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This programming is sponsored by the

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UH Health Family Care Center, offering

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primary care and behavioral health services

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on the University of Houston campus.

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Health insurance plans, including Medicare and

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Medicaid, accepted. New patient appointments and

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more at 832-UH CARES. This

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is the Engines of Our Ingenuity,

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made possible by the Friends of

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KUHF Houston. Today,

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we move energy. The University of

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Houston's College of Engineering presents this

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series about the machines that make

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our civilization run, and the people

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whose ingenuity created them. This

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week, engineers will meet from all over

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the world for the National Heat Transfer

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Conference here in Hot Houston. When I

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tell people I'm going to a heat

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transfer meeting, they look at me oddly.

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What's that, they wonder? Yet these same

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people live in and worry about a

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world that eats huge amounts of energy.

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The central issue we worry about is how

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energy moves from place to place. Ever

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since Einstein, we've known that energy and

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matter are two faces of the same

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coin, the very stuff of which the

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entire universe is made. Matter

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can be seen. We watch it

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moving on trucks and trains, in

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earthquakes, tides and hurricanes. Energy

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also swirls around us, but because

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it's invisible, we're less aware of

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it. Wherever there are differences in

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temperature, pressure, voltage, energy can flow.

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And so, 600 engineers will gather

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and tell each other what they know

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about how temperature drives energy, how heat

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flows. To help you catch some of

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the flavor of the subtleties, I'll put

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three riddles before you. One,

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we're supposed to wear white clothes in

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the summer because black absorbs more sunshine.

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Why then does nature put dark-skinned people on

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the equator where the sun pours down energy

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and light-skinned people in the far north? Two,

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how did the story that hot water freezes

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more quickly than cold get started? and

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three, why does metal seem colder than

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wood in your office? First,

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skin color. While dark skin is better

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protected from ultraviolet radiation, it does absorb

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more energy and visible light than light

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skin does. But most of

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the sun's heat comes in invisible

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infrared radiation. Dark and light skin

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are the same color in that

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range. Dark skin absorbs no more

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heat than light skin does. Next,

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the hot water freezes faster story. When

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we put trays of water in frosty

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freezers to make ice cubes, frost insulates

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them. Hot trays melt the frost and

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make better thermal contact with the cooling

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coils, but there's more. Some of the

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hot water evaporates in the cold dry

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air. There's less to freeze and evaporation

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speeds cooling, so that story really can

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be true. And what about

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metal feeling colder than wood? Your

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body has to be warmer than the

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room to shed heat. Your nerve endings

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are warmer than either wood or metal,

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but metal conducts heat away more quickly

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and it holds more heat. Your finger

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is cooled as it rapidly drives heat

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into the metal. That's why metal at

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the same temperature feels far colder than

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wood. A large diamond would

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feel even colder than metal, but real

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diamonds are small and they suck the

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heat out of your finger so very

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fast that they quickly match your finger's

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temperature. That's why people like to say,

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diamonds are warm. Heat flow has many

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ways of fooling us. Scale these ideas

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up to a huge power plant or

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down to a laptop computer and they

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offer wonderful fun and challenge. I'd like

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to say we meet to build a

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better quality of life. Well sure, there's

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that, but we really do it for

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the exquisite pleasure of facing the

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questions themselves. I'm John

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Leinhardt at the University of Houston,

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where we're interested in the way

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inventive minds work. you