Letter: Sky TV for free
The ‘impossible’ (Letters, 29 February) is quite a widespread phenomenon,
and is usually caused by the use of a videosender by a close neighbour.
Because of the range of these devices, which are used to relay TV to different
rooms in houses equipped with satellite TV reception, their signals can
be picked up on televisions some distance away.
D. Phillips Northampton
Letter: Sky TV for free
No doubt Raymond Rawcliffe has a communal satellite distribution system
in his neighbourhood. These systems amplify the signal received so that
it can be divided among the users. A signal leakage, probably caused by
a defective junction somewhere in the system, permits the radiation of the
amplified signal on the selected distribution channel. If Rawcliffe enjoys
the programme, he should not publicise the leakage, since the community
concerned would gain by having it removed.
Bernard Beaven Madrid, Spain
Letter: Triffid terror
Just to add my ha’porth about the appalling ignorance of science both
at the level of the public and policy makers, witness the exchange between
a presenter on Radio 4’s Today programme and Brian Ager. Ager, from the
Senior Advisory Group for Biotechnology in Brussels, was being interviewed
about an exhibition on Biotechnology, recently opened in London. It was
a brief piece, and the two comments from the presenter which stuck in my
mind were to the effect of ‘What’s to stop scientists from making a triffid
or something?’ and ‘Are we all going to be attacked by giant mutant flies?’
(Apologies to the BBC if I haven’t remembered the wording quite right –
but they wouldn’t let me have a transcript of the interview.)
Today is a programme listened to by the Great and the Good, and normally
the level of questioning by the interviewers is astute and well-informed.
If Brian Redhead were to ask Douglas Hurd, ‘So when will the European Parliament
be making us all eat frogs’ legs?’ or if Sue McGregor asked Paddy Ashdown,
‘Just what colour are your pyjamas?’, it wouldn’t keep its audience for
long.
Peter Lund University of Birmingham
Letter: Microwave climate
Andrew Deacon’s use of a kitchen microwave oven to produce copper sulphate
crystals has produced an interesting result that has nothing to do with
microwaves (Letters, 15 February and 7 March).
The growth of copper sulphate or any other crystals from saturated solutions
is governed by the rate of cooling of the hot solution and also by the stability
of the external air temperature. Perfectly formed large crystals grow when
saturated solutions cool very slowly at constant temperatures. A microwave
oven provides an ideal environment.
Stewart Hird Aldershot, Hampshire
Letter: Naughty dreams
While Donald Gould complains about his nightmare dream about struggling
with an examination, he appears to have lost touch with the master’s masterpiece.
Should Gould care to turn to page 337 of the Interpretation of Dreams
in the Pelican Freud Library, he will find a section headed Examination
Dreams. There he will read that it is only people who passed their examinations
who have dreams about failing. Those who have failed have no need for such
dreams.
Freud’s way of interpreting dreams was not, as Gould says, half-decent,
but almost wholly indecent. Examination dreams, failing or passing, are
basically infantile sexual, the master says.
Stanley Hurwitz Cirencester, Gloucestershire
Letter: Damming the Bio-Bio
Having just returned from a two-week trip down the Bio-Bio river in
Chile, I was struck by the article, ‘The hidden cost of Canada’s cheap power’
(15 February).
In a project conceived under the former military regime, but supported
by the current civilian government’s National Energy Commission, Chile currently
plans to dam the Bio-Bio in six places to create new hydroelectric power
centres. Work has already begun on the first dam, the Pangue Hydroelectric
Centre.
The Pangue Centre would generate an estimated 2.156 million kilowatts
of energy, approximately 12 per cent of Chile’s current annual consumption.
This massive project (total costs are projected at over $500 million) would
flood thousands of hectares of land, displacing hundreds of indigenous Penhuenche
families. The fragile ecosystem of the area includes a number of protected
species.
The proposed dams are sited in a region surrounded by active volcanoes,
one of which, Lonquimay, erupted only four years ago. Concepcion, one of
Chile’s largest cities, is located at the mouth of the Bio-Bio, and the
potential for massive loss of life in a country as seismically and volcanically
active as Chile seems far from remote.
Leaders of the National Commission of Indigenous Peoples and many Chilean
scientists and intellectuals, including Nobel laureate Manfred Max-Neef
and distinguished poet Nicanor Parra, have spoken out against the project.
