Letters: Too big to breed
I was interested by the article on the relative sizes of living and
extinct mammals and reptiles (New 杏吧原创, Science, 13 February). Surely
the reason for the small size of marine dinosaurs relative to modern whales
lies in their breeding behaviour? An egg-laying dinosaur, like a modern
marine turtle, would have to return to land every breeding season to lay
her eggs and therefore could not grow to the size of the largest whales,
whose lungs collapse if they become stranded in shallow water.
Of course, some modern reptiles hatch their eggs internally and give
birth to live young, but I doubt if this would work for a large aquatic
reptile because it would be difficult to provide the young in the brood-pouch
with enough oxygen.
P. Donovan London
Letters: Still secret
I wish to comment on John Emsley’s article ‘The secret of Bath’s methane-fuelled
microbes’ (New 杏吧原创, Science, 20 February). The bacterium was originally
isolated by us and was given to Stephen Lippard and his colleagues by us.
To give the distinct impression that the Americans have now ‘unlocked’ the
secret of the mechanism is preposterous. What they have done is identify
one possible mechanism that does not involve radicals. Even Lippard and
his colleagues say this in their conclusions. No, they have not discovered
the mechanism I’m afraid. Furthermore, the article contains several factual
errors. (Pseudomonas oleovorans does not consume methane; the components
and their function were discovered by us, not Lippard) Their proposals are
merely an extension of our earlier work. Had Emsley read the paper more
carefully or consulted with us on it he might have come to a different
conclusion.
Howard Dalton University of Warwick Coventry
Letters: Funny Frenchman
L’Abbe Caselli was not ‘a French engineer’ but an Italian physicist
(‘Just give me the fax’, 13 February).
Giovanni Caselli was born in Sienna in 1815 and studied in Florence
with the well-known Leopoldo Nobili (1784-1835). In 1836 he became a priest
(and later an abbe).
From 1856 he worked for many years in France (some of the time in Paris
with Leon Foucault) but eventually returned to Italy. He died in Florence
in 1891.
A reconstruction of his ‘pantelegraphe’ (pantelegrafo, in Italian) is
still working in the Museo della Scienza e della Tecnica in Milan.
Emanuele Vinassa de Regny Milan, Italy
* * *
Tim Hunkin writes: Neither the Musee des Techniques, where Caselli’s
pantelegraphes live, nor the paper written about them by the Centre National
d’Etudes des Telecommunications, mention Caselli’s Italian origins. The
French apparently prefer to forget he was not one of their own countrymen.
Letters: Sexy cockroaches
Re your item about cockroach sex pheromones (This Week, 20 February).
Females are not alone in producing such alluring materials. The male lobster
cockroach produces a sex attractant named, by a more imaginative entomologist,
seducin. Presumably this is the cockroach equivalent of aftershave.
Insect sex attractants are now used for detecting and monitoring several
pest moth and beetle species. Combined with growth regulators such as methoprene
and hydroprene they make elimination of pests from buildings possible with
virtually no risk to non-target species.
Peter Bateman Rentokil East Grinstead
Letters: Let's move Venus
Instead of beavering away on climate control research to render Mars
habitable in the distant future, wouldn’t it be better in the long term
to accelerate Venus into the position once thought to be occupied by Erehwon?
It might sort out its own climate.
What I had in mind is deflecting some of the minor planets, whose motional
energy exceeds Venus’s, to adjust Venus’s orbit progressively by direct
collision. This would also increase its total mass, but the increase need
not be excessive.
To leave Venus where it is seems such a waste of a potentially habitable
planet.
With sophistication (and a bit of luck!) we might also be able to give
it a moon – we could bump Mercury out a bit.
Bernard Howlett Loughton, Essex
Letters: Buzzing and biting
Jeremy Holden writes (20 February) to ask why mosquitoes buzz, and suggests
that natural selection should ensure that the insects evolve to a stealthily
silent strain.
It seems clear that Holden has never actually been taunted by a mosquito:
they are quite impossible to catch, the buzz does not pinpoint the mosquito
as might be expected.
Possibly the increase in blood circulation due to the exertion of trying
to catch one’s tormentor enables it to feed more easily, once its weary
victim falls into an exhausted slumber. Increased perspiration may also
make the sleeper easier to find.
James Henderson Alton, Hampshire
Letters: Buzzing and biting
My guess is that not enough time has passed for ‘stealthy’ mosquitoes
to have evolved. Presumably, for most of the thousands of years during which
mosquitoes have attacked soft human flesh, the humans did not live in small,
confined bedrooms where a noisy insect would be trapped after betraying
its presence. But the mosquitoes of the future may discover aerodynamics
and hush their engines, so to speak.
Peter Lynch Blackrock, Co. Dublin Ireland
Letters: Buzzing and biting
The bulk of the mosquitoes’ diet is the blood of creatures that are
in no position to ‘jump out of bed and hunt down and kill the mosquito’.
So the evolutionary pressure working against the irritating buzz may not
be so great.
