[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:01.60,Default,,0000,0000,0000,,- [Voiceover] Let's talk a little bit
Dialogue: 0,0:00:01.60,0:00:04.33,Default,,0000,0000,0000,,about the water cycle, which\Nwe're all familiar with.
Dialogue: 0,0:00:04.33,0:00:06.10,Default,,0000,0000,0000,,In fact, we're all part\Nof the water cycle,
Dialogue: 0,0:00:06.10,0:00:07.51,Default,,0000,0000,0000,,every moment of our lives.
Dialogue: 0,0:00:07.51,0:00:09.31,Default,,0000,0000,0000,,We might not fully appreciate it.
Dialogue: 0,0:00:09.31,0:00:11.01,Default,,0000,0000,0000,,So let's just jump in the cycle.
Dialogue: 0,0:00:11.01,0:00:12.71,Default,,0000,0000,0000,,I'll start with evaporation.
Dialogue: 0,0:00:12.71,0:00:15.29,Default,,0000,0000,0000,,So we could start with the\Nsurface of the ocean here,
Dialogue: 0,0:00:15.29,0:00:17.70,Default,,0000,0000,0000,,or this river, or this lake.
Dialogue: 0,0:00:17.70,0:00:19.07,Default,,0000,0000,0000,,And at any given moment,
Dialogue: 0,0:00:19.07,0:00:22.07,Default,,0000,0000,0000,,there's going to be water\Nevaporating off of that surface.
Dialogue: 0,0:00:22.07,0:00:24.83,Default,,0000,0000,0000,,Water molecules that were\Nin their liquid state,
Dialogue: 0,0:00:24.83,0:00:28.64,Default,,0000,0000,0000,,liquid state, they just have\Nenough energy to bounce away
Dialogue: 0,0:00:28.64,0:00:30.81,Default,,0000,0000,0000,,and go into the gas state.
Dialogue: 0,0:00:32.92,0:00:37.07,Default,,0000,0000,0000,,And water in a gaseous state\Nwe call vapor, water vapor.
Dialogue: 0,0:00:37.07,0:00:38.65,Default,,0000,0000,0000,,Water, water vapor.
Dialogue: 0,0:00:41.44,0:00:45.40,Default,,0000,0000,0000,,And so that water vapor,\Nit is going to rise,
Dialogue: 0,0:00:45.40,0:00:49.68,Default,,0000,0000,0000,,likely with the air that has\Nbeen heated on the surface,
Dialogue: 0,0:00:49.68,0:00:54.30,Default,,0000,0000,0000,,due to the sun, and there's\Nother more complex dynamics
Dialogue: 0,0:00:54.30,0:00:57.55,Default,,0000,0000,0000,,at play, but as it rises, and\Nas the overall temperature
Dialogue: 0,0:00:57.55,0:01:01.72,Default,,0000,0000,0000,,cools, that water vapor will\Ncondense into little droplets.
Dialogue: 0,0:01:02.65,0:01:04.87,Default,,0000,0000,0000,,It'll condense around\Nlittle, tiny air particles,
Dialogue: 0,0:01:04.87,0:01:06.95,Default,,0000,0000,0000,,little particles of dust\Nthat you can't even see
Dialogue: 0,0:01:06.95,0:01:09.85,Default,,0000,0000,0000,,with your eye, and\Nthat's what forms clouds.
Dialogue: 0,0:01:09.85,0:01:14.01,Default,,0000,0000,0000,,So this is little droplets,\Nso the water's actually back
Dialogue: 0,0:01:16.29,0:01:19.32,Default,,0000,0000,0000,,to the liquid form, they're\Nnot individual water molecules
Dialogue: 0,0:01:19.32,0:01:23.51,Default,,0000,0000,0000,,anymore, they're now able\Nto interact with each other,
Dialogue: 0,0:01:23.51,0:01:26.95,Default,,0000,0000,0000,,and they're condensing\Naround these little,
Dialogue: 0,0:01:26.95,0:01:31.11,Default,,0000,0000,0000,,microscopic dust particles\Nto form these water droplets.
