Chairs are weightless
Modern Problems in Science is an improvisational show, where three American
masters, Dick Costolo, Rich Fulcher and Phil Granchi, prove ridiculous
hypotheses provided by the audience, such as Chairs are Weightless, Broccoli
causes Cancer and John, Paul, George and Ringo are the Fundamental Units of
the Genetic Code. To quote from the show’s publicity, “Ask them to prove
something and they will.”
The show has received critical acclaim in the US and Britain and was a big
success at the Edinburgh Festival.
As a special deal which is open to New 杏吧原创 readers, we are offering
reduced price tickets (the best 拢8.00 seats for 拢6.00 and
拢6.00 concession seats for 拢5.00) on Tuesday 19 and Wednesday 20
March and 20 pairs of tickets at a two for the price of one rate for the 6pm
show on Saturday 23 March when the show will appear at the Bloomsbury Theatre,
London. For more information or to reserve seats, phone the Bloomsbury Theatre
on 0171 388 8822 and quote “New 杏吧原创 offer”.
Also, be sure to check out your opportunity to have Modern Problems in
Science prove your own improbable hypothesis live on New 杏吧原创’s Web Site,
Planet Science (http: //www.newscientist.com) in the No Limit section.
Correction: The Sri Lankan snake mentioned in the article, “A kinder
antidote to snakebite” (Technology, 3 February, p 18), is not a rattlesnake as
stated in the article, but a viper. The snake should have been referred to as
the Sri Lankan Russell’s viper (Daboia russelli pulchella). We apologise for
any confusion this error may have created.
Also: the photograph in the Technology story “Satellite on a string rides
again” (17 February, p 23) showed the Daimler-Benz Aerospace Eureca satellite,
not the Italian Tethered Satellite as suggested.
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Supercool
Having read David Auerbach’s article on the “Mpemba effect” (American
Journal of Physics, vol 63, p 882, 1995: the effect is that initially hot
water, or ice cream solution, may “freeze quicker” than cold) and the note and
letters on the same subject in New 杏吧原创 (Science, p 22, and The Last
Word, 2 December 1995), I wish to point out a wonderful reference on freezing
that has been overlooked.
N. E. Dorsey’s “The Freezing of Supercooled Water” (Transactions of the
American Philosophical Society, vol 38, p 247, 1948) is an extensive study of
freezing that ought to interest anyone concerned with the Mpemba effect or
similar phenomena. The experiments are simple to the point of being
appropriate for high school science projects, and the results are instructive
for anyone interested in freezing.
Dorsey was the head of the US National Bureau of Standards, and in
compiling his monumental reference book on water (The Properties of Ordinary
Water Substance, Reinhold, Scranton, PA, 1940) he came across a lot of popular
lore about freezing, such as hot water pipes bursting more readily than cold,
and agitation inducing freezing in supercooled water (it doesn’t in general,
but cavitation does).
He undertook a ten-year series of experiments in his spare time that
resulted in the article, which concerns the causes of the variability of
nucleation temperature for bulk samples of water and the presence or absence
of systematic influences on it.
The basic experiment was to cool sealed, glass ampoules half-filled with 3
to 4 cubic centimetres of water from different sources, and measure the
supercooling at which freezing commenced – the nucleation temperature. It was
never above -3 掳C, and often as low as -20 掳C.
The freezing was done repeatedly for each ampoule, and the nucleation
temperature varied a lot, with a general tendency to decrease by 10 掳C or
more after a few dozen repeated freezings.
Dorsey’s main conclusion was that nucleation of freezing was caused by
“motes”, very tiny particles of foreign matter. This is no surprise today,
since heterogeneous nucleation is much more familiar now, but it was a
significant conclusion to Dorsey at the time. The non-reproducibility of
nucleation temperature for the sealed ampoules was ascribed to changes of
properties of the most active motes with time, not to the fundamental
randomness of the nucleation process itself.
Directly relevant to the Mpemba effect was his finding that heating the
water served to deactivate the most active motes, leading immediately to
large increases in supercooling before nucleation.
