Before the herds
The author of your article on Africa’s environmental past seemed only to be
interested in the impact that Europeans had made on Africa
(12 August, p 30).
No interest was shown in what Africa would have been like before the herders moved
in, when hunter-gatherers dominated. It seems to me that the herders were just
as much colonists as the Europeans.
Was the bush in East Africa infested with tsetse-fly before the herders
arrived? Would buffalo and wildebeest have been as effective as cows at keeping
the grassland open? Did herders really live “in harmony” with wildlife?
Perhaps even the preceding hunter-gatherers influenced their
environment鈥攊n Australia, for example, aborigines used fire to alter the
landscape.
These questions have to be answered before we can talk about “the real world
before the arrival of colonists”.
Ill winds
We have a number of objections to Ben Eastlund’s proposal for killing tornadoes
(12 August, p 24).
First, the consequences of missing the target could be substantial. We don’t
doubt that gigawatt microwave beams would cause damage if they missed.
Secondly, we do not know the consequences of trying to prevent tornadoes
through modification of their parent thunderstorms. Even if it were possible to
actually stop tornadoes in this way, it seems irresponsible to conduct tests of
such a scheme. Since we are not sure of the outcome, we might actually increase
the likelihood of tornadoes.
Additionally, thunderstorm downdraft dynamics are extremely sensitive to the
concentration, type and size of the water particles they contain. The current
generation of cloud models, including that at the Center for Analysis and
Prediction of Storms, are not designed to fully model these “microphysical”
characteristics. Nor are they capable of simulating tornadoes.
In fact, recent research at the National Severe Storms Laboratory by Paul
Markowski shows that it is warm, not cold, downdrafts that are the most likely
to start tornadoes, and contribute to their strength and longevity. If you want
to prevent a tornado, cooling the downdraft might be a better idea.
Perhaps in 5 to 10 years, cloud models will be able to simulate correctly the
all-important downdraft that is associated with the formation of tornadoes.
Until then, it is foolish to consider tornado mitigation based on today’s
inadequate numerical models.
And suppose Eastlund’s idea works? Given that there are roughly 1000
tornadoes per year in the US, how many of them does Eastlund propose to prevent?
If he suggests stopping all tornadoes, it seems to us that he’s going to have to
disrupt virtually every thunderstorm, and perhaps even clouds that haven’t begun
to thunder. This could have a major environmental impact. If only some tornadoes
are stopped, who decides which ones?
We are not unwilling to consider new ideas, but (as Carl Sagan once noted)
extraordinary claims require extraordinary evidence. Eastlund’s claims may be
extraordinary, but his evidence is far from it.
Letter
When there is no storm in the way, what you have is a weapon that kills
biological units, leaving buildings and mechanical units intact. I hope that
Eastlund realises this before he hands the satellite’s keys to the Pentagon.
Cinnamon safety
Following your news item on the benefits of cinnamon for people with type II diabetes
(12 August, p 10),
I feel I should point out that we have recently
published an article in our health and food newsletter Gezond, where we
warned about the risks of cinnamon consumption.
The article is about the risks of coumarin, a recognised carcinogen and
genotoxic agent in animal studies, and also one of the flavourings in
cinnamon.
Many different ingredients in food products can have both positive and
negative effects. The total balance in terms of effects on our health is in many
cases still unclear.
In light of the above, we recommend that readers wait until the cinnamon
extract developed by Richard Anderson’s team is readily available. “People can
benefit from cinnamon,” Anderson notes, “but the extract will be free of toxic
ingredients such as aldehydes and cinnamic acid which could cause liver and
kidney problems”鈥擡d
More is better
The technique of multiple antennas for improving difficult reception situations
(19 August, p 20)
is well known and already in use.
UHF radio microphone systems by Sony, Sennheiser and others have used this
method for years. It has also been used in car radio installations.
The method is known as Diversity and does provide significant improvements
over single antenna systems.
