Letter: Hubble telescope
I refer to the article by Helen Gavaghan (This Week, 7 July) and also
to a recent similar article in Physics World.
I have not seen any comment yet on the effect of zero gravity on the
Hubble telescope. Surely such a large mirror, figured within the Earth’s
gravitational field, would distort when placed in zero gravity, even if
it survived the high G of rocket takeoff? This would seem to be more likely
than a serious figuring error by the participants in the project.
Many complex solutions have been discussed in your pages and others.
Perhaps a simple aperture stop would reduce the spherical aberration significantly,
while enabling an acceptable compromise in resolution and light-gathering
power to be achieved, until a permanent solution can be installed.
One hopes that the august bodies now sitting will be able to find a
cost-effective solution without the strong smell of blame which seems to
pervade such expensive endeavours.
I suspect that such a large mirror might suffer from Moon tides!
GR Bonye Raggleswood Chislehurst, Kent
Letter: Cold comfort
Tom Christie claims (Letters, 4 August) that the refrigeration industry
is abandoning HFC-152a as a CFC alternative, but that’s hardly the case.
China’s refrigerator industry, for example, is actively testing 152a in
its factory laboratories. The US Environmental Protection Agency’s Division
of Global Change has been championing the chemical as the most ozone-friendly,
climate-friendly, and energy-efficient alternative currently available,
and Underwriters Laboratories (UL) is nearing completion of its study of
the flammability problem.
If UL approves the chemical, and US appliance standards are rewritten
to allow flammable refrigerants, the home refrigeration industry could switch
to 152a with a minimum investment in new equipment (152a is a ‘near drop-in’
replacement for CFC-12). This makes 152a rather more economically attractive
than HFC-134a, an equally ozone-friendly but less-efficient alternative
(with higher global warming potential to boot) that will require a greater
investment in retooling/redesign.
Flammability is a significant drawback, but it can be rationalised.
My flat has a gas stove in the kitchen and a gas hot-water heater in the
basement. I’m fully aware that a leak in either of those appliances could
blow me and my loved one to smithereens, as one did to a neighbour last
year. I choose to live with that risk. I would also choose to live with
the risk of owning an HFC-152a refrigerator (though I don’t know if I can
say the same for a propane one), even if that meant doubling the slight
chance of my early cremation.
The key, of course, is being aware of the risk so you can make an informed
choice. People know that gas stoves can be dangerous, but the refrigerator
is just a harmless white box in the corner, full of beer, ice cream, and
last night’s vegetables. If 152a makes it to the home refrigerator market,
industry and government will need to launch an extensive public education
programme to change that perception.
Brad Hurley Global Environmental Change Report Arlington, Massachusetts,
US
Letter: University blues
After three years as managing director of Kent Scientific and Industrial
Projects Ltd, the Consultancy, R & D, Technical Services and technology-transfer
company owned by the University of Kent, I am well aware of the need for
university departments to up-date their equipment stock for research and
teaching.
The ABRC survey is very revealing; I believe in general that universities
can benefit from the routines adopted to produce the returns. Since replacement
cost was part of the data sought, it should be possible now to introduce
procedures to value properly the equipment stock and its use for research.
One of the ways in which university research obtains new equipment is
through sponsorship by industry and government departments for particular
projects, for which equipment is purchased. Frequently, the sponsor reserves
the right to the equipment at the end of the project, but often this right
is not exercised. The university therefore reaps the benefit of the equipment
then usually only two or three years old and capable of being used on other
projects.
There may be an anomaly over valuation because of the rights of the
sponsor, and it is usual practice for the equipment to be written down to
zero value by the university at the time of purchase. So what does a university
do when it wants to consider the equipment value in relation to the ‘well
found’ laboratory, or even more importantly if the equipment is of a special
nature? Other considerations include the cost of replacement and the cost
of maintenance and operation.
Another way in which universities can, and do, obtain returns on equipment
is using it for technical service work. An example in the context of KSIP
Ltd was to purchase a high-value analytical instrument which not only was
used for research in biotechnology and chemistry, but also replaced a 14-year-old
equipment to broaden the capability of the University Chemical Analysis
Centre. The centre then found it was able to increase its business.
You propose that savings resulting from lower defence costs might be
channelled towards the universities to support research. I doubt very much
if this will happen bearing in mind the current fairly large cuts taking
place as a result of the Ministry of Defence running out of money or being
overspent. If money did become available, then I believe that it would be
difficult for any new organisation to distribute it equitably. It might
be better that the money was left with the MOD so that it might spend the
money on sponsoring ‘peace’-orientated projects. After all, defence technology
does have its peaceful applications.
John Maxwell Jones Oxted, Surrey
Letter: Biodegradable plastics
John Emsley’s Forum article ‘On being a bit green’ (30 June) dismisses
in a somewhat cursory manner biodegradable polymers. The article attracted
a letter and supporting article from Friends of the Earth in favour of banning
biodegradable plastics (21 July).
I would draw the attention of Emsley and your readers to ICI’s Biopol,
a fully biodegradable thermoplastic manufactured by fermentation using a
carbohydrate feedstock. On what environmental grounds anyone could seek
to ban Biopol, I do not know. It’s manufacture requires a modicum of electricity,
salts and steelwork–so does a bicycle. (FoE is keen on bikes – I believe.)
I admit that in the main, so- called biodegradable polymers are a quick-fix
utilising accelerators to enhance degradation by ultraviolet light, or incorporating
a standard petrochemical-based polymer in a polysaccharide matrix. However,
to suggest they should be banned is plain Luddism.
Peter Senior Nottingham
Letter: Hot air
John Gribbin’s Talking Point article ‘Why caution is wrong on global
warming’ (28 July) is well intended but I believe futile.
Serious policy action on the greenhouse effect is unlikely because:
(a) The world’s largest coal reserves (and therefore the largest greenhouse
gas reserves) are in the USSR, the People’s Republic of China and the US,
and the largest oil reserves are in the Middle East – three of the four
are poor candidates for demonstrating a global social conscience.
(b) Predictive models of global climate cannot be convincingly verified
until the predicted event occurs . . . quite late to be of value. We should
not give up, of course, but should put our real effort into adaptation to
a new climate state – a potentially rich but unploughed intellectual landscape.
David Slade Silver Spring, Maryland, US
Letter: Pedal power
Never make sweeping statements in science. This was driven home to me
by a chemistry lecturer during my A-level studies. However, Richard Gould
did just this in his article ‘The bike built to win’ (30 June) when he wrote
that ‘In this year’s Tour, every competitor will use an up-to-date version
of the 1985 (clipless pedal) prototype’. Many riders didn’t, including the
famous Irishman, Sean Kelly.
Also, on the advantages of toe-straps, Gould mentioned that the strap
can loosen at inconvenient moments, leaving riders stranded due to loss
of power. The problem is not restricted to toe-straps and many stages have
been lost due to riders’ feet becoming detached from clipless pedals during
a sprint. I disagree with the claim that toe-straps are dangerous. I have
been using them for more than six years and have yet to have a problem in
unbuckling them in an emergency.
Gould also stated that the purpose of toe-straps is to allow a forceful
upstroke of the pedals. This is not necessarily true. The main purpose is
to hold the ball of the foot over the pedal axle and thus keep it in the
most energy-efficient position.
Regarding the handlebars used by Greg LeMond in the 1989 Tour de France,
calculations show that these bars are only beneficial at speeds of over
50 kilometres per hour. Below this, they are of no aerodynamic advantage
and the extra weight will hinder the cyclist.
A. M. Jordan Rochdale, Lancashire