What's the problem?
I searched your articles for amplification of the case against extended DNA
fingerprinting
(5 May, p 3,
p 9 and
p 10).
The evidence was derisory.
I was informed the police could get their filthy mitts on a marker “close to
the gene for insulin”, which could tell them whether suspect Q had a slightly
greater or lesser chance of getting diabetes. Wow!
I was told there was a 1 in 37 million chance that a DNA sample might
implicate the wrong person. If only identification parades were so reliable.
It was suggested that the deterrent effect of DNA records would be offset by
the greater care that will be taken by forensically aware offenders. Oh, come
on!
The odd worry that “the huge emphasis being placed on DNA evidence will tempt
police to arrest people on trumped-up minor charges just to get a DNA sample”
would be eradicated if the police had the same right to take a saliva sample as
they do now to interview anyone they please “to help them with their enquiries”.
Monsanto's case
I feel some clarification is necessary to Steve Denton’s letter, in which he
seems to believe that Monsanto will “demand compensation from farmers whose land
has been contaminated with GM crops from a neighbouring farm”
(5 May, p 48).
Readers should be aware that Monsanto has never demanded compensation from
farmers in cases of accidental appearance of Roundup-tolerant crops. Indeed, the
highly publicised case of Percy Schmeiser versus Monsanto Canada had nothing to
do with GM crops showing up on a farmer’s field by accident and a farmer being
prosecuted as a result
(7 April, p 13).
In the Canadian legal case, Justice MacKay ruled
(www.fct-cf.gc.ca/bulletins/whatsnew/T1593-98.pdf)
that the amount of
Roundup-tolerant canola (oilseed rape) present in Schmeiser’s 1030 acres was of
commercial quantity (95 to 98 per cent Roundup-tolerant) and that when Schmeiser
saved and then replanted this Roundup-tolerant seed, he knew or ought to have
known that he was infringing Monsanto’s patent.
In addition, Monsanto Canada has a well-established stewardship programme for
responding to farmers’ calls in the very limited number of situations where
Roundup-tolerant crops appear unexpectedly in a farmer’s field. Since 1996, when
Roundup Ready canola was first commercialised in Canada, Monsanto has responded
to fewer than 30 such calls.
Those who have taken advantage of our stewardship programme, two of whom
testified at Schmeiser’s trial, found the situation addressed professionally and
to their satisfaction. The unwanted plants were removed, usually by hand or
through tillage.
Blowing in the wind
There is a standard demonstration of the Bernoulli principle in any textbook
on flight theory
(5 May, p 40).
You take a piece of paper and hold it in front
of your mouth. You then blow across the upper surface and the paper rises. If
accelerating air across the surface doesn’t reduce pressure and cause the sheet
to rise, then what does?
David Anderson replies: The “Bernoulli strip”, as this is called, is
one of the many common misapplications of the Bernoulli principle, though it is
a good demonstration of the physics of lift. (Other examples are the ping-pong
ball in a jet of air and the curve of a spinning ball. See
www.aa.washington.edu/faculty/eberhardt/Lift_AAPT.pdf.
In brief, a fast-moving, unconfined fluid has the same pressure as the
surroundings. Viscosity causes the breath to follow the surface of the paper
strip. Newton’s first law says that for the air to bend there must be a force on
the air (down) and the third law says that there must be an equal and opposite
force on the strip (up). The breath is diverted from the horizontal to a
downward direction.
Letter
The interview with Anderson made us think of perhaps the most elementary
aeronautical machine. It has the simplest imaginable wing design, and is made
from basic natural materials, but can still fly relatively long distances. It
fits very well with Anderson’s description of flight, and certainly does not
have any curved surfaces. Known to every schoolchild worldwide, it is the paper
aeroplane!
Letter
Anderson seems to claim that Bernoulli effects contribute nothing to lift.
This could easily be tested. Does a humped wing with a flat bottom and zero
angle of attack provide any lift?
Anderson replies: Zero effective angle of attack is taken to be the angle
that gives zero lift. The orientation described by your reader has a positive
effective angle of attack and does have lift. The backside of the wing is sloped
down and so the air comes off the wing with downwash, producing lift.
Deep-sea vision
I am surprised there is so much puzzlement at the lack of blue cones in the
eyes of marine mammals
(28 April, p 14).
I assume those investigating the
phenomenon are too young to remember black-and-white photography.
In those days we used a yellow filter to block out the blue from the sky, to
make the clouds stand out and to increase the contrast overall. Not having any
blue cones will have the same effect.