Keep your head
No one would dream of drawing conclusions as to whether it is worthwhile
buying a lottery ticket by just sampling a group of prizewinners.
Why then should we heed the recommendations of hospital surgeons (and others)
that all cyclists should wear safety helmets? Their judgement is informed by
coming face to face with the very small proportion of cyclists whose heads
have been injured.
Moreover, these helmets provide very limited protection in collisions with
motor vehicles, which account for the great majority of serious head
injuries鈥攁 fact which is acknowledged neither by proponents of helmet
wearing nor the manufacturers and retailers.
If the aim of those who advocate helmet wearing is to reduce the number of
people who die as a result of a head injury, then logically they
should press for wider use of safety helmets. Five times as many pedestrians
and car occupants die in this way than do cyclists.
Letter
Your correspondent Peter Robinson of New Zealand
(12 August, p 51) asks if
the British Medical Association has investigated the health effects of
cycling.
The answer is yes. The BMA has produced two reports from its Board of Science
and Education, the first, Cycling: Towards Health & Safety (1992), and more
recently, Road Transport and Health (1997).
The BMA reports examined both the health benefits of cycling, such as
reducing the risk of coronary heart disease, and the disadvantages, such as
cycling accidents and exposure to pollutant emissions such as nitrogen oxides
and particulates (PM10s).
The BMA concluded that, even in the current hostile traffic environment, the
benefits gained from regular cycling were likely to outweigh the health risks
from cycling accidents or pollution for the population of regular cyclists.
However, we recommended that the Department of Health should continue to
research and monitor the medical effects of air pollution, with stringent limits
on diesel emissions.
What’s needed is less motor transport and more opportunities for safe
cycling.
Little islander
Feedback’s tendency to parade anything outside British experience on your
little island as “absurd” has become more than irritating. Take your
29 July column:
First, zero-depth water parks are very popular in North America, and not just
for toddlers. They are lots of fun, with sprays and fountains that appear
unexpectedly from hidden openings, and water cannons to launch surprise attacks
on the unwary.
Secondly, it’s not uncommon to receive an e-mail receipt with tomorrow’s date
when the recipient is in a different time zone. I may receive one when I send
this message to New 杏吧原创.
Thirdly, Ronald Reagan’s love letter may not have been poetic, but it was
hardly “frightening”. It was good to know he took time to write love letters to
his spouse鈥攈ow many of us never do?
Speed beacons
I recall many years ago reading a futuristic article about cars on motorways.
In this article, the author imagined all cars being fitted with a speed beacon in the form of
a lamp on the roof.
Below 30 miles per hour, this beacon remained unlit; between 30 and 70 it
flashed with a mark-space ratio dependent on the speed; and above 70 it was lit
continuously. I think this lamp was also repeated, for the benefit of the
driver, on the dashboard.
With modern electronics enabling communication from the roadside to a car, it
must be possible to relay the local speed limit into a car’s speedometer and so
to arrange for it, and such a beacon, to indicate the car’s current speed
relative to the local speed limit.
Such a device would not stop the driver travelling at any speed they wish, but it
does give everyone else clear, objective and advanced warning of the speed of the approaching
vehicle.
Net tax returns
Feedback talks of the e-mail difficulties members of the Virgin Atlantic
Flying Club had with spaces in their membership numbers
(12 August).
In Britain, the recent Inland Revenue campaign for self-assessment tax
return over the Internet omitted to warn anyone submitting their forms in this
way that they must not copy faithfully the form of any references as mailed by
them鈥攂ut must omit the spaces.
Odd one in
The letter from Eric Whitehead on IQ questions and the ambiguity of answers
(19 August, p 51)
reminded me of a question in my eleven-plus exam many years ago.
I was asked to select the odd one out from a cat, a dog and a television.
Should I select the television as the only non-animal, the cat as the one that
did not require a licence (as dogs then did) or, indeed, the dog as the one that
is not an odd one out? I do not remember my answer, but it taught me a lot about
those who ask questions.