BBC Focus

Y OUR QUE S TIO N S ANS WERED

DR

CHRISTIAN

JARRETT

Christian is a

psychology

and neurosci-

ence writer.

His latest

book isGreat

Myths Of

The Brain.

DR

ALASTAIR

GUNN

Alastair is an

astronomer

at the

Jodrell Bank

Centre for

Astrophysics

atthe

University of

Manchester.

PROF

ROBERT

MATTHEWS

Robert is

aphysicist

and science

writer. He’s

visiting

professor

in science

atAston

University.

DR PETER

JBENTLEY

Peterisa

computer

scientist and

author who

isbasedat

University

College

London. His

latest book is

Digitized.

LUIS

VILLAZON

Luis is a

freelance

science and

tech writer

with a BSc in

computing

and an MSc

in zoology

from Oxford

University.

OCTOBER 2016 EDITED BY EMMA BAYLEY

ALEXANDRA

CHEUNG

Alexandra

has a degree

in envi-

ronmental

science,and

hasworked

forCERNand

Imperial Col-

legeLondon.

PH

OT

O:

GETTY

The warmer water gets, thefaster its molecules

move. This extra energy allows water to

evaporate morequickly.Byshieldingthewater

from sunlightandkeeping it cool,droughtballs

(alsoknown as shadeballs)can slow evaporation

from waterbodies. In 2014, theLosAngeles

Department ofWater andPower released 96

million of these plastic balls into the city’s main

reservoir. Their goal was not to save water but to

reduce thegrowthofmicroorganisms and

prevent thecreationofbromate, a carcinogen

thatforms throughachemicalreaction triggered

by UV light. The balls did, however, reduce

evaporationby up to 90 per cent.AC

Howdodrought

balls work?

ANNA KENDAL,TIVERTON

The drought balls in

Los Angeles will last for

10 years, and will then

be recycled

PHOTO: ZUMA PRESS/EYEVINE