WEBVTT - BrainStuff Classics: Why Does Ice Get Cloudy?

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<v Speaker 1>Welcome to brain Stuff, a production of iHeartRadio. Hey brain Stuff,

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<v Speaker 1>Lauren Vogel Bomb here with another classic episode of the

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<v Speaker 1>show for you. In this one, we talk about the

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<v Speaker 1>strange physics of ice. We are pretty used to it

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<v Speaker 1>looking cloudy and semi opaque when we pull it out

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<v Speaker 1>of our freezers or skate along its surface. But under

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<v Speaker 1>the right circumstances, ice can freeze very clear, creating beautiful

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<v Speaker 1>and sometimes dangerous circumstances. Hey brain Stuff, Lauren Vogel Bomb here.

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<v Speaker 1>When temperatures dip below freezing, it adds a number of

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<v Speaker 1>extra hazards to driving, but perhaps none so tricksy as

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<v Speaker 1>black ice. These are slick patches of ice that blend

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<v Speaker 1>in with the black pavement beneath them because they're so transparent.

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<v Speaker 1>When drivers, blind to the danger steer their cars over

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<v Speaker 1>the ice, they can lose traction and wind up in

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<v Speaker 1>an accident. Other kinds of ice are easier to see.

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<v Speaker 1>You've no doubt noticed that homemade ice cubes usually look

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<v Speaker 1>cloudy in the little opaque in the middle, like whitish

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<v Speaker 1>blocks of cotton candy. That stands in contrast to the

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<v Speaker 1>frightening clarity of black ice. So how come black. Ice

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<v Speaker 1>is see through, but the cubes and your typical ice

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<v Speaker 1>trays are not. Liquid. Water appears to be clear. That's

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<v Speaker 1>because the material neither absorbs nor reflects most of the

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<v Speaker 1>spectrum of visible light. Most wavelengths and spectrum pass right

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<v Speaker 1>through it. And that's right, I said most. Technically, water

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<v Speaker 1>is not colorless, although it often looks that way. Believe

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<v Speaker 1>it or not. The liquid has a natural bluish tint,

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<v Speaker 1>owing to the fact that it absorbs red, yellow, and

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<v Speaker 1>orange light more easily than blue light. But our human

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<v Speaker 1>eyes can only observe this azure quality in deep bodies

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<v Speaker 1>of water. This helps explain why ocean water in glacial

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<v Speaker 1>ice look blue to us, while glassfuls of drinking water

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<v Speaker 1>look transparent. Yet there is a deceptive quality to water.

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<v Speaker 1>No matter how fresh and clear it may seem, it's

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<v Speaker 1>never one hundred percent pure. A sample of H two

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<v Speaker 1>O might contain floating bits of organic matter like algae

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<v Speaker 1>or plant remains, along with suspended sediments, a dust, particles,

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<v Speaker 1>or flex of minerals like calcium and lime. It may

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<v Speaker 1>also harbor lots of dissolved gases, such as oxygen. Without

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<v Speaker 1>said oxygen, fish wouldn't be able to breathe. A Gases

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<v Speaker 1>and physical impurities are the key to understanding why those

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<v Speaker 1>ice cubes in your tray are so darn cloudy. When

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<v Speaker 1>water freezes, internal debris and air bubbles can become concentrated

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<v Speaker 1>the cluster's impede light, causing all the differently colored frequencies

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<v Speaker 1>on the visible light spectrum to scatter. When this happens,

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<v Speaker 1>it makes the ice look white and clouded. But it

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<v Speaker 1>doesn't always happen. Let's take for a case study, a

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<v Speaker 1>YouTuber who once appeared to walk on water. In twenty fourteen,

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<v Speaker 1>Thomas Nunnak filmed himself in a travel companion walking across

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<v Speaker 1>velke Hinkovo Pleso, a deep freshwater lake in the Slovakian Mountains.