He suspected that heating just speeded up the same change observed in
repeated freezing runs. This is directly contrary to Auerbach’s suggestion,
but since the effect depends upon the motes, the opposite trend is not
impossible in other samples and might even be present systematically in ice
cream solutions. It would be easy to repeat Dorsey’s experiments and find
out.
Dorsey also speculated that the observation that hot-water pipes burst more
often than cold when frozen might be due to the much less permeable texture of
the ice framework that forms quickly in the water after nucleation at the
lower temperature.
There is a great deal more in this reference, which should have
considerable value for anyone interested in the Mpemba effect or in the
phenomenology of freezing in general. Extensive work on freezing supercooled
water has been done since that time, and is to be found mostly in the
literature on cloud physics, in atmospheric science, but I think Dorsey’s
article is still the best basic entry into the phenomenon
itself.
High kicks
I would like to correct the ideas of martial arts perceived by Robert
Kennan (Letters, 24 February, p 52).
It is true that in many martial arts the risk of brain damage is reduced as
the whole body is used as a target, not just the head and torso. But many
styles allow kicking to the head which can cause far more damage if executed
properly.
However, as a practitioner and friend to many older exponents, my major
area for concern is not the fighting, but more the degradation of the body
through years of constant training.
The training has a high impact on muscles and joints, leading many to
arthritis and torn muscles. This is without mentioning the tendons and
ligaments stretched above and beyond the normal stresses of everyday life. As
in any other sport, the dangers are always there but not necessarily
noticeable.
Deeply wrong
Bill McColl is already behind the times when he says “Before the end of
1996 you’ll even be able to buy multiprocessor PCs”. (“Truly, madly, deeply
parallel”, 24 February, p 36).
It has already been possible for more than a year to buy these. There is
even a choice. You can buy desktop machines which contain up to five powerful
RISC processors working in parallel.
You can also buy machines which simultaneously use both an RISC processor
and another processor – for example a Pentium chip-running together.
These machines aren’t “specialist” items. Nor are they more expensive than
bogstandard “Pentium-boxes”. They are even being used right now in many
schools and universities around Britain. So, if you don’t want to wait with
Bill McColl for the future, try an Acorn RiscPC!
In poor paste
Presumably Feedback is too young to remember the days when “cut and paste”
editing involved using a pair of scissors. Otherwise you would have realised
that the error in the UAP advert (2 March, p 84) was not a spelling mistake,
but a pasting mistake.
Turbines colossus
I awaited with some interest your article on turbines and pumps (“Blades at
the cutting edge”, 24 February).
I was staggered by the disparaging reference to William Hawthorne,
described as “an engineer at the University of Cambridge”. He was at that time
Professor of Thermodynamics, for heaven’s sake, specialising in that subject’s
application to gas turbines, but you make him sound like the assistant
caretaker.
I am not sufficiently apprised of the chronological order of all the facts,
but I do know that Sir William, as he later became, worked with Frank Whittle
and others on jet engine development during the war, and has been continuously
involved with that, and many other subjects ever since. Along the way he
became Master of Churchill College, and was knighted for his services to the
aviation industries.
Sir William is still very active in the field of gas turbines – big ones,
not overgrown water pumps – and I feel quite saddened at Justin Mullins’s
apparent denigration of this towering technological colossus of our time.
One statement in your article must be challenged. The claim that “the
conventional pumps that supply cooling water to British nuclear power stations
must be replaced every few months” is simply nonsense.
The main cooling water pumps at Hunterston Nuclear Power Station were still
operating reliably after 27 years of high load factor running, having received
no more than routine maintenance. As far as I know this is common experience
in large fuel fired as well as nuclear stations.
Six to nine
I was intrigued by Marina Earwood’s letter (Letters, 24 February, p 52)
where she points out that the digit 6 in 1461 was changed (inadvertently no
doubt) to 9 giving 1491. This is uncannily like a problem I suffer on an
almost day-to-day basis.
