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영어 10:51 Science & Tech

There’s Fresh Water Under the Ocean. Can You Drink It?

SciShow · 239,192 조회수 · 추가됨 1개월 전

자막 (214 세그먼트)

00:00

More than 2000 years ago,

00:01

a Roman geographer told a strange tale

00:04

about the Mediterranean Sea.

00:05

The locals would hop on a boat,

00:07

travel to a specific spot four  kilometers off the coast of Syria,

00:10

and collect seawater with a  funnel connected to a long tube.

00:14

Then, they would drink it.

00:16

Amazingly, this water was fresh.

00:18

Two millennia and one Talking Heads song later,

00:21

we know this story isn’t complete malarky.

00:24

Scientists have discovered fresh water under  the ocean in locations around the globe.

00:28

But how much is there?

00:30

And more importantly, can we access it?

00:33

[SciShow Intro]

00:36

Like many discoveries throughout history, modern scientists stumbled across fresh

00:40

undersea groundwater by happenstance. In the 1970s,

00:43

expeditions off the coasts of  Massachusetts and New Jersey

00:47

were collecting sediment samples  from beneath the seafloor.

00:50

At the time, the prevailing assumption

00:52

was that salty ocean water would  completely penetrate the sediment

00:55

beneath the seafloor.

00:57

But in the samples they pulled  up, the water was fresh.

01:00

Somewhere, that Roman geographer’s  skeleton must have shouted,

01:03

“Vindicatio- wait what the heck is an old Jersey?”

01:08

But let’s back up and cover some basics.

01:10

The saltiness of water is often  measured in units of parts per thousand.

01:15

Basically, it compares the  weight of dissolved salts…

01:18

like sodium, chloride, magnesium, and sulfate…to  the weight of water in a given volume.

01:23

Seawater typically has a saltiness  of about 35 parts per thousand.

01:27

Which our props people have approximated

01:29

by dissolving 35 grams of  table salt in a liter of water,

01:33

and handing me a sample to taste test.

01:39

“OK, don’t try this at home.”

01:41

The water found by those expeditions in the 1970s

01:44

was a lot fresher than seawater,  less than 3 parts per thousand.

01:48

Which I have also been asked to taste test.

01:54

Still not great I'm gonna be honest,

01:55

but not as bad as the first one.

01:57

Tastes a little like soup

01:58

Now, 3 parts per thousand is technically on  the lower end of what’s called brackish water.

02:03

While it’s ten times fresher  than the rest of the ocean,

02:06

it’s not quite fresh enough to drink comfortably.

02:08

The US Geological Survey, or USGS,

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