Letter: Digital manouevres
When I got my first digital watch (it was also my last), I was struck
by the impossibility of the compass problem that Ariadne mentioned last
month (20 January). How was I to point the hour hand at the Sun, and, by
means of the method Ariadne described, find the direction of South? After
thinking for all of 3 milliseconds (or was it 5?) I twigged to the brilliant
thought experiment of imagining where the hour hand could possibly be (the
watch tells me – geddit?) and pointing that at the Sun instead.
I guess the old girl must be losing her thread.
Simon Goodman Erlangen, West Germany
Letter: Duck!
If, as you aver, Comet Austin will come closest to the Earth at 37 kilometres
(This Week, 20 January), perhaps you could tell us where we should go to
put a safe distance between the comet and our heads.
David Thomas Cheadle,
Cheshire It should have been 37 million kilometres – Ed.
Letter Conforming to type?
How could New 杏吧原创 print such an article as that written by Bruce
Charlton (‘If the shoe fits’, Forum, 27 January)? I have been trying for
the past 20 years, with an occasional glimmer of hope, to get my husband
to wear something other than tweed jackets (sorry, a tweed jacket), baggy
trousers and comfy Clarks shoes, but what chance have I got now?
The worry that I have is that New 杏吧原创 will publish further evidence
on the behaviour of male scientists – perhaps the majority only bath once
a week or never use perfumed toiletries. I can see that in future I shall
have to vet each issue as it comes through my door before putting it into
general family circulation.
Jill Cliffe Bakewell, Derbyshire
Letter: Tropical grasslands
The reassessment of grassland productivity which Peter de Groot described
in his article ‘Are we missing the grass for the trees?’ (6 January) is
needed given the shortcomings of the earlier methods used by the International
Biological Programme (IBP). However, he gives the misleading impression
that increased estimates of grassland productivity mean that a hectare of
tropical grassland can rival a hectare of tropical forest as a reservoir
of carbon, with obvious implications for models of the carbon cycle.
Since trees accumulate carbon in their wood and grasses have no equivalent
way of locking up carbon out of reach of decomposers, carbon fixed by grasses
returns rapidly to the atmosphere. The rate of turnover of grass tissue
may have previously been underestimated, leading to an underestimate of
productivity, but this will be of little significance to the bottom line
of the carbon budget unless there is extra carbon stored somewhere that
cannot re-enter the atmosphere. If this did happen, IBP’s methods, based
on measuring accumulation, would presumably have detected it.
Jonathan Silvertown Open University, Milton Keynes
Letter: Irradiated food
Your editorial on food irradiation starts with the statement that the
ideal way to render food safer for human consumption would be to find a
process that kills off all the bacteria and other organisms that could harm
anyone who eats it, and suggests that irradiation comes close to that ideal
(‘Rays of confusion’, 20 January). But the ideal way to render food safer
is not to find a way of killing off dangerous organisms in it, but to produce
food that has little or no dangerous contamination in the first place. This
goes to the heart of the debate because you seem to think that irradiation
will deal with the growing levels of food poisoning we are seeing. It won’t.
Irradiation can be used only on a limited range of foods: it is no good
for pate, or worse still for eggs. And even the poultry producers have doubts
that chicken can be irradiated sufficiently without making it inedible.
The danger of your position is that it shifts the responsibility for
the production of safer, wholesome food away from the producers because
they will believe contaminated foods will be rendered ‘safe’ by irradiation
at the last stage in the process, so their hygiene standards don’t matter.
There are also a number of outstanding questions about the safety of food
irradiation itself: its effects on packaging materials, food additives and
pesticide residues, for example.
You place great faith in technical regulations and policing of the process.
I’m afraid, however, that there is evidence that abuses are occurring all
over the world, and where are the proposals to strengthen and train the
inspectors who will be needed? Irradiation may be a slightly less risky
way to treat herbs and spices that are currently subjected to ethylene oxide
gas, but there are just too many question marks about it for its widespread
use. It would be more helpful if you were to look at some more interesting
questions, such as: Who wants it? What is the role of the International
Atomic Energy Authority in promoting it? What are the commercial advantages
to prolonging shelf life and who benefits from this, consumers or producers?
The answers to these could be very revealing.
John Beishon Chief Executive Consumer’s Association London NW1