Letters : Zero and beyond
Oxford
After your comments about the “zeroth” draft
(Feedback, 2 August), I am sure
that you will be interested to know that at the University of Oxford, the week
before the beginning of each term can be referred to as the “noughth” week, and
the one before that as the “pre-noughth” week.
Thus the standard eight-week teaching term is preceded by two weeks and also
followed by two weeks鈥攂ut these are more logically called the “ninth” and
“tenth” weeks.
Letters : Spelling it out
Cambridge
It has been suggested that subtitled films are responsible for Swedes’
proficiency in English
(Letters, 2 August, p 49). How about exploiting this
phenomenon to improve literacy within the English-speaking
world鈥攅specially in Britain.
Legislation to add English subtitles to all films, including those already in
English, and to ban all dubbing, could be a cheap way of improving British
people’s command of languages, including their own.
Letters : Specs from cheese
London
I have just viewed one of the stereoscopic Pathfinder images put out by NASA
on the Internet, using a pair of 3D glasses given away several years ago for an
experimental 3D TV programme
(Feedback, 2 August). The picture quality was
excellent. The lenses I used were probably more purely and intensely coloured
than Martyn Harvey’s sweet wrappers and, importantly, the right one was cyan not
blue.
The only way to make such a viewer is to use sheets of coloured acetate. You
might be able to improvise the red lens from the cellophane that Edam cheese is
wrapped in, but I can’t think of anything that comes with cyan cellophane.
Perhaps a bit of exploration in a supermarket would yield some.
As for the “deluxe” thermohygrograph that didn’t work as well as the standard
model (Feedback, same issue),
Rover, the manufacturer of the Mini Cooper car,
has come up with a special “Sports Pack” option, which reduces the car’s speed
by about 5 miles per hour, thanks to the extra drag created by the “cool” wide
wheels.
Letters : Clever cats
“鈥 single quantum atom can be in two places at once鈥ut a
single classical cat鈥an’t.”
So says your correspondent Ian Percival
(Letters, 2 August, p 49). He has
obviously never met any of the cats I have owned鈥攏or T. S. Eliot’s cat Mr.
Mistoffelees, whose “voice has been heard on the roof/When he was curled up by
the fire”.
Letters : Fair to farmers
Brussels
Contrary to the claims in Mark Ward’s article on “cheating” farmers
(This Week, 17 May, p 6),
it is controllers in member states, not European Commission
officials, who carry out checks on compliance with the Common Agricultural
Policy (CAP). This has been the case since the CAP was introduced. The
Commission has a general supervisory role and prepares common technical
specifications to ensure that the checks are properly carried out and that all
farmers are treated equally.
It is not true that only 5 per cent of applicants for CAP subsidies are
checked. A compulsory administrative check is carried out on all applications to
ensure that they have been completed correctly. They are also cross-checked
against historical data to catch double declarations or inconsistencies.
The 5 per cent referred to above is a minimum for physical
checks鈥攄uring 1996 the average was 7 per cent. Every farm that is
physically checked is monitored by remote sensing.
Large farms are targeted where remote sensing is most efficient. Satellite
images cost between 20 pence and 拢1.10 per square kilometre controlled,
not 拢50, as your story says.
The imaging itself represents only between 10 and 20 per cent of the
costs鈥攖he remainder covers the digitisation of applications,
photo-interpretation, categorisation, reports and so on.
My department has had several contacts with Jean-Pierre Florens and his team.
They based some of their initial assumptions on partial or outdated information
and they are currently revising them.
This will presumably lead them to different conclusions.
Letters : Nukes and carbon
Melbourne
Howard Wright raises the old and sometimes exaggerated question of energy
inputs to nuclear power generation
(Letters, 19 July, p 52).
The main energy input to the nuclear fuel cycle is in enriching uranium,
which can be relatively energy-intensive. Consider a 1000-megawatt reactor
running at 80 per cent of its capacity and so generating 7000 gigawatt-hours per
year. Based on average world data from 1995 for energy produced per tonne of
uranium, this would require about 190 tonnes of natural uranium.
The uranium might be enriched to produce 24.5 tonnes of fuel containing 3.5
per cent uranium-235. This would need 6.3 gigawatt-hours of electricity to
enrich it in a modern centrifuge plant, or up to 250 gigawatt-hours in an older
diffusion plant. Hence, the major energy inputs to the nuclear fuel cycle
represent 0.1 per cent or nearly 4 per cent of the energy output
respectively.
Now contrast the amounts of coal and uranium needed to run a 1000-megawatt
power station at 80 per cent capacity. Assuming the coal-fired plant managed 33
per cent thermal efficiency and that the coal produced 25 megajoules per
kilogram, it would require 3 million tonnes of coal. By comparison, if natural
uranium produced 443 gigajoules per kilogram, the reactor would need 171 tonnes
of natural uranium. (The uranium figure here is slightly different from above
because I’ve used figures typical of a modern reactor rather than average world
figures.)
