New Scientist - USA (2019-07-13)

22 | New Scientist | 13 July 2019

W

HEN I was 4, my

favourite book was

Balloonia by Audrey

Wood. It tells the story of a little

girl who realises that balloons

have an afterlife when they

float away. Wielding a sharp pin,

she takes a balloon hostage,

demanding that it take her to

Balloonia. There, she experiences

a world where everything is made

of balloons, including the animals

and the landscape they populate.

It is a wonderful tale. It is only

later in life that I have come to

worry it might be predicated on

the continued availability of the

second most abundant element

in the universe: helium. Trouble

is, helium is running out on Earth.

When we fill a balloon with

helium, it floats because helium

is lighter than air. Sound also

travels through helium faster

than it travels through air, which

is why inhaling helium makes

people’s voices sound temporarily

more high-pitched.

Beyond its entertainment value,

helium is also a crucial coolant in

its liquid form. It pops up in diverse

technologies, from fancy medical

equipment like MRI machines

to big physics toys such as space

rockets and the Axion Dark Matter

Experiment, which searches for

axion particles, my favourite

candidate to make up the

universe’s missing dark matter.

On a day-to-day basis, we

rarely give much thought to the

origins of helium, but they are

fascinating. Almost all of the

helium in the universe was

produced when space-time as

we know it was only a few minutes

old. This period is called big bang

nucleosynthesis, an era that

began when the universe became

cool enough that radiation could

no longer prevent protons and

neutrons coming together to

form the first atomic nuclei.

During that time, the first

element in the periodic table,

hydrogen, formed in great

quantities, making up 75 per cent

of the luminous matter in the

universe. Nearly all the rest is the

second lightest element – helium.

These two elements make up

most of the gas clouds that hang

around the universe. Along with

a small amount of lithium made

at the same time, they formed

the foundation for the first

generation of stars.

Stars aren’t just made from

helium; they are also a site for

making it. Stars are collections

of tightly packed hydrogen and

helium atoms whose high density

causes the initiation of nuclear

explosions. These explosions are

extremely bright, producing light

across the electromagnetic

spectrum, including at visible

wavelengths. That is what we

have to thank for every sunrise

and the beauty of the night sky.

But these explosions also smash

and glue elements together to

make heavier ones. In our sun,

hydrogen nuclei fuse into helium,

producing high-energy radiation

in the form of gamma rays. In

more massive stars, this stellar

nucleosynthesis is more complex,

leading to the production of

heavier elements like the carbon

that is the basis for human life.

We really are made of star stuff!

There is an irony in this cosmic

abundance, however. All the

helium we have on Earth, from

the stuff we put in balloons to

the stuff we put in MRI machines,

originates not directly in stars,

but in radioactive decays in

Earth’s crust. Over time, the

heavy elements uranium and

thorium – themselves made when

stars explode at the end of their

lives or when neutron stars

collide – break down. The products

include alpha particles consisting

of two protons and two neutrons

bound together, otherwise known

as helium nuclei.

Unfortunately for Earth

(and Balloonia), helium isn’t

endlessly abundant. In fact,

we are currently facing a global

shortage. More than 90 per cent

of the world’s helium supply

comes from just three countries –

the US, Qatar and Algeria – with

most of it a byproduct of natural

gas extraction.

Current sources are running low

and efforts to tap new ones have

been delayed. Scientists have tried

to get the US Congress to improve

the management of existing

supplies, but political challenges

have got in the way.

The link between natural gas

and helium supplies is one reason

this is complicated: accelerating

global warming demands that we

move away from fossil fuels as

energy sources, not look for more

of them. But unlinking helium

from fossil fuels raises difficult-to-

address questions given current

economic structures.

Changing how we do things

often seems like an impossibility.

The case of helium reminds us

that the universe is a vast and

wonderful place, but also how

we need to make do with – and

LU cherish – what we have on Earth.  ❚

XX

IM

AG

ES

/GE

TT

Y

This column appears

monthly. Up next week:

Graham Lawton

“ The existence of

a world of floating

balloons is

predicated on

the availability

of helium”

No laughing matter Helium is one of the most abundant elements

in the universe, yet supplies on Earth are running out – a reminder of

how precious our resources are, says Chanda Prescod-Weinstein

Field notes from space-time

What are you reading?

I am working my way

through C. Riley Snorton’s

Black on Both Sides:

A racial history of

trans identity.

What are you watching?

I have been glued to

the soccer Women’s

World Cup for the past

few weeks. I have also

finally managed to see

Avengers: Endgame.

What are you

working on?

I want to better

understand the dynamics

between galaxies and

their dark matter haloes.

Chanda’s week

Chanda Prescod-Weinstein

is an assistant professor of

physics and astronomy,

and a core faculty member

in women’s studies at the

University of New Hampshire.

Find her on Twitter

@IBJIYONGI and the web

at cprescodweinstein.com

Views Columnist