In the United States, a network of ecologists, conservationists and
anthropologists has formed to try to help save the unique ecosystem and
magnificent scenic beauty of the Bio-Bio. For more information, readers
can contact the Bio-Bio Action Committee, PO Box 1303, Angels Camp, CA 95222,
US, or the International Rivers Network, 301 Broadway, Suite B, San Francisco,
CA 94133, US.
Robert High New York, US
Letter: Damming the Bio-Bio
Your article on Canada’s hydro power was fair, so far as this resident
of Quebec can judge. However, for even better balance, and had space permitted,
one would have liked to see some comparison with the known and potential
evils of other forms of power. While current or under-construction generating
capacity seems sufficient in the short to medium term, given reasonable
energy conservation, more capacity of some sort will be required eventually.
One suspects that hydro power is still the lesser evil.
H. H. Langshur St. Lambert, Quebec, Canada
Letter: Men who knit
About Sexism and Knitting (Letters, 15 February): it is not sexist to
assume all women and only women knit, but rather Euro-centric. In other
cultures it is perfectly acceptable for men to knit. In Jamaica, men can
be seen on streetcorners knitting and chatting. They are usually making
the colourful tams used to cover Rastafarian dreadlocks and for sale to
tourists. Women are more likely to crochet. On Taquile Island, on Lake Titicaca,
Peru, knitting is a man’s job; women weave. Supposedly, the men used to
knit on long cactus spines; nowadays they use sharpened lengths of coat
hanger wire.
The value of Margaret Boden’s metaphor is that it allows us to look
at a concept in a different way. Car engines are useful too, but haven’t
we heard that one before (along with Descartes’ body as a machine, and more
recently, the mind as computer)?
Carol Hayman Austin Community College Texas, US
Letter: Space for elephants
The leader ‘Who will pay to save the elephant?’ raises a number of highly
pertinent issues (Comment, 29 February).
The ivory ban and the financial assistance contributed to elephant conservation
are only partial solutions. The truth is, we will not save the elephant
without the support of the people who have to live with it, see their crops
occasionally destroyed by it and in some cases, the lives of their friends
and relatives. Unless conservation measures include initiatives aimed at
making the elephant more pertinent to the average African than it is at
present, we will never obtain the support needed to insure its long-term
survival. In a context of abject poverty, how on earth can we expect elephant
conservation to be relevant, let alone a priority, unless there is a vested
interest?
Elephants are under threat on all fronts, not only from the murderous
illegal activities we are so familiar with, but also from straightforward
pressure and conflict resulting from increased proximity to man and competition
for space. Imagine what it will it be like in just 25 years, when Africa’s
population will be double what it is now.
Conserving elephants into the next century will require a much greater
willingness on the part of people and organisations in the West to look
at the problem through African eyes, from African perspectives and in an
African context. Wise use of species through culling, safari hunting and
tourism must contribute to traditional conservation activities in order
to guarantee continued survival.
John Newby World Wide Fund for Nature Gland Switzerland
Letter: Techno-women
We on the Women in Technology project were delighted that New 杏吧原创
chose to celebrate International Women’s day with the achievements of women
in technology (‘The women who went back to technology’, 7 March).
May I point out though, that the nightmare of approaching up to 100
Training and Enterprise Councils (TECs) and Local Enterprise Councils, as
reported in your article, has so far been averted. Since the demise of the
Training Agency, WIT has been supported from the Department of Employment’s
central funds under Higher Technology National Training and has been channelled
via the Leeds TEC. This is however a temporary strategy. Funding, as ever,
remains uncertain.
Ailsa Swarbrick WIT Project The Open University Leeds
Letter: CDs are safe
I really must put to rest the concerns of Simon Gardner and Peter Conners
(Letters, 8 February and 7 March) regarding the problem of electromagnetic
radiation affecting aircraft electronic and electrical systems.
This is a design problem of which the avionics and aerospace industries
are fully aware, and treat with the respect and thoroughness accorded to
all other aspects which might affect flight safety. I can assure your readers
that the spurious outputs from CD players, laptops, electronic games and
so on, and the intentional radiation from cell phones, are many orders of
magnitude down on the test levels to which aircraft equipment and the complete
aircraft itself are subjected.
Certification currently requires that civil aircraft continue to fly
safely in field strengths up to 820 V/m (mean) and 8300 V/m (peak). Meanwhile,
emissions from personal equipment that can be plugged into the mains (which
includes laptops, and which most respectable manufacturers extend to apply
to CD players) are restricted by international standards to a few tens of
mu V/m when measured at 1m range, and it is hard to envisage an uncontrolled
electronic toy generating more than a few hundred mu V/m. Even the cell
phone would be pushed to deliver a couple of volts per metre.
