WEBVTT FILE 1 00:00:00.020 --> 00:00:04.020 [slate] 2 00:00:04.040 --> 00:00:08.040 [slate] 3 00:00:08.060 --> 00:00:12.070 [slate] 4 00:00:12.090 --> 00:00:16.140 5 00:00:16.160 --> 00:00:20.220 So on August 21st of this year, the moon, sun and Earth 6 00:00:20.240 --> 00:00:24.360 will line up just perfectly so that the moon 7 00:00:24.380 --> 00:00:28.480 comes between the Earth and the sun and casts its shadow 8 00:00:28.500 --> 00:00:32.510 down onto the United States. And 9 00:00:32.530 --> 00:00:36.610 starting in Oregon, the core of its shadow 10 00:00:36.630 --> 00:00:40.740 called the umbra is going to travel across the U.S. in about 11 00:00:40.760 --> 00:00:44.930 1.500 miles per hour ending in South Carolina 12 00:00:44.950 --> 00:00:49.020 and everyone in North America, Central America and 13 00:00:49.040 --> 00:00:53.120 a good portion of South America are going to also experience a partial 14 00:00:53.140 --> 00:00:57.250 solar eclipse. And if you happen to be in that 70 mile 15 00:00:57.270 --> 00:01:01.380 wide path we just saw then you'll get to experience a total 16 00:01:01.400 --> 00:01:05.450 solar eclipse where the moon completely blocks out the bright solar 17 00:01:05.470 --> 00:01:09.500 disk allowing us to see the faint wispy outer 18 00:01:09.520 --> 00:01:13.520 atmosphere of the sun we call the corona. 19 00:01:13.540 --> 00:01:17.620 [slate] 20 00:01:17.640 --> 00:01:21.700 Well this is a special opportunity because at any given 21 00:01:21.720 --> 00:01:25.790 location an eclipse, a total eclipse, is only about 2 to 7 minute 22 00:01:25.810 --> 00:01:29.960 But this one is traveling across the entire United States 23 00:01:29.980 --> 00:01:34.030 and so instead of having an individual observation of 24 00:01:34.050 --> 00:01:38.060 about 2 minutes, we actually get an observation of an hour 25 00:01:38.080 --> 00:01:42.160 and 30 minutes by putting together telescopes all 26 00:01:42.180 --> 00:01:46.210 along the path as well as balloons and sensors all along the path 27 00:01:46.230 --> 00:01:50.410 giving us a unique opportunity to see the rich outer 28 00:01:50.430 --> 00:01:54.490 atmosphere of the sun where all the solar activity happens 29 00:01:54.510 --> 00:01:58.570 In addition we get to the changes in the environment 30 00:01:58.590 --> 00:02:02.730 locally as this shadow passes across the Earth creating its own 31 00:02:02.750 --> 00:02:06.900 microclimate and we get to see the response of animals and plants. 32 00:02:06.920 --> 00:02:11.010 So it's a really amazing opportunity to see not only solar science but 33 00:02:11.030 --> 00:02:15.120 also Earth science in a special unique way. 34 00:02:15.140 --> 00:02:19.160 [slate] 35 00:02:19.180 --> 00:02:23.290 You know we've been looking at the 36 00:02:23.310 --> 00:02:27.440 corona, this outer atmosphere we see during a total solar eclipse 37 00:02:27.460 --> 00:02:31.530 at a distance for hundreds of years. But now we're 38 00:02:31.550 --> 00:02:35.620 launching a spacecraft in 2018, the Parker Solar Probe, which 39 00:02:35.640 --> 00:02:39.770 is going to go to the corona and we're going to get to experience 40 00:02:39.790 --> 00:02:43.970 up close and personal. Literally touching the sun 41 00:02:43.990 --> 00:02:48.040 We will now have unique and critical understanding 42 00:02:48.060 --> 00:02:52.180 that we've never had before of this really vital area in the sun's atmosphere. 