Dialogue: 0,0:01:31.96,0:01:33.42,Default,,0000,0000,0000,,And if it's cold enough,\Nthey might also form
Dialogue: 0,0:01:33.42,0:01:37.57,Default,,0000,0000,0000,,small ice crystals, and\Nthat's what clouds are.
Dialogue: 0,0:01:37.57,0:01:40.56,Default,,0000,0000,0000,,And we see here, they're\Ntalking about transportation,
Dialogue: 0,0:01:40.56,0:01:42.45,Default,,0000,0000,0000,,you can have these clouds, we\Nobviously, if you look outside
Dialogue: 0,0:01:42.45,0:01:45.84,Default,,0000,0000,0000,,and you see clouds, those\Nclouds are moving with the wind.
Dialogue: 0,0:01:45.84,0:01:48.45,Default,,0000,0000,0000,,And so they could be moving\Nall of those droplets
Dialogue: 0,0:01:48.45,0:01:51.02,Default,,0000,0000,0000,,with the overall wind.
Dialogue: 0,0:01:51.02,0:01:52.60,Default,,0000,0000,0000,,And when those droplets get heavy enough,
Dialogue: 0,0:01:52.60,0:01:55.96,Default,,0000,0000,0000,,they will precipitate,\Nthey will precipitate down.
Dialogue: 0,0:01:55.96,0:01:58.89,Default,,0000,0000,0000,,Now they could precipitate\Nback into where we started,
Dialogue: 0,0:01:58.89,0:02:01.35,Default,,0000,0000,0000,,they could go back to the ocean there.
Dialogue: 0,0:02:01.35,0:02:04.23,Default,,0000,0000,0000,,Or you could go onto a mountain here,
Dialogue: 0,0:02:04.23,0:02:07.71,Default,,0000,0000,0000,,and since if the air is cold enough,
Dialogue: 0,0:02:07.71,0:02:09.46,Default,,0000,0000,0000,,and if you have the right conditions,
Dialogue: 0,0:02:09.46,0:02:10.97,Default,,0000,0000,0000,,that precipitation might be snow,
Dialogue: 0,0:02:10.97,0:02:14.59,Default,,0000,0000,0000,,and it might stay snow right over there.
Dialogue: 0,0:02:14.59,0:02:18.51,Default,,0000,0000,0000,,Or ice, but then eventually\Nthings might warm up,
Dialogue: 0,0:02:18.51,0:02:20.88,Default,,0000,0000,0000,,or they might not warm up,\Nbut if they do warm up,
Dialogue: 0,0:02:20.88,0:02:22.62,Default,,0000,0000,0000,,well, then, they would melt,
Dialogue: 0,0:02:22.62,0:02:25.65,Default,,0000,0000,0000,,and there would be snow melt run-off.
Dialogue: 0,0:02:25.65,0:02:26.84,Default,,0000,0000,0000,,And that's what you're seeing there.
Dialogue: 0,0:02:26.84,0:02:29.67,Default,,0000,0000,0000,,If that rain is falling in this area,
Dialogue: 0,0:02:29.67,0:02:33.99,Default,,0000,0000,0000,,so let's say it's not cold\Nenough for it to be snow,
Dialogue: 0,0:02:33.99,0:02:36.25,Default,,0000,0000,0000,,we are talking about rain.
Dialogue: 0,0:02:36.25,0:02:38.64,Default,,0000,0000,0000,,Well, most of that water\Nis actually going to
Dialogue: 0,0:02:38.64,0:02:41.06,Default,,0000,0000,0000,,percolate down into the soil.
Dialogue: 0,0:02:42.42,0:02:44.60,Default,,0000,0000,0000,,So most of it goes down.
Dialogue: 0,0:02:44.60,0:02:46.63,Default,,0000,0000,0000,,We look around us and we\Nsee these rivers and lakes,
Dialogue: 0,0:02:46.63,0:02:48.26,Default,,0000,0000,0000,,and we say wow, there's\Na lot of water there.
Dialogue: 0,0:02:48.26,0:02:50.37,Default,,0000,0000,0000,,But it turns out, there's\Nactually a lot more water
Dialogue: 0,0:02:50.37,0:02:53.29,Default,,0000,0000,0000,,inside the ground and\Nobviously, in the ocean.
