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The experts
Why do poppy fl owers
open in the morning
ROBERT MATTHEWS
and close at night?
After studying physics
at Oxford University, ROSEMARY WHITTINGTON, EAST LOTHIAN
Robert began a
career in research. He
is currently a Visiting
This behaviour is called nyctinasty, and and then grow more cells on the inside to
Reader in Science at
although it is by no means universal, there open them again in the morning.
Aston University are lots of other fl owers besides poppies The most likely explanation for this
that do it. Most of them instigate the closure behaviour is to protect the pollen. At night
by pumping water out of cells at the base the insects that pollinate most fl owers are
of the petals so that they wilt themselves dormant and closing the fl ower keeps the
shut. But the genus Kalanchoe of tropical pollen dry and contained. Some fl owers
succulents actually grow new cells on the that are pollinated by moths or bats do the
outside of the petal base to force them shut opposite and only open at night. LV
LUIS VILLAZON
Luis has an MSc in
zoology from
Oxford University.
His published
work includes
How Cows Reach
the Ground
GARETH MITCHELL
Gareth started out
as a broadcast
Y engineer. He is now
a broadcaster, writer
IBRAR and presenter of Why does polystyrene
L
Digital Planet on the
How do we know the
T
O
BBC World Service
used for packaging
stick to everything?
speed of light is the same
, SCIENCE PHO
SHARON PHILIPPIDIS, BY EMAIL for everyone?
ARD
Polystyrene is the material of choice for
HARRIET BEST, BY EMAIL
packaging because it’s nice and light. It’s
3
, MOODBO
easy to snap in half or crumble but, crucially,
This is the assertion behind the theory of special relativity – and it’s not
LEN FISHER obvious. The speed of a train may be 200km/h to a stationary observer, but
AMY X
it’s strong in compression and therefore
Len is an Honorary
protects delicate objects if dropped or
400km/h relative to a train coming the other way. Einstein’s claim that the
Research Fellow in
Physics at Bristol
crushed. Polystyrene is also a very good
speed of light is the same for everyone, regardless of how they’re moving,
Y
.
COM, AL
University and the insulator, meaning that it quickly accrues
was confi rmed by experiments at CERN in Geneva. Sub-atomic particles
author of several
electrical charge. This gives it a strong
were accelerated to 99.975 per cent of the speed of light, but when the
popular science
L
IBRAR
electrostatic attraction to other objects,
speed of light they emitted was measured, it turned out to be 300,000km/s
T
O books including How
to Dunk a Doughnut
causing it to readily stick to things. GM
– the same as when the particles are stationary, as Einstein predicted. RM
PHO
42 November 2008 www.bbcfocusmagazine.com
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