BBC Sky at Night - UK (2021-08)

Interview with

the author

Dr Harry Cliff

What is particle

physics?

It’s where you get if

you keep asking

‘why?’. It describes

how the Universe works

deep down. What is the world made

of? What are the ingredients and how

do they behave, how do they interact?

It started 100 or so years ago when we

realised there was a substructure

within what we thought of as the most

basic building blocks of matter. Since

the discovery of the electron we’ve

discovered dozens and dozens and

dozens of [subatomic] particles.

Do we understand why anything exists?

We can tell a lot of the story. You can

break an apple pie down to chemical

elements and trace their origins

through the Universe’s history.

Everything, including apple pies,

contains hydrogen, carbon, oxygen,

the chemical elements across the

periodic table. We have a pretty

complete description of where these

come from, forged inside stars or in

the first minutes after the Big Bang.

We can tell this story back to about a

trillionth of a second after the Big

Bang, but it’s less clear beyond that.

What does the Large Hadron

Collider do?

What it does is simple and pretty

brutal: it accelerates particles to high

energies and smashes them into each

other. It does that 40 million times a

second, 24 hours a day, seven days a

week for nine months of the year.

When two protons collide, they have a

lot of kinetic energy and that is turned

into new matter. You are making

particles from energy, and you might

make a Higgs boson, for example. That

is how these particles were discovered.

Dr Harry Cliff is a particle physicist

at the University of Cambridge

working on the Large Hadron

Collider beauty experiment

Harry Cliff

Picador

£20 z HB

Unless you’re a big

fan of the late

astronomer Carl

Sagan, you might

EHDWƅUVWSX]]OHG

about whether the title

of this book, by particle

physicist Dr Harry Cliff,

actually belongs on the

same shelf as other popular

physics books. I would say,

however, that this is one of

the best books of that

genre I have read.

Starting with an apple pie, Cliff works

backwards, breaking down the

ingredients to their elements, then atoms,

and keeps on going to describe what

we believe is happening on the smallest

of scales. This book is a wonderful

exploration into the origins of matter

• and how you got to be here reading
  these words.
  What sets this book apart are the human
  stories that are woven into the physics
  being described. Of course you’ll read about
  the giants of particle physics, but Cliff also
  introduces a new generation of scientists
  who are pushing the boundaries of our
  understanding. You’ll be connected to the
  experiments these ordinary scientists are
  working on, and share in their passion. My
  favourite examples include the DeLorean-
  like machine under London’s streets that is
  ORRNLQJIRUXQGLVFRYHUHGTXDQWXPƅHOGVRU
  the Borexino experiment below an Italian
  mountain that is studying solar neutrinos.
  The storytelling is really captivating and
  easy to follow. This book soon replaced
  my usual bedtime reading: something a
  popular physics book has never done. I will,
  however, admit that the last third of the
  book gets heavy. If you’ve heard the terms
  ŜTXDQWXPƅHOGWKHRU\ŝŜVXSHUV\PPHWU\ŝRU
  WKHŜ+LJJVƅHOGŝDQGZRQGHUHGZKDWLWZDV
  all about, here is where you’ll
  learn. This is another great
  element of the book.
  Cliff stares right in the
  face of some of the
  most bizarre physics
  concepts we have.
  Instead of brushing
  over quantum
  electrodynamics,
  for instance, you
  will instead come
  away with a good
  understanding of what
  it’s all about.
  So, at the end of the book
  you may be able to ‘invent
  the Universe’: take the
  ingredients, which include
  a smidge of spacetime,
  and follow the witty instructions that
  detail how to actually make an apple pie
  from scratch. ★★★★★

Laura Nuttall is a Reader of
Astrophysics at the Institute of
Cosmology and Gravitation at
BO the University of Portsmouth

RE
XIN

O^ C

OL
LA
BO

RA

TIO

N

How to Make an

Apple Pie from

Scratch

Deep below an Italian

mountain, Gran Sasso, the

Borexino detector is on the

look out for solar neutrinos

94 BBC Sky at Night Magazine August 2021

BOOKS

New astronomy and space titles reviewed

PACKED (^)
WITH
IDEAS