Dialogue: 0,0:02:53.29,0:02:55.23,Default,,0000,0000,0000,,And we'll talk about that in a little bit.
Dialogue: 0,0:02:55.23,0:02:58.62,Default,,0000,0000,0000,,So you have all of this water that forms
Dialogue: 0,0:02:58.62,0:03:01.62,Default,,0000,0000,0000,,in these underground aquafiers here.
Dialogue: 0,0:03:02.60,0:03:05.44,Default,,0000,0000,0000,,But some of it also ends up in these lakes
Dialogue: 0,0:03:05.44,0:03:07.54,Default,,0000,0000,0000,,and these lakes are usually\Nin a situation where
Dialogue: 0,0:03:07.54,0:03:12.07,Default,,0000,0000,0000,,the ground is either already\Nsaturated with water,
Dialogue: 0,0:03:12.07,0:03:14.11,Default,,0000,0000,0000,,or there's the right types of rocks,
Dialogue: 0,0:03:14.11,0:03:15.82,Default,,0000,0000,0000,,so it can contain the water up here,
Dialogue: 0,0:03:15.82,0:03:18.80,Default,,0000,0000,0000,,and similarly, rivers\Nare formed by runoff,
Dialogue: 0,0:03:18.80,0:03:22.85,Default,,0000,0000,0000,,it's snow melt run-off\Ncan famously form rivers.
Dialogue: 0,0:03:22.85,0:03:25.37,Default,,0000,0000,0000,,And in general, if you\Nsee a creek or a river
Dialogue: 0,0:03:25.37,0:03:28.33,Default,,0000,0000,0000,,near your house, especially\Nwhen it rains it fills up,
Dialogue: 0,0:03:28.33,0:03:31.00,Default,,0000,0000,0000,,that's a good indication\Nthat the ground water's
Dialogue: 0,0:03:31.00,0:03:32.93,Default,,0000,0000,0000,,already saturated and so\Nthings are running off
Dialogue: 0,0:03:32.93,0:03:34.26,Default,,0000,0000,0000,,into that river.
Dialogue: 0,0:03:35.48,0:03:38.07,Default,,0000,0000,0000,,And so that in general is the water cycle.
Dialogue: 0,0:03:38.07,0:03:39.92,Default,,0000,0000,0000,,You have evaporation, it\Ncondenses into clouds,
Dialogue: 0,0:03:39.92,0:03:42.11,Default,,0000,0000,0000,,it eventually precipitates,\Nand it keeps going,
Dialogue: 0,0:03:42.11,0:03:44.04,Default,,0000,0000,0000,,round and round and round.
Dialogue: 0,0:03:44.04,0:03:46.11,Default,,0000,0000,0000,,Now of course, there's\Nothers actors at play.
Dialogue: 0,0:03:46.11,0:03:47.89,Default,,0000,0000,0000,,You have things like plants.
Dialogue: 0,0:03:47.89,0:03:51.69,Default,,0000,0000,0000,,Plants will take up water\Nfrom the upper soil,
Dialogue: 0,0:03:51.69,0:03:54.04,Default,,0000,0000,0000,,as far as the plant's roots go.
Dialogue: 0,0:03:54.04,0:03:57.25,Default,,0000,0000,0000,,And it will use that water\Nto transport nutrients
Dialogue: 0,0:03:57.25,0:03:59.83,Default,,0000,0000,0000,,down from the soil up into the leaves.
Dialogue: 0,0:03:59.83,0:04:02.20,Default,,0000,0000,0000,,It also uses that water as part of
Dialogue: 0,0:04:02.20,0:04:03.76,Default,,0000,0000,0000,,the photosynthesis\Nprocess that we've studied
Dialogue: 0,0:04:03.76,0:04:05.62,Default,,0000,0000,0000,,in many videos.
Dialogue: 0,0:04:05.62,0:04:09.84,Default,,0000,0000,0000,,And a lot of that water\Ngets transpired out.
Dialogue: 0,0:04:09.84,0:04:12.86,Default,,0000,0000,0000,,So once again, this is\Ntranspiration, essentially,
Dialogue: 0,0:04:12.86,0:04:15.50,Default,,0000,0000,0000,,evaporation out the leaves of the water.
