Letters: Solid state
Since the Shetland oil disaster, I wonder if the following idea might
attract some attention from oil and shipping companies or any other interested
parties.
A concentrated gelling agent such as lithium stearate as a powder or
a highly concentrated liquid is mixed into the oil in the event of a leak
or similar emergency.
An emergency pumping system is introduced to pump the oil around the
container and ensure rapid mixing of gelling agent and oil (perhaps ships’
pumps can be modified). The material is added and the pumps cut in if any
leak, major collision or other disaster occurs. The gelling agent would
be rapidly mixed into the oil, the particular reagent chosen to give a set
reaction time, ensuring an appropriate concentration and degree of mixing
has occurred before the gel point is reached. The mixed oil/reagent becomes
solid. The oil once gelled will no longer leak from the container. It will
help prevent loss of volatile components, keep oil in one place and prevent
slicks if a ship somehow sinks or runs aground and ruptures any of its tanks.
The oil gel should also be easily liquefied again by a simple procedure
such as heating or addition of chemicals, in order to pump it easily to
a transfer vessel when conditions such as weather are suitable.
The principle may also be useful in situations where a tanker that does
not have such a system is leaking. The gelling agent could be mixed into
the oil to prevent further leakage until such time that it can be removed
or the vessel repaired.
Justin Galey-Jones Norwich
Letters: Snakes alive
It was disappointing to see a decline in Australian snake populations,
attributed to coastal development, the spread of the introduced cane toad
and the use of pesticide, described as ‘the good news’ (This Week, 2 January).
Australia already has an appalling record of native mammal extinctions since
European settlement. Surely the fact that we may now be pushing some of
the continent’s unique reptiles towards a similar fate is not something
to celebrate.
Michael Bedward Balmain, NSW, Australia
Letters: What gnats know
Ian Stewart’s article on testing for prime numbers (New 杏吧原创, Science,
31 October) brings to mind the feats of (often mentally retarded) calculating
prodigies. The ‘Twins’ described by Oliver Sacks in The Man who Mistook
his Wife for a Hat were able to recognise 20-digit primes with little effort.
A rough calculation would reveal that, using known methods, a gifted person
with a photographic memory could not possibly accomplish this in several
lifetimes.
All this suggests some relatively simple, subconscious algorithms which
have not, as yet, been explicitly formulated. Research in this direction
might well result in new mathematical insights.
It need not be surprising that mathematical insight is more fundamental
than language. Even a primitive animal brain is ‘wired’ to perform exceedingly
complex computations, essential for survival in an unpredictable environment.
The latest ‘smart’ weapons are rudimentary compared with a humble gnat.
Mathematics could be a by-product of these functions. Language is a comparatively
recent evolutionary innovation and it is quite possible that conscious manipulation
of abstract symbols has not caught up with an innate ability to perceive
quantitative relationships.
Joel Margolis Pyrmont, Australia
Letters: Good for Godel
Hugh ApSimon (Forum, 19/26 December) perpetuates a common myth when
he suggests that Godel’s achievement was to invent statements such as ‘This
statement can not be proved.’ Such statements have been around since antiquity,
and have failed to provide a paradox because ‘This statement’ has no meaning
before the statement is made.
What Godel found was a cunning way around this. He devised a way of
coding any statement uniquely as an integer – he used products of powers
of prime numbers, but coding the sentence as ASCII text would work just
as well – and applied it to an algebraic representation of ‘The statement
represented by the number X cannot be proved.’ He then showed that X can
be the number that represents the whole statement, without needing to refer
to anything not yet defined.
Thus he showed that any system which can make algebraic statements about
numbers – including the mathematics we all once believed to be infallible
– must either contain at least one true statement that cannot be proved
(meaning the system is incomplete), or at least one false statement that
can be proved true (meaning the system is self-contradictory).
This is a far more important result than ApSimon’s simple riddle, and
could neither be solved nor brushed aside by either of his hypothetical
machines – though I doubt whether the machine would blow a fuse or go into
a sulk, the way it is usually portrayed in these stories.
Tim Bierman London
Letters: Problem pings
I was most interested to read about John Dowding’s telephone pinging
during the night (Letters, 2 and 16 January) as I too have that problem
– but in my case it occurs at midnight. What I find even more interesting
is that Dowding was assured by BT that it is not engineers testing the lines,
because when I queried it with BT I was told that this is exactly what
it was. One feels that there are crossed lines somewhere.
Michael Afek Inverness
Letters: Ideas wanted
The Economic and Social Research Council and the Science and Engineering
Research Council have set up a joint panel to examine research at the interface
between the two councils. It replaces the previous joint committee which
had been criticised for working in a largely responsive mode.
The new panel aims to identify themes arising out of the interface
between the councils which have the potential for high-quality research
of national and international significance.
In order to ensure that the panel chooses the most appropriate initiatives,
it is now looking for advice from researchers on those areas most appropriate
for funding. Any suggestions should lend themselves to research of academic
excellence and to interaction between social scientists, natural scientists
and engineers.
Proposals and suggestions should be directed as soon as possible to
me as the panel’s chairman, c/o Department of Government, University of
Manchester, Oxford Road, Manchester M13 9PL Tel: 061 275 4878.
Roger Williams University of Manchester
Letters: Giant sperm
Your item on the advantages of large sperm (Science, 2 January) mentioned
only mammals. However, some invertebrate sperm make the bonobo’s look like
pygmies. Certain ostracods (small crustaceans), for instance, can have
sperm up to 15 millimetres long. This is all the more striking when you
consider that the males are only 2 millimetres long themselves. Monstrous
sperm can also be found in feather-winged beetles, backswimmers, fruit
flies and mites. The world record holder is a 20-millimetre sperm produced
by a fruit fly (Drosophila) species.
