Letters: Coriolis force
I enjoyed Frank Close’s musings on the Coriolis force and how the bath
water runs out of the bath in opposite senses in the northern and southern
hemispheres (‘Science down the plughole’ Forum, 23 November). His short
article ignores two manifestations of the Coriolis force which are much
closer to home.
We all see weather maps on television and in the daily papers and are
depressingly familiar with the ubiquitous anticyclone centred over the North
Sea. Its counterpart in the southern hemisphere is the cyclone: both result
from the Coriolis force whose effect is to try to align the angular momentum
associated with the cyclone (anticyclone) with the direction of the Earth’s
rotation.
Much more dramatic effects can be seen in atomic nuclei, which, in nuclear
reactions, can rotate 1020 times per second instead of once a day as in
the case of the Earth. The gamma rays emitted in the decay of these highly
unstable nuclear systems reveal the effects of extreme rotational velocities.
杏吧原创s using the Daresbury Nuclear Structure Facility have pioneered
the techniques needed to observe gamma rays. One sees dramatic changes in
the gamma-ray pattern with rotational velocity; effects due to the Coriolis
force acting on individual nucleons and breaking down the normal ‘superfluid’
structure of nuclei.
One also sees superdeformed nuclear states, shaped like rugby balls
with 2:1 axis ratios, whose existence is stabilised by the rapid rotation.
The United Kingdom has led the World in this field for the past ten
years. Despite the impending closure of the facility at Daresbury we are
striving, in collaboration with our French colleagues, to build EUROGAM
a gamma-ray spectrometer with a sensitivity two orders-of-magnitude better
than any comparable device. We plan to run it for a year at Daresbury before
we close. It will allow us to explore in detail the subtle effects of rapid
rotation. In a sense Frank Close didn’t mean, we will be trying hard not
to let the UK’s nuclear science go down the plughole.
William Gelletly Nuclear Structure Facility Daresbury Cheshire
Letters: Not drowning
It will be interesting to hear more of Michael Honey’s research into
the characteristics of the Mexican wave (‘Just waving’ Letters, 4 January)
as the Australian cricket season progresses this winter.
A valuable addition to his findings would be evidence of whether Mexican
waves in the antipodes travel round the stadium in the opposite direction
to those in the northern hemisphere.
If so, it could be explained by the Coriolis effect on tubular alcoholic
fluids running down the gullet and the consequent reflex of the subject
in responding to the right or to the left.
Nicholas Macy Epping Essex
Letters: Making waves
While observing a motorway car jam, I noticed a peculiar thing – when
the cars begin moving again, each car in turn starts up a short interval
after the one in front, creating a wave.
This wave, or signal, travels back along the queue from beginning to
end against the flow of traffic.
The same happens when they stop again (in close spaced traffic). The
point is the cars do not start or stop in unison.
Now, in a communications line, a modulated flow of electrons carries
information from A to B – but not, on the same line, from B to A.
But, I thought, using the above principle, would it be possible to send
information back down the same line, while information is travelling in
the usual direction?
By stopping and starting the flow, the ‘start/stop’ signal would travel
back along the line, against the flow, in much the same way as the queue
of cars, possibly coding the signal digitally against an analogue signal
in the opposite direction.
Would this be possible without interference?
I presume a subtle delay occurs electrically as with each car or a ‘no
current flow’ signal would have to travel back to B instantaneously if the
cable was cut at A, giving faster-than-light communication.
Should I be in the patent office protecting my future millions? Have
I just doubled the global communications capacity?
Rian Hughes London
Letters: Shedding light
In their article ‘What is light?’ (New 杏吧原创, 2 November), Dipankar
Home and John Gribbin have shed much light on a dark area of our understanding.
But they seem to envisage a quantum world without complementarity. That
is, they would have Hamlet without the Prince of Denmark.
A microparticle simply can not be in a state which is a simultaneous
state of position and momentum. This is the bedrock of quantum mechanics.
Complementarity expositions in terms of set-ups which will exclude a precise
value for the one or the other attribute are verbal transcriptions of this
central fact, dubbed ‘mystery’ by some.
