cities are 27 inches apart on the map then they are 2700 miles apart in reality. We are going to make a map of our solar system. The solar system is defined as the whole collection of planets, moons, asteroids, and comets which orbit our Sun, a star. Since the name of our star is Sol, the collection of things orbiting it is the solar system. In addition, I will also give you the real sizes of each of the planets (an added feature, whereas each city on a map is represented by a dot, we will have real markers representing each of the planets). As a result, we will not just be making a map, but rather a real scale model of the solar system.

2 Page 2 Instructions Since the city of Redlands is famous for its oranges and other citrus I would like the Sun in our model to be the size of a large orange or grapefruit: 5 inches in diameter. We will now determine how big our model will need to be in order for the Sun to be an orange. 1. A big orange is about 5 inches in diameter. If the sun is really 1,392,000 km in diameter, what will the scale of this solar system model be in km/inch? In other words, every inch we measure will represent how many kilometers in the solar system? Scale = km/inch 2. We now need to shrink each of the planets by this amount. On Table 1, calculate the diameter of each planet in inches based on the scale you just found. If you ve done everything correctly you should get the same diameter for the Sun as you started with: 5 inches. 3. We will now shrink the distances between the Sun and planets by the same scale. In Table 1, calculate the distance to each planet using the same scale you already found. NOTE: You are going to wind up with A LOT of inches between the Sun and planets, so write your answer in Table 1 in units of YARDS instead of INCHES. Round your answer off to the nearest whole yard.

3 Page 3 Table 1: The size and distances of the planets. Planet Sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Planet Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto Diameter (km) 1,392,000 4,880 12,100 12,800 6, , ,000 52,000 49, Distance (km) 57,000, ,000, ,000, ,000, ,000,000 1,430,000,000 2,880,000,000 4,500,000,000 5,910,000,000 Scaled Diameter (inches) Scaled Distance (yards)

4 Page 4 PART 2: THE STARS BEYOND Our Sun is just one star of 100 billion stars that make up our galaxy called the Milky Way. A galaxy is a collection of billions of stars, gas clouds, and dust that orbit in a large swirling disk or sphere. All the stars you see at night are in our galaxy. There are vast stretches of empty space between galaxies. On the scale of our model solar system let s determine how far away the nearest star is to our own. 1. The nearest star to our own is called Proxima Centauri. It is located 4.3 light years away from us. A light year is the distance light travels in a year. One light year = km. For reference the Earth is located 8 light minutes away from the Sun. How many kilometers away is Proxima Centauri? Distance to Proxima Centauri = km. 2. Given the scale you calculated for our model solar system, how many yards away is the nearest star? Distance to Proxima Centauri = yards. 3. This is a large number of yards. Let s convert this to a more intuitive distance like miles. There are 1760 yards/mile. On the scale of our model, how far away is the nearest star in miles? Distance to Proxima Centauri = miles. 4. Where is this if the Sun is on campus? a) Downtown Redlands b) Downtown Los Angeles c) Downtown Las Vegas d) Downtown New York City Where our Sun is located, on the outskirts of our galaxy, this is the average distance between stars. There are 100 billion stars in our galaxy, and our galaxy is just one of hundreds of billion galaxies in our universe.

5 Page 5 PART 3: For Class Discussion Chapter 1: The Shores of the Cosmic Ocean The following are for you to think about as you read the chapter. They are not to be turned in with the rest of the Homework. They are simply to guide you in our first class discussion. 1. On page 5. Consider the paragraph that starts "The Earth is a place. It is by no means the only place. It is not even a typical place..." This paragraph can be read as very grim and depressing, or very hopeful and optimistic. Which do you feel it is? Which do you think Carl feels it is? Compare this passage (and feeling) with the statement many folks make when looking up at a dark starry sky: "It makes me feel so small and insignificant." 2. The chapter begins with Carl zooming through the Universe in the "realm of the nebulae," but ends with a tour of a library in ancient Egypt. Why does Carl connect these two events? 3. In the Introduction (which begins on page xi) Carl gives his reasons for writing this book. How do you feel about these reasons? How are these reasons supported by the contents of Chapter 1 (including the above quote in Question 1 and the above scenes in Question 2)?