1 00:00:00,000 --> 00:00:04,030 Now this is a familiar scene. 2 00:00:04,050 --> 00:00:08,050 The Sun's heat causes water 3 00:00:08,070 --> 00:00:12,070 from plants, lakes and oceans to turn from a liquid to a vapor. 4 00:00:12,090 --> 00:00:16,080 High in the atmosphere 5 00:00:16,100 --> 00:00:20,090 the water vapor then cools down and condenses from a gas 6 00:00:20,110 --> 00:00:24,150 back into a liquid. The liquid 7 00:00:24,170 --> 00:00:28,190 water then falls back to the surface in the form of rain, snow, ice, 8 00:00:28,210 --> 00:00:32,240 or hail. Water 9 00:00:32,260 --> 00:00:36,270 runs off into streams, lakes and oceans or is stored in the ground or 10 00:00:36,290 --> 00:00:40,300 in snowpack. 11 00:00:40,320 --> 00:00:44,320 This is the water cycle, and it describes 12 00:00:44,340 --> 00:00:48,340 how our most vital resource moves through the whole Earth system. 13 00:00:48,360 --> 00:00:52,360 But like most things in our world, when we 14 00:00:52,380 --> 00:00:56,370 look at the tiny parts that make up the whole, we can learn a lot more about the 15 00:00:56,390 --> 00:01:00,420 phenomena. Take 16 00:01:00,440 --> 00:01:04,440 the shape of a single raindrop. Small droplets of 17 00:01:04,460 --> 00:01:08,450 water in the atmosphere are spherical in shape due to the surface tension, or 18 00:01:08,470 --> 00:01:12,470 "skin," of the water molecules. As these droplets grow 19 00:01:12,490 --> 00:01:16,490 they become heavier and start to fall through the air. 20 00:01:16,510 --> 00:01:20,500 As they fall, the raindrop collides with other drops and continues to get 21 00:01:20,520 --> 00:01:24,510 bigger. These larger raindrops fall through the air faster. 22 00:01:24,530 --> 00:01:28,520 The wind resistance on the underside of the drop causes the bottom 23 00:01:28,540 --> 00:01:32,580 of the drop to flatten, resulting in a drop looking like a hamburger bun. 24 00:01:32,600 --> 00:01:36,630 As the drop continues to fall and grow, at some point, it becomes too 25 00:01:36,650 --> 00:01:40,670 large for the surface tension to hold it together, so the raindrop breaks 26 00:01:40,690 --> 00:01:44,710 apart into smaller spherical drops. Investigating the proceses 27 00:01:44,730 --> 00:01:48,740 we can't see with the naked eye is nothing new. Science and technology 28 00:01:48,760 --> 00:01:52,760 drive each other forward and often lead to insights and discoveries along the way. 29 00:01:52,780 --> 00:01:56,780 With the invention of high-speed photography, we finally saw 30 00:01:56,800 --> 00:02:00,800 the most basic elements of our watery planet in action. 31 00:02:00,820 --> 00:02:04,810 Understanding how a tiny 32 00:02:04,830 --> 00:02:08,860 raindrop falls through the atmosphere does more than debunk the myth that a 33 00:02:08,880 --> 00:02:12,960 raindrop falls like a teardrop. It actually makes a difference when it comes to 34 00:02:12,980 --> 00:02:17,000 measuring precipitation, in particular, for ground radars. 35 00:02:17,020 --> 00:02:21,040 Ground radars look at the sides of the raindrops and then estimate 36 00:02:21,060 --> 00:02:25,070 the vertical and horizontal size. A heavier flatter drop allows 37 00:02:25,090 --> 00:02:29,100 radars to identify heavier precipitation. In fact the two 38 00:02:29,120 --> 00:02:33,130 radars on board the GPM satellite can also measure drop sizes 39 00:02:33,150 --> 00:02:37,140 from space and so a more accurate look at raindrops gives us a more 40 00:02:37,160 --> 00:02:41,150 accurate look at how global rainfall is shaping up. 41 00:02:41,170 --> 00:02:45,160 42 00:02:45,180 --> 00:02:50,017