If the coal contains, say, 67 per cent carbon, it would produce 7.37 million
tonnes of CO2 per year, whereas in the worst-case scenario of a
coal-fuelled enrichment plant, nuclear energy would generate 300 000 tonnes (or
more typically 10 000 tonnes). Mining and transport of coal and uranium would
add slightly to both figures.
Letters : Patenting time
London
You recently described a patent for a clock that will only work until the
dawn of the millennium. The clock continually subtracts time from the turn of
the century, and displays the difference
(This Week, 26 July, p 9).
There are already various clocks in London and elsewhere which show the
number of days until the millennium, such as the one in Piccadilly Circus.
Does this violate the patent or invalidate it?
Letters : Finding flights
Stamford, Connecticut
Robert Matthews omits one of the key modern approaches to solving the
“queueing” class of problem: discrete event simulation
(“Hurry up and wait”, 19 July, p 24).
In the late Fifties, I worked as a systems engineer designing computer
systems for airline passenger seat reservations. One problem was determining the
peak period traffic that the system would handle. This was critical because too
much traffic would cause the system to fail catastrophically.
Initially we based the system on a mathematical solution designed to predict
peak traffic volumes for telephone systems. Then one day we went to observe the
system in operation and discovered to our dismay that real-time airline
reservations traffic was not like telephone traffic. Instead of carrying out a
series of independent transactions, our agents tried many related transactions
in as short a time as possible to find a flight with available seats. Our
systems were vulnerable when demand reached a peak.
A search of queueing theory literature indicated that the handling of
nonindependent events was mathematically difficult and should be avoided. The
alternative was to use simulation, following the newly launched General Purpose
Simulation System model, GPSS.
My first use of GPSS aimed to determine the frequency of interference on a
communications line when two devices attempted to control the line at the same
instant. A quick survey of the experts produced two main responses: “no problem”
and “won’t work”. Who was right?
I was surprised by the speed and ease of setting up and running the GPSS
model. The results showed the value of simulation. Instead of “no problem” and
“won’t work”, the system came up with something in between. It indicated a
reasonable system performance and produced numerical values that were different
from either initial prediction.
Since then, the cost of simulation has been greatly reduced. Yet the
predictions are still inadequately implemented. It is obvious that the problem
is not economic or technical, but political and bureaucratic.
Letters : Burning issue
Cardiff
David Pearce persists in claiming that incineration of waste is best for
Britain, though perhaps not for Europe
(Letters, 12 July, p 49). He disputes
your report of the Coopers & Lybrand finding that incineration is generally
inferior to landfill (This Week, 21 June, p 6).
Pearce’s reasoning is wrong. As he says, the Centre for Social and Economic
Research on the Global Environment assumed “for policy purposes” that
electricity from waste combustion displaces the marginal sources from the grid,
calculating the pollution cost from the worst coal-fired plant.
For practical purposes, that’s nonsense. In some areas, such as the London
Borough of Lewisham, waste incinerators generate power continuously, 24 hours a
day. At night they displace electricity from some of the most modern stations.
Only for short periods, to meet peak demand during winter, do they displace the
marginal coal-fired and diesel generators.
Three years ago, Alan Watson and I pointed out CSERGE’s basic error in
assuming pollution levels of marginal coal-fired plant from the 1980s鈥攖he
plant long since closed and of no relevance in future planning (Energy
World, vol 224, p 16).
Letters : Compelled to ponder
Middlesborough, Cleveland
I was pleased to be able to read your article on obsessive-compulsive
disorders several times without anxiously retracing my steps or doubting my
understanding (“Over and over . . .”, 2 August, p 26).
As one of the unlucky people tainted by this horrid mental conundrum, and
having a scientific background, my spirits were raised. I can only hope that
great care is taken in pursuing this OCD felon, which has robbed me of so much
quality of consciousness.
I have spent the majority of my waking life ruminating on this and that, and
the rest of the time I have been speculating on my ruminations. The feeling that
“something is not right” mentioned in your article permeates most of my day; I
just have to ignore this and carry on regardless. This feels normal to me.
Perhaps this is why OCD sufferers rarely seek help. This and the idea that maybe
they are some kind of freak.
I agree with the point mentioned in the article, that people with OCD-type
behaviours may have an evolutionary role to fulfil鈥攖hat of tidying up and
fussing over details.
I was quite amazed that you didn’t tackle the question of free will. If I’m
not really in control of my compulsions, if they are simply the result of brain
chemistry, then what about the choices I make鈥攁m I being duped about
these, just as I’m duped about “something not being right”?
I feel obliged now to sign off.