BBC_Science_Focus_-_08.2019

Q&A

GETTY IMAGES X5 ILLUSTRATIONS: DAN BRIGHT

Once a particle of light (‘photon’) passes the ‘event horizon’ of a black hole, it can no longer

escape, but there’s nothing to suggest that it is destroyed. Like maer, the photon is rapidly

sucked towards the ‘singularity’ at the centre of the black hole, where a huge mass is packed

into an infinitely small space. What happens to photons at these extreme conditions, however,

is one of physics’ big unanswered questions.AGu

RUTH DIETRICH

WHAT HAPPENS TO THE LIGHT THAT’S

BEEN SUCKED INTO A BLACK HOLE?

THE FULL MOON

MAKES PEOPLE

MAD

OLD WIVES’

TA L E S...

The origins of this idea date back at least
to the Ancient Greeks, with Aristotle
2,300 years ago claiming that the Moon
could inuence the human mind. But
madness wasn’t the only outcome: the
original meaning of ‘lunatic’ referred to
epilepsy rather than insanity. The Roman
naturalist Pliny the Elder argued that the
Moon was able to exert its inuence via
the water content of the brain – rather
like the tides. This is now known to be
nonsense: the forces involved are far
too small.
Even so, the belief persists and has
been investigated scientifically many
times. A 1985 review of dozens of studies
of alleged links between the Moon and
everything from psychiatric issues to
criminal behaviour found no compelling
evidence. But it still remains an active
research topic. Earlier this year, the
respected journalBMJ Openpublished a
study claiming to show that a full Moon
actually makes murderslesslikely,
although the author admits that the
reason isn’t clear, and that other factors
may play a role.
So how did the idea of a lunar inuence
on humans get traction in the first place?
One suggestion is that in ancient times a
bright full Moon was more likely to
disturb sleep – and sleep deprivation is
known to exacerbate mood disorders in
some people.RM

JAMES COLLEY, VIA TWITTER

WHAT ACTUALLY HAPPENS WHEN A CATERPILLAR BECOMES A BUTTERFLY?

IS IT A POKÉMON SITUATION OR MORE OF A CRONENBERG THING?

It’s more of a messy, Cronenberg-esque

transformation than a tidy Pokémon one. When

a caterpillar starts to change into a pupa (or

‘chrysalis’), its own digestive enzymes begin to

break down most of its cells into a chemical soup.

Some of the caterpillar’s structures do remain

intact, however, such as the gut, the tracheal

tubes (for breathing), and some of the central

nervous system. Also resistant to the

transformation process are clumps of cells called

‘imaginal discs’, which are contained within the

caterpillar’s body for its entire life. During

metamorphosis, the imaginal cells divide rapidly.

At first, these are treated as invaders and

aacked by the caterpillar’s immune system. But

eventually the imaginal cells overwhelm the

dwindling caterpillar cells and begin to use the

raw materials around them to assemble new

buery structures, such as wings, legs,

eyes and antennae. These structures eventually

connect up with the remaining caterpillar parts,

and the newly assembled buery emerges.

The whole process can take just two weeks in

some species.LV

EGG CATERPILLAR PUPA EMERGING BUTTERFLY ADULT BUTTERFLY