1 00:00:00,000 --> 00:00:04,000 Hey, Dr. Crouch. 2 00:00:04,000 --> 00:00:05,000 Hello, Jennifer. 3 00:00:05,000 --> 00:00:10,000 Math is very important to everyone, but especially to scientists and engineers. 4 00:00:10,000 --> 00:00:14,000 We use ratios in every aspect of research in a microgravity environment. 5 00:00:14,000 --> 00:00:16,000 So, Dr. Crouch, what is microgravity? 6 00:00:16,000 --> 00:00:20,000 Microgravity is a condition where the effects of gravity are, or appear to be, 7 00:00:20,000 --> 00:00:23,000 very much smaller than they normally are here on Earth. 8 00:00:23,000 --> 00:00:28,000 The prefix micro comes from the Greek root mikros, which simply means small. 9 00:00:28,000 --> 00:00:35,000 However, in the scientific metric system, micro literally means one part in a million, or one to one million. 10 00:00:35,000 --> 00:00:41,000 We use the term microgravity to describe the environment on board a spacecraft in orbit around the Earth. 11 00:00:41,000 --> 00:00:42,000 Gravity is everywhere. 12 00:00:42,000 --> 00:00:48,000 We usually call it high gravity if it's more than here on Earth, and low gravity if it's less than here on Earth. 13 00:00:48,000 --> 00:00:51,000 An example of a low-gravity environment would be the Moon. 14 00:00:51,000 --> 00:00:54,000 The gravity on the Moon is about one-sixth of that here on Earth. 15 00:00:54,000 --> 00:00:57,000 Hey, one-sixth, that's a ratio. 16 00:00:57,000 --> 00:00:58,000 That's right. 17 00:00:58,000 --> 00:01:01,000 What are the quantities being compared in this statement? 18 00:01:01,000 --> 00:01:04,000 The gravity of the Moon is about one-sixth that on Earth. 19 00:01:04,000 --> 00:01:10,000 If you said the Moon's gravity to the Earth's gravity, then you're starting to understand ratios. 20 00:01:10,000 --> 00:01:15,000 The ratio one-sixth means that the gravity of the Moon is six times smaller than the gravity on Earth. 21 00:01:15,000 --> 00:01:22,000 We sometimes use the term microgravity to describe a condition where gravity is not small, but appears to be small. 22 00:01:22,000 --> 00:01:27,000 This is a condition experienced on orbiting spacecraft such as the International Space Station, or ISS, 23 00:01:27,000 --> 00:01:30,000 the space shuttle, and all objects in free fall. 24 00:01:30,000 --> 00:01:33,000 That's me appearing to float inside the space shuttle. 25 00:01:33,000 --> 00:01:37,000 Really, I'm not floating, but falling at the same rate as the shuttle. 26 00:01:37,000 --> 00:01:39,000 So to the observer, it looks like I'm floating. 27 00:01:39,000 --> 00:01:42,000 So microgravity is not really zero gravity. 28 00:01:42,000 --> 00:01:43,000 That's right. 29 00:01:43,000 --> 00:01:48,000 It diminishes relatively quickly with distance, so it's weaker on the space station than it is on Earth. 30 00:01:48,000 --> 00:01:55,000 But it's 6,400 kilometers from the surface to the center of the Earth, which is considered the origin of the Earth's gravity field. 31 00:01:55,000 --> 00:01:59,000 Then the ISS is only another 400 kilometers above the surface of the Earth. 32 00:01:59,000 --> 00:02:08,000 So at that altitude, the gravitational acceleration is still about 89 percent, or 89 one-hundredths, of that of the Earth's surface. 33 00:02:08,000 --> 00:02:13,000 If the gravitational acceleration on the surface of the Earth is 9.8 meters per second squared, 34 00:02:13,000 --> 00:02:18,000 what would the gravitational acceleration be 400 kilometers above the surface of the Earth? 35 00:02:18,000 --> 00:02:19,000 Let's see. 36 00:02:19,000 --> 00:02:30,000 You would approximate the gravitational acceleration at 400 kilometers above the Earth's surface by calculating the product of 9.8 and .89, or 89 one-hundredths. 37 00:02:30,000 --> 00:02:31,000 That's correct. 38 00:02:31,000 --> 00:02:42,000 By multiplying 9.8 and .89, we see that the gravitational acceleration at 400 kilometers above the Earth's surface is about 8.7 meters per second squared. 39 00:02:42,000 --> 00:02:50,000 Comparing 9.8 and 8.7 meters per second squared, gravity at the altitude of the ISS is nearly the same as that on Earth. 40 00:02:50,000 --> 00:02:56,000 But given the images of floating astronauts, it appears that gravity is reduced by much more than 11 percent. 41 00:02:56,000 --> 00:02:58,000 So Dr. Crouch, what is happening here? 42 00:02:58,000 --> 00:03:02,000 Gravity attracts all objects towards the center of the Earth at the same rate. 43 00:03:02,000 --> 00:03:12,000 If I release two objects of different weight and they have room to fall, they will accelerate towards the center of the Earth at the same rate until they meet the resistance in the form of the floor, for instance. 