Home and Gribbin have taken the view that what happens to the light
incident on their ‘two prisms with an air-gap’ set-up is either a tunnelling
across the gap or a reflection in the first prism in a mutually exclusive
way.
Now, wave theory gives both a transmitted wave and a reflected wave,
which in quantum mechanics means non-zero probability amplitudes for both
the paths.
Only when the photon is absorbed at one of the detectors, does it acquire
a localisation, with the concomitant collapse of the wave function everywhere
else.
There is thus no qualitative difference between the double prism with
a gap, and a half-silvered mirror.
In any case, one is not saying much to say that a given single photon
behaves as a wave at the double-slit and as a particle at the detector in
the same set-up. One can only conclude, even as the authors themselves have
taken the precaution to do, that Einstein was perhaps right about understanding
the photon.
S. Sachidanandam Bhabha Atomic Research Centre Bombay India
Letters: Closet history
I would rather not get to the bottom of the lavatory cistern (Letters,
14 December) but I can clear some turbid water.
Thomas Crapper’s great-grandson has been a patient of mine and after
getting to know him I felt compelled to quench my inquisitiveness about
his name and made discreet inquiries. His great-grandfather was a plumber
and in the late 19th century he did indeed invent the valveless water waste
preventer but he did not invent the water closet, despite the claim by his
great-grandson and others that he did.
In fact, Sir John Harington, a godson of Queen Elizabeth I, described
a valve water closet that he had invented in a book entitled ‘The Metamorphosis
– Ajax’ published in 1596. (Ajax was a pun on ‘a jakes’ – a latrine).
His invention did not catch on until increasing urbanisation and epidemics
of cholera in the 19th century necessitated improvements in sanitation.
In 1870, Mr Twyford of Hanley produced a washout closet which was very
popular despite major design faults.
The contemporary washdown closet system was introduced in 1889 by D.
T. Bostel.
Although it had a valve this could be left open which permitted continuous
water flow thus wasting large amounts of water. Even when closed the valve
seal was inadequate to prevent continued water wastage.
And this is where Thomas Crapper appears in the story with his valveless
system to prevent water waste. An early environmentalist.
Amanda Isdale Harrogate Yorkshire
Letters: Fossil future
There is an interesting note to the story concerning the Maastricht
chalk (Comment, 21/28 December). In 1776, it yielded a large fossil skull
(later identified as a mosasaur).
In 1795, the French revolutionary troops were poised to take the town,
and the (German-born) anatomist Baron Cuvier persuaded the French to capture
the skull. Twelve grenadiers received the ‘finders’ fee’ of 600 bottles
of wine.
The skull still resides in the Jardin des Plantes in Paris.
R. V. Taylor Abingdon Oxfordshire
Letters: Plastic sax
A plastic saxophone was invented, patented and marketed 40 years ago.
As Graham Lyons predicts (Technology, 21/28 December) it did have superb
acoustic qualities, and it was played by Johnny Dankworth for years.
The inventor was my stepfather, Hector Sommaruga, who left school in
Milan at the age of 12 to work in a butcher’s shop.
Martin Gregory British Veterinary Project San’a Republic of Yemen
Letters: Fertile orgasms
I was surprised to read the note by Peter Spinks (Science, 21/28 December)
that scientists carrying out a study on humans in Denmark claim to have
recently shown that penetration of the vagina by the penis from behind or
the side results ‘in the most climactic orgasm for the female and the best
chance of fertilisation’.
Particularly curious is the sentence, ‘The deeper the penetration, the
more profound the resultant orgasm and hence the greater the chance of ejaculated
sperm entering the ovaries’. Viviparous bony fish exhibit intraovarian fertilisation
(and gestation) but does this really take place in humans as well?
Secondly, it would be interesting to see the evidence for the apparent
causal relationship between orgasm and fertilisation, as many factors, including
the time of ejaculation in relation to that of ovulation, determine whether
or not fertilisation takes place.
Thirdly, since the Kinsey report of 1953, the primary site for stimulation
to orgasm in the female has generally been considered to be the clitoris
not that of