New Scientist – August 17, 2019

17 August 2019 | New Scientist | 17

Geology

Marine biology Animal behaviour

Tectonics may be

billions of years old

Earth’s continents may

have been moving for

longer than we thought.

Metamorphic rocks are

changed by heat in the

crust, influenced by plate

tectonics. A look at the

depths at which these rocks

formed suggests tectonics

developed over 2.5 billion

years ago, not 700 million

years ago as thought

(Nature, doi.org/c88w).

Self-powered

electronic garments

A new technique could

make your favourite T-shirt

smart. It uses embroidery

and the spraying of small

particles to turn cloth into

an energy harvester that

generates electricity from

the wearer’s movements.

This could be used to power

a sensor or remote control.

(Advanced Functional

Materials, doi.org/c88f).

Blood test guides

cancer treatment

A new blood test is 100

times more sensitive than

existing ones to DNA

mutations particular to a

person’s tumours (Science

Translational Medicine,

doi.org/c883). The test can

tell whether treatments for

breast cancer are working

and possibly save people

from unnecessary surgery.

Rapid flip of poles

looking less likely

CONTRARY to recent suggestions,

we appear to be safe from a fast,

catastrophic reversal of Earth’s

north and south magnetic poles.

A new analysis found that

the most recent magnetic field

reversal took at least 22,000 years

to complete. This is several times

longer than previous estimates.

Earth’s magnetic field, which

shields us from cosmic rays and

the sun’s harmful radiation, has

been acting strangely in recent

SOME types of shark have special

glow-in-the-dark skin that they

can see but other animals may not.

David Gruber at City University

of New York and his colleagues

found chain cat sharks (Scyliorhinus

retifer, pictured) and swell sharks

(Cephaloscyllium ventriosum) have

patches on their skin that glow

bright green.

When they analysed skin samples

from the species, they found that

this glow comes from a previously

unknown type of small, fluorescent

molecule: brominated tryptophan-

kynurenine. In a process called

biofluorescence, it absorbs blue

wavelengths of light and re-emits

them as longer wavelength green

light (iScience, doi.org/c88t).

Other marine creatures like eels,

seahorses and turtles also exhibit

biofluorescence, but they typically

use larger fluorescent molecules,

like green fluorescent proteins, to

convert blue light into other colours.

Previous research has shown that

chain cat sharks and swell sharks

can see the green colour emitted

by the small fluorescent molecules,

but the team suggests other marine

animals may not be able to.

This could mean the sharks use

fluorescence to find each other in

the depths while being camouflaged

to other animals, says Gruber. RPS

years. The magnetic north pole

has unexpectedly moved away

from Canada and is speeding

towards Siberia.

At the same time, the strength

of the field seems to be weakening,

prompting worries among some

scientists who say we may be on

the cusp of a reversal.

To investigate, Brad Singer at the

University of Wisconsin-Madison

and his team analysed features

including lava flows, which act like

a ledger of Earth’s magnetic field.

Shifts in its direction and intensity

affect iron atoms in the lava in a

way that means they reveal the

Stay eagle-eyed to

deter thieving gulls

HAVING an ice cream or chips

taken by a gull will be familiar

to anyone who goes on seaside

holidays in the UK, but a study

suggests there is a way to keep

them at bay: stare them down.

Madeleine Goumas at the

University of Exeter, UK, and her

colleagues ran an experiment

with 19 gulls in seaside towns in

Cornwall. An experimenter placed

a bag of chips on the ground and

crouched behind it, 1.5 metres

away. When a gull approached

the chips, the person started a

stopwatch, and either stared at

the bird or looked away.

When they were being watched,

only 26 per cent of the gulls

touched the chips. Those that

did touch the food took around

20 seconds longer to do so when

watched. This shows that gulls are

sensitive to the human gaze and

change their behaviour when they

are being watched (Biology Letters,

doi.org/c88s).

If you are eating outdoors by

the sea, Goumas advises sitting

with your back to a wall so gulls

can’t approach from behind. Most

importantly, be aware of your

surroundings. “I often see people

staring at their food or holding ice

creams up in the air, and I think

that’s just asking for it.” Sam Wong

direction and strength of the

magnetic field at the time the

lava flow cooled.

They found that the strength

of the field dropped a lot, but not

enough to flip polarity, 795,

years ago and again 784,000 years

ago. Over the following 12,

years, the field was unstable, and

eventually the poles flipped

completely into the orientation

we have today (Science Advances,

doi.org/c88q).

This suggests the magnetic

field’s recent strange behaviour

is less worrying than previously

assumed. RPS

Sharks give off a ghostly

green glow in deep waters

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Really brief

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