How heavy is air? - Dan Quinn
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0:07 - 0:08You may not realize it,
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0:08 - 0:10but from the moment you got out of bed today
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0:10 - 0:13to the point where you sat down to watch this video,
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0:13 - 0:14you've essentially been swimming.
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0:14 - 0:18Why? Because air is a fluid just like water.
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0:18 - 0:20It has waves and eddies.
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0:20 - 0:21It flows.
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0:21 - 0:23And when you push air out of the way,
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0:23 - 0:25it rushes around you into a wake.
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0:25 - 0:27So why don't we notice it most of the time?
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0:27 - 0:31We commonly think of air as empty space.
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0:31 - 0:34But while one cubic centimeter of interstellar space,
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0:34 - 0:36the volume in the tip of your pinky finger,
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0:36 - 0:38contains roughly one atom,
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0:38 - 0:43the same volume of air has about 10 quintillion molecules.
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0:43 - 0:45If that sounds hard to wrap your head around,
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0:45 - 0:47it happens to be about the same
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0:47 - 0:49as the number of insects alive on the planet,
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0:49 - 0:52all crawling, climbing, and flying over each other
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0:52 - 0:56in an enormous, tightly packed swarm.
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0:56 - 0:58When this swarm of molecules runs into things,
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0:58 - 1:01it exerts a force, pressing against the boundaries of the fluid,
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1:01 - 1:05like water pressing against the glass of a bottle.
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1:05 - 1:07This is known as air pressure.
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1:07 - 1:08And while air is lighter than water,
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1:08 - 1:11all those molecules still get pretty heavy,
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1:11 - 1:13with the total air filling a typical school gym,
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1:13 - 1:16weighing about as much as an adult elephant.
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1:16 - 1:18So when you walk into a gym,
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1:18 - 1:19how come you're not immediately crushed
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1:19 - 1:21by the elephant of air in the room?
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1:21 - 1:23Well, first of all,
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1:23 - 1:26because most of it is pressing on the floor and the walls,
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1:26 - 1:27and the part that is pressing on you
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1:27 - 1:31is pushed back by the pressure inside you!
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1:31 - 1:34You see, the air, as well as the water and everything else,
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1:34 - 1:37that fills our bodies exerts an amount of pressure
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1:37 - 1:39equal to that of the air outside.
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1:39 - 1:41Of course, this is no accident.
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1:41 - 1:43It's precisely what allows us to survive
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1:43 - 1:45in the normal atmosphere,
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1:45 - 1:46and what makes it more difficult
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1:46 - 1:48at high altitudes or deep water.
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1:48 - 1:51And we normally don't feel the air pressing on us
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1:51 - 1:53because it's generally uniform.
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1:53 - 1:55So even though different amounts of air molecules
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1:55 - 1:57are hitting you at different times,
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1:57 - 1:58the swarm is so thick
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1:58 - 2:01that all those little differences average out.
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2:01 - 2:04What happens when air pressure isn't uniform?
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2:04 - 2:06This means that the molecules are pushing harder
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2:06 - 2:08in one region of air than another,
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2:08 - 2:10driving the air flow from the higher pressure region
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2:10 - 2:12to the lower.
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2:12 - 2:14We feel this flow directly as wind,
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2:14 - 2:16and the pressure systems
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2:16 - 2:17that meteorologists are always going on about
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2:17 - 2:20are responsible for other weather changes,
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2:20 - 2:23from the mundane to the catastrophic.
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2:23 - 2:25But differences in air pressure
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2:25 - 2:27do more than just let us complain about the weather;
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2:27 - 2:29they're the very reason we're alive.
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2:29 - 2:32We breathe by lowering the pressure in our lungs,
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2:32 - 2:34allowing air to rush in.
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2:34 - 2:36So the next time you take a deep breath,
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2:36 - 2:39think of the unfathomable number of air molecules
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2:39 - 2:40you're commanding to move.
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2:40 - 2:42We look up at the night sky
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2:42 - 2:44to ponder the infinity of space,
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2:44 - 2:46but unless you're watching this video
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2:46 - 2:48from that deep space,
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2:48 - 2:50there are more air molecules
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2:50 - 2:51in and around your body
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2:51 - 2:54than there are grains of sand in all the world's beaches and deserts,
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2:54 - 2:56stars in the visible universe,
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2:56 - 2:59or both of those numbers combined.
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2:59 - 3:00The vastness of the universe
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3:00 - 3:02is right in front of you
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3:02 - 3:04and inside you.
- Title:
- How heavy is air? - Dan Quinn
- Description:
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View full lesson: http://ed.ted.com/lessons/how-heavy-is-air-dan-quinn
Too often we think of air as empty space — but compared to a vacuum, air is actually pretty heavy. So, just how heavy is it? And if it's so heavy, why doesn't it crush us? Dan Quinn describes the fundamentals of air pressure and explains how it affects our bodies, the weather and the universe at large.
Lesson by Dan Quinn, animation by Sandro Katamashvili.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 03:19
Caroline Cristal approved English subtitles for How heavy is air? - Dan Quinn | ||
Caroline Cristal accepted English subtitles for How heavy is air? - Dan Quinn | ||
Jessica Ruby edited English subtitles for How heavy is air? - Dan Quinn | ||
Jessica Ruby edited English subtitles for How heavy is air? - Dan Quinn |