Swinging chickens
Your reader’s comment on a chicken perch solution to London’s “swinging”
Millennium Bridge reminded me of something
(Feedback, 7 April).
In the early part of the 20th century, a number of isolated electric power
systems were set up in towns throughout New Zealand. In one of these, the local
authority responsible decided to utilise the “free” energy available at night
from the local hydro-based electricity scheme to run street lighting. However
there were numerous complaints about the forgetfulness of the official
“lamplighter”, as well as the switch-on and switch-off times being out of sync
with the vagaries of the weather and the seasons.
The young electrical engineer responsible for the operation of the plant was
asked to devise an automatic system to avoid the problems. His solution was to
go into his chicken house where he prised up the end of the roost and connected
a spring and an electrical switch to it. These were adjusted to switch on in the
evening when about half of his chickens had roosted as it got dark, and to
switch off in the morning when it got light. It worked perfectly whatever the
weather and season.
I'm feeling sick
I think I have too vivid an imagination for my own good. Simply reading your
article about amusement-park rides and imagining all those loops and twists made
me queasy
(28 April, p 32).
I normally don’t achieve that state unless I have spent a hot day on the
worst (or best) rides in any given amusement park. But this year I won’t have to
spend money on rides鈥擨’ll just reread your article.
How to solve our energy problems鈥攆orever
Your correspondent Adam Quantrill is right
(5 May, p 48). If we painted all
the deserts white it would make quite a difference to the global energy
balance.
However, he has missed the point on solar cells. The albedo of a surface
covered by solar cells will not be very different from that of sand and rock. In
other words, covering the desert with solar cells will not significantly
increase global warming.
More importantly, we do not have to cover very much desert with solar cells
anyway. Little more than 20,000 square kilometres could replace the world’s
entire electricity generation. Draw a square of this area on a map showing the
Sahara and you will see what I mean. If you put a 150-square-kilometre array of
cells in each of three low-latitude deserts鈥攕o that one will always face
the Sun鈥攜ou would solve our fuel and carbon dioxide emission problems
forever. Easier, and probably cheaper, than “Star Wars 2” and certainly worthier
of investment.
We should think more seriously about this green option, and the electrolytic
production of hydrogen to fuel the world’s needs. It is difficult to understand
why it is not already being done.
Global environment
Thank you for the remarkable supplement “Judgement Day”. What especially
struck me was that you had the good sense to include a section on population
(28 April, Global Environment Supplement, p 14).
It has become fashionable in the last decade for environmental organisations to
spurn any reference to the growth in human numbers as a contributory cause of
environmental devastation, so this appraisal was a welcome departure.
This section presented a stark picture of what could happen if scientists
continually try to boost food production to meet the needs of growing numbers of
humans (and their demands for high-quality protein). So I am greatly puzzled by
a concluding statement: “We did once have the technology鈥攐r the ability to
develop it鈥攖hat would have fed 9 billion, kept them free from disease and
perhaps living in peace.”
I have no idea what this fantastic technology was that would have been
ecologically sustainable and still have fed such numbers. Can we suppose that
organic agriculture would feed 9 billion? And what exactly would be noble or
desirable about propping up a 9 billion human population anyway, when that would
create intolerable stresses on the habitat of the myriad wild species with which
we share the planet?
Surely social, political and economic organisations worldwide should regret
that they failed to curb population growth beyond the 6 billion that most
ecologists consider disastrous enough now.
Letter
It was disappointing to see New 杏吧原创 joining the fashionable
and entirely unscientific anti-cat campaign in your Global Environment
Supplement
(p 20).
Domestic cats might have “achieved densities that no natural ecosystem could
support”, but there is no such ecosystem in Britain. The other, wild, species
that preyed on small birds and rodents have been virtually exterminated.
Furthermore, the birds killed by cats in suburban gardens are also above
natural numbers, having been fed by humans and provided with extra nesting
boxes. It is the small animals鈥攎ammals and birds鈥攊n rural areas that
are really in trouble. This is thanks to “modern” agricultural practices, such
as excessive use of pesticides and destruction of hedgerows鈥攁lso not
“natural” in their day.
The anti-cat brigade is one with those demanding the “culling” of marine
mammals because they eat fish and it should be treated to justified ridicule for
the same reasons.
Letter
There was a question missing from your supplement. What’s the most
environmentally friendly way to dispose of the plastic folder the issue and
supplement came in?