WEBVTT - Does Smog Make Sunsets More Beautiful?

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<v Speaker 1>Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff, Lauren Boblobam. Here,

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<v Speaker 1>there aren't too many positives to be found in air pollution.

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<v Speaker 1>It's unhealthy, unsightly, and damaging to this planet that we

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<v Speaker 1>as a species hope to spend a lot more time on.

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<v Speaker 1>But there's a pervasive urban legend of sorts that there

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<v Speaker 1>is an upside here that's Smoggy Cities like Los Angeles

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<v Speaker 1>and Beijing, which host hazy skies most of the time,

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<v Speaker 1>at least get to have extra brilliant sunsets to cough

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<v Speaker 1>at as a result. Could the phenomenon known as smog

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<v Speaker 1>actually enhance sunsets? The short answer is well sort out,

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<v Speaker 1>but only to a certain extent. To explain why, first,

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<v Speaker 1>let's go over the science of sunsets and how different

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<v Speaker 1>colors come to splash across the sky. To begin with,

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<v Speaker 1>We've talked about this a bit before on the show,

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<v Speaker 1>but it's worth going over. Basically, the sky appears to

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<v Speaker 1>be whatever color it is due to atmospheric distortion and

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<v Speaker 1>the limits of human eyesight. Okay, when the sun is

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<v Speaker 1>high in the sky, its light travels a relatively short

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<v Speaker 1>path through the atmosphere, to reach your eye. A sunlight

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<v Speaker 1>usually appears white to our eyes because it's a mix

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<v Speaker 1>of all of the wavelengths of visible light. You know ROIGBIV, red, orange, yellow, green, blue, indigo,

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<v Speaker 1>and violet. Now, all of those wavelengths are different lengths.

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<v Speaker 1>Red light has the longest among them, violet light has

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<v Speaker 1>the shortest. The colors all have their own amount of

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<v Speaker 1>energy too. Red light is relatively sluggish, a violet light

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<v Speaker 1>is comparatively zippy. This stuff that makes up our air

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<v Speaker 1>will scatter some of those wavelengths more than others. It's

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<v Speaker 1>a phenomenon called Rayleigh scattered. Our atmosphere is composed of

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<v Speaker 1>a very thin soup of atoms and molecules. Ninety nine

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<v Speaker 1>percent of this soup, the broth, if you will, is

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<v Speaker 1>atoms of nitrogen and oxygen. These atoms are tiny, hundreds

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<v Speaker 1>of times smaller than even the shortest wavelengths of visible light.

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<v Speaker 1>Because of that, those atoms simply don't have the power

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<v Speaker 1>to knock around the longer wavelengths. The zippier light with

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<v Speaker 1>shorter wavelengths is more likely to hit the tiny air

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<v Speaker 1>atoms and get scattered around by them, bouncing until it

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<v Speaker 1>eventually hits our eyes from any number of possible directions,

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<v Speaker 1>meaning that violet light scatters the most. However, the sky

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<v Speaker 1>does not appear violet during the daytime because the Sun

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<v Speaker 1>doesn't release that much violet light and because our eyes

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<v Speaker 1>aren't super good at detecting it. The sky instead appears

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<v Speaker 1>blue because it is the fastest, shortest, and thus most

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<v Speaker 1>wavelength of light that the Sun puts off a lot

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<v Speaker 1>of and that we detect easily. But as the Sun

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<v Speaker 1>moves across the sky, the game changes. The Earth is

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<v Speaker 1>a sphere, so the distance between the Sun and your

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<v Speaker 1>eye changes as the planet rotates. At high noon, the

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<v Speaker 1>distance is the shortest. At sunset, when the sun is

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<v Speaker 1>at the horizon, that distance is longer. When the distance

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<v Speaker 1>is longer, there's more atmosphere for the light to travel

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<v Speaker 1>through before you perceive it. Raleigh scattering is still an effect,

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<v Speaker 1>but it produces an entirely different result. That's because those

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<v Speaker 1>shorter wavelengths of light, the violet, indigo, and blue, have

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<v Speaker 1>so much more atmosphere to travel through that they get

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<v Speaker 1>scattered out before they reach you. That leaves only the

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<v Speaker 1>longer wavelengths in the sky for you to see, thus

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<v Speaker 1>turning the sunset sky all shades of yellows, oranges, and reds.

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<v Speaker 1>The scattered blue light is busy creating a blue daytime

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<v Speaker 1>sky somewhere else on the planet. But okay, so far

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<v Speaker 1>we've been talking about all of this happening in a

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<v Speaker 1>clear sky with mostly nitrogen and oxygen atoms doing the scattering.

