[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.63,0:00:10.92,Default,,0000,0000,0000,,In 1977, the physicist Edward Purcell
Dialogue: 0,0:00:10.95,0:00:14.17,Default,,0000,0000,0000,,calculated that if you push\Na bacteria and then let go,
Dialogue: 0,0:00:14.20,0:00:16.92,Default,,0000,0000,0000,,it will stop in about\Na millionth of a second.
Dialogue: 0,0:00:16.95,0:00:21.15,Default,,0000,0000,0000,,In that time, it will have traveled less\Nthan the width of a single atom.
Dialogue: 0,0:00:21.17,0:00:24.64,Default,,0000,0000,0000,,The same holds true for a sperm\Nand many other microbes.
Dialogue: 0,0:00:24.66,0:00:27.59,Default,,0000,0000,0000,,It all has to do with being really small.
Dialogue: 0,0:00:27.62,0:00:31.32,Default,,0000,0000,0000,,Microscopic creatures inhabit\Na world alien to us,
Dialogue: 0,0:00:31.34,0:00:34.70,Default,,0000,0000,0000,,where making it through an inch of water\Nis an incredible endeavor.
Dialogue: 0,0:00:34.72,0:00:37.72,Default,,0000,0000,0000,,But why does size matter\Nso much for a swimmer?
Dialogue: 0,0:00:37.74,0:00:40.74,Default,,0000,0000,0000,,What makes the world of a sperm\Nso fundamentally different
Dialogue: 0,0:00:40.76,0:00:42.60,Default,,0000,0000,0000,,from that of a sperm whale?
Dialogue: 0,0:00:42.62,0:00:46.08,Default,,0000,0000,0000,,To find out, we need to dive\Ninto the physics of fluids.
Dialogue: 0,0:00:46.10,0:00:47.93,Default,,0000,0000,0000,,Here's a way to think about it.
Dialogue: 0,0:00:47.96,0:00:49.83,Default,,0000,0000,0000,,Imagine you are swimming in a pool.
Dialogue: 0,0:00:49.86,0:00:52.59,Default,,0000,0000,0000,,It's you and a whole bunch\Nof water molecules.
Dialogue: 0,0:00:52.62,0:00:57.13,Default,,0000,0000,0000,,Water molecules outnumber you\Na thousand trillion trillion to one.
Dialogue: 0,0:00:57.15,0:01:00.50,Default,,0000,0000,0000,,So, pushing past them\Nwith your gigantic body is easy,
Dialogue: 0,0:01:00.53,0:01:02.69,Default,,0000,0000,0000,,but if you were really small,
Dialogue: 0,0:01:02.71,0:01:05.07,Default,,0000,0000,0000,,say you were about the size\Nof a water molecule,
Dialogue: 0,0:01:05.09,0:01:07.11,Default,,0000,0000,0000,,all of a sudden, it's like you're swimming
Dialogue: 0,0:01:07.13,0:01:08.24,Default,,0000,0000,0000,,in a pool of people.
Dialogue: 0,0:01:08.26,0:01:11.58,Default,,0000,0000,0000,,Rather than simply swishing by\Nall the teeny, tiny molecules,
Dialogue: 0,0:01:11.60,0:01:13.53,Default,,0000,0000,0000,,now every single water molecule
Dialogue: 0,0:01:13.56,0:01:16.04,Default,,0000,0000,0000,,is like another person\Nyou have to push past
Dialogue: 0,0:01:16.07,0:01:17.35,Default,,0000,0000,0000,,to get anywhere.
Dialogue: 0,0:01:18.07,0:01:20.96,Default,,0000,0000,0000,,In 1883, the physicist Osborne Reynolds
Dialogue: 0,0:01:20.98,0:01:23.08,Default,,0000,0000,0000,,figured out that there is\None simple number
Dialogue: 0,0:01:23.10,0:01:25.99,Default,,0000,0000,0000,,that can predict how a fluid will behave.