Dialogue: 0,0:04:15.50,0:04:18.84,Default,,0000,0000,0000,,Over here you see this word sublimation.
Dialogue: 0,0:04:19.71,0:04:22.88,Default,,0000,0000,0000,,That's going straight from\Nthe solid form of water, ice,
Dialogue: 0,0:04:22.88,0:04:27.10,Default,,0000,0000,0000,,into the gas form of\Nwater, or water vapor.
Dialogue: 0,0:04:27.10,0:04:29.74,Default,,0000,0000,0000,,And this will happen in\Nsituations where it's cold
Dialogue: 0,0:04:29.74,0:04:32.22,Default,,0000,0000,0000,,and it's very, very, very, very dry.
Dialogue: 0,0:04:32.22,0:04:35.50,Default,,0000,0000,0000,,And you have, in general, low pressure.
Dialogue: 0,0:04:35.50,0:04:38.65,Default,,0000,0000,0000,,So instead of going into the liquid state,
Dialogue: 0,0:04:38.65,0:04:40.86,Default,,0000,0000,0000,,right then the water\Nmolecules start just leaving
Dialogue: 0,0:04:40.86,0:04:42.11,Default,,0000,0000,0000,,as water vapor.
Dialogue: 0,0:04:44.42,0:04:46.15,Default,,0000,0000,0000,,And of course, I said, we're part of it.
Dialogue: 0,0:04:46.15,0:04:47.30,Default,,0000,0000,0000,,Well, how are we part of it?
Dialogue: 0,0:04:47.30,0:04:49.76,Default,,0000,0000,0000,,We will drink some of this fresh water,
Dialogue: 0,0:04:49.76,0:04:52.11,Default,,0000,0000,0000,,our bodies are actually mostly water.
Dialogue: 0,0:04:52.11,0:04:54.63,Default,,0000,0000,0000,,The cells in our bodies are 70% water.
Dialogue: 0,0:04:54.63,0:04:58.54,Default,,0000,0000,0000,,Everything we study in biology,\Nwater is a key environment
Dialogue: 0,0:04:58.54,0:05:01.84,Default,,0000,0000,0000,,for all of these things to occur.
Dialogue: 0,0:05:01.84,0:05:03.59,Default,,0000,0000,0000,,And then we use that water,
Dialogue: 0,0:05:03.59,0:05:07.27,Default,,0000,0000,0000,,and then we will get that\Nwater out of our body,
Dialogue: 0,0:05:07.27,0:05:11.75,Default,,0000,0000,0000,,and then it continues on as\Npart of this water cycle.
Dialogue: 0,0:05:11.75,0:05:13.72,Default,,0000,0000,0000,,Now one thing that I\Nfind really interesting,
Dialogue: 0,0:05:13.72,0:05:17.58,Default,,0000,0000,0000,,as an organism that is\Ndependent on fresh water,
Dialogue: 0,0:05:17.58,0:05:18.58,Default,,0000,0000,0000,,when people say fresh water,
Dialogue: 0,0:05:18.58,0:05:19.94,Default,,0000,0000,0000,,we're talking about water without salt,
Dialogue: 0,0:05:19.94,0:05:21.77,Default,,0000,0000,0000,,as opposed to salt water.
Dialogue: 0,0:05:21.77,0:05:24.53,Default,,0000,0000,0000,,So we really need the\Nfresh water in this lake,
Dialogue: 0,0:05:24.53,0:05:27.49,Default,,0000,0000,0000,,or in this river, or we might dig wells,
Dialogue: 0,0:05:27.49,0:05:30.76,Default,,0000,0000,0000,,so that we can get the water\Nout of these aquafiers.
Dialogue: 0,0:05:30.76,0:05:33.45,Default,,0000,0000,0000,,It actually turns out that\Nvery little of the overall
Dialogue: 0,0:05:33.45,0:05:36.28,Default,,0000,0000,0000,,water in the world is fresh water.
Dialogue: 0,0:05:37.77,0:05:41.14,Default,,0000,0000,0000,,And so let me show you\Nthis chart over here.
