3 October 2020 | New Scientist | 21Renewable energySpace Marine biologyWhy frogs can
have such big eyesThe size of a frog’s eyes
compared with its body
scales depending on its
environment, according
to a study of thousands
of specimens representing
220 frog species. Tree
frogs have the biggest
eyes and frogs from murky
waters have small eyes
(Proceedings of the Royal
Society B, doi.org/d97n).Birdsong got deeper
during lockdownAs covid-19 restrictions
went into place and there
was less human noise in
urban areas, birds changed
their tunes. A study in
San Francisco shows that
white-crowned sparrows
started singing in lower
pitches, making their songs
travel further and sound
more appealing to mates
(Science, doi.org/d97p).Microbot puts
neuron in its placeTiny robots steered by
magnetic fields have
moved brain cells to create
a neural circuit, which
could help us to study brain
disorders. The robots are
made of a polymer coated
in nickel and titanium, and
have grooves that neurons
can grow along (Science
Advances, DOI: 10.1126/
sciadv.abb5696).Energy harvested
from gentle breezesA SMALL device can harvest
energy from the breeze generated
as you walk and could potentially
be used to power your gadgets.
Ya Yang at the Chinese Academy
of Sciences in Beijing and his
colleagues have developed a
device that takes advantage of the
triboelectric effect, which occurs
when materials become electrically
charged as they rub together.
The team used an 8-centimetre-
long tube containing two thinASTRONAUTS on the moon would
face nearly three times as much
radiation exposure as those on the
International Space Station (ISS),
which could make long-term
missions riskier than thought.
“Once you’ve survived being on
the moon and come back to Earth,
radiation damage is what stays with
you for the rest of your life,” says
Robert Wimmer-Schweingruber
at the University of Kiel in Germany.
Wimmer-Schweingruber and
his colleagues analysed data from
China’s Chang’e 4 lander, which
became the first spacecraft to land
on the far side of the moon last year.
Levels of radiation exposure on themoon were between 200 and
1000 times higher than on Earth’s
surface and some 2.6 times higher
than those astronauts on the ISS
experience (Science Advances,
DOI: 10.1126/sciadv.aaz1334).
“There is still uncertainty on
whether this increased level of
exposure to heavy-charged particle
radiation will have significant short
and long-term impacts on human
health,” says Jeff Chancellor
at Louisiana State University.
“If you wanted to live on the
surface of the moon, you’d want
to dig down pretty deep or cover
yourself with a lot of lunar dirt,”
says Wimmer-Schweingruber. LLfilms, each made up of a layer of
plastic on top of a layer of silver
that acts as an electrode. The two
films flutter in response to winds
as slow as 1.6 metres per second.
The wind speed required for
most wind turbines to generate
power is 3 metres per second.
As they brush against each
other, the films generate an
electric current, which is
transmitted through the
silver electrodes to drive a
tiny generator in the device.
Yang and his team put the
device on a volunteer’s arm and
found that the airflow generatedWhale breaks record
for the longest diveA CUVIER’S beaked whale has
made the longest recorded dive by
any mammal, lasting 3 hours and
42 minutes. The previous record
was just 2 hours and 43 minutes.
“It’s pretty amazing,” says
Nicola Quick at Duke University
in North Carolina, part of the
team that revealed the dive.
The record for humans holding
their breath underwater is 24
minutes, and that is while floating
motionless. By contrast, whales
are active during dives. “They are
hunting down there, and moving
and echolocating,” says Quick.
The 23 species of beaked
whale dive deeper and stay under
longer than any other mammal.
They routinely reach depths of
1000 metres or more, and hold
their breath for around an hour.
The latest record-breaking dive
was made in September 2017.
The same individual made
another dive lasting 2 hours and
53 minutes (Journal of Experimental
Biology, doi.org/d96w). Why it
stayed under so long isn’t clear.
Perhaps it found many squid
to suck up, says Quick.
The record-setting dive wasn’t
particularly deep, though, she
says. The record for the deepest
dive remains 2992 metres.
Michael Le Pageby swinging the arm when
walking was enough to generate
power (Cell Reports Physical
Science, doi.org/d96v).
Yang’s device can produce
2.5 milliwatts of power, enough
for 100 tiny LED lights, a
thermometer or a pressure sensor.
“Such wind energy harvesters
can be used to power wireless
sensors deployed in open space
where breezes are available,” says
Dibin Zhu at the University of
Exeter, UK. They could also power
wireless sensors put in heating
and air conditioning ducts for air
quality monitoring, he says. LLRadiation levels on the moon
may make lunar living harder
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NASAReally brief
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