Letters : Icy blast
Epping, Essex
Your article on ice cubes hitting the Earth states that if ice chunks struck
the Moon they “should generate measurable seismic tremors and leave telltale
impact craters. So far, there has been no evidence”
(This Week, 31 May, p 7).
But could the impact of these snowballs explain what astronomers know as
transient lunar phenomena? Surely these rare, localised, gas-like obscurations
of the lunar surface could easily be caused by impacting ice vapourising. It
might also explain their occasionally red or bluish tints, since the expanding
water vapour would cause a rainbow effect.
Letters : Profitable nukes
London
Your report on the recent Vienna Conference of the International Atomic
Energy Agency (This Week, 14 June, p 7)
gives the impression that the nuclear
industry sees itself as a special case and requires special treatment from world
governments to become viable.
This is not the case, as British Energy’s recent financial results and the
increasing share of Britain’s electricity demand being met by nuclear power
prove. The industry is convinced that there is an economic case for nuclear
power, provided that it is treated in the same way as other sources of energy.
It does not take the view that it should be supported by subsidies or levies on
other fuels.
Neither has the industry suggested that a relaxation of radioactive emissions
is required to aid its competitiveness or that a carbon tax on coal and oil
power stations is required to make the market back nuclear power. The
environmental advantages of a CO2-free nuclear power industry are all
too apparent.
It is true that the industry’s vision of a nuclear fuel cycle in which
plutonium is used in fast breeder reactors is not at present a reality. But
there is little doubt that fast breeder reactor technology will become viable in
the future. In the meantime the nuclear fuel cycle is a commercial reality, with
fuel from existing power stations being commercially reprocessed and
recycled鈥攁 source of sustainable energy as well as considerable overseas
earnings for Britain.
Letters : Moving story
Chandlers Ford, Hampshire
It surprises me that neither Rosie Mestel
(“Feeling a little strange?”, 14 June, p 24),
nor any of the academics researching the subject, commented that
motion sickness is mostly a modern phenomenon. For all of our evolutionary
history, the motion available to humankind was largely that provided by our own
limbs, and these do not cause sickness.
It is only in this technological age that appreciable numbers of people are
regularly exposed to sensory mismatch. It follows that motion sickness cannot be
an evolved response to sensory mismatch. It must be an accidental side effect or
some other mechanism.
Letters : Coup for county
by e-mail
Roger Green suggests (Letters, June 7, p 53)
that there were better ways to
get information on election night than the Internet. Maybe, but on the afternoon
of 2 May, it was the county council’s Web pages which told me who my new
councillor was. The national media, including teletext, did not seem interested
in publishing the results of the county council elections.
Letters : Time travel
Nottingham
I notice that the Last Word has been time travelling. In the question on
“Lots of space” (31 May) it quotes a
New 杏吧原创 reference of 24
August 1997. This seems very clever to me.
Letters : Out of synch
Schofields, New South Wales
Michael Gro脽 (Forum, 7 June, p 50)
complains about dubbed sound in movies.
Due to sloppy engineering practice many broadcasters routinely transmit
programmes where the picture is not synchronised with the sound. This means that
dialogue can be heard before the actors open their mouths鈥攕omething that I
find extremely irritating, but that most people never seem to notice.
Gro脽 should be grateful he doesn’t live in some Southeast Asian countries.
Because of the poor literacy rates, subtitles aren’t an option and many
countries economise by using just one male and one female actor to add all the
dubbed voices.
Letters : Power cuts
Tring, Hertfordshire
The pros and cons of deregulation
(Forum, 14 June, p 47) seemed very relevant
to the electricity supply in our rural location.
Forty years ago there were some minor failures and an occasional major one.
One memory is of an entire winter during which we had no failures of any
kind鈥攐ur old-fashioned electric clock never needed to be restarted
manually.
In recent years the power cuts seem to have become steadily worse. We have
had to purchase a backup supply to overcome the problems caused by numerous
short breaks鈥攅ven in the summer. During the last winter we also had the
serious inconvenience of seven major breaks鈥攎ost in apparently good
weather鈥攖otalling about 25 hours. Our local ironmonger does a good trade
in domestic paraffin lamps, and we now keep several ready filled. Is this merely
a local anomaly?
Letters : Hot stuff
Harwell, Oxfordshire
Roger Allan’s excellent account of the role of silicon carbide in
high-temperature electronics
(“Crystal powers”, 14 June, p 34) is very welcome,
particularly in indicating many of the ways in which the rapid advance of
high-temperature electronics will lead to a safer, more efficient and cleaner
world.
However, the article is misleading in one respect鈥攖he status of silicon
as a high-temperature semiconductor. While it is true that most silicon chips
are not specified for operation at temperatures above 125 掳C, this is a result
of old military specifications and not a fundamental property of silicon. The
reality is that silicon can be used at temperatures as high as 250 掳C. This is
important, as the majority of high-temperature electronic applications are
expected to be within the 125 掳C to 250 掳C range for at least the next decade,
and the cost of silicon semiconductors is currently only a fraction of that of
silicon carbide. For higher temperatures, wide band-gap semiconductors such as
silicon carbide are still required.
