1 00:00:01,840 --> 00:00:07,600 Speaker 1: Welcome to brain Stuff, a production of iHeartRadio. Hey brain Stuff, 2 00:00:07,640 --> 00:00:10,360 Speaker 1: Lauren Vogel Bomb here with another classic episode of the 3 00:00:10,360 --> 00:00:13,200 Speaker 1: show for you. In this one, we talk about the 4 00:00:13,280 --> 00:00:16,520 Speaker 1: strange physics of ice. We are pretty used to it 5 00:00:16,600 --> 00:00:19,320 Speaker 1: looking cloudy and semi opaque when we pull it out 6 00:00:19,320 --> 00:00:22,759 Speaker 1: of our freezers or skate along its surface. But under 7 00:00:22,800 --> 00:00:27,520 Speaker 1: the right circumstances, ice can freeze very clear, creating beautiful 8 00:00:27,720 --> 00:00:34,240 Speaker 1: and sometimes dangerous circumstances. Hey brain Stuff, Lauren Vogel Bomb here. 9 00:00:34,760 --> 00:00:37,640 Speaker 1: When temperatures dip below freezing, it adds a number of 10 00:00:37,680 --> 00:00:41,280 Speaker 1: extra hazards to driving, but perhaps none so tricksy as 11 00:00:41,320 --> 00:00:44,960 Speaker 1: black ice. These are slick patches of ice that blend 12 00:00:45,040 --> 00:00:48,000 Speaker 1: in with the black pavement beneath them because they're so transparent. 13 00:00:48,520 --> 00:00:51,319 Speaker 1: When drivers, blind to the danger steer their cars over 14 00:00:51,360 --> 00:00:53,519 Speaker 1: the ice, they can lose traction and wind up in 15 00:00:53,560 --> 00:00:57,040 Speaker 1: an accident. Other kinds of ice are easier to see. 16 00:00:57,280 --> 00:00:59,880 Speaker 1: You've no doubt noticed that homemade ice cubes usually look 17 00:01:00,040 --> 00:01:02,600 Speaker 1: cloudy in the little opaque in the middle, like whitish 18 00:01:02,640 --> 00:01:06,040 Speaker 1: blocks of cotton candy. That stands in contrast to the 19 00:01:06,080 --> 00:01:09,759 Speaker 1: frightening clarity of black ice. So how come black. Ice 20 00:01:09,840 --> 00:01:12,080 Speaker 1: is see through, but the cubes and your typical ice 21 00:01:12,120 --> 00:01:16,240 Speaker 1: trays are not. Liquid. Water appears to be clear. That's 22 00:01:16,280 --> 00:01:19,080 Speaker 1: because the material neither absorbs nor reflects most of the 23 00:01:19,120 --> 00:01:22,520 Speaker 1: spectrum of visible light. Most wavelengths and spectrum pass right 24 00:01:22,560 --> 00:01:26,640 Speaker 1: through it. And that's right, I said most. Technically, water 25 00:01:26,760 --> 00:01:29,840 Speaker 1: is not colorless, although it often looks that way. Believe 26 00:01:29,880 --> 00:01:32,600 Speaker 1: it or not. The liquid has a natural bluish tint, 27 00:01:32,880 --> 00:01:35,280 Speaker 1: owing to the fact that it absorbs red, yellow, and 28 00:01:35,319 --> 00:01:38,840 Speaker 1: orange light more easily than blue light. But our human 29 00:01:38,880 --> 00:01:41,959 Speaker 1: eyes can only observe this azure quality in deep bodies 30 00:01:41,959 --> 00:01:45,000 Speaker 1: of water. This helps explain why ocean water in glacial 31 00:01:45,000 --> 00:01:47,680 Speaker 1: ice look blue to us, while glassfuls of drinking water 32 00:01:47,720 --> 00:01:52,080 Speaker 1: look transparent. Yet there is a deceptive quality to water. 