Speaker 1: Welcome to brain Stuff, a production of iHeartRadio. Hey brain Stuff,
Speaker 1: Lauren Vogel Bomb here with another classic episode of the
Speaker 1: show for you. In this one, we talk about the
Speaker 1: strange physics of ice. We are pretty used to it
Speaker 1: looking cloudy and semi opaque when we pull it out
Speaker 1: of our freezers or skate along its surface. But under
Speaker 1: the right circumstances, ice can freeze very clear, creating beautiful
Speaker 1: and sometimes dangerous circumstances. Hey brain Stuff, Lauren Vogel Bomb here.
Speaker 1: When temperatures dip below freezing, it adds a number of
Speaker 1: extra hazards to driving, but perhaps none so tricksy as
Speaker 1: black ice. These are slick patches of ice that blend
Speaker 1: in with the black pavement beneath them because they're so transparent.
Speaker 1: When drivers, blind to the danger steer their cars over
Speaker 1: the ice, they can lose traction and wind up in
Speaker 1: an accident. Other kinds of ice are easier to see.
Speaker 1: You've no doubt noticed that homemade ice cubes usually look
Speaker 1: cloudy in the little opaque in the middle, like whitish
Speaker 1: blocks of cotton candy. That stands in contrast to the
Speaker 1: frightening clarity of black ice. So how come black. Ice
Speaker 1: is see through, but the cubes and your typical ice
Speaker 1: trays are not. Liquid. Water appears to be clear. That's
Speaker 1: because the material neither absorbs nor reflects most of the
Speaker 1: spectrum of visible light. Most wavelengths and spectrum pass right
Speaker 1: through it. And that's right, I said most. Technically, water
Speaker 1: is not colorless, although it often looks that way. Believe
Speaker 1: it or not. The liquid has a natural bluish tint,
Speaker 1: owing to the fact that it absorbs red, yellow, and
Speaker 1: orange light more easily than blue light. But our human
Speaker 1: eyes can only observe this azure quality in deep bodies
Speaker 1: of water. This helps explain why ocean water in glacial
Speaker 1: ice look blue to us, while glassfuls of drinking water
Speaker 1: look transparent. Yet there is a deceptive quality to water.
Speaker 1: No matter how fresh and clear it may seem, it's
Speaker 1: never one hundred percent pure. A sample of H two
Speaker 1: O might contain floating bits of organic matter like algae
Speaker 1: or plant remains, along with suspended sediments, a dust, particles,
Speaker 1: or flex of minerals like calcium and lime. It may
Speaker 1: also harbor lots of dissolved gases, such as oxygen. Without
Speaker 1: said oxygen, fish wouldn't be able to breathe. A Gases
Speaker 1: and physical impurities are the key to understanding why those
Speaker 1: ice cubes in your tray are so darn cloudy. When
Speaker 1: water freezes, internal debris and air bubbles can become concentrated
Speaker 1: the cluster's impede light, causing all the differently colored frequencies
Speaker 1: on the visible light spectrum to scatter. When this happens,
Speaker 1: it makes the ice look white and clouded. But it
Speaker 1: doesn't always happen. Let's take for a case study, a
Speaker 1: YouTuber who once appeared to walk on water. In twenty fourteen,
Speaker 1: Thomas Nunnak filmed himself in a travel companion walking across
Speaker 1: velke Hinkovo Pleso, a deep freshwater lake in the Slovakian Mountains.
Speaker 1: His video went viral because it shows the two men
Speaker 1: standing on some unbelievably clear ice. The lake bottom rocks
Speaker 1: below them are pristinely visible through frozen water. The ice
Speaker 1: in linux video was so transparent that some viewers assumed
Speaker 1: the footage had been faked, but the phenomenon is very real,
Speaker 1: and when the lake freezes over, as it often does,
Speaker 1: the surface ice can be crystal clear. An ice sheet
Speaker 1: needs to be almost entirely free of both air bubbles
Speaker 1: and debris. In order to have this degree of clarity,
Speaker 1: there are other requirements as well. Ice is made up
Speaker 1: of crystals, and when water freezes rapidly, those crystals tend
Speaker 1: to be small and numerous. That makes the ice look
Speaker 1: whiter because each of those crystals have reflective surfaces, so
Speaker 1: if there are more crystals, there'll be more reflection going on,
Speaker 1: which will help scatter in coming light. On the other hand,
Speaker 1: ice that's been slowly frozen is built out of fewer
Speaker 1: and larger crystals, and those promote transparency. So ice will
Speaker 1: only be see through and crystal clear if it freezes
Speaker 1: slowly and doesn't have too many impurities or crystals. Thomas
Speaker 1: Ninnock's now famous YouTube video is what it looks like
Speaker 1: when all these conditions are met. On the day of
Speaker 1: his track, the lake was topped with an icy blanket
Speaker 1: that was around two centimeters thick that's about three quarters
Speaker 1: of an inch. The water must have frozen gradually during
Speaker 1: a tranquil period with no strong winds to deposit debris
Speaker 1: in the lake or to churn up the water. We
Speaker 1: see the same kind of thing happening in roadway black ice.
Speaker 1: Although Not all of this stuff comes from the same source.
Speaker 1: It can start out as fog, mist, drizzle, or melted snow.
Speaker 1: It always freezes slowly during low wind periods. It's consistently thin,
Speaker 1: and it contains very few impurities. That's why black ice
Speaker 1: is so transparent and frustrating to motorists, but highway annoyances. Nonwithstanding,
Speaker 1: transparent ice isn't as common in nature as the white
Speaker 1: clouded variety. There are a lot of reasons why a
Speaker 1: given ice chunk you find out in nature might not
Speaker 1: be clear. Some ice is made up of fallen snowflakes,
Speaker 1: whose angular shapes and irregular crystals scatter light, and sometimes
Speaker 1: temperatures drop rapidly, resulting in ice with those smaller crystals.
Speaker 1: Artificial ice is subject to these same physical laws. A
Speaker 1: Most household ice trays are designed to freeze little blocks
Speaker 1: of water from the outside. In doing so has the
Speaker 1: side effect of driving impurities within the water toward the
Speaker 1: center of each cube. The finished products therefore look white
Speaker 1: and hazy in the middle. To get clearer, more attractive cubes,
Speaker 1: some restaurants use expensive machines that freeze water very gradually
Speaker 1: and exclusively from one side that lets the impurities escape outward. Though,
Speaker 1: if you want to make clearer cubes at home, you
Speaker 1: can do it on the cheap. Try boiling the water first,
Speaker 1: thus ridding it of dissolved gases before the freezing process starts.
Speaker 1: Just let it cool of it before you add it
Speaker 1: to your ice tray. You wouldn't want to melt the plastic.
Speaker 1: Today's episode is based on the article why ice usually
Speaker 1: freezes cloudy not clear on HowStuffWorks dot com, written by
Speaker 1: Mark Mancini. Brain Stuff is production of iHeartRadio in partnership
Speaker 1: with how stuffworks dot Com and is produced by Tyler Klang.
Speaker 1: Four more podcasts from my heart Radio. Visit the iHeartRadio app,
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