Letter: Bursting to measure
With regards to your recent article, ‘Is there a radio link to gamma-ray
bursters?’ (New 杏吧原创, Science, 23 October), you may be interested to
know that there is a similar, but more direct approach to the problem of
measuring the distance scale of gamma-ray bursts.
In the soft X-ray part of the electromagnetic spectrum (energies between
0.1 and 2 kiloelectronvolts), photons from the burst are absorbed by intervening
matter via the photo-electric effect. The farther away the source of the
burst is, the greater the amount of intervening matter and the greater the
degree of absorption. Hence, measuring the soft X-ray spectra of a selection
of bursts would also give you an idea of their general distance scale.
The origin of gamma-ray bursts is one of the most fascinating topics
in astronomy today. They could be the most luminous events in the Universe
but, without a measure of their distance, we have no way of knowing.
Our group, in collaboration with colleagues in Europe and the US, have
designed a concept for a satellite-based instrument to measure the soft
X-ray spectra of gamma-ray bursts with the prime intention of determining
the distance scale from the amount of absorption that you observe.
This instrument would monitor around 3/4 of the sky at any one time
and, because the expected brightness in soft X-rays is reasonably predictable,
we would confidently expect to detect around 30 bursts per year of sufficient
brightness to measure the absorption. The instrument would be a relatively
low-cost mission and could be flown as a piggy-back on a larger instrument.
Persuading NASA or the European Space Agency to build it is, of course,
another problem.
Steven Sembay University of Leicester
Letter: Famous geese
As an acknowledged world leader in the field of whisky consumption,
and having spent a few years studying geese in various parts of the globe,
I must write to take issue with your piece about graylag geese threatening
Scotland’s whisky industry (Feedback, 23 October).
Firstly, Icelandic-nesting greylag geese come to Britain for the winter,
and therefore do not spend their summer in whisky country.
Annual counts of greylag geese show that although the population of
greylag geese breeding in Iceland and wintering in Britain (mainly Scotland)
did increase from around 30 000 to just over 100 000 during the late 1980s,
their numbers have now stabilised and show something of a decline in very
recent winters. They have certainly never approached the level of 200 000
which your normally meticulously accurate column claims.
Indeed, rather than be greatly encouraged by the present numbers, sporting
wildfowlers have actually expressed concern at the impact of overseas shooters
coming to Scotland to secure large bags of Icelandic greylags. The species
is, under domestic legislation, a perfectly legal quarry species during
the open season in winter.
While there is no dispute that agricultural conflict does occur in some
areas as a result of goose activities, it stretches credibility to believe
that so much damage is done to the barley crop throughout the whole of Scotland
as to cause distilleries to close, even for short periods.
As to defaecating in ‘the waters’, agricultural contamination has been
a far greater cause of changes in groundwater and lakewater chemistry
than the combined might of many greylag goose bottoms.
I was actually sipping leisurely on a dram of ‘Famous Grouse’ at the
very moment I read your column, and look forward to the day when geese and
whisky can both be free of manufactured controversy such as this story.
Tony Fox National Environmental Research Institute Denmark
Letter: Flywheel firsts
In the item ‘Oxford goes electric without flywheels’ (Technology, 30
October), Oliver Tickell and his informant seem to have been unaware of
the Gyrobuses built by the Oerlikon company. The first one was tested in
December 1950 in Aarau, in Switzerland. Two more ran for a number of years
in the Swiss town of Yverdon and three in Gent, Belgium.
The Swiss buses had 1.5 tonne flywheels 1162 mm in diameter mounted
horizontally under the floor in a sealed chamber containing hydrogen at
low pressure. The flywheel was driven up to a speed of 3000 rpm by a 3-phase
motor, the power being taken by roof-mounted contact arms from roadside
poles at the terminals. The vehicles could run at up to 25 mph. The Swiss
route apparently had a journey time of 15 minutes, 5 minutes being allowed
for recharging the flywheel at the terminals.
With regard to Oxford’s battery buses, I have a feeling of deja vu.
There have been many attempts at using conventional batteries for buses
ranging from the London Electrobus in 1906 to the Seddon-Chloride Silent
Rider in Manchester in 1974. In between were many experiments including
Lancaster in 1916 and Leeds in 1972. The Manchester Silent Rider was joined
by a smaller Lucas midi-bus in 1975.
It will be interesting to see if the Oxford experiment is any more successful
than its predecessors over the last 90 years or if they too will be defeated
by the ratio of charging time to operating time.
N. C. Friswell Horsham, W. Sussex
Letter: Flywheels first
The flywheel energy store in your article on Oxford’s electric buses
seems to be very underrated to only store one kilowatt hour. A spin stressed
hoop of carbon fibre reinforced resin of a density of 2300 kilograms per
cubic metre and tensile strength of 1.5 times 1010 newtons per square metre
could store a maximum kinetic energy of 3.26 times 106 joules per kilogram
(Or 0.905 kilowatt hours per kilogram). This is 226 times more than that
used in the bus.
