1 00:00:00,000 --> 00:00:03,000 Now that you have a better understanding of scaling, 2 00:00:03,000 --> 00:00:06,000 let's turn our attention to the focus of today's program, 3 00:00:06,000 --> 00:00:09,000 which is scaling the solar system. 4 00:00:09,000 --> 00:00:11,000 Dr. Stan Odenwald, an astronomer and scientist 5 00:00:11,000 --> 00:00:14,000 at NASA Goddard Space Flight Center, has a scoop. 6 00:00:17,000 --> 00:00:18,000 Thanks, Jennifer. 7 00:00:18,000 --> 00:00:21,000 When we talk about the distances between points of interest, 8 00:00:21,000 --> 00:00:23,000 we instinctively use units that make sense to us 9 00:00:23,000 --> 00:00:25,000 and that are convenient. 10 00:00:25,000 --> 00:00:27,000 For example, what unit of measure would you use 11 00:00:27,000 --> 00:00:29,000 to describe the distance from Washington, D.C. 12 00:00:29,000 --> 00:00:31,000 to Los Angeles, California? 13 00:00:31,000 --> 00:00:35,000 Would you use miles, inches, kilometers, or meters? 14 00:00:35,000 --> 00:00:37,000 What about your height? 15 00:00:37,000 --> 00:00:40,000 Would you measure it in inches or feet? 16 00:00:40,000 --> 00:00:42,000 And how about the width of your classroom? 17 00:00:42,000 --> 00:00:45,000 Do you use kilometers, meters, or feet? 18 00:00:45,000 --> 00:00:48,000 You can choose any unit of measure you wish, 19 00:00:48,000 --> 00:00:51,000 as long as it's convenient for everyone to understand. 20 00:00:51,000 --> 00:00:54,000 When describing distances at the scale of the solar system, 21 00:00:54,000 --> 00:00:56,000 even units like miles and kilometers 22 00:00:56,000 --> 00:00:59,000 lead to numbers that are in the millions or the billions, 23 00:00:59,000 --> 00:01:01,000 and that makes it very hard to understand them. 24 00:01:01,000 --> 00:01:04,000 For example, the distance between the Earth and the Sun 25 00:01:04,000 --> 00:01:07,000 is about 149 million kilometers. 26 00:01:07,000 --> 00:01:09,000 Between the Sun and Pluto, 27 00:01:09,000 --> 00:01:12,000 the distance is about 5.9 billion kilometers. 28 00:01:12,000 --> 00:01:15,000 But suppose we wanted to compare these two numbers. 29 00:01:15,000 --> 00:01:17,000 It's not easy to see that Pluto 30 00:01:17,000 --> 00:01:21,000 is about 40 times as far from the Sun as Earth is. 31 00:01:21,000 --> 00:01:24,000 It would make sense to use a smaller scale 32 00:01:24,000 --> 00:01:27,000 in order to get a better idea of the distances between the planets. 33 00:01:27,000 --> 00:01:30,000 To come up with that scale, we have to define a baseline. 34 00:01:30,000 --> 00:01:32,000 The baseline that astronomers use 35 00:01:32,000 --> 00:01:34,000 is the distance between the Earth and the Sun. 36 00:01:34,000 --> 00:01:37,000 This distance is known as the astronomical unit. 37 00:01:37,000 --> 00:01:40,000 The astronomical unit, or AU, 38 00:01:40,000 --> 00:01:43,000 represents the distance between the Earth and the Sun, 39 00:01:43,000 --> 00:01:45,000 which is about 93 million miles. 40 00:01:45,000 --> 00:01:48,000 The astronomical unit is the baseline that astronomers use 41 00:01:48,000 --> 00:01:51,000 to determine the distances to the planets in our solar system 42 00:01:51,000 --> 00:01:53,000 and to the stars beyond. 43 00:01:53,000 --> 00:01:56,000 So let's have a look at the scale of the solar system 44 00:01:56,000 --> 00:01:59,000 where one astronomical unit equals 93 million miles. 45 00:01:59,000 --> 00:02:01,000 Based on the astronomical unit, 46 00:02:01,000 --> 00:02:03,000 it's easy to compare the distances 47 00:02:03,000 --> 00:02:06,000 between all the other objects in the solar system. 48 00:02:06,000 --> 00:02:09,000 The accompanying chart shows the distances to the planets from the Sun 49 00:02:09,000 --> 00:02:11,000 in terms of astronomical units. 50 00:02:11,000 --> 00:02:13,000 Let's look at Mars. 51 00:02:13,000 --> 00:02:15,000 We can quickly see that Mars 52 00:02:15,000 --> 00:02:18,000 is one and a half times further away from the Sun than Earth is. 53 00:02:18,000 --> 00:02:21,000 So how far is Mars from the Sun in miles? 