My work number is almost exactly the same as another totally unconnected
business in my locality. The only difference is that my number contains a 6
and the other establishment’s number contains a 9 in the same place. I’m sure
you can guess the rest of the story.
The odd part is not the number of people who mistakenly dial 6 instead of 9
but the small number of people who honestly believe that the number of the
other place contains a 6 and not a 9.
I can only worry at the hellish consequences if they tried ringing for an
ambulance.
Soaring career
With reference to the four members of staff of Gloster Aircraft with “bird”
surnames (Feedback, 27 January, p 96), the team leader, Harry Peacock (who
later worked for me in the department of science at North Gloucestershire
College of Technology in Cheltenham) was a flutter engineer.
Turing's curse
I read with interest “If only they could think” (13 January, p 32) by Gary
Flood. I must say that some of the positions reported seemed to have missed
the essence of the remarks made by Pat Hayes and Kenneth Ford. As I see it,
the Hayes/Ford position is simply that the Turing test is outdated as the
primary mechanism for guiding research and development in AI. In essence they
seem to be saying that much wasted effort can result from attempts to fit the
mould fashioned by such a test.
What I find objectionable is that the critics of Hayes and Ford seem to be
engaged in unwarranted quibbling. The report on the remarks by Danny Bobrow
implies that Ford and Hayes believe that it is not important to synthesise the
results of AI research.
This implication is patently ridiculous to anyone familiar with the work of
either Hayes or Ford. Their talk did not advocate avoiding efforts toward
synthesis and integration of research results – only that simulation should
not be the goal. Aircraft are highly integrated complex systems, but not
simulations of birds.
The article leaves me with the impression that Hayes and Ford are
suggesting that AI has failed because of the Turing test. This is quite
misleading. Actually, AI is doing a good job at making useful, intelligent
machines – and would be recognised for such if not for misdirection arising
partly from the Turing test. The rather dim view of AI woven through the
article certainly does not reflect the upbeat mood of their talk. I also have
difficulty accepting the reported assertion by Robert Epstein that Hayes and
Ford have made “very primitive” objections by taking the test too literally.
If this is meant to suggest that they are unaware of the possibility of using
a modernised version of the test, I believe that Epstein is way off the mark
on this one.
As for the remark that John Searle “scored a near-mortal blow to AI in
1980″, does the author have anything to support this incredible assertion?
Perhaps no assertion was intended, only a description of some fanciful,
Searleian dream.
I believe that the following statement made by the author allows matters to
be brought into proper perspective:
“Yet it may be the curse of AI that the Turing test still defines what it
is they can and cannot do.”
As I see it, Hayes and Ford are attempting to remove this “curse” and
should therefore be commended for their efforts to do so.
Case against cables
Presumably chemical pollutants as well as radon would be concentrated near
high-tension cables (This Week 17 February, p 4).
Some people living near high-voltage power lines have reported headaches
and other minor health problems. Organic compounds and smoke particles from
vehicle exhausts for example, if concentrated by electrical fields might
explain this. Furthermore, high-tension cables tend to generate ozone. This
gas reacts with organic compounds to give reactive, toxic substances similar
to those that are created in photochemical smog.
Surely the most obvious cause of ill health would in fact be the large
amounts of ozone produced in substations and pylons due to electrical
discharges. (These discharges also cause the chattering sound which one hears
when close to a pylon). Some weeks ago while walking near Kirkstall substation
I could distinctly smell ozone at a distance of around 50 metres from the
station. Ozone is a fairly reactive oxidising agent which should be
investigated if one is seriously looking for the mysterious link between
substations and ill health.
Security for snails
It was fascinating to be informed by the national press, TV radio and by
New 杏吧原创 (This Week, 17 February, p 5) of the presence of a small snail,
Vertigo moulinsiana, in the way of the newsworthy Newbury bypass. What was
singularly lacking in all the accounts that I saw was an objective assessment
of the significance of the snail and the function of special areas of
conservation (SACs).