Dialogue: 0,0:05:41.14,0:05:43.37,Default,,0000,0000,0000,,I always knew that, but\NI didn't fully appreciate
Dialogue: 0,0:05:43.37,0:05:45.58,Default,,0000,0000,0000,,how little was fresh water.
Dialogue: 0,0:05:45.58,0:05:47.99,Default,,0000,0000,0000,,So of all the water on our planet,
Dialogue: 0,0:05:47.99,0:05:52.74,Default,,0000,0000,0000,,97.5% is salt water, for the\Nmost part, in our oceans.
Dialogue: 0,0:05:52.74,0:05:55.06,Default,,0000,0000,0000,,Only 2-1/2% is fresh water.
Dialogue: 0,0:05:55.06,0:05:58.82,Default,,0000,0000,0000,,And even of that 2-1/2% fresh water,
Dialogue: 0,0:05:58.82,0:06:01.43,Default,,0000,0000,0000,,very little of it is what\Nwe traditionally associate
Dialogue: 0,0:06:01.43,0:06:03.30,Default,,0000,0000,0000,,fresh water, the lakes and the rivers.
Dialogue: 0,0:06:03.30,0:06:05.15,Default,,0000,0000,0000,,When I think of fresh\Nwater, I'm gonna say oh,
Dialogue: 0,0:06:05.15,0:06:06.75,Default,,0000,0000,0000,,let me go to a lake or a river,
Dialogue: 0,0:06:06.75,0:06:08.63,Default,,0000,0000,0000,,that's stuff that we\Ncould potentially drink.
Dialogue: 0,0:06:08.63,0:06:11.52,Default,,0000,0000,0000,,But most of it is actually in glaciers
Dialogue: 0,0:06:11.52,0:06:13.83,Default,,0000,0000,0000,,and permanent snow cover.
Dialogue: 0,0:06:13.83,0:06:17.49,Default,,0000,0000,0000,,So it's ice, snow, that\Nis just not melting.
Dialogue: 0,0:06:18.90,0:06:20.47,Default,,0000,0000,0000,,And it makes you think\Nabout what would happen
Dialogue: 0,0:06:20.47,0:06:22.29,Default,,0000,0000,0000,,if this stuff were to melt.
Dialogue: 0,0:06:22.29,0:06:24.08,Default,,0000,0000,0000,,And then you also have ground water,
Dialogue: 0,0:06:24.08,0:06:25.46,Default,,0000,0000,0000,,which we could have access to.
Dialogue: 0,0:06:25.46,0:06:28.97,Default,,0000,0000,0000,,That's why people dig wells,\Nso we're talking about,
Dialogue: 0,0:06:28.97,0:06:31.72,Default,,0000,0000,0000,,well, ground water includes soil moisture,
Dialogue: 0,0:06:31.72,0:06:33.81,Default,,0000,0000,0000,,swamp water, and permafrost.
Dialogue: 0,0:06:33.81,0:06:37.64,Default,,0000,0000,0000,,Very little of the water is\Nactually in lakes and rivers,
Dialogue: 0,0:06:37.64,0:06:39.62,Default,,0000,0000,0000,,which I personally find fascinating.
Dialogue: 0,0:06:39.62,0:06:43.30,Default,,0000,0000,0000,,It wasn't obvious to me before\NI, frankly, saw this chart.
Dialogue: 0,0:06:43.30,0:06:45.18,Default,,0000,0000,0000,,Now another really interesting thing is,
Dialogue: 0,0:06:45.18,0:06:48.29,Default,,0000,0000,0000,,how long, on average,\Nwater molecules might stay
Dialogue: 0,0:06:48.29,0:06:50.75,Default,,0000,0000,0000,,in different parts of this water cycle.
Dialogue: 0,0:06:50.75,0:06:53.89,Default,,0000,0000,0000,,Going back here, you can\Nimagine that a water molecule
Dialogue: 0,0:06:53.89,0:06:56.86,Default,,0000,0000,0000,,can stay for a very\Nlong time in the ocean,
Dialogue: 0,0:06:56.86,0:06:58.97,Default,,0000,0000,0000,,especially, you know it's\Ngoing to be moving around,
Dialogue: 0,0:06:58.97,0:07:01.74,Default,,0000,0000,0000,,depending on ocean\Ncurrents and temperature
Dialogue: 0,0:07:01.74,0:07:03.20,Default,,0000,0000,0000,,and all of that, but you can imagine,
Dialogue: 0,0:07:03.20,0:07:05.50,Default,,0000,0000,0000,,it could stay in that\Nliquid form in that ocean
Dialogue: 0,0:07:05.50,0:07:06.91,Default,,0000,0000,0000,,for a very long time.
