1 00:00:00,000 --> 00:00:14,420 Welcome to NASA Connect, I'm Jennifer Follate and this is the National Museum of the American 2 00:00:14,420 --> 00:00:15,420 Indian. 3 00:00:15,420 --> 00:00:19,280 And I'm Dr. Stan Odenwald at an archeological site in Mexico. 4 00:00:19,280 --> 00:00:20,400 Hola! 5 00:00:20,400 --> 00:00:26,960 This is NASA Connect, the show that connects you to math, science, technology and NASA. 6 00:00:26,960 --> 00:00:32,480 On today's program, you will see how ancient cultures found a connection to the stars. 7 00:00:32,480 --> 00:00:37,840 You will also learn how many of these societies were very sophisticated when making celestial 8 00:00:37,840 --> 00:00:38,840 observations. 9 00:00:38,840 --> 00:00:43,160 You'll also learn about the mathematics and geometry used by these ancient peoples to 10 00:00:43,160 --> 00:00:45,000 make their observations. 11 00:00:45,000 --> 00:00:48,000 What you will learn today will absolutely astound you. 12 00:00:48,000 --> 00:00:50,600 But first, Jennifer, tell us about that building that you're in. 13 00:00:50,600 --> 00:00:56,140 Stan, this is the newest museum in our nation's capital. 14 00:00:56,140 --> 00:01:01,840 As you enter the museum, hundreds of written and spoken words, meaning welcome, in native 15 00:01:01,840 --> 00:01:06,500 languages throughout the Americas are projected onto this wall. 16 00:01:06,500 --> 00:01:12,260 These people, not only here in the Americas, but also their brothers and sisters in Africa, 17 00:01:12,260 --> 00:01:17,540 Asia, Europe and the Pacific, looked at our starry skies. 18 00:01:17,540 --> 00:01:21,180 All of these people had a connection to the sun. 19 00:01:21,180 --> 00:01:24,700 In the museum, this room celebrates the sun. 20 00:01:24,700 --> 00:01:33,380 In this circle, the four cardinal directions, north, south, east and west, extend out of 21 00:01:33,380 --> 00:01:34,380 the building. 22 00:01:34,380 --> 00:01:38,420 The angles of solstices and equinoxes are mapped on the floor. 23 00:01:38,420 --> 00:01:44,100 A light spectrum is cast by the sun, which shines through the prisms set into the south-facing 24 00:01:44,100 --> 00:01:45,100 wall. 25 00:01:45,100 --> 00:01:50,380 Each prism is sighted to the sun for a particular time of day and season. 26 00:01:50,380 --> 00:01:55,620 The dramatic designs in this modern museum show the connection between astronomy, nature 27 00:01:55,620 --> 00:01:56,620 and people. 28 00:01:56,620 --> 00:02:01,740 That connection is the key to understanding how the ancients looked at our universe, which 29 00:02:01,740 --> 00:02:04,340 is the theme of today's program. 30 00:02:04,340 --> 00:02:07,260 Today we will talk to Native American astronomers. 31 00:02:07,260 --> 00:02:13,140 Dr. Stan Odenwald will treat us to the foundations of astronomy as we know it today. 32 00:02:13,140 --> 00:02:17,620 And he will fill us in on the celestial accomplishments of the Mayans. 33 00:02:17,620 --> 00:02:22,300 Throughout the program, you will be asked to answer several inquiry-based questions. 34 00:02:22,300 --> 00:02:26,660 After the questions appear on the screen, your teacher will pause the program to allow 35 00:02:26,660 --> 00:02:29,980 you time to answer and discuss the questions. 36 00:02:29,980 --> 00:02:34,340 This is your time to explore and become critical thinkers. 37 00:02:34,340 --> 00:02:38,260 Now let's learn more about ancient observatories. 38 00:02:38,260 --> 00:02:43,580 The science of interpreting the relationship between the sun and the daily lives of primitive 39 00:02:43,580 --> 00:02:47,500 people is called archaeoastronomy. 40 00:02:47,500 --> 00:02:54,140 Archaeo meaning archaeology, and astronomy meaning the study of stars. 41 00:02:54,140 --> 00:03:00,060 Observing celestial phenomena is the one constant that unifies humankind throughout space and 42 00:03:00,060 --> 00:03:02,020 time. 43 00:03:02,020 --> 00:03:08,260 Ancient man knew celestial events followed cycles, circles, and these events could be 44 00:03:08,260 --> 00:03:09,940 recorded. 45 00:03:09,940 --> 00:03:16,380 Approximately 5,000 years ago, they devised a way to place stones in certain positions 46 00:03:16,460 --> 00:03:20,180 to align for lunar and solar events. 47 00:03:20,180 --> 00:03:25,460 Events like seasons were noted and found to recur regularly with certain positions 48 00:03:25,460 --> 00:03:27,580 of the sun and stars. 49 00:03:27,580 --> 00:03:32,620 The Earth spins on its axis once every day and gives us the familiar experience of daytime 50 00:03:32,620 --> 00:03:33,780 and nighttime. 51 00:03:33,780 --> 00:03:38,940 For thousands of years, humans have used this cosmic cycle to regulate their workday, their 52 00:03:38,940 --> 00:03:41,400 meals, and their sleep. 53 00:03:41,440 --> 00:03:48,600 The Earth orbits the sun once every year and from this we get the familiar 365-day cycle. 54 00:03:48,600 --> 00:03:53,200 Earth's orbit around the sun is an ellipse, basically that means an oval, with the sun 55 00:03:53,200 --> 00:03:55,720 offset from the center of the ellipse. 