54 00:02:21,000 --> 00:02:24,000 Remember the process Jennifer demonstrated earlier in the program 55 00:02:24,000 --> 00:02:27,000 to solve problems involving scaling? 56 00:02:27,000 --> 00:02:30,000 We can solve the Mars distance problem using a proportion. 57 00:02:30,000 --> 00:02:32,000 The first ratio is the scale, 58 00:02:32,000 --> 00:02:35,000 and the second ratio is the distance of Mars to the Sun. 59 00:02:35,000 --> 00:02:39,000 N miles represents the distance from Mars to the Sun. 60 00:02:39,000 --> 00:02:42,000 After setting these ratios equal to each other, 61 00:02:42,000 --> 00:02:44,000 let's find the cross products. 62 00:02:44,000 --> 00:02:51,000 The equation becomes 1 times N equals 93 million times 1.52. 63 00:02:51,000 --> 00:02:54,000 Multiplying, we get the distance from Mars to the Sun 64 00:02:54,000 --> 00:02:57,000 to be approximately 141 million miles. 65 00:02:57,000 --> 00:03:01,000 Using the astronomical unit instead of the mile or the kilometer 66 00:03:01,000 --> 00:03:03,000 makes it easier to compare the distances 67 00:03:03,000 --> 00:03:05,000 between the planets and the Sun. 68 00:03:05,000 --> 00:03:07,000 For example, it's easier to remember 69 00:03:07,000 --> 00:03:10,000 that Mars is one and a half times further away from the Sun than the Earth 70 00:03:10,000 --> 00:03:13,000 than it is to remember that it's 48 million miles 71 00:03:13,000 --> 00:03:16,000 farther away from the Sun than the Earth. 72 00:03:16,000 --> 00:03:19,000 If you recall from earlier in the program, 73 00:03:19,000 --> 00:03:21,000 the Voyager spacecraft is 8 billion miles 74 00:03:21,000 --> 00:03:24,000 or 13 billion kilometers from the Earth. 75 00:03:24,000 --> 00:03:26,000 It's at the far edge of our solar system, 76 00:03:26,000 --> 00:03:29,000 ready to head out into interstellar space. 77 00:03:29,000 --> 00:03:32,000 Based on what you've learned about scaling and the astronomical unit, 78 00:03:32,000 --> 00:03:35,000 can you estimate the distance of Voyager 1 from the Earth 79 00:03:35,000 --> 00:03:37,000 in astronomical units? 80 00:03:37,000 --> 00:03:39,000 Working with a partner, take a few minutes 81 00:03:39,000 --> 00:03:41,000 and see if you can solve this problem. 82 00:03:41,000 --> 00:03:44,000 Voyager 1 is over 8 billion miles away from Earth. 83 00:03:44,000 --> 00:03:47,000 Estimate how far, in astronomical units, 84 00:03:47,000 --> 00:03:50,000 Voyager 1 is from the Earth. 85 00:03:50,000 --> 00:03:55,000 Remember the scale is 1 astronomical unit equals 93 million miles. 86 00:03:55,000 --> 00:03:57,000 Teachers, you may now pause the program 87 00:03:57,000 --> 00:04:00,000 so students can answer the problem. 88 00:04:00,000 --> 00:04:02,000 Okay, so what did you come up with? 89 00:04:02,000 --> 00:04:06,000 If you said that Voyager was 86 astronomical units away from the Earth, 90 00:04:06,000 --> 00:04:07,000 you were correct. 91 00:04:07,000 --> 00:04:10,000 Do you have a sense for how far that is? 92 00:04:10,000 --> 00:04:13,000 The planet Pluto is 40 astronomical units away from the Earth. 93 00:04:13,000 --> 00:04:18,000 So that means Voyager is twice as far away from the Earth as the planet Pluto. 94 00:04:18,000 --> 00:04:20,000 Suppose that Voyager 1 were stationary 95 00:04:20,000 --> 00:04:25,000 and you were able to ride in a car traveling at 55 miles per hour to get to it. 96 00:04:25,000 --> 00:04:30,000 The trip would take you over 16,000 years just to reach the satellite. 97 00:04:30,000 --> 00:04:33,000 That would be quite a lengthy and expensive vacation. 98 00:04:33,000 --> 00:04:36,000 Jennifer, I think the students are ready for that hands-on activity now. 99 00:04:36,000 --> 00:04:38,000 Could you send them back to me when you're finished? 100 00:04:38,000 --> 00:04:41,000 I have a real tough question for them to answer.