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<v Speaker 1>His video went viral because it shows the two men

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<v Speaker 1>standing on some unbelievably clear ice. The lake bottom rocks

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<v Speaker 1>below them are pristinely visible through frozen water. The ice

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<v Speaker 1>in linux video was so transparent that some viewers assumed

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<v Speaker 1>the footage had been faked, but the phenomenon is very real,

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<v Speaker 1>and when the lake freezes over, as it often does,

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<v Speaker 1>the surface ice can be crystal clear. An ice sheet

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<v Speaker 1>needs to be almost entirely free of both air bubbles

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<v Speaker 1>and debris. In order to have this degree of clarity,

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<v Speaker 1>there are other requirements as well. Ice is made up

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<v Speaker 1>of crystals, and when water freezes rapidly, those crystals tend

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<v Speaker 1>to be small and numerous. That makes the ice look

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<v Speaker 1>whiter because each of those crystals have reflective surfaces, so

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<v Speaker 1>if there are more crystals, there'll be more reflection going on,

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<v Speaker 1>which will help scatter in coming light. On the other hand,

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<v Speaker 1>ice that's been slowly frozen is built out of fewer

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<v Speaker 1>and larger crystals, and those promote transparency. So ice will

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<v Speaker 1>only be see through and crystal clear if it freezes

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<v Speaker 1>slowly and doesn't have too many impurities or crystals. Thomas

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<v Speaker 1>Ninnock's now famous YouTube video is what it looks like

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<v Speaker 1>when all these conditions are met. On the day of

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<v Speaker 1>his track, the lake was topped with an icy blanket

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<v Speaker 1>that was around two centimeters thick that's about three quarters

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<v Speaker 1>of an inch. The water must have frozen gradually during

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<v Speaker 1>a tranquil period with no strong winds to deposit debris

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<v Speaker 1>in the lake or to churn up the water. We

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<v Speaker 1>see the same kind of thing happening in roadway black ice.

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<v Speaker 1>Although Not all of this stuff comes from the same source.

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<v Speaker 1>It can start out as fog, mist, drizzle, or melted snow.

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<v Speaker 1>It always freezes slowly during low wind periods. It's consistently thin,

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<v Speaker 1>and it contains very few impurities. That's why black ice

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<v Speaker 1>is so transparent and frustrating to motorists, but highway annoyances. Nonwithstanding,

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<v Speaker 1>transparent ice isn't as common in nature as the white

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<v Speaker 1>clouded variety. There are a lot of reasons why a

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<v Speaker 1>given ice chunk you find out in nature might not

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<v Speaker 1>be clear. Some ice is made up of fallen snowflakes,

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<v Speaker 1>whose angular shapes and irregular crystals scatter light, and sometimes

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<v Speaker 1>temperatures drop rapidly, resulting in ice with those smaller crystals.

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<v Speaker 1>Artificial ice is subject to these same physical laws. A

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<v Speaker 1>Most household ice trays are designed to freeze little blocks

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<v Speaker 1>of water from the outside. In doing so has the

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<v Speaker 1>side effect of driving impurities within the water toward the

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<v Speaker 1>center of each cube. The finished products therefore look white

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<v Speaker 1>and hazy in the middle. To get clearer, more attractive cubes,

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<v Speaker 1>some restaurants use expensive machines that freeze water very gradually

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<v Speaker 1>and exclusively from one side that lets the impurities escape outward. Though,

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<v Speaker 1>if you want to make clearer cubes at home, you

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<v Speaker 1>can do it on the cheap. Try boiling the water first,

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<v Speaker 1>thus ridding it of dissolved gases before the freezing process starts.

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<v Speaker 1>Just let it cool of it before you add it

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<v Speaker 1>to your ice tray. You wouldn't want to melt the plastic.

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<v Speaker 1>Today's episode is based on the article why ice usually

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<v Speaker 1>freezes cloudy not clear on HowStuffWorks dot com, written by

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<v Speaker 1>Mark Mancini. Brain Stuff is production of iHeartRadio in partnership

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<v Speaker 1>with how stuffworks dot Com and is produced by Tyler Klang.

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<v Speaker 1>Four more podcasts from my heart Radio. Visit the iHeartRadio app,

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