Letters: Timber trade
Fred Pearce’s article (This Week, 4 April) will fuel the popular misconception
that the retail timber trade bears significant blame for the demise of tropical
forests. Less that 1 per cent of internationally traded tropical timber
is used in articles that are distributed through retail outlets. This tiny
percentage represents the highest value sector of the timber market and
has the greatest potential to generate revenues to pay for forest conservation
and management in the tropics. The initiative by WWF and the timber trade
to base this trade on timber from sustainable sources represents one of
the few constructive international initiatives in favour of tropical forest
conservation.
There are many things wrong with the tropical timber industry, but logging
has never been directly responsible for the destruction of any tropical
forests. Forests are lost because people are forced by poverty to clear
them for agriculture. The obsession of some environmental groups with the
timber trade and their mindless persistence in calling for boycotts is simply
alienating tropical countries and compromising other international conservation
initiatives.
Jeff Sayer The World Conservation Union Gland, Switzerland
Letters: No chaos
The conclusions of a paper co-written by J. C. Vassilicos and F. Tata,
and presented at a BCS Displays Group conference on Applications of Fractals
and Chaos, may be of interest to readers of your article ‘Making maths make
money’ (11 April). The paper, Is There Chaos in Economic Time Series? A
Study of the Stock and the Foreign Exchange Markets, studied foreign exchange
rate data and New York Stock Exchange returns using over 20 000 data points
for each series in a search for chaos.
The authors applied ‘a battery of three alternative mathematical tests,
but fail to find any signs of chaotic behaviour. It is suggested that earlier
announced findings of chaos in economic time series may have been due to
using time series with too few data points.’
Whilst the American profit seekers featured in your article accept the
need to use ‘huge bodies of financial data, both historical and current’,
they appear to diverge from the comments of the European academics in stating
‘some parts are unpredictable because of chaos’.
Huw Jones Middlesex Polytechnic
Letters: Stick to change
Greenhouse effect, global warming and climate change are often used
interchangeably (This Week, 11 April), but we should emphasise change rather
than warming. Too many people envisage a benevolent warming, bringing the
Mediterranean to the Baltic. Unfortunately, it won’t be like that, but will
probably be more erratic. Consider the El Nino Southern Oscillation, apparently
triggered by a small warming of the Pacific, which causes droughts, floods
and severe storms across half the world. Please, can we call it climate
change, and not global warming?
Jerry Vanclay Copenhagen, Denmark
Letters: Mean mode
I am afraid that Mr Broomfield (Letters, 18 April) is as mixed up as
the politicians when criticising Feedback (14 March) for getting muddled
about what an ‘average’ is.
Even as an A-level student I know that there are three measures of central
tendency, the mean, median and mode. The ‘average’ that Broomfield is writing
about is the mean, which is obtained, as the Oxford English Dictionary says,
by ‘dividing the aggregate of several quantities by the number of quantities’.
The measure of central tendency that Feedback, and less successfully
the politicians, were discussing is the median. This is the value at which
half the sample lie above, and half below it, whether the distribution is
skewed or not. Feedback was therefore right.
Gavin McKay Dunmurry, County Antrim Ireland
Letters: Killing noise
There seems to be some confusion among your correspondents about anti-sound
in cars (Letters, 18 April). Lassi Hyvarinen is right that ‘one cannot kill
energy by adding more energy’ but wrong to imply that the only way to eliminate
noise is therefore to absorb it by conversion to heat (implicitly, by conventional
sound-proofing) or to change it to some other form of energy.
He overlooks the fact that when a loudspeaker is driven in an appropriate
phase relative to the ambient acoustic environment, it can absorb acoustic
energy, just as a radio aerial absorbs electromagnetic energy. Anti-noise
is thus able in principle to reduce sound levels globally, and one can kill
noise by adding noise.
In practice, the imple-mentation is extremely difficult, if not impossible,
especially for random incident noises, and the car and aircraft cabin demonstrations
that have been performed in the last few years all use the periodic nature
of the annoying noise – each engine/propeller/whatever cycle makes roughly
the same sound, so one knows a priori what one has to cancel. This means
that Colin Deane need not worry about horn and siren noises not being heard
by the driver; they are random and uncorrelated with the engine cycles so
the controller is unable to affect them. In fact, reducing engine noises
will make these other sounds louder relative to the in-car ambient sound
and easier for the driver to detect.
Incidentally, the original article (Technology, 28 March) referred to
‘white noise’ technology: surely they meant ‘anti-noise’ technology?
Kimon Roussopoulos University of Cambridge
Letters: Better before
Regarding the recent changes in New 杏吧原创, I can only say that any
change which eliminates Ariadne is most definitely a change for the worse.
For all the years I have been a subscriber to your magazine, her page has
been the one I have saved for last, as one eats an exquisite dessert after
a fine meal. I also mourned the passing of Albert (or was it Alfred?) the
experimental rat.
I can understand you wanting to improve the layout of the magazine,
however the recent changes in layout seem to have made things worse. It
now appears unclear whether a title announces a new piece, or whether it
is only a sub-heading to one introduced several pages earlier. To find an
example of how clear and inviting an excellent layout can be, you need only
browse through your own New 杏吧原创 archives from several years back.
It had a much cosier look in those days. Recent issues appear rather cold
and uninviting: a great pity.
I have nothing against change as long as it is for a good reason. Change
for the sake of change, however, is nonsense and brings no advantage. If
I were you, I would get on the next plane to Naxos as soon as I could, and,
on my knees, beg Ariadne to return.