Ornolfur Thorlacius Hamrahlid College Reykjavik, Iceland
Letters: Problem for Sir
Archaeologists dig up dinosaurs (‘Diggers at Dinosaur Cove’, 13 February)
and the Cretaceous is now an era (picture caption, ‘It came from outer space’,
20 February). Oh dear. Sir will have a hard time teaching correct terminology
if his students quote New 杏吧原创 back at him.
Anthony Gouldwell Aylestone, Leicester
Letters: Metallic gas
Can anyone help me? As a teacher I point out to students every year
that helium is a non-metal although the ending -ium is usually reserved
for metallic elements. Helium was discovered in the Sun by spectroscopy
and no one knew if it was metallic or non-metallic, so why was the -ium
suffix used and why wasn’t helium renamed helion when its nature was discovered?
Tony Turner Pakuranga, Auckland New Zealand
Letters: Lockerbie lessons
I applaud Daniel Clery’s article ‘Can we stop another Lockerbie?’ (27
February), and particularly his comment that passengers do not appreciate
a game of Russian roulette.
Before Lockerbie the US Federal Aviation Administration ruled that all
US airlines must identify all unaccompanied suitcases and physically inspect
them. The British took the view that only the bags of passengers who had
failed to board had to be removed from the aircraft before take off. Since
the Lockerbie bomb case had never had a passenger with it, the British position
was impotent to detect it, whereas the US regulations should have done so.
Unfortunately the US did not enforce its regulations nor did the British
police theirs. The result was that apart from the bag with the bomb inside
it, the Lockerbie aircraft took off with the bags of a no-show passenger
on board as well.
As Clery says, the airlines cry out about how regulations requiring
identification of all unaccompanied hold baggage would damage the smoothness
of their operations, but most of us would put up with a lot to safeguard
those we love. The human animal has a natural fear of falling five miles
to his or her death.
There was on the market before Lockerbie an electronic system (produced
by the company BRaLS) capable of generating and reading bar-coded luggage
tags and so identifying unaccompanied bags.
Now a second British system is available (produced by Videcom) which
has been put into operation by Virgin at Gatwick and has also been extensively
tested by British Airways. Such electronic systems will actually make hold
baggage handling quicker and more accurate, will virtually put a stop to
the expensive misrouting of bags, and will be cost-effective.
Meanwhile, the Department of Transport recently announced reconciliation
of all hold baggage mandatory ‘as soon as practicable’ – this could be by
the end of 1993. Since, as Clery’s article suggests, the world is mercifully
short of terrorists who are prepared to travel knowingly with their own
bombs, the ability to identify the unaccompanied ones will mean that ‘in-depth
security procedures’ can be concentrated on that small group of bags, perhaps
five per jumbo.
We, the relatives of those who died at Lockerbie, cannot see how the
current aviation security system can justify keeping terrorist threats hidden
from the public, while at the same time failing to put into place adequate
security to provide protection against those threats. With the new electronic
hold baggage sorting systems, even the airlines’ cries of ‘loss of profit’
are no longer valid.
If a passenger ‘fails to board’, his or her bag must be removed from
the plane. The resultant delay to a large jet at Heathrow will cost around
拢400 per minute and the plane will miss its ‘slot’. Add this to the
high cost of retrieving misrouted bags from the ends of the earth, and using
electronic bag sorting systems becomes financially viable, without even
invoking the need to protect life.
If the Department of Transport sticks to its timetable, and enforces
meaningful security procedures for unaccompanied bags, then Britain should
have an aviation security service second to none by the end of 1993.
I hope the Lockerbie relatives will be in the forefront of those who
sing its praises.
Jim Swire Bromsgrove, Worcestershire
Letters: Optics and aliens
Those of us in the NASA Search for Extra Terrestrial Intelligence programme
who hosted Nigel Henbest’s visit a few months ago feel saddened and disappointed
by his article ‘When will Earthlings see the light?’ (Forum, 12 December).
The essential problem with optical SETI as compared with microwave SETI
is the orders of magnitude greater power required when all factors are taken
into account. This is because of the thousand-times-higher energy per photon.
It is true that the sharpness of antenna beams depends on the diameter
measured in wavelengths and beams are therefore obtained at a given sharpness
with much smaller radiators at optical frequencies. The other side of that
coin is that one cannot get as large a collecting area for the receiver
at optical frequencies without the beam becoming too sharp to use. So the
directivity is a two-edged sword.
One cannot in fact make full use of the directivity obtainable in the
transmit mode without much better data than is now available on the proper
motion of stars. One cannot point a sharp beam at a star and expect to hit
its planets. One must aim where the star will appear one round-trip light-time
from now.
Henbest states that lasers have two great advantages: their high frequencies
permit you to send a lot of information very quickly, and their beams do
not spread out as they travel while radio signals do. Is he confusing channel
bandwidth with operating frequency? And did he miss the point that our use
of the narrowest channels we could economically produce was a deliberate
attempt to match our detectors to the narrow bandwidth of steady components
of the received signal?
Microwaves per se are hardly low frequencies: they are octaves higher
than our TV channels. In any event, he should be glad that laser beams do
spread just as radio beams. Otherwise, he would never thread the eye of
any receiving antenna light years distant.
Bernard Oliver SETI Office, Ames Research Center Moffett Field, California