43 00:02:52.200 --> 00:02:56.200 [slate] 44 00:02:56.220 --> 00:03:00.400 Well the 45 00:03:00.420 --> 00:03:04.450 sun is extremely active. Not only does it's outer atmosphere stream 46 00:03:04.470 --> 00:03:08.530 away and fill the whole solar system. But it also sends out these 47 00:03:08.550 --> 00:03:12.630 huge explosions of light and material and magnetic field 48 00:03:12.650 --> 00:03:16.750 out into the solar system. It interacts with all of our planets. And 49 00:03:16.770 --> 00:03:20.940 this actually is important for how we define habitability 50 00:03:20.960 --> 00:03:25.020 and what determines whether a planet is like Earth 51 00:03:25.040 --> 00:03:29.160 or a planet is like Mars which actually had its atmosphere stripped away 52 00:03:29.180 --> 00:03:33.320 over billions of years. And this not only tells us about our own 53 00:03:33.340 --> 00:03:37.390 solar system, but also about extra solar systems. Planets 54 00:03:37.410 --> 00:03:41.460 outside of our own solar system and other ones potentially 55 00:03:41.480 --> 00:03:45.580 at some point even in other galaxies, this is. Understanding 56 00:03:45.600 --> 00:03:49.760 our sun and it's interaction with the solar system is telling 57 00:03:49.780 --> 00:03:53.780 us how this happens everywhere in the universe. 58 00:03:53.800 --> 00:03:57.800 [slate] 59 00:03:57.820 --> 00:04:01.990 Well what happens is 60 00:04:02.010 --> 00:04:06.050 the moon doesn't actually orbit in the same plane 61 00:04:06.070 --> 00:04:10.140 as the Earth is orbiting around the sun. In fact 62 00:04:10.160 --> 00:04:14.260 it is slightly inclined approximately 5 degrees 63 00:04:14.280 --> 00:04:18.460 And so what that means is sometimes the moon is 64 00:04:18.480 --> 00:04:22.530 a little bit above the Earth when it casts its shadow 65 00:04:22.550 --> 00:04:26.640 and sometimes it's a little bit below the Earth when it casts its shadow. But 66 00:04:26.660 --> 00:04:30.780 every so often it actually lines up just perfectly 67 00:04:30.800 --> 00:04:34.980 and the shadow is cast on the Earth giving us a partial 68 00:04:35.000 --> 00:04:39.000 and sometimes a total solar eclipse. 69 00:04:39.020 --> 00:04:43.020 [slate] 70 00:04:43.040 --> 00:04:47.040 [slate] 71 00:04:47.060 --> 00:04:51.110 One of the really spectacular things that we've gotten out of 72 00:04:51.130 --> 00:04:55.210 the Lunar Reconnaissance Orbiter, NASA's mission at the moon right now, is the highest resolution 73 00:04:55.230 --> 00:04:59.360 topographic map of any planetary body in the solar system. And that 74 00:04:59.380 --> 00:05:03.390 allows us to accurately predict the path of totality, the shadow 75 00:05:03.410 --> 00:05:07.460 upon the face of the Earth. We now know that path is not a perfect 76 00:05:07.480 --> 00:05:11.560 circle or an ellipse. It's actually an irregularly shaped object. 77 00:05:11.580 --> 00:05:15.730 We can predict exactly where that path will pass across 78 00:05:15.750 --> 00:05:19.910 the United States and allow folks the best opportunities to predict 79 00:05:19.930 --> 00:05:24.010 what and when they'll see the total eclipse. 80 00:05:24.030 --> 00:05:28.020 [slate] 81 00:05:28.040 --> 00:05:32.130 [Young] You can learn more about 82 00:05:32.150 --> 00:05:36.250 eclipses and safety and all the exciting stuff we're doing at 83 00:05:36.270 --> 00:05:40.290 eclipse2017.nasa.gov and check us out on Twitter 84 00:05:40.310 --> 00:05:44.858 @NASASun.