14 September 2019 | New Scientist | 27It is time to consider an
ammonia energy economy
Letters, 3 August
From Phil Pope, Bristol, UK
Scott McNeil raises concerns
about producing batteries for
electric vehicles and welcomes
the discussion of hydrogen power
(8 June, p 20). It is some years since
you have covered the potential for
an ammonia-based fuel economy.
Ammonia can be compressed
and stored much more easily than
hydrogen. We already have some
infrastructure for producing and
transporting it, due to its use in
fertiliser production. It can be a
direct substitute for natural gas
in domestic boilers. It can be
produced using electricity
from intermittent renewable
sources, storing energy without
batteries, and be used in fuel cells
or internal combustion engines.
It seems to be a technology that
is ripe for implementation.
Classifying dementia may
help find treatments
17 August, p 10
From Bob Kahn,
Warrington, Cheshire, UK
It is true that cancer kills far more
people in the UK than dementia,
as Clare Wilson reports. But the
many different types of cancer
can be readily identified. Dementia
is much less clearly defined and it
has many side effects, such as
falls and pneumonia. Researchers
at University College London
and the Alzheimer’s Disease
Neuroimaging Initiative have
reclassified dementia into
subtypes and stages (Nature
Communications, doi.org/gfhbx4).
This could lead to drugs that failed
earlier pharmaceutical trials being
shown to work for some subtypes.
Surely giraffes’ necks must
confer some advantage
20 July, p 28
From Derek Bolton,
Sydney, Australia
Simon Ings reviews Daniel Milo’s
Good Enough: The tolerance for
mediocrity in nature and society,
which argues that, in the absence
of proof of a specific evolutionary
advantage, giraffes’ long necks
should be considered the fruit
of chance. But since they clearly
have major disadvantages, if they
had no significant advantage they
would have been bred out.
Milo dismisses competition
with other browsers, saying their
nearest competitor is 2 metres
shorter. The nearest competitor
to a giraffe is another giraffe.There is a study on the
effects of organic food
Letters, 3 August
From Ann Wills, London, UK
We need to look at an organic
diet and compare the health
outcomes in groups of people
who consume organic foods with
those who don’t, suggests Aroha
Mahoney. There is a study that
monitored the diet and health of
nearly 70,000 people for seven
years. It found 25 per cent lower
rates of cancer diagnosis among
those eating large amounts of
organic food (JAMA Internal
Medicine, doi. org/gfgt5w).I am thrilled by artificial
islands’ potential uses
20 July, p 10
From Brian Wood,
Lenzie, East Dunbartonshire, UK
My first reaction on seeing your
report on artificial islands for
wind farms at sea was dismay at
the potential for environmental
damage. On second thought,
they have exciting potential.
Such islands could host wave
energy harvesting devices, using
the same infrastructure to get
energy to the mainland, and could
also bear solar panels. Could they
be used to farm salt-marsh plants
such as samphire, purslane,
seakale and sea beet, someWant to get in touch?
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newscientist.com/lettersof which command high prices?
Encouraging seaweeds to grow
around their margins could
protect from erosion, as well
as supplying another crop.
This could also provide
nurseries for fish. Offshore
oil rigs, often seen as pollution
sources, show greatly enhanced
productivity compared with the
open sea.Prospecting for minerals
from the remains of leaves
17 August, p 12
From Kevin Privett,
Llandough, South Glamorgan, UK
I read your article on gold
prospecting using tree leaves
with interest. One way to improve
detection might be to analyse
the shallow soil where leaves fall
and rot each year, concentrating
the metals locally over time.
As an undergraduate in the
1970s, I saw this on the Downs, a
park in Bristol. Trees there take up
naturally occurring uranium into
their leaves. Using a radiation
detector, I mapped elliptical halos
on the ground beneath each tree;
their long axes were parallel to the
prevailing wind. These persisted
where trees had been removed
or blown down.People saw tree stumps
being kept alive earlier
3 August, p 18
From Brian Tagg,
Cheddon Fitzpaine, Somerset, UK
Ruby Prosser Scully reports that
tree stumps are being kept alive
by nearby trees. In 2000, Peter
Thomas wrote in Trees: Their
natural history that grafts between
roots of individuals of the same
species are common in both
hardwoods and conifers. There
are cases where stumps have
been kept alive via root grafts
for a decade or two.Peacock feathers put
in their proper place
10 August, p 14
From Bill Naylor,
Wilsford, Lincolnshire, UK
You say peacocks have elaborate
tail feathers to impress peahens.
The iridescent feathers that make
up the bird’s train and fan out to
impress mates are the upper tail
coverts. The male peacock’s actual
tail is dull and is raised to support
the train. It is much shorter than
the tails of other members of the
Phasianidae family.Is a slow magnetic pole flip
really less worrying?
17 August, p17
From Bryn Glover, Kirkby Malzeard,
North Yorkshire, UK
I don’t understand why Ruby
Prosser Scully thinks that the
erratic behaviour of the magnetic
poles is less worrying than once
thought, because any flip will take
longer than previously imagined.
Surely any flip would leave Earth
unprotected from solar wind, and
the longer the flip takes, the longer
the danger period will be.The editor writes:
It is less worrying because the
researchers suggest it may happen
more gradually than previously
thought, so there will be time to
adapt over thousands of years.
That could include devising
protections against solar wind.For the record
❚ The eruption that caused a mini
ice age in the 6th century AD was
somewhere in the northern
hemisphere (31 August, p 14).
❚ Waggle room: male drone bees
have only one set of chromosomes
(17 August, p 38).
❚ Ouch. Many gallstones are
composed of cholesterol and
crystals of calcium compounds
(24 August, p 17).
❚ Glowing reference: coral
absorbs short-wavelength light
and re-emits it at a safer, longer
wavelength (24 August, p 8).