Interestingly, the groups in which giant sperm occur most commonly
(ostracods and feather-winged beetles) are also very promiscuous. Perhaps,
therefore, these giant sperm are used to block the passage of competing
sperm to the unfertilised ova. Further evidence to support this interpretation
comes from the shape of the sperm, which have a swollen posterior that neatly
plugs the female tract. Large sperm may be good competitors, but it seems
that giant sperm can be even better.
Richard Ladle, Rufus Johnston Department of Zoology University of Oxford
Letters: Now you see it . . .
Your list of the 10 best inventions from your Feedback summer competition
(19 September) was very interesting. In fact, the idea submitted by Steve
Anastasi about a printer’s ink which, when subjected to a catalyst, breaks
down into a clear substance, thus avoiding expensive de-inking plants when
recycling paper, inspired me to work out a solution to this problem.
The complex of starch (amylase) with iodine, which is blue-black, is
very stable under room conditions and at high temperatures. This can be
used as the inexpensive ink. To remove the ink when recycling, you simply
spray the enzyme a-amylase onto the paper. This will completely remove
the ink in a matter of minutes. The paper is then heated to destroy the
enzyme and so can be reused as new paper.
Shiva Jaggernauth Trinidad, West Indies
Letters: Secrets of swing
In reply to the inquiry by Mike Hogan (Letters, 9 January), the ‘self
propulsion’ of a swing is a matter of successive minor alterations of the
centre of gravity combined with the inertial effects of a moving mass.
The initial position is when the centre of gravity of the swing and
its passenger is directly below the swing pivot and there is no movement.
Now if the person leans back, the centre of gravity if shifted and the swing
seat moves forward slightly to compensate and bring the C of G back to the
equilibrium position.
As it is a low-friction system, this initial ‘forward’ movement overshoots
the equilibrium slightly. If now, during the overshoot, the person leans
forward, the C of G is displaced further from the equilibrium than it would
have been by the ‘pendulum momentum’ effect alone, and the subsequent ‘back
swing movement’ is more vigorous than it would have been with a static passenger.
Repeated shifting of the person’s C of G at the appropriate phases of the
cycle gives an amplitude build-up.
T. Robertson Abingdon, Oxfordshire
Letters: Secrets of swing
Mike Hogan could tell his children that a person on a swing becomes
the weight of an ‘intelligent’ pendulum, able both to monitor its own position
and to move its own centre of gravity.
He could also say that similar changes in angular momentum were the
operational ‘secret’ of all those perpetual motion machines which had curious
weights mounted around the circumference of a wheel. He could point out
that the ‘weight’ on a swing has to work jolly hard to achieve the desired
result, something the inventors failed to appreciate.
It will fall to him to replace this lost energy with ice cream and hot
dogs, with the implied reminder that, in physics, there is no such thing
as a free lunch.
Chris Randall Swindon, Wiltshire
Letters: Secrets of swing
I can assure you that it is perfectly possible, from an inert sitting
position, to strike up full swings in approximately 30 seconds (no touching
ground) as proved in Highgate Wood children’s playground on 6 December,
1992 by myself, Lettie aged 7, Ishbel aged 5, and John aged 54. Ten forward
and backward rocks of the body produce enough momentum to start swings and
then at the height of each arc, one’s body rhythm naturally senses the impulse
to change from stretch to tuck positions.
Barry Jackson (aged 54) London
Letters: Motors and magnets
Your article of 24 October (Technology) refers to the Posivlow motor
fuel device. The maker, McKeown Industries, promises the results of independent
tests in April or May 1993. In the interim readers may be interested in
our experience of this device here in southern New Zealand.
We operate 43 vehicles and were approached last August by a McKeown
representative. We were surprised we had not heard of a new ceramic with
such magnetic strength and we wondered how such a field might influence
the mixing of fuel vapour and air.
Nevertheless, extrapolation of the claims suggested that on vehicles
driving over 20 000 kilometres per year, each device would pay for itself
through fuel savings in 18 months and then endure, on a series of vehicles,
for more than 80 years at full effectiveness. Feeling also that we had a
moral duty to reduce exhaust emissions if we could, as well as minimising
costs, we agreed to a free no-obligation three-month trial of one unit.
We chose to install Posivlow on a Toyota HiLux double-cab four-wheel-drive
utility with a 2.2-litre petrol engine which had been new in December 1990
and had clocked up 41 468 kilometres by the end of 1991. This vehicle is
one of three in a local pool in a busy section of the university.
The device was installed on 5 September by a senior member of our technical
staff, who seldom has occasion to drive any of the vehicles, and without
telling anyone else. Thus no driver during the September-November trial
knew the device was present. The HiLux’s journey pattern was unchanged.
Our fuel-purchasing arrangement is by debit card, one card for each
vehicle positively and uniquely identified to that vehicle, and able to
be used by every driver of that vehicle. The card-issuing company provides
monthly reports detailing all purchases per card, fuel volume as well as
cost and odometer reading. We log every kilometre run, for our internal
charging system.
We accordingly felt that our trial was as objective, consistent, comprehensive
and independent as we could reasonably make it ‘on the road’. The (auditable)
summarised results are: Jan-Aug 1992 (without Posivlow): the vehicle drove
23 882 kilometres, using 3120.5 litres of fuel; consumption was 13.07 litres
per 100 kilometres.
Sep-Nov 1992 (with Posivlow): the vehicle drove 9350 kilometres, using
1255.9 litres of fuel; consumption was 13.43 litres per 100 kilometres.
These results suggest that on this trial at least, Posivlow made no
appreciable difference to the fuel consumption of the vehicle to which it
was fitted and certainly did not reduce it.
Roger Gonin University of Otago Dunedin, New Zealand