The snail is described as “rare” in the British Red Data Books 3:
Invertebrates other than insects, and is recognised as a vulnerable species in
the European Red List of Globally Threatened Animals and Plants published by
the Economic Commission for Europe in 1991.
Whatever its category, its present abundance and distribution in the United
Kingdom is probably not perfectly known.
At least we know now that it is more common than previously thought, from
the detailed survey carried out in the flood plains of the Rivers Lambourn and
Kennet.
It was known from about 25 sites in 1991 so the 10 new sites mentioned in
the New 杏吧原创 article substantially add to this. Does this mean that V
moulinsiana is not extremely rare, as suggested in your article?
It is also possible that gaps in its current known distribution would be
filled in with careful study; it is often the case that distribution maps of
the more obscure invertebrates in Britain’s fauna are very similar to those of
the specialists working on them!
Although the snail is not listed as a protected species under the Wildlife
and Countryside Act 1981, it is specifically mentioned in the habitats
directive of May 1992 in a list of animal and plant species of community
interest whose conservation requires the designation of SACs. It is not in the
directive’s list of animals in need of strict protection.
To paraphrase the directive, its function is to ensure that SACs, in this
case, are designated so that the snail’s habitat “is maintained or, where
appropriate, restored at a favourable conservation status in [its] natural
range”. The directive does not require that all of the habitats where such a
species is found have to be declared SACs.
According to the British Red Data Book, published in 1991, it was known
from 11 SSSIs in England, including six nature reserves. It occurs in three
sites which have been proposed as SACs. With a number of sites already
offering Desmoulin’s snail some security, it could be suggested that its
conservation status is satisfactorily protected and that the spirit of the
habitats directive is already being met.
Besides it is very likely that the road engineers would be able to ensure
that the species persists in at least parts of its present site near
Newbury.
Not our bugs
We, at the Embassy of the Republic of China on Taiwan in St George’s
Grenada, are very disappointed to learn that the inference could be drawn from
an article in your prestigious magazine.
The article “Stowaway wrecks island’s crops” by Fred Pearce (This Week, 17
January, p 9) states: “Alleged by some to have arrived in the diplomatic bag
of the Taiwanese mission in St George’s, the Grenadian capital, the pink mealy
bug has attacked more than a hundred species of trees and crops in the past
two years.”
We would like to make a few points for clarification:
This embassy has never brought any agricultural item into Grenada without
going through quarantine.
The embassy and its agricultural mission have always strictly abided by,
and give full support to, the quarantine regulations of Grenada. All the items
imported for the use of the agricultural mission and required to meet the
quarantine standards are jointly handled by the Grenadian Ministry of
Agriculture and Taiwan’s agricultural mission.
Had the agricultural mission brought in pink mealy bugs, then the site of
the mission should have been the first to be infested by mealy bugs. The truth
is that the first place found to have been infested is the Old Fort George
area, approximately 10 miles from the site of the mission.
This embassy is very concerned about the seriousness of the infestation of
the mealybugs, and is in full cooperation with the government of Grenada to
keep it under control.
Condom chemical
In recent years, we have seen a great deal of concern emerging about the
effects of potentially oestrogenic pollutants on the environment.
One group of materials particularly singled out as undesirable are the
ethoxylated alkylphenols. This group includes nonoxinol-9, the spermicidal
surfactant found in almost all condoms.
Given the understandable concern regarding this molecule’s potential
harmful effects on the reproductive system, can anyone explain why no one is
worried about people routinely placing high concentrations of this chemical
around, or inside, their genitalia? Surely such exposure is likely to be far
higher than any from the environment.
Strung up
I read the article “Satellite on a string rides again” (Technology, 17
February, p 23) and I cannot see how towing a cable through the Earth’s
magnetic field can work usefully. Am I missing something here? It seems to me
that this is no more than an exotic dynamo.
Surely, therefore, if you take current from the cable you will get drag on
it as it moves through the Earth’s magnetic field. This would act as a brake
and cause the satellite to re-enter. As far as using the electricity generated
to produce rocket thrust, I fail to see how the thrust produced could exceed
or even equal the drag.