I am certain the real reason for the CD ban has more to do with the
possibility of disturbing a fellow passenger’s comfort, either as the induction
of audio frequency into the earphone cables of the next seat (unlikely)
or as direct airborne sibilance, although it beats me why tape cassette
players aren’t banned.
J. L. Edmonson Yeovil, Somerset
Letter: Fecund universes
Lee Smolin’s hypothesis about the evolution of the Universe by natural
selection (New 杏吧原创, Science, 1 February) certainly is intriguing,
but there seem to be some short cuts in the logic. The mechanism he proposes
may indeed increase the number of universes in which the fundamental constants
of physics favour the production of black holes, but that does not necessarily
allow predictions about the nature of our Universe.
The major flaw is that there is no positive correlation between the
constant values that favour the development of black holes and those that
favour the development of life.
Ours could actually be one of the least fecund universes and the fundamental
constants could be markedly sub-optimal as far as black hole production
is concerned. The only prediction we can make is that our Universe will
have physical constants that will allow (but not necessarily favour) the
development of our kind of life form.
We are not even really talking about natural selection, as there is
no competition for limiting resources. Smolin is looking at the probability
of particular constant values being replicated and the relative frequency
of these values at any point in time.
The point is, with no selection operating, even universes of very low
fecundity will continue to increase in absolute numbers even though they
will simultaneously decrease in relative abundance.
I suspect there could be several equally successful strategies, but
I predict that the primary trend will be towards producing more black holes,
earlier. This increases the fecundity of younger age classes and reduces
the mean average generation length. This sort of universe will multiply
more rapidly over a given generation time interval than one which produces
the same number of black holes later in its development or over a longer
period of time.
So the most common universe may be one which produces untold billions
of small black holes in the first few milliseconds of its existence. What
happens later will, in most cases, be irrelevant; as is whether or not life
can develop.
Mark Fletcher Marrickville, New South Wales Australia
Letter: Poles cracked Enigma
Jim Lesurf in his interesting paper about codes and chaos (‘A spy’s
guide to chaos’, 1 February) stated that the secret of Enigma (German scrambling
machine) was uncovered by British code breakers from Bletchley. That is
not true. The Enigma code was broken by three mathematicians of Polish intelligence:
Marian Rejewski, Jerzy Rozcki, and Henry Zygalski. The first message was
decoded by these three as early as January 1933.
I am aware that this may be unconvincing for some readers. I refer them
to Gordon Welchman’s article ‘From Polish Bomba to British Bombe: Birth
of Ultra’, Intelligence and National Security, London, January 1986. (Gordon
Welchman was one of the key cryptanalysts of the Bletchley centre.)
Adam Blazekewski Poznan, Poland
Letter: Threading DNA
Your article about microscopes pointing the way to seeing DNA (Technology,
29 February) stressed a problem in actually looking at DNA strands due to
the strands coiling up. The article also failed to point out the difficulty
of identifying which direction the DNA should be read.
However a possible way of overcoming these problems would be to use
immobilised enzyme complexes that read DNA and can therefore be used like
the eye of a needle through which the DNA can be threaded and located. Having
two such needles close together would generate a short region of uncoiled
DNA in a known location. Antibodies could be used to hold the enzyme complexes
at a correct spacing to allow the fine metal tip of a scanning tunnelling
microscope to read the DNA sequence.
The use of a suitable DNA polymerase and helicase would allow reading
of single-stranded DNA at a controllable rate and in a known direction.
In other words, you could exploit the natural structure of the replication
fork that occurs during DNA synthesis in nature.
Robin Hereward Winney University of Surrey
Letter: Under the Sun
Talk about an idea whose time has come. I remember dermatologists trying
to warn anyone who would listen that sunbathing was bad for the skin, producing
wrinkles and other signs of premature ageing, back in the 1930s. I remember
less well when I first heard that sunlight might also cause skin cancer,
but the idea was certainly current in 1949/50, when I spent a couple of
years in Australia.
This is not some sudden ecological dawning of the light, but a long-standing
menace. Of course thinning of the ozone layer makes the whole subject even
more urgent. But the increases in cases of malignant melanoma could and
should have been avoided if the experts had done their stuff in warning
people, even in the face of the apathy which normally greets such warnings
at first.
Alec Vans Newnham, Gloucestershire