Dialogue: 0,0:01:26.02,0:01:27.54,Default,,0000,0000,0000,,It's called the Reynolds number,
Dialogue: 0,0:01:27.56,0:01:31.58,Default,,0000,0000,0000,,and it depends on simple properties\Nlike the size of the swimmer,
Dialogue: 0,0:01:31.60,0:01:33.72,Default,,0000,0000,0000,,its speed, the density of the fluid,
Dialogue: 0,0:01:33.74,0:01:36.49,Default,,0000,0000,0000,,and the stickiness,\Nor the viscosity, of the fluid.
Dialogue: 0,0:01:37.57,0:01:40.72,Default,,0000,0000,0000,,What this means is that creatures\Nof very different sizes
Dialogue: 0,0:01:40.74,0:01:42.72,Default,,0000,0000,0000,,inhabit vastly different worlds.
Dialogue: 0,0:01:42.74,0:01:44.68,Default,,0000,0000,0000,,For example, because of its huge size,
Dialogue: 0,0:01:44.71,0:01:48.00,Default,,0000,0000,0000,,a sperm whale inhabits\Nthe large Reynolds number world.
Dialogue: 0,0:01:48.72,0:01:50.10,Default,,0000,0000,0000,,If it flaps its tail once,
Dialogue: 0,0:01:50.13,0:01:52.49,Default,,0000,0000,0000,,it can coast ahead\Nfor an incredible distance.
Dialogue: 0,0:01:52.51,0:01:56.18,Default,,0000,0000,0000,,Meanwhile, sperm live\Nin a low Reynolds number world.
Dialogue: 0,0:01:56.21,0:01:58.36,Default,,0000,0000,0000,,If a sperm were to stop flapping its tail,
Dialogue: 0,0:01:58.38,0:02:00.91,Default,,0000,0000,0000,,it wouldn't even coast past a single atom.
Dialogue: 0,0:02:01.27,0:02:03.61,Default,,0000,0000,0000,,To imagine what it would\Nfeel like to be a sperm,
Dialogue: 0,0:02:03.63,0:02:06.27,Default,,0000,0000,0000,,you need to bring yourself down\Nto its Reynolds number.
Dialogue: 0,0:02:06.29,0:02:09.15,Default,,0000,0000,0000,,Picture yourself in a tub of molasses\Nwith your arms moving
Dialogue: 0,0:02:09.18,0:02:12.12,Default,,0000,0000,0000,,about as slow as the minute\Nhand of a clock,
Dialogue: 0,0:02:12.14,0:02:15.59,Default,,0000,0000,0000,,and you'd have a pretty good idea\Nof what a sperm is up against.
Dialogue: 0,0:02:15.61,0:02:17.82,Default,,0000,0000,0000,,So, how do microbes\Nmanage to get anywhere?
Dialogue: 0,0:02:17.85,0:02:20.16,Default,,0000,0000,0000,,Well, many don't bother swimming at all.
Dialogue: 0,0:02:20.19,0:02:22.77,Default,,0000,0000,0000,,They just let the food drift to them.
Dialogue: 0,0:02:22.80,0:02:24.32,Default,,0000,0000,0000,,This is somewhat like a lazy cow
Dialogue: 0,0:02:24.34,0:02:27.05,Default,,0000,0000,0000,,that waits for the grass\Nunder its mouth to grow back.
Dialogue: 0,0:02:27.07,0:02:29.02,Default,,0000,0000,0000,,But many microbes do swim,
Dialogue: 0,0:02:29.04,0:02:31.98,Default,,0000,0000,0000,,and this is where those\Nincredible adaptations come in.
Dialogue: 0,0:02:32.01,0:02:35.80,Default,,0000,0000,0000,,One trick they can use\Nis to deform the shape of their paddle.
Dialogue: 0,0:02:35.83,0:02:37.53,Default,,0000,0000,0000,,By cleverly flexing their paddle
Dialogue: 0,0:02:37.55,0:02:41.40,Default,,0000,0000,0000,,to create more drag on the power stroke\Nthan on the recovery stroke,
Dialogue: 0,0:02:41.42,0:02:44.92,Default,,0000,0000,0000,,single-celled organisms like paramecia
Dialogue: 0,0:02:44.94,0:02:47.84,Default,,0000,0000,0000,,manage to inch their way\Nthrough the crowd of water molecules.