44 00:03:12,000 --> 00:03:15,000 In other words, they'll hit the floor at the same time. 45 00:03:15,000 --> 00:03:18,000 It's the force of the floor that we feel is our weight. 46 00:03:18,000 --> 00:03:23,000 When gravity is the only force acting on an object, then it is said to be in a state called free fall. 47 00:03:23,000 --> 00:03:26,000 Objects in free fall can be said to be weightless. 48 00:03:26,000 --> 00:03:30,000 Imagine you have an apple on a scale which displays the apple's weight. 49 00:03:30,000 --> 00:03:33,000 If you drop the scale, the apple and the scale will fall together. 50 00:03:33,000 --> 00:03:38,000 But the apple will no longer compress the scale, so the scale will show zero weight. 51 00:03:38,000 --> 00:03:44,000 In the same way, astronauts inside the ISS or the space shuttle are falling around the Earth. 52 00:03:44,000 --> 00:03:55,000 Unlike the apple on the scale, both the astronauts and the spacecraft free fall by circling the Earth at approximately 7,870 meters per second or 17,000 miles per hour. 53 00:03:55,000 --> 00:03:58,000 They're falling towards the Earth, they just never get there. 54 00:03:58,000 --> 00:04:03,000 How are the concepts of measurement and graphing important to NASA researchers and scientists? 55 00:04:03,000 --> 00:04:10,000 Research in the space environment gives scientists a new tool for looking at phenomena in ways that is just not possible here on Earth. 56 00:04:10,000 --> 00:04:17,000 But these discoveries won't take place without understanding and applying the math concepts of measurement and graphing. 57 00:04:17,000 --> 00:04:20,000 To demonstrate how scientists and researchers use these concepts, 58 00:04:20,000 --> 00:04:26,000 Dr. Sandra Olson, a microgravity combustion scientist at the NASA Glenn Research Center, will tell us more. 59 00:04:26,000 --> 00:04:28,000 Oh, great. Thank you so much, Dr. Crouch. 60 00:04:28,000 --> 00:04:29,000 Thank you, Jennifer. I enjoyed it. 61 00:04:29,000 --> 00:04:34,000 Now, before we visit Dr. Olson, let's review the math concepts of measurement and graphing. 62 00:04:34,000 --> 00:04:41,000 Measurement. It usually tells us the size of something and consists of a number and a unit. 63 00:04:41,000 --> 00:04:48,000 For example, the gravitational acceleration at the surface of the Earth is 9.8 meters per second squared. 64 00:04:48,000 --> 00:04:53,000 9.8 is the number, and meters per second squared is the unit. 65 00:04:53,000 --> 00:04:58,000 The unit in the measurement is a fixed quantity with a size that is understood. 66 00:04:58,000 --> 00:05:02,000 The number in a measurement tells how many units there are in what is being measured. 67 00:05:02,000 --> 00:05:07,000 This allows us to compare the size of what's being measured to the size of the unit. 68 00:05:07,000 --> 00:05:19,000 For example, Dr. Crouch indicated that the gravitational acceleration 400 kilometers above the Earth's surface is 8.7 meters per second squared units, 69 00:05:19,000 --> 00:05:27,000 compared to the gravitational acceleration at the Earth's surface, which is 9.8 meters per second squared units. 70 00:05:27,000 --> 00:05:31,000 Notice that the unit of measurement is the same for both numbers. 71 00:05:31,000 --> 00:05:37,000 And in case you're wondering, what does the unit meters per second squared mean? 72 00:05:37,000 --> 00:05:42,000 Well, one meter per second squared, or one meter per second per second, 73 00:05:42,000 --> 00:05:48,000 means that for every second of travel, the velocity increases by one meter per second. 74 00:05:48,000 --> 00:05:54,000 So, if the acceleration due to gravity is 9.8 meters per second squared, 75 00:05:54,000 --> 00:06:00,000 then for every second of travel, the velocity increases by 9.8 meters per second. 76 00:06:00,000 --> 00:06:04,000 Okay guys, the next math concept for today's show is graphing. 77 00:06:04,000 --> 00:06:13,000 And graphing is really important because it creates a visual representation of relationships that may not be easily determined using numbers alone. 78 00:06:13,000 --> 00:06:17,000 And there are many different types of graphs that can be used to visually represent data. 79 00:06:17,000 --> 00:06:25,000 There are bar graphs, circle graphs, line graphs, pictographs, and scatter plots, just to name a few. 80 00:06:25,000 --> 00:06:32,000 Remember when Dr. Crouch told us that gravity diminishes as we get farther and farther away from the Earth? 81 00:06:32,000 --> 00:06:35,000 We can represent this visually with a graph. 82 00:06:35,000 --> 00:06:39,000 The x-axis, or horizontal axis, represents distance. 83 00:06:39,000 --> 00:06:44,000 And the y-axis, or vertical axis, represents gravity. 84 00:06:44,000 --> 00:06:49,000 From the graph, you can see that gravity decreases with increasing distance.