Dialogue: 0,0:07:06.91,0:07:09.24,Default,,0000,0000,0000,,And maybe it spends a shorter\Namount of time in a cloud.
Dialogue: 0,0:07:09.24,0:07:11.34,Default,,0000,0000,0000,,And people have actually studied this,
Dialogue: 0,0:07:11.34,0:07:12.63,Default,,0000,0000,0000,,which I find fascinating.
Dialogue: 0,0:07:12.63,0:07:14.64,Default,,0000,0000,0000,,I'd be curious to figure\Nout how they actually
Dialogue: 0,0:07:14.64,0:07:16.25,Default,,0000,0000,0000,,got this data.
Dialogue: 0,0:07:16.25,0:07:20.60,Default,,0000,0000,0000,,But this is the average residence\Ntime for water molecules.
Dialogue: 0,0:07:20.60,0:07:24.90,Default,,0000,0000,0000,,And you can see here that\Nwater can stay in glaciers
Dialogue: 0,0:07:24.90,0:07:27.27,Default,,0000,0000,0000,,and permafrost for a very long time,
Dialogue: 0,0:07:27.27,0:07:29.65,Default,,0000,0000,0000,,we're talking it could\Nbe up to 10,000 years,
Dialogue: 0,0:07:29.65,0:07:31.00,Default,,0000,0000,0000,,and these are all rough numbers.
Dialogue: 0,0:07:31.00,0:07:33.56,Default,,0000,0000,0000,,It can stay as ground water\Nanywhere from two weeks,
Dialogue: 0,0:07:33.56,0:07:35.91,Default,,0000,0000,0000,,to 10,000 years, I guess,\Ndepending on how isolated
Dialogue: 0,0:07:35.91,0:07:37.98,Default,,0000,0000,0000,,that ground water is.
Dialogue: 0,0:07:37.98,0:07:40.59,Default,,0000,0000,0000,,It could be in the oceans\Nand seas as salt water
Dialogue: 0,0:07:40.59,0:07:43.39,Default,,0000,0000,0000,,for 4,000 years, and we\Ncan look at all of these,
Dialogue: 0,0:07:43.39,0:07:46.47,Default,,0000,0000,0000,,all the way, within living organisms,
Dialogue: 0,0:07:47.37,0:07:50.35,Default,,0000,0000,0000,,it'll stay about, on\Naverage, a water molecule
Dialogue: 0,0:07:50.35,0:07:52.97,Default,,0000,0000,0000,,will last about a week in the atmosphere,
Dialogue: 0,0:07:52.97,0:07:55.86,Default,,0000,0000,0000,,so that's getting water\Nvapor, turning into a cloud,
Dialogue: 0,0:07:55.86,0:07:59.17,Default,,0000,0000,0000,,precipitating down, on\Naverage, one and a half weeks.
Dialogue: 0,0:07:59.17,0:08:00.41,Default,,0000,0000,0000,,And once again, these are averages.
Dialogue: 0,0:08:00.41,0:08:01.95,Default,,0000,0000,0000,,It doesn't mean that every\Nwater molecule will stay
Dialogue: 0,0:08:01.95,0:08:04.52,Default,,0000,0000,0000,,exactly one and half\Nweeks in the atmosphere,
Dialogue: 0,0:08:04.52,0:08:06.64,Default,,0000,0000,0000,,but it's a pretty interesting\Nthing to think about,
Dialogue: 0,0:08:06.64,0:08:08.58,Default,,0000,0000,0000,,and it gives you a\Nlittle bit more sense of,
Dialogue: 0,0:08:08.58,0:08:10.12,Default,,0000,0000,0000,,well, one, where all the water is,
Dialogue: 0,0:08:10.12,0:08:12.86,Default,,0000,0000,0000,,and how it all works together\Nwith the water cycle.