33 00:01:52,600 --> 00:01:55,440 Speaker 1: No matter how fresh and clear it may seem, it's 34 00:01:55,520 --> 00:01:59,040 Speaker 1: never one hundred percent pure. A sample of H two 35 00:01:59,040 --> 00:02:01,919 Speaker 1: O might contain floating bits of organic matter like algae 36 00:02:02,000 --> 00:02:05,560 Speaker 1: or plant remains, along with suspended sediments, a dust, particles, 37 00:02:05,640 --> 00:02:08,680 Speaker 1: or flex of minerals like calcium and lime. It may 38 00:02:08,720 --> 00:02:12,280 Speaker 1: also harbor lots of dissolved gases, such as oxygen. Without 39 00:02:12,320 --> 00:02:15,440 Speaker 1: said oxygen, fish wouldn't be able to breathe. A Gases 40 00:02:15,480 --> 00:02:18,480 Speaker 1: and physical impurities are the key to understanding why those 41 00:02:18,480 --> 00:02:21,480 Speaker 1: ice cubes in your tray are so darn cloudy. When 42 00:02:21,480 --> 00:02:25,320 Speaker 1: water freezes, internal debris and air bubbles can become concentrated 43 00:02:25,800 --> 00:02:29,280 Speaker 1: the cluster's impede light, causing all the differently colored frequencies 44 00:02:29,280 --> 00:02:32,520 Speaker 1: on the visible light spectrum to scatter. When this happens, 45 00:02:32,520 --> 00:02:35,440 Speaker 1: it makes the ice look white and clouded. But it 46 00:02:35,560 --> 00:02:39,080 Speaker 1: doesn't always happen. Let's take for a case study, a 47 00:02:39,200 --> 00:02:43,480 Speaker 1: YouTuber who once appeared to walk on water. In twenty fourteen, 48 00:02:43,680 --> 00:02:46,880 Speaker 1: Thomas Nunnak filmed himself in a travel companion walking across 49 00:02:46,960 --> 00:02:51,160 Speaker 1: velke Hinkovo Pleso, a deep freshwater lake in the Slovakian Mountains. 50 00:02:51,720 --> 00:02:54,280 Speaker 1: His video went viral because it shows the two men 51 00:02:54,360 --> 00:02:58,240 Speaker 1: standing on some unbelievably clear ice. The lake bottom rocks 52 00:02:58,240 --> 00:03:02,000 Speaker 1: below them are pristinely visible through frozen water. The ice 53 00:03:02,040 --> 00:03:05,120 Speaker 1: in linux video was so transparent that some viewers assumed 54 00:03:05,120 --> 00:03:08,760 Speaker 1: the footage had been faked, but the phenomenon is very real, 55 00:03:09,080 --> 00:03:11,280 Speaker 1: and when the lake freezes over, as it often does, 56 00:03:11,480 --> 00:03:15,280 Speaker 1: the surface ice can be crystal clear. An ice sheet 57 00:03:15,320 --> 00:03:18,120 Speaker 1: needs to be almost entirely free of both air bubbles 58 00:03:18,120 --> 00:03:20,679 Speaker 1: and debris. In order to have this degree of clarity, 59 00:03:21,400 --> 00:03:24,320 Speaker 1: there are other requirements as well. Ice is made up 60 00:03:24,320 --> 00:03:28,040 Speaker 1: of crystals, and when water freezes rapidly, those crystals tend 61 00:03:28,040 --> 00:03:30,839 Speaker 1: to be small and numerous. That makes the ice look 62 00:03:30,880 --> 00:03:34,440 Speaker 1: whiter because each of those crystals have reflective surfaces, so 63 00:03:34,480 --> 00:03:37,160 Speaker 1: if there are more crystals, there'll be more reflection going on, 64 00:03:37,240 --> 00:03:40,280 Speaker 1: which will help scatter in coming light. On the other hand, 65 00:03:40,440 --> 00:03:43,200 Speaker 1: ice that's been slowly frozen is built out of fewer 66 00:03:43,240 --> 00:03:47,880 Speaker 1: and larger crystals, and those promote transparency. So ice will 67 00:03:47,880 --> 00:03:50,640 Speaker 1: only be see through and crystal clear if it freezes 68 00:03:50,680 --> 00:03:54,480 Speaker 1: slowly and doesn't have too many impurities or crystals. Thomas 69 00:03:54,560 --> 00:03:57,080 Speaker 1: Ninnock's now famous YouTube video is what it looks like 70 00:03:57,120 --> 00:03:59,600 Speaker 1: when all these conditions are met. On the day of 71 00:03:59,640 --> 00:04:01,960 Speaker 1: his track, the lake was topped with an icy blanket 72 00:04:02,000 --> 