New Scientist - USA (2019-12-21)

21/28 December 2019 | New Scientist | 17

Genetics

Physics Solar power

Predators prompt

fish to get big brains

Stress can have surprising

effects. When there are

more predators around,

killifish (Rivulus hartii) in

Trinidad in the Caribbean

grow around twice as many

brain cells as those that

face no predators, and they

do so even into adulthood

(Proceedings of the Royal

Society B, doi.org/dgwc).

Polar sea ice may

be on the brink

A strange discrepancy in

global temperatures 8000

years ago can be explained

if sea ice is more vulnerable

to the effects of warming

than we thought, scientists

have found. The result

means frozen Arctic waters

could melt sooner than was

deemed likely (Science

Advances, doi.org/dgwb).

Why Earth has so

much oxygen

It may have been

unexpectedly easy for

Earth’s air to become rich in

oxygen. A new simulation

suggests that the rise in

oxygen was driven by the

planet itself, and needed

little help from living

organisms (Science, doi.

org/dgwd). The finding

implies that planets with

oxygen-rich atmospheres

could be more common

than we thought.

AI calculates lifespan

of species from DNA

ARTIFICIAL intelligence has been

used to estimate the maximum

lifespan of extinct species and

early humans from DNA.

Benjamin Mayne at the

CSIRO, Australia’s national

science research agency, and

his colleagues built an AI to

predict the lifespan of different

animals. To do this, they first

trained it on the known genomes

and maximum lifespans of

252 animal species.

HEAT can jump a total vacuum

thanks to a strange quantum effect.

Minuscule quantum fluctuations in

a vacuum allow heat to transfer

between two objects that aren’t

touching or emitting any radiation.

At the quantum level, even a total

vacuum isn’t completely empty: it is

roiling with quantum fluctuations of

energy. In 1948, physicist Hendrik

Casimir predicted this could create a

force that pulls objects in a vacuum

towards one another – the Casimir

effect. In theory, it may also allow

heat to jump a vacuum, but this

has never been measured before.

Hao-Kun Li at the University

of California, Berkeley, and his

colleagues used the effect to show

heat leaping between two tiny

drum-like membranes. The two

membranes were placed about

300 nanometres apart in a vacuum,

each attached to a reservoir

of a different temperature.

The heat from the reservoirs

caused the drums to vibrate, the

hotter one faster than the colder.

The vibrations became coupled at a

quantum level, the hotter membrane

transferring heat to the cooler one

until both vibrated at a similar rate,

which meant they were at a similar

temperature (Nature, doi.org/dgvm).

The effect could be used to help

cool computers. Leah Crane

The AI focused on 42 regions of

DNA related to lifespan, devising a

formula for maximum longevity

based on those regions.

The team tried the AI on extinct

species. It estimated the woolly

mammoth could live for up to

60 years and Denisovans, the

mysterious extinct cousin of

modern humans, for about 38.

The researchers also found that

Pinta Island tortoises could reach

120 years old. The oldest known

individual is estimated to be more

than 100. And the oldest bowhead

whale is thought to be 211, but the

model predicts 268 is possible

Tiny holes make

panels see-through

WINDOWS in urban buildings

could be replaced with a new type

of transparent solar panel.

It might be crucial to increasing

the uptake of solar power in cities,

says Kwanyong Seo at the Ulsan

National Institute of Science and

Technology, South Korea. This is

because roof space is relatively

fixed, whereas window space is

growing as buildings get taller.

Seo and his colleagues wanted

to develop transparent solar

cells from the commonly used

material, crystalline silicon wafers.

They took 1-centimetre-square

cells made from crystalline silicon,

which is opaque, then punched

tiny holes into them to let the

light through. The holes are

100 micrometres in diameter,

around the width of a human

hair, and they let light through

without changing its colour. Other

transparent panels tend to give the

light that passes through them a

red or blue hue.

The team’s panels convert 12 per

cent of the energy in sunlight to

electricity, substantially better

than the 3 to 4 per cent other

transparent cells have achieved,

but lower than the 20 per cent

that the best opaque cells on the

market manage (Joule, doi.org/

dgvz). Ruby Prosser Scully

(Scientific Reports, doi.org/dgzm).

While the formula was off by

around four years on average

for animals that we know the

lifespan of, it predicted that the

maximum lifespan for humans is

38, suggesting the results should

be taken with a pinch of salt.

However, it is hard to gauge

how far out it is for extinct species:

ancient DNA is more degraded and

harder to analyse, says Mayne, so it

needs extra information. To arrive

at 60 years for the mammoth, for

example, the researchers had to

incorporate the African elephant’s

genome. Gege Li

Quantum leap lets heat

move across a vacuum

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Really brief

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