Robert Eliscu Ta Zaandam, The Netherlands
Letters: Row the boat
I was surprised to see that Antony Anderson, in discussing Artificial
Intelligence from A to Z (Review, 18 April), only used two of each in the
classic puzzle: it was always three missionaries and three cannibals in
my youth. The sequence went as follows:
1. M takes 1C over river; 2. M takes 1C over river; 3. M takes 1M over
river, returning with 1C; 4. M takes 1M over river; 5. M takes 1C over river;
6. M takes 1C over river.
C. H. Parker Sherborne, Dorset
Letters: Einstein's cuppa
I refer to ‘Storm in a Teacup’ (Letters, 18 April and 2 May). Steven
Onley’s puzzlement over why tea leaves move to the centre of a stirred cup
of tea was addressed by none less than Albert Einstein. His paper was published
in 1926, and is reprinted, complete with a diagram of a teacup, in Einstein:
a Centenary Volume by A. P. French (Harvard University Press, 1980).
The essence of Einstein’s argument is that a layer of liquid near the
base of the cup is held stationary by friction. In the rotating liquid above
it, there is a pressure gradient from the periphery inwards to combat the
centrifugal force. By continuity this gradient also operates in the stationary
boundary layer where, being unopposed, it causes a migration of the fluid
towards the centre.
Incidentally, I discovered by careful observation that a similar phenomenon
occurs on the top surface of the tea. Surface tension causes a boundary
layer there to cease rotating while the body of the liquid continues to
move, and the migration of small floating particles towards the centre is
quite pronounced.
Paul Davies The University of Adelaide Australia
Letters: Einstein's cuppa
Tea leaves migrate to the centre to avoid being swallowed.
N. E. B. Cowern Antwerp, Belgium
Letters: Einstein's cuppa
When I put this problem to my 77-year old mother, never to be confused
by science, her response was unhesitating: ‘Mr Onley should use a teabag.’
John Allsop Rayleigh, Essex
Letters: Unanswerable
The increasing concern about lab animals demonstrates that people are
tired of hearing the same excuses from vivisectors for the misery they inflict.
More and more of us now realise that animals react differently to chemicals,
they suffer from different diseases, and artificial disease created in the
laboratory is not the same as disease suffered by people in the real world.
For example, morphine calms people and rats, but has the opposite effect
in cats and mice. Tamoxifen was patented as a contraceptive drug – it is
in rats, but in women it increases fertility. All drugs are tested and passed
as safe in animals before going onto the market, but many have injured or
even killed people – for example Opren, Eraldin, Flosint and clioquinol.
On the other hand, important medical advances can be delayed, or even missed
altogether, because of adverse effects in animal tests.
Research charities now concede that only a very minor part of their
research budget is spent on animal experiments. It is time that this discredited
form of research is halted altogether.
Jan Creamer National Anti-Vivisection Society London
Letters: Unanswerable
Re your front cover headline ‘Do animals feel pain?’ (25 April). Is
this the first of many questions that will plumb the depths of stupidity?
I can think (with a nod to P. G. Wodehouse) of an equally cretinous question:
Are the stars God’s daisy chain?
Of course, this lacks the provocation and inflammatory bite of your
question. To equal that we would need something like: ‘Are blacks fully
human?’ or ‘Do Jews enjoy being gassed?’
Don’t think I am against provocative questions as such. Copernicus once
asked if the Earth went round the Sun instead of vice versa. But I am, and
you should be, against stupidity.
Moreover, I’m an animal.
Jan Holt Skeaboat Bridge Isle of Skye
Letters: Solution solution
I was intrigued by John Emsley’s article, ‘Molecular footprints in the
sand’ (New 杏吧原创, Science, 4 April) – yet I wondered why Kensaku Morihara
could not obtain pure d-alanine anhydride.
Should it not be possible to use the silica gel to absorb l-anhydride
from a half-and-half mixture, leaving the d form in solution?
R. D. Lucas Theale, Berkshire
Letters: Variable approach
In reply to Mike Price (Letters, 4 April) it is common to investigate
the effects of more than one variable in experiments. However, one should
vary one variable whilst holding all the others constant (if possible).
This is an approach which should be instilled in pupils because the behaviours
of most systems in the real world are dependent on many variables (the weather
for example). This approach should not confuse pupils if they understand
what they are doing.
Making detailed predictions before performing experiments is also common
practice. This is because the purpose of an experiment is to provide evidence
in support of or against a particular theory. If the experimental results
agree with the predictions then this is supporting evidence for the theory,
otherwise not. Again, if pupils understand what they are doing they should
be able to be objective and not let knowledge of their predictions prejudice
their observations.
G. G. Scott Fordington, Dorchester
Letters: Unanswerable
Patrick Wall’s article was longer than the ’10-second sound bites’ of
the British Association’s declaration on animal experiments, but some of
his assumptions were as simplistic (‘Neglected benefits of animal research’,
18 April).
He dismissed anti-vivisectionists as ’emotional’ and ‘anti-research’,
but praised groups such as the Committee for the Reform of Animal Experimentation
(CRAE) for asking ‘answerable’ questions.
I’m a qualified scientist and an animal rightist who has worked in the
antivivisection movement for 13 years. I do feel emotional about animal
(and human) suffering, but this doesn’t mean I’m incapable of rational thought.
My organisation, the Dr Hadwen Trust, is ethically opposed to animal experimentation
and for 22 years has been funding non-animal research – paid for by antivivisectionists,
who therefore can hardly be called ‘anti-research’. Stereotyping can be
convenient and soothing, but it tends to stifle fair debate.
Moderate groups such as CRAE (of which I am, incidentally, a member)
may ask answerable questions, but if people had never asked the unanswerable
ones then topics such as human experimentation, fetal research, the origins
of the Universe and global warming would never have been debated at all.
Gill Langley Hitchin, Hertfordshire