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<v Speaker 1>If you add other molecules into the mix, the ones

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<v Speaker 1>in smog, for instance, the game changes again. Smog is

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<v Speaker 1>a portmanteau of the words smoke and fog, coined in

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<v Speaker 1>the early nineteen hundreds in London to describe the dark,

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<v Speaker 1>foggy pollution that often hung over and through the city.

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<v Speaker 1>It was coined specifically by people concerned with the health

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<v Speaker 1>effects of the phenomenon at the time. A smog is

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<v Speaker 1>made up of small particles of solids and liquids that

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<v Speaker 1>wind up suspended in the air, called aerosols. Aerosols can

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<v Speaker 1>come from natural sources like sea spray, trees, breathing and

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<v Speaker 1>pollinating dust from sandstorms, forest fires, smoke and debris, and

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<v Speaker 1>volcanic eruptions that send tons of ash into the air,

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<v Speaker 1>but for the most part, the aerosols in big cities

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<v Speaker 1>are human made. Think of all of this stuff we

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<v Speaker 1>put into our air coal power, exhaust, car emissions, and

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<v Speaker 1>gasoline fumes and the byproducts of everything from manufacturing to

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<v Speaker 1>construction sites to cleaning solvents. Exhaust is full of nitrogen

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<v Speaker 1>oxide compounds alike from combustion engines. Fumes can contain volatile

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<v Speaker 1>organic compounds like from paint or petrol. It turns out,

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<v Speaker 1>and we only figured this out in the nineteen fifties,

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<v Speaker 1>that when exhaust and fumes combine in the air, and

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<v Speaker 1>then that combo gets hit by sunlight, a chemical reaction

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<v Speaker 1>occurs that produces ground level ozone and other airborne particles.

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<v Speaker 1>Ozone is helpful when it's high up in the atmosphere,

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<v Speaker 1>but is hazardous for us to breathe in directly so

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<v Speaker 1>in cities. Smog is this human made mixture of chemicals

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<v Speaker 1>composed of countless different moments of different sizes. Now, having

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<v Speaker 1>some aerosols in the air can help scatter more light

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<v Speaker 1>in the Rayleigh way. As long as the particles are

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<v Speaker 1>small enough, this can bring out beautiful deep reds in

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<v Speaker 1>the sunset. But once you've got a lot of aerosols

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<v Speaker 1>and including particles that are closer to the same size

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<v Speaker 1>of the wavelengths of visible light that will scatter all

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<v Speaker 1>the colors indiscriminately. It winds up creating a washed out, grayish,

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<v Speaker 1>hazy sky. So smoggy cities can experience extra vivid sunsets

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<v Speaker 1>when that smog is particularly minimal. However, I also want

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<v Speaker 1>to talk about these sometimes spectacular sunsets that occur following

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<v Speaker 1>volcanic eruptions. After all, the aerosols released by a volcano

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<v Speaker 1>are just another form of atmospheric pollution, right, true, but

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<v Speaker 1>it matters what part of the atmosphere that pollution is in.

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<v Speaker 1>Oh when we're talking about smog or the smoke from

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<v Speaker 1>a forest fire. Those aerosols are hanging out in the

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<v Speaker 1>layer of the atmosphere nearest to the ground, the troposphere.

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<v Speaker 1>Here they create haze and more muted colors in the sky.

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<v Speaker 1>But a volcano shoots aerosols all the way up into

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<v Speaker 1>the stratosphere, higher than an airplane would go. From up there,

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<v Speaker 1>the aerosols can bounce extra light to you for longer

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<v Speaker 1>during a sunset, after the sun has passed below the horizon.

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<v Speaker 1>This is also why some clouds that are way high

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<v Speaker 1>up in the atmosphere turn brilliant shades of orange and red.

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<v Speaker 1>During a sunset. They block any remaining blue light from

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<v Speaker 1>above and reflect those longer wavelengths remaining, thus lighting the

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<v Speaker 1>whole landscape up in glowing ambers. Today's episode is based

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<v Speaker 1>on the article does smog make for Beautiful Sunsets? On

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<v Speaker 1>HowStuffWorks dot Com? Written by Julia Layton. Brain Stuff is

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<v Speaker 1>production of iHeartRadio in partnership with HowStuffWorks dot Com. It

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<v Speaker 1>is produced by Tyler Klange. Four more podcasts from my

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