Readers can find a considerable amount of information on this and other
topics in high-temperature electronics at http://www.hiten.com.
Letters : Send in the clones
Sheffield
It is interesting that heredity plays so large a part in behaviour,
especially as we get older
(New 杏吧原创, Science, 14 June, p 16).
Perhaps those newspaper editors who favoured human cloning in the wake of the
controversy over Dolly should be told. The line that seemed to be standard at
the time in a number of liberal broadsheets was that human cloning would not
matter, as personality is shaped by environment. Cloned individuals would have
different experiences and therefore different personalities, so clones would not
be carbon copies.
Although it would be an exaggeration to say that a set of cloned individuals
would be identical, they would certainly have very similar personalities. There
would therefore be scope to produce large numbers of people sharing certain
desired characteristics. This does not mean a mad tyrant breeding armies of
supermen. In reality, much more subtle forces, such as the requirements of the
labour market, would shape choice in these matters, its invisible hand moulding
the human genome.
Letters : Slave takeover
Northampton, Massachusetts
You report that a new genetics company based in Iceland hopes to profit by
the genetic homogeneity of the country’s population
(This Week, 3 May, p 12).
You said that almost all Icelanders are descendants of Vikings from Norway.
I admit that the Icelandic population is homogeneous, but its ancestors were
not exclusively鈥攐r even mostly鈥擭orwegian. A study done on blood
proteins several years ago showed that, on the contrary, the single group with
the greatest similarity to the Icelanders is the population of Ireland. The
strikingly high rate of red-haired people in Iceland and Ireland provides
another indirect indication of the relationship.
If you read English translations of the old Norse sagas, you notice fairly
frequent references to the Vikings taking slaves from Ireland. In other words,
the kidnapped women and men who went unwillingly to Iceland appear to have made
a bigger contribution to the human population there today than did their
kidnappers. As a third-generation Irish-American biologist, I couldn’t resist
writing to set the record straight!
Letters : Crumbs from cookies
Richmond, British Columbia, Canada
While it is true that cookies can only contain what the server sent
(Letters, 31 May, p 52),
much of the debate centres around the prospect of sites trading
cookies, and of companies tracking users across hundreds of sites by using
cookies in advertising banners. Your e-mail address can sometimes be obtained
without your knowledge, and some sites demand names or credit card numbers for
registration. The possibility therefore exists of building a profile of a user’s
browsing habits: from http://www.nsplus.com to CNN.
Cookies come in two flavours: session cookies, which disappear when you exit
the browser, and permanent cookies, which are saved in a file.
Counterintuitively, permanent cookies are identified by an expiry date. The
paranoid may read and delete their cookies file, at the risk of being presented
with the same advertising sequence every time, or do their browsing via an
anonymous service.
Letters : Virus attacks
by e-mail
Computer viruses took off in the late 1980s for two reasons. The first was
the widespread use of a common machine architecture鈥攖he IBM PC. The second
was the greater transfer of data between machines鈥� either by users
swapping discs or by the swapping of files via bulletin boards. The effect of
Internet has been to increase data swapping possibly by a couple of orders of
magnitude.
In his article
“The Internet strikes back” (24 May, p 35),
Kurt Kleiner lays
the correct emphasis on antivirus scanners. They can only detect viruses that
they know about. The big problem is the huge delay between the release of a
virus and its inclusion in a virus scanner. Buying a virus scanner off the shelf
from a dealer is almost a complete waste of money, as the product is likely to
be several months out of date.
The approach Steve White and Jeffrey Kephart take is interesting and novel,
and would certainly have the desired effect of shortening the delay. But they
are also putting into place the basic building blocks for a virus that operates
over the entire Internet, because anyone can plug in and feed fake scan strings
to the antivirus scanners.
A way around this would be to require authentication of the input strings.
This is not as simple as it sounds. While it is easy enough for IBM to sign its
strings, and for the scanner to recognise the signature, it assumes that the
user has a genuine scanner, and that it has not been attacked.
The system may have other drawbacks. The most common viruses are macro
viruses, in particular those infecting Microsoft Word documents. Will users be
happy to have confidential documents automatically sent to IBM? Unless hard
encryption is used鈥� contrary to US regulations鈥攁nyone and everyone
would be able to read these files!
Letters : Meaty mistake
Radcliffe-on-Trent, Nottingham
The largest known meat-eating animal, according to your article
(In Brief, 31 May, p 13) was
Giganotosaurus carolinii. What about
Kronosaurus or the sperm whale? Both are huge marine meat eaters, if one
counts the sperm whale’s diet of giant squid as meat.
It may be the largest known terrestrial carnivore. But it is not the largest
meat eater.