New Scientist - USA (2019-06-08)

8 June 2019 | New Scientist | 11

Animal cognition Solar system

Chelsea Whyte Leah Crane

WHEN it comes to quantities, an

elephant’s nose knows. The animals

can use their sense of smell to

detect larger amounts of food, even

when the food is hidden from sight.

Joshua Plotnik at the City

University of New York and his

colleagues worked with six Asian

elephants in Thailand, testing their

ability to discern between different

amounts of sunflower seeds.

Two buckets with locked lids

were set on a long table, each

containing different quantities

of seeds. Each trial used one of

11 ratios of seeds between the

buckets, for example 1:2 or 3:5,

and each elephant did 10 trials.

Once they had sniffed the buckets,

the animals picked one to eat from.

The elephants chose the greater

quantity 69 per cent of the time.

As the difference between the seed

quantities increased, the elephants

selected the larger amount more

often (PNAS, doi.org/c6rr).

To eliminate the chance that

the animals were using cues

from humans, the team ran a

double-blind test in which the

experimenters didn’t know which

bucket had the most seeds. They

also accounted for residual odour

in the buckets from earlier tests.

In all cases, the elephants could tell

the larger quantity.

“After that, I thought maybe they

are just smelling the larger quantity

better because the seeds reach

higher in the bucket,” says Plotnik.

When his team ensured seeds were

at the same level, the elephants

could still tell the difference. ❚

Elephants know

a bigger snack

when they sniff it

THE power of planetary

alignments is normally the

stuff of unscientific horoscopes,

but it turns out they might

have  some importance after

all. The sun has an 11-year

cycle of activity, and it may

be shepherded by alignments

of  Venus, Earth, and Jupiter.

The sun’s cycle includes

variations in sunspot numbers,

the total energy it emits and the

structure of its magnetic field.

Since this cycle was discovered

in 1843, people have struggled

to explain its periodicity.

Now Frank Stefani at the

Helmholtz-Zentrum Dresden-

Rossendorf research centre in

Germany and his colleagues

have calculated that an

alignment of Venus, Earth and

Jupiter that occurs once every

11 years could be the answer.

They used data on the past

1000 years of the solar cycle,

including historical records of

sunspots and aurorae, which

occur more often during

periods of high solar activity.

They found that the solar

cycle seems to have been

remarkably consistent and

the average length of the cycle

lines up very well with the time

between alignments of Venus,

Earth and Jupiter, which are the

three planets with the strongest

gravitational effect on the sun.

Just as the moon contributes

to tides in Earth’s oceans, the

planets could slosh the plasma

about within the sun.

“If the planets are aligned,

you have a sort of spring tide

pulling on the sun,” says Stefani.

“And then comes the point

which many people consider

strange and ridiculous.” The

combined gravity of those three

planets displaces plasma inside

the sun by about 1 millimetre.

“Plasma circulation in the sun

is of the order of half a kilometre

a second, cells move up and

down within the sun that are

the size of Texas,” says Leif

Svalgaard at Stanford University

in California. “Imagine

that being influenced by a

millimetre-sized tidal effect.”

The minuscule strength

of the tidal effect has always

thwarted astronomers trying

to tie the solar cycle to planetary

alignments, says Svalgaard.

“It is probably a coincidence.”

But Stefani and his colleagues

think otherwise. They have

calculated a way for even a tiny

displacement of plasma to

dramatically affect circulation

inside the sun and thus its

magnetic field, making the

planets the “clock” that keeps

the solar cycle on time.

They do this through a

phenomenon in the sun’s

magnetic field called the alpha

effect. This describes how our

star’s magnetic field gets twisted

into loops as the sun rotates.

The researchers calculate that

even the small amount of

energy added by the planets’

alignment can cause an

instability in the alpha effect

(Solar Physics, doi.org/c6rz).

It acts a bit like a child on a

swing – they might be swinging

at their own pace, but if they are

pushed every once in a while,

their swinging will eventually

synchronise with the frequency

at which they are pushed. A push

just once every 11 years could

set the sun’s magnetic field

swinging into the cycle that we

observe now, Stefani and his

colleagues say.

They plan to test the proposed

mechanism behind their idea

in the laboratory, using very hot

liquid metal as a stand-in for the

sun’s plasma. ❚

The sun may have got its

rhythm from the planets

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1mm

The displacement of plasma

inside the sun due to the planets

Earth (dark crescent

at top) aligns with

Venus and Jupiter

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Elephants

can sense

a generous

helping of

food without

even seeing it