Gingered up
Your article states that ginger can help to quell nausea
(18 March, p 21).
This has been known for years, but it’s nice to see it tested scientifically.
I’ve worked with many different charter boat skippers, and several of them
carried a packet or two of Ginger Nut biscuits to offer to more susceptible crew
and passengers to fend off sea sickness. However, no one has yet been able to
explain to me just how ginger achieves this, so it would be interesting to know
the mechanism.
Hole in the head
In the article about an allegedly Roman terracotta head found in Mexico, it
was said that the Max Planck Institute of Nuclear Physics in Heidelberg used
thermoluminescence (TL) analysis to estimate that this head was fired 1800 years ago
(12 February, p 7).
This is not correct. A couple of years ago, drilled powder from this head was
submitted by anthropologist R. Hristov and geoscientist P. Schaaf to our
laboratory for thermoluminescence dating.
For methodological reasons, one can only apply an “authenticity TL test” to
such drill powder, resulting in larger uncertainties than in proper
TL dating. However, even when applying this authenticity procedure to the
sample powder, major difficulties were encountered, since the material did not
pass the so-called plateau test. We finally concluded that the figurine has an
apparent TL age range of between 730 years and 2880 years.
Although this result does not disprove the alleged Roman manufacture date, it
certainly cannot be used in support of the statement that the terracotta head
“was fired 1800 years ago”.
Right to spy
You state that the human rights group Liberty is concerned about commercial
organisations making it possible to eavesdrop on satellite telephone calls
(11 March, p 15).
In fact, all countries have laws allowing phone-tapping in case of serious crime.
No police force would want to permit a communications system to operate that
prevented it from solving crimes, as such a system would attract criminals.
Motorola, the originator of the patent mentioned in the article, was not
offering to set up a commercial spy service, but merely showing that a satellite
telephone service can support national laws.
This just leaves the difficult task of determining which nations have
jurisdiction over a particular satellite call, given that in Europe the
satellite may pass over two or three nations in the course of a single call, and
that the call may be routed via satellites over entirely different nations.
Telltale tattoo
All your correspondents on the subject of “tan tattoos” are far too young
(11 March, p 57).
The tattoos date back even further than the 1960s.
I had a cousin who, because her mother was Spanish, had the sort of skin
which took on a very enviable tan. When she returned to England after living in
Italy for several years, she had the name of her current boyfriend “tattooed” on
her arm by having had a paper cut-out of his name stuck to her for a few hours
in the strong Italian sunshine. And that was in 1934.
She was actually en route for South America and had to stay with us for
several weeks before venturing on her new life, where she married someone with a
quite different name.
Put salt on it
As your correspondent’s story about a hospital moved to a salt mine during
the Second World War suggests, it is entirely credible that high concentrations
of salt in the environment could help to prevent the spread of infectious diseases
(11 March, p 57).
The vast majority of bacteria that infect humans are inhibited from growing by
sodium chloride.
Fish and meats are prepared by adding large amounts of salt or soaking in
brine to preserve them. The salt draws out the water from the cells and
essentially dries them, thereby preventing the foodstuff from serving as fodder
for organisms that can cause food spoilage or food poisoning.
There are one or two notable exceptions, however, to salt as a universal
panacea for preventing the spread of human disease. The first is cholera and the
other is the MRSA “superbug”. Both of these can tolerate quite high salt
levels.
Indeed, in the medical microbiology laboratory, “salt enrichment” is used to
find these dangerous pathogens. For example, to find MRSA amongst the
environmental soup of other organisms, a swab is taken of the thing or person
being tested and incubated at body heat in a 5 per cent sodium chloride solution
for a day or two. The salt kills everything鈥攅xcept the MRSA, which grows
merrily in the culture.
I would hesitate to spread salt around the hospital just yet鈥攊t would
kill everything in sight but leave the wards full of MRSA, putting the patients
at increased risk rather than preventing trouble.
Cut off in Kent
You suggest that, by the time Iridium launched its satellite phones in 1998,
cellphone companies had already expanded to cover the majority of locations that
people want to phone from
(25 March, p 9).