Dialogue: 0,0:02:47.87,0:02:49.91,Default,,0000,0000,0000,,But there's an even more\Ningenious solution
Dialogue: 0,0:02:49.93,0:02:52.28,Default,,0000,0000,0000,,arrived at by bacteria and sperm.
Dialogue: 0,0:02:52.79,0:02:55.22,Default,,0000,0000,0000,,Instead of wagging\Ntheir paddles back and forth,
Dialogue: 0,0:02:55.24,0:02:57.34,Default,,0000,0000,0000,,they wind them like a cork screw.
Dialogue: 0,0:02:57.36,0:02:59.18,Default,,0000,0000,0000,,Just as a cork screw on a wine bottle
Dialogue: 0,0:02:59.21,0:03:01.97,Default,,0000,0000,0000,,converts winding motion\Ninto forward motion,
Dialogue: 0,0:03:01.99,0:03:04.80,Default,,0000,0000,0000,,these tiny creatures\Nspin their helical tails
Dialogue: 0,0:03:04.83,0:03:06.60,Default,,0000,0000,0000,,to push themselves forward
Dialogue: 0,0:03:06.63,0:03:10.36,Default,,0000,0000,0000,,in a world where water\Nfeels as thick as cork.
Dialogue: 0,0:03:10.38,0:03:12.48,Default,,0000,0000,0000,,Other strategies are even stranger.
Dialogue: 0,0:03:12.51,0:03:14.51,Default,,0000,0000,0000,,Some bacteria take Batman's approach.
Dialogue: 0,0:03:14.53,0:03:17.23,Default,,0000,0000,0000,,They use grappling hooks\Nto pull themselves along.
Dialogue: 0,0:03:17.25,0:03:19.01,Default,,0000,0000,0000,,They can even use this grappling hook
Dialogue: 0,0:03:19.04,0:03:21.74,Default,,0000,0000,0000,,like a sling shot\Nand fling themselves forward.
Dialogue: 0,0:03:21.77,0:03:24.20,Default,,0000,0000,0000,,Others use chemical engineering.
Dialogue: 0,0:03:24.22,0:03:27.48,Default,,0000,0000,0000,,H. pylori lives only\Nin the slimy, acidic mucus
Dialogue: 0,0:03:27.51,0:03:29.23,Default,,0000,0000,0000,,inside our stomachs.
Dialogue: 0,0:03:29.26,0:03:32.70,Default,,0000,0000,0000,,It releases a chemical\Nthat thins out the surrounding mucus,
Dialogue: 0,0:03:32.72,0:03:34.65,Default,,0000,0000,0000,,allowing it to glide through slime.
Dialogue: 0,0:03:34.67,0:03:35.72,Default,,0000,0000,0000,,Maybe it's no surprise
Dialogue: 0,0:03:35.75,0:03:38.88,Default,,0000,0000,0000,,that these guys are also responsible\Nfor stomach ulcers.
Dialogue: 0,0:03:39.38,0:03:43.09,Default,,0000,0000,0000,,So, when you look really closely\Nat our bodies and the world around us,
Dialogue: 0,0:03:43.11,0:03:45.09,Default,,0000,0000,0000,,you can see all sorts of tiny creatures
Dialogue: 0,0:03:45.11,0:03:48.96,Default,,0000,0000,0000,,finding clever ways to get around\Nin a sticky situation.
Dialogue: 0,0:03:48.98,0:03:52.60,Default,,0000,0000,0000,,Without these adaptations,\Nbacteria would never find their hosts,
Dialogue: 0,0:03:52.63,0:03:55.58,Default,,0000,0000,0000,,and sperms would never\Nmake it to their eggs,
Dialogue: 0,0:03:55.60,0:03:57.94,Default,,0000,0000,0000,,which means you would never\Nget stomach ulcers,
Dialogue: 0,0:03:57.96,0:04:00.46,Default,,0000,0000,0000,,but you would also never be born\Nin the first place.
Dialogue: 0,0:04:00.49,0:04:01.49,Default,,0000,0000,0000,,(Pop)