56 00:03:55,720 --> 00:03:59,400 Does this mean that we have summer when the Earth is closest to the sun and winter when 57 00:03:59,400 --> 00:04:01,800 the Earth is farthest from the sun? 58 00:04:01,800 --> 00:04:06,160 The surprising fact is that the distance from the Earth to the sun has absolutely nothing 59 00:04:06,160 --> 00:04:08,200 to do with the changing seasons. 60 00:04:08,200 --> 00:04:12,320 Our northern hemisphere is closest to the sun in January and farthest from the sun in 61 00:04:12,320 --> 00:04:13,540 July. 62 00:04:13,540 --> 00:04:16,160 So what is causing the change in temperature? 63 00:04:16,160 --> 00:04:21,440 Earth's axis is tilted by 23.5 degrees from a line perpendicular to Earth's orbit. 64 00:04:21,440 --> 00:04:22,800 What does this mean? 65 00:04:22,800 --> 00:04:26,560 To understand this tilt, we have to use a bit of basic geometry. 66 00:04:26,560 --> 00:04:29,520 An angle has two sides and a vertex. 67 00:04:29,520 --> 00:04:34,500 The sides are rays that share a common endpoint called the vertex. 68 00:04:34,500 --> 00:04:38,860 The angle formed by two rays can be named in a variety of ways. 69 00:04:38,860 --> 00:04:50,340 For example, the angle formed by ray AB and ray AC can be named angle BAC, angle CAB or 70 00:04:50,340 --> 00:04:52,420 angle A for short. 71 00:04:52,420 --> 00:04:59,580 Notice that A must be the middle letter in both three-letter names because it's the vertex. 72 00:04:59,580 --> 00:05:02,360 You can measure angles using a protractor. 73 00:05:02,360 --> 00:05:05,320 The unit of measure is degrees. 74 00:05:05,320 --> 00:05:12,920 Angles can be classified by their measures as acute, right, obtuse and straight. 75 00:05:12,920 --> 00:05:19,140 If the Earth rotated on its axis perpendicular to or at a right angle to the orbit, there 76 00:05:19,140 --> 00:05:21,960 would be no changes in temperature. 77 00:05:21,960 --> 00:05:28,000 The Earth rotates at an angle 23.5 degrees from this perpendicular line. 78 00:05:28,000 --> 00:05:33,520 Notice a very small tilt but enough to affect the sun's rays hitting the Earth. 79 00:05:33,520 --> 00:05:39,000 This is a great time to pause the program and think about the following questions. 80 00:05:39,000 --> 00:05:43,800 Why is the area near Earth's equator hotter than the areas near the poles? 81 00:05:43,800 --> 00:05:50,720 If the tilt of Earth's axis measured 33 degrees rather than 23.5, how might seasonal changes 82 00:05:50,720 --> 00:05:52,800 and temperature ranges differ? 83 00:05:52,800 --> 00:05:56,800 Teachers, it's now time to pause the program. 84 00:05:56,800 --> 00:05:59,680 The tilt of the Earth's axis gives us our seasons. 85 00:05:59,680 --> 00:06:04,000 And because of the extremes in heat and cold, it's very important to keep track of the changing 86 00:06:04,000 --> 00:06:06,520 seasons if you're growing food. 87 00:06:06,520 --> 00:06:11,040 This seasonal cycle is important to ancient and even modern people. 88 00:06:11,040 --> 00:06:16,320 In some parts of the world, like the arid climates of the southwest states of the USA, 89 00:06:16,320 --> 00:06:20,680 the growing season was so short that people could not waste much time getting the seeds 90 00:06:20,680 --> 00:06:23,400 in the ground at the start of spring. 91 00:06:23,400 --> 00:06:26,720 But how do we predict when the growing season will begin in the spring? 92 00:06:26,720 --> 00:06:30,560 For that matter, how can we tell when the other seasons begin and end? 93 00:06:30,560 --> 00:06:35,080 It turns out that just by keeping track of how high up the sun gets over the horizon 94 00:06:35,080 --> 00:06:39,720 at noon, you can determine the start of the seasons exactly. 95 00:06:39,720 --> 00:06:45,360 Almost all ancient people that relied on planting times discovered this little relationship. 96 00:06:45,360 --> 00:06:51,520 The start of the four seasons, summer, fall, winter, and spring, are noted by what astronomers 97 00:06:51,520 --> 00:06:58,360 call the summer solstice, the fall equinox, the winter solstice, and the spring equinox. 98 00:06:58,360 --> 00:07:03,160 At the start of summer around June 21st in the northern hemisphere, the sun is at its 99 00:07:03,160 --> 00:07:06,480 highest point above the horizon at noon. 100 00:07:06,480 --> 00:07:11,360 As the sun begins its movement back away from its maximum height, the number of daylight 101 00:07:11,360 --> 00:07:16,200 hours has declined to an equal number of daylight and nighttime hours. 102 00:07:16,200 --> 00:07:19,720 This is the fall equinox near September 21st. 103 00:07:19,720 --> 00:07:24,600 A few months later, the path of the sun arrives at its lowest point at noon. 104 00:07:24,600 --> 00:07:28,760 The sun spends very little time above the horizon of the northern hemisphere, and the 105 00:07:28,760 --> 00:07:31,160 night is much longer than day. 106 00:07:31,160 --> 00:07:37,140 Welcome to the winter solstice, or start of winter, around December 21st. 107 00:07:37,140 --> 00:07:42,280 After a few more months, the path of the sun works its way higher in the sky, eventually 108 00:07:42,280 --> 00:07:45,760 arriving at a path where day and night are equal. 109 00:07:45,760 --> 00:07:50,640 This happens March 21st at the spring equinox, a vital time for planting crops.