New Scientist - 14.09.2019

16 | New Scientist | 14 September 2019

Animal behaviour

Closing in on true

size of protons

WE AREN’T sure what the radius

of the proton is but a new way of

measuring it is helping.

Until 2010, we were fairly sure

about the proton’s size. We had

measured it using hydrogen

atoms made of one proton and an

electron. Then, a measurement

using muonic hydrogen – in which

the electron is replaced by another

particle called a muon – found a

value 4 per cent lower.

Single head injury

can spark decline

ONE major blow to the head is

enough to trigger progressive

brain deterioration and long-term

cognitive decline in some people.

We already know that repeated

knocks to the head – like those

sustained in boxing and American

football – can lead to personality

changes, cognitive problems and

depression years later. This

condition, known as chronic

traumatic encephalopathy (CTE),

is associated with gradual build-up

of a protein called tau in the brain.

David Sharp at Imperial College

London and his team wondered if

similar changes can occur after

just one bad head injury.

To find out, they scanned the

brains of 21 men and women who

had a single major head injury

18 to 51 years ago in a car accident,

assault or fall. They all experienced

severe initial symptoms like loss

of consciousness for more than

Neuroscience Physics

YOU can often tell where a

person comes from when they

speak. The same thing seems to

apply to humpback whales: their

songs can reveal their origin.

Ellen Garland at the University of

St Andrews in the UK and her team

made the discovery by recording the

songs of humpback whales passing

near the Kermadec Islands in the

South Pacific. They also recorded

whale songs at spots where they

gather to feed and breed across the

western and central South Pacific,

and off east and west Australia.

The team broke down each song

into units, like notes, that build

together to make a phrase, and

several phrases that repeat to form

a theme. A few themes are sung in a

set order to form a song. They found

three song types from 52 whales.

Song type 1 was dominant in the

central Pacific, including the Cook

Islands and French Polynesia. Song

type 2 was most common in the

west, including New Caledonia,

Tonga and Niue. And song type 3

was only recorded in the waters

near eastern Australia.

Then the researchers compared

these songs with those of the

whales near the Kermadec Islands,

a migratory stopover. Based on the

percentage of similarity between

recordings, the team could pinpoint

where the whales at the Kermadec

Islands originated.

These findings were confirmed

with genetic and photographic

identification of the singing whales.

The team concluded most of the

Kermadec whales came from New

Caledonia, Niue and the Cook

Islands (Royal Society Open Science,

doi.org/c96d). Chelsea Whyte

Song of the wandering

whale betrays its origins

Now Eric Hessels at York

University in Canada and his

team have developed a way to

measure the proton’s radius by

sending hydrogen atoms through

two sets of radio waves with

slightly different frequencies. This

excited some of the atoms into a

higher energy state. By measuring

how many atoms remained in the

lower energy state, the researchers

could calculate the proton’s radius.

The result matched that from

the muonic hydrogen, supporting

the idea that the proton is smaller

than we thought before 2010, at

around 0.83 femtometres, or

slightly less than one million-

billionth of a metre (Science,

doi.org/c96c).

“More and more measurements

seem to pile up at the smaller

radius now, so maybe this puzzle

will diffuse away,” says Thomas

Udem at the Max Planck Institute

of Quantum Optics in Germany.

Other experiments are under way

to provide further evidence.

Leah Crane

30 minutes. Many later developed

problems with thinking, memory

and motivation. The scans showed

that 15 of them have unusually

high levels of tau in their brains,

particularly in the outer layers.

That may be because these layers

are most vulnerable to external

impacts (Science Translational

Medicine, doi.org/c96b).

High levels of tau have also

been found in the outer brain

layers of former athletes with

CTE, particularly in those who

have had the most head blows.

This is consistent with the idea

that brain deterioration can come

from either several relatively

minor brain injuries or from a

single severe one, says the team.

Both types of head injury

probably damage brain structures

called microtubules that are

stabilised by tau proteins, say the

researchers. This, in turn, could

make the tau proteins turn rogue

and start forming large tangled

clumps that gradually harm the

rest of the brain. Alice Klein

TONY WU/NATUREPL.COM

LAGUNA DESIGN/SCIENCE PHOTO LIBRARY

News In brief