BBC Knowledge Asia Edition

&

BY OUR EXPERT PANEL

YOUR QUESTI0NS ANSWERED

Susan is a visiting

psychology

professor at the

University

of Plymouth. Her

books include The

Meme Machine

SUSAN

BLACKMORE

Alastair is a

radio astronomer

at the Jodrell

Bank Centre for

Astrophysics at

the University of

Manchester

DR ALASTAIR

GUNN

After studying

physics at Oxford,

Robert became a

science writer. He’s

a visiting reader in

science at Aston

University

ROBERT

MATTHEWS

Starting out

as a broadcast

engineer, Gareth

now writes and

presents Digital

Planet on the BBC

World Service

GARETH

MITCHELL

Luis has a BSc in

computing and an

MSc in zoology

from Oxford. His

works include

How Cows Reach

The Ground

LUIS

VILLAZON

[email protected]

PHOTO: GETTY

How are the colours and shapes of fireworks created?

Despite being invented in China

almost 1,000 years ago, fireworks involve

some pretty sophisticated science. The

spectacular colours are the result of

metal compounds combining with

oxidisers that supply oxygen. This

produces heat, which kicks electrons in

the chemicals into higher energy levels.

They rapidly return to their normal

‘ground state’, and shed the energy as light.

Relatively cool-burning strontium carbonate

gives red, sodium nitrate produces yellow,

and barium chloride gives green. The hardest

colour to produce is an intense blue, which

needs the firework to reach a high

temperature, but not so high that it simply

burns up. Manufacturers often use copper

chloride to hit the right temperature range and

achieve a bright, rich blue.

The spectacular shapes are produced by

embedding the packets containing the

colour-making chemicals – known as ‘stars’

• in gunpowder, together with a burst
  charge. Once the firework reaches the right
  altitude, the burst charge explodes,
  detonating the gunpowder, and blasting the
  stars out into the pre-arranged pattern. RM

In China, fireworks were

traditionally used to

scare off evil spirits