26 | New Scientist | 22 June 2019
There are more ways to
profit from going green
25 May, p 5
From Liam O’Keeffe,
Abinger Hammer, Surrey, UK
While I agree with your leader
about the political response to
global warming, I believe that
you are too pessimistic when
you say that “dealing with
climate change comes with a cost”.
On the contrary, making the
transition to renewable energy is
a natural investment. As the price
of energy storage comes down,
the marginal cost of renewable
energy generation is falling to
zero, since wind, sun and waves
are free resources. This is in sharp
contrast to hydrocarbon fuels that
must be extracted at great cost.
Countries that continue to
invest in hydrocarbon resources
are saddling themselves with
technology that will soon be
obsolete and unable to compete
directly with renewable energy.
Those that lead the way with
renewables will enjoy a
competitive advantage in global
markets. For once, greed is good!How long till we reach
peak population?
25 May, p 24
From Paul McKinley,
Dublin, Ireland
I am not sure why Graham Lawton
thinks population growth is a
taboo subject. I have recently
read three books that discuss it
and it would seem overpopulation
is a battle that is mostly won.
A great deal of the world
already has a fertility rate at,
or below, replacement level.
Even in those parts of the world
where birth rates are higher,
graphs of fertility over the past 30
to 50 years show a sharp decline.
Industrialisation, urbanisation
and especially education are
drivers of population decline
and there is no reason to suppose
those declines won’t continue.
Hans Rosling at the Gapminder
Foundation thought the year
of “peak child” was 2000. InEnlightenment Now: The case for
reason, science, humanism and
progress, Steven Pinker examines
how the fertility decline that took
Europe 200 years was reached by
the developing world in just two
generations. In Empty Planet:
The shock of global population
decline, authors Darrell Bricker
and John Ibbitson make a strong
case that the human population
will peak at around 9 billion in
20 to 30 years, then decline.
It may be that the fear of too
many people will soon be replaced
(as it already has been in Japan and
Singapore) with a fear of too few:
not enough tax payers to support
a greying population and not
enough young consumers to
drive an economy.Age is just a number,
unless you’re giving blood
8 June, p 7
From Richard Lucas,
Camberley, Surrey, UK
Ruby Prosser Scully continues a
story that has rumbled through
the pages of New Scientist for the
past couple of years, lending hope
that ageing could be delayed by
transfusions of young blood.Having been a regular blood
donor for 45 years, I observe that
the majority of donors are, like
myself, older. The likelihood is
that the donated blood will find
its way into a younger recipient,
presumably having the opposite
effect to young blood. Has this
been thought through? Should
donated blood be “age stamped”?Weighty theories on the
matchbox illusion
25 May, p 13
From Michael Jessop,
Stratford-upon-Avon,
Warwickshire, UK
You report an illusion whereby
three matchboxes together appear
to be lighter than the heaviest box
on its own. I believe this error
occurs because we are comparing
the weight of the heaviest box not
to the total weight of all three, but
to the average weight of them.
We can’t compare grouped
items directly. Instead, we must
identify differences by comparing
individual items with the group
average. For example, we identify
the heaviest of the boxes because
it is the one that feels heavier than
the average of the three, notbecause we compare the weights
of the individual boxes.
Similarly, suppose you look at a
black square that is beside a white
square. The black square appears
darker than the white one, not
because you are comparing the
two squares, but because the
black square is darker than the
average of the two, which is grey.From Thomas Patrick Reid,
Dundee, UK
I have a couple of observations
following your article on the
matchbox illusion. First, an item
of flat pack furniture seems to be
far less heavy once assembled.
Second, when the head of a pint
of Guinness settles, it appears
to have gained weight.
Could an object’s density fool
our perception of its weight?Which countries take part
in nuclear inspections?
18 May, p 11
From David J. Plews,
Rotherham, South Yorkshire, UK
I commend Debora MacKenzie’s
article about Iran’s nuclear
programme, which points out
the unintended consequencesViews You r le t te r s