Even with a safety factor of 10 the energy to run the bus could be stored
in a device whose moving element had a mass of only 22.6 kilograms (comparable
to a heavy duty lead acid battery). With automatic pick-up points, either
overhead at bus stops or from embedded coils underneath in bus lanes, a
bus could operate more or less continuously with no performance penalty
compared with ordinary buses.
A. C. Henderson Braco, Falkirk
Letter: Long-lasting women
Roy Collins asks ‘Why do women last longer than men?’ (Forum, 23 October)?
He claims that the ‘gender gap . . . is very new, a 20th-century phenomenon’.
His assumptions as to the novelty of the present century in this respect
are false. In Sweden in the late 18th century women had a 10 per cent advantage
over men in life expectancy at birth and in England and Wales an advantage
of 4 per cent in the late 1840s, rising to 7 per cent by the end of the
19th century. After that the margin narrowed in Sweden rather than increasing
whilst with us it was static. In the national censuses in Denmark in 1787
and 1801 the sex ratios of people over sixty (numbers of males over females)
were 0.83 and 0.87.
These are not isolated instances and whenever we have been able to establish
the relevant fact for the past, women have been in the lead in west European
countries, though not so evidently in eastern Europe and much less so in
India, China or Asia generally. Accounting for the differences and their
changes over time is an important subject of research.
Peter Laslett History of Population and Social Structure Group University
of Cambridge
Letter: Long-lasting women
If one actually looks at X and Y chromosomes, it is plainly obvious
that the so-called Y chromosome is actually an X chromosome with one of
its ‘legs’ missing.
The fact of parthenogenesis indicates that the natural form of all species
is female. Males exist merely so that females can reproduce themselves.
Men are, in fact, mutant women.
This explains why men have nipples, why far more men than women suffer
from physical and mental gender disorders, why women are generally healthier,
and why they live longer.
Robert Taylor Notting Hill, London
Letter: Right rain
Fred Pearce, in his article ‘Wrong kind of rain fools warning system’
(This Week, 23 October), states quite incorrectly that the Meteorological
Office’s Frontiers system failed to provide the National Rivers Authority
with adequate warning of the recent severe rainfall that caused flooding
in London and the South East.
The main function of Frontiers is to predict the passage of frontal
systems and provide early warning of areas likely to suffer heavy rainfall.
This allows the NRA to make informed decisions on flood warning and flood
prevention precautions as much as six hours in advance of a rainfall event.
In addition, Frontiers forecasts accumulations of rainfall based on
data derived from a network of radars covering the whole of Britain on a
5 kilometre grid. In the London area, however – and only in the London area
– there is the additional provision of a dense network of rain gauges maintained
by the NRA. What recent events demonstrated was that, used together, Frontiers
and the NRA’s rain gauge network provide even better forecasts of the amount
of convective rainfall for the two-hour period before the actual event.
The two systems are complementary, not mutually exclusive, as Fred Pearce
implies. The comments of NRA flood control managers, had they been reported
in full, would have reflected this point.
Chris Birks National Rivers Authority London Mike Nicholls The Met Office
Bracknell, Berkshire
Letter: Europe's poor
Your Comment (2 October) serves to discourage the endeavours of the
World Health Organization to advance the wellbeing of people in countries
such as Albania, Bosnia, Kyrgystan, Tajikistan, the former Yugoslav republic
of Macedonia, Turkmenistan and Uzbekistan – WHO member states that are far
from being the ‘rich nations’ by which you characterise the WHO’s Region
for Europe.
Your Comment advocates decentralisation away from the organisation’s
headquarters in Geneva. But with a curious logic, you also advocate abolishing
one of the decentralised offices that was established precisely for the
purpose of taking operations closer to the customers. The programme and
staff resources of the WHO Region for Europe are focused on the newly independent
states and the countries of central and eastern Europe. These are deployed
purposefully with the aim of reducing profound health inequalities that
are being aggravated by the process of economic transition.
The WHO’s slender human resources in the region are directed to relieving
unnecessary suffering – from diseases that can be prevented by vaccines,
for example; to preventing deaths that occur prematurely as a result of
health-damaging behaviour; to reducing environmental risks to health, and
to ensuring appropriate use of health technology. It is surely not your
wish to discourage this.
Ten countries continue to report poliomyelitis occurrences to the European
region of the WHO. The operations that your Comment would have us close
down include targeted efforts to reduce poliomyelitis incidence to zero
by the year 2000. When this is achieved, historians will marvel not that
human ingenuity produced a vaccine, but that there was a will and an organisation
to carry this technology to all humankind. I am sorry that your readers
were so poorly informed of the work of the WHO in Europe by your Comment.
David Macfadyen WHO Region for Europe Copenhagen, Denmark