00:04:04,520 Speaker 1: that was around two centimeters thick that's about three quarters 73 00:04:04,560 --> 00:04:07,200 Speaker 1: of an inch. The water must have frozen gradually during 74 00:04:07,200 --> 00:04:09,920 Speaker 1: a tranquil period with no strong winds to deposit debris 75 00:04:10,040 --> 00:04:12,640 Speaker 1: in the lake or to churn up the water. We 76 00:04:12,680 --> 00:04:15,720 Speaker 1: see the same kind of thing happening in roadway black ice. 77 00:04:16,279 --> 00:04:18,640 Speaker 1: Although Not all of this stuff comes from the same source. 78 00:04:18,760 --> 00:04:21,760 Speaker 1: It can start out as fog, mist, drizzle, or melted snow. 79 00:04:22,120 --> 00:04:26,400 Speaker 1: It always freezes slowly during low wind periods. It's consistently thin, 80 00:04:26,640 --> 00:04:30,240 Speaker 1: and it contains very few impurities. That's why black ice 81 00:04:30,320 --> 00:04:35,960 Speaker 1: is so transparent and frustrating to motorists, but highway annoyances. Nonwithstanding, 82 00:04:36,160 --> 00:04:39,039 Speaker 1: transparent ice isn't as common in nature as the white 83 00:04:39,120 --> 00:04:41,919 Speaker 1: clouded variety. There are a lot of reasons why a 84 00:04:41,920 --> 00:04:44,000 Speaker 1: given ice chunk you find out in nature might not 85 00:04:44,080 --> 00:04:47,000 Speaker 1: be clear. Some ice is made up of fallen snowflakes, 86 00:04:47,000 --> 00:04:51,160 Speaker 1: whose angular shapes and irregular crystals scatter light, and sometimes 87 00:04:51,160 --> 00:04:54,880 Speaker 1: temperatures drop rapidly, resulting in ice with those smaller crystals. 88 00:04:55,680 --> 00:04:59,000 Speaker 1: Artificial ice is subject to these same physical laws. A 89 00:04:59,080 --> 00:05:01,960 Speaker 1: Most household ice trays are designed to freeze little blocks 90 00:05:01,960 --> 00:05:04,960 Speaker 1: of water from the outside. In doing so has the 91 00:05:05,000 --> 00:05:07,680 Speaker 1: side effect of driving impurities within the water toward the 92 00:05:07,760 --> 00:05:11,160 Speaker 1: center of each cube. The finished products therefore look white 93 00:05:11,240 --> 00:05:14,720 Speaker 1: and hazy in the middle. To get clearer, more attractive cubes, 94 00:05:14,880 --> 00:05:18,440 Speaker 1: some restaurants use expensive machines that freeze water very gradually 95 00:05:18,600 --> 00:05:23,719 Speaker 1: and exclusively from one side that lets the impurities escape outward. Though, 96 00:05:23,760 --> 00:05:25,680 Speaker 1: if you want to make clearer cubes at home, you 97 00:05:25,680 --> 00:05:28,480 Speaker 1: can do it on the cheap. Try boiling the water first, 98 00:05:28,600 --> 00:05:32,080 Speaker 1: thus ridding it of dissolved gases before the freezing process starts. 99 00:05:32,480 --> 00:05:34,120 Speaker 1: Just let it cool of it before you add it 100 00:05:34,120 --> 00:05:36,320 Speaker 1: to your ice tray. You wouldn't want to melt the plastic. 101 00:05:45,600 --> 00:05:48,560 Speaker 1: Today's episode is based on the article why ice usually 102 00:05:48,560 --> 00:05:51,760 Speaker 1: freezes cloudy not clear on HowStuffWorks dot com, written by 103 00:05:51,800 --> 00:05:55,320 Speaker 1: Mark Mancini. Brain Stuff is production of iHeartRadio in partnership 104 00:05:55,320 --> 00:05:57,760 Speaker 1: with how stuffworks dot Com and is produced by Tyler Klang. 105 00:05:58,279 --> 00:06:01,360 Speaker 1: Four more podcasts from my heart Radio. Visit the iHeartRadio app, 106 00:06:01,440 --> 00:06:04,200 Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows.