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You're listening to Shortwave

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from NPR. Hey,

0:06

short wavers. Aaron Scott here. With

0:08

Regina Barber. And Ari Shapiro. Ari

0:11

has taken a break from hosting All Things Considered

0:13

to chat with us for another Shortwave Roundup

0:15

of Science in the Headlines. If only I were taking

0:17

a break. I'm doing both and, my friends. I

0:19

know, I can see it. And here we are talking about

0:21

a black hole that is both super

0:24

big and the oldest ever confirmed. Yes,

0:27

and also how rising temperatures and

0:29

pollution are tipping the balance of

0:31

the sexes, at least for

0:33

sea turtles.

0:34

And the potential health benefits of cutting

0:36

a teaspoon of salt in your diet. You're

0:39

listening to Shortwave, the science podcast

0:41

from NPR.

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2:07

Okay Ari, so you are the guest.

2:09

You get first choice where we

2:11

begin. Okay, let's start with a black hole. The

2:13

oldest one scientists have been able

2:16

to confirm?

2:16

Yeah, and it's ginormous. It's

2:18

called a supermassive black hole. It's super

2:20

far away from us, which means we're seeing what it looked

2:22

like just 470 million

2:25

years after the universe was created. And

2:27

this really early period of time in the

2:29

universe was something astronomers didn't have much data

2:32

for, just a lot of theories.

2:33

Until now. So the James Webb

2:35

Space Telescope is allowing us to test

2:38

all those theories by letting us look

2:40

this far back in time. It works kind of like a

2:42

time machine to study how bits

2:44

of the universe came together. Like in this

2:46

case, this supermassive black hole.

2:48

And Ari, these supermassive black holes, they

2:51

exist at the center of almost every galaxy

2:53

in the universe, including ours, the Milky Way,

2:55

and they shape how galaxies

2:56

form. And what do scientists

2:58

hope to learn by finding these enormous

3:00

ancient black holes?

3:02

Well, they're trying to solve a mystery, which is how these

3:04

supermassive black holes form at

3:05

all. They know one way to make black

3:07

holes for sure, and that's when a massive star

3:10

dies, like much, much bigger than our sun. They

3:12

explode, they collapse, and they create a black hole.

3:14

But supermassive black holes are thousands

3:17

of times the mass of our sun, and they couldn't

3:19

have been made just by dying stars.

3:22

They're just too big.

3:23

Yeah, and Priya Natarajan is a theoretical

3:25

astrophysicist at Yale, and way back in 2006,

3:28

she and her colleagues proposed that a supermassive

3:30

black hole could get their start by a huge

3:32

amount of dust and gas collapsing and

3:34

then grow from there, rather than from a dying

3:36

star.

3:37

But they needed evidence

3:39

for this theory, and that's where the detection

3:41

of this really old supermassive black hole comes

3:43

in. Priya co-authored this latest

3:45

research in the journal Nature Astronomy, and

3:48

it provides some evidence in favor of

3:50

their theory on how these things form

3:52

from collapsing clouds of gas and

3:55

not from collapsing stars.

3:59

long to demonstrate this.

4:01

Yeah, she said it took three space

4:03

telescopes to verify this, the Hubble Space Telescope,

4:06

the new James Webb Space Telescope or

4:08

JWST, and the Chandra X-ray

4:10

Observatory.

4:11

And it's kind of a miraculous

4:13

lining up of things, right? Because all

4:15

three NASA flagship missions

4:18

were involved in this. And Priya says

4:20

thanks to JWST in particular,

4:22

we're getting a window into what's happening in the early

4:25

universe. And this discovery is just opening

4:27

it up just

4:28

a crack. All right, from massive

4:30

ancient black holes, let's go to tiny baby

4:32

sea turtles. And climate

4:35

change and pollution are endangering

4:37

sea turtles by skewing the

4:39

balance of females to males? How? Yes,

4:42

yes. So let's take the two

4:44

apart. First temperature, fun

4:47

science fact for you, Ari, if you change

4:49

the temperature of a sea turtle egg, along

4:51

with a number of other reptile eggs, you

4:54

can actually change the sex of the

4:56

embryo. It's called temperature dependent

4:58

sex determination.

5:00

And this happens because hotter and cooler

5:02

temperatures activate different genes that produce

5:04

either female or male sex hormones.

5:07

And in the case of sea turtles, rising temperatures on

5:09

the beaches

5:09

where they bury their eggs push the embryos

5:11

to become female. And we are

5:13

not talking about a slight imbalance

5:16

here. This is huge in warmer

5:18

places like the northern part of the Great Barrier

5:20

Reef. Over 99% of the hatchlings are

5:23

female, 99%. Wow. Okay, so that's how temperature

5:29

affects the balance of male to female. What

5:31

about pollution?

5:32

Yeah, well, the scientists who conducted this research

5:34

realized that temperature couldn't explain everything.

5:37

So they wondered if something else was

5:38

playing a role. And previous research had shown

5:40

that heavy metals and some other contaminants

5:43

can disrupt hormones for other reptiles

5:45

like alligators and cause them to have skewed

5:47

sex ratios. So these researchers

5:50

decided to test green sea turtle nests

5:52

for a number of these pollutants. This

5:54

is Arthur Baraza, the lead author of the paper

5:56

that came out this week in Frontiers in Marine

5:58

Science.

5:59

One of the things that I found was that certain heavy metals

6:02

were associated with more females in the nest

6:04

than predicted.

6:05

Things like cadmium and antimony, along

6:08

with a couple organic chemicals, basically

6:10

compounds that come from things like urban runoff,

6:12

mining, and fossil fuels, and

6:15

plastic waste.

6:15

And Arthur says this isn't really

6:17

a problem now, but it could be a big threat

6:20

to the survival of turtles in coming years

6:22

because they'll have an incredibly difficult

6:24

time finding a mate and reproducing. I

6:26

mean, you can imagine that turtle tinder

6:29

is just going to be tumbleweeds.

6:32

Terrible. Okay, so what can

6:34

we do about it?

6:35

Yeah, conservationists are experimenting

6:37

with using seawater to irrigate turtle

6:40

nests to cool them down and create a more

6:42

mixed ratio of the sexes. So they're watering

6:44

turtle nests to grow the next generation

6:46

of males. Uh-huh. Yeah, there's

6:48

a joke in there somewhere, probably. Let's

6:51

end on the third story you've brought us, this research

6:53

about salt and blood pressure. I'm

6:55

going to take a wild guess and say that eating

6:58

more salt drives your blood pressure

7:00

up.

7:01

Yeah, so cutting it is going to make it better. Cutting

7:03

one teaspoon of salt a day results in a decline

7:05

of blood pressure

7:06

comparable to taking medication,

7:08

actually. Just one teaspoon? Wow. Yeah.

7:12

Yeah, and this is from a new study published in JAMA, or the Journal of the

7:14

American Medical Association. And before

7:16

we go further, we should start with

7:18

just some basics. So we mentioned

7:21

salt, like table salt, but the thing we're

7:23

really talking about is sodium, which is in

7:25

the salt.

7:26

Right, and we know we need some sodium for

7:28

our bodies to work properly. It plays an important

7:30

role, for instance, in nerve and muscle

7:32

function, but too much sodium is bad

7:34

for our health. Like for some of us, it can contribute

7:37

to high blood pressure, which can cause stroke

7:39

or heart disease. How exactly

7:40

does that work? Why does salt make

7:43

blood pressure go up?

7:43

It has to do with our bodies absorbing

7:46

more water because of the salt. Like, so extra

7:48

sodium in your blood pulls more water into

7:50

your blood vessels, increasing the amount of blood

7:53

in your blood

7:53

vessels. And that in turn increases

7:55

the pressure leading in some people, high

7:58

blood pressure. already

8:00

have high blood pressure, it could make it worse, and

8:02

then all of this can result in damaged

8:04

deer blood vessels and organs. It sounds from

8:06

this study like people don't have to make a dramatic

8:09

change in their diet to have a real impact. Yeah,

8:11

they saw these blood pressure lowering

8:13

effects in just one week, even

8:15

for people already on blood pressure medication. So

8:18

quick effects, but it's

8:20

not necessarily going to be easy, Ari.

8:23

According to the FDA, Americans eat on average

8:26

about 3400 milligrams of sodium per

8:29

day, and a teaspoon of table salt

8:31

has about 2300 milligrams

8:33

of sodium in it. So in this case, you're

8:35

going to need to cut your daily sodium intake

8:38

by two thirds. Oh, forget that. Yeah.

8:41

And

8:41

for many of us, this sodium actually

8:43

comes from packaged and prepared foods.

8:45

So maybe just make sure you check out those

8:47

nutritional labels. Bottom line, though,

8:50

the researchers say that really any

8:52

amount of sodium reduction in your diet for most people

8:54

will

8:54

be better for your blood pressure compared to no reduction

8:56

at all. You know what? We all have our vices and I'm not giving

8:59

up French fries.

9:02

All right. Thank you, as always, for

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taking some time out of your day and hanging

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out with us. You know, I love a good crossover.

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Find out more at plus dot

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This episode was produced by Rachel Carlson and

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Kai McNamee. It was edited by Christopher

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and Talia, the at lay and Rebecca

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Ramirez.

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Great. Hanson, check the facts and the audio engineers

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were Patrick Murray, Ted, me, Bain and Stu

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Rushfield. Beth Donovan is our senior

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