This may be so in London, but beyond the M25 motorway cellphone coverage is
more patchy than the cellphone companies admit. Their “98 per cent of Britain
covered” actually means “98 per cent of homes covered”. This is very different
from 98 per cent of Britain’s land area.
At my home in Kent (which is hardly bandit country), cellphones only work out
of doors, and there are many areas where they are utterly useless. Strikes me
that a satellite phone might be rather useful.
Shifty images
Despite research that suggests that half of Britons will not switch to
digital TV, the British government intends to end analogue broadcasts in 2010
(18 March, p 5).
In my experience, digital TV is worse than analogue. First, you create a
system in which signals can be broadcast perfectly, then you compress the hell
out of the video. The result is very poor quality TV, in complete contradiction
to the purpose of going digital.
Perhaps compression will improve, but the demand to deliver more channels at
least expense will always push broadcasters towards the cheapest solution. My
bet is that the current batch of bad artefacts鈥攕uch as “compression
halos”, loss of texture (with grass, bricks and so on), shifty images (shadows
moving against stationary objects) and more鈥攁re not going to go away.
We're not alone
So Peter Ward believes that the life on our planet is unique and would have
the Earth returned to the centre of the Universe
(18 March, p 46).
Let us examine his main points. The stable supply of stellar energy that life
needs to evolve is not the sole preserve of spectral class G2V stars like our
Sun. There are thousands of stars in our galaxy with lifetimes and stability
characteristics conducive to the emergence of multicellular organisms and
possibly intelligent life.
As for the idea that Jupiter’s orbit鈥攚hich may help protect Earth from
collisions鈥攊s unusual, the kind of extrasolar planets discovered to date
has been biased by the method of discovery. Planet hunters look for Doppler
shifts in a star’s light, which will be most pronounced when the associated
planet has a very short orbital period (in other words, is very close to the
star), a high degree of orbital eccentricity and a mass of several Jupiters.
Caution is thus justified when constructing hypotheses on such a skewed data
set.
As for the notion that the chemical composition of the Earth is “right” for
life鈥攖he make-up of any stellar system is derived from the composition of
the interstellar gas cloud, which collapses to form stars and their associated
planets. The composition of the interstellar cloud is, in turn, derived from the
number of supernovae (in which heavy elements are formed) that have occurred in
a galaxy since its formation. This is not a “happy accident”, merely a function
of time and the physics of stellar evolution.
Peter Ward also states that the Earth’s position in our Galaxy is important.
Granted, but many stars occupy the habitable zone some 1500 light years wide and
30 000 light years from the galactic centre. It has been estimated there are 1
billion stars in this zone, of which 100 million may have habitable (stellar)
ecospheres.
I suspect that when better instrumentation and analytical techniques have
been developed, we will find that Earth-like planets are numerous and not a
cosmic quirk.
Letter
Let’s not rest on our laurels just yet. Even if we don’t find any little
green men, I’m sure the adventure of looking for them will repay our efforts
many times over.
High risk jobs
In the issue of “Inside Science” on radiation and risk
(18 March),
you make the statement: “Workers choose to risk exposure, whereas the public
is likely to be exposed unwittingly or unknowingly.”
The idea that workers are sufficiently empowered to make decisions on the
risk they face is a dangerous one. It is managers who control the processes, and
managers who carry out risk assessments. Workers are rarely given sufficient
information about the hazards they face or the consequences of exposure. Even
when they are informed, what choice do they have but to accept the risk or leave
their job?
The public sector union UNISON has argued for years that the levels of
radiation exposure deemed acceptable for workers in this country are far too
high.
There is no “safe” level, yet the European Union’s recommended maximum dose
for workers in any one year is 50 times that for the public, and even that is
often exceeded.
Noninterference
Michael Heyman opposes introducing into Asia the genetically modified “golden
rice” that can reduce vitamin A deficiency
(26 February, p 57).
He argues that this would be Western interference.
Wouldn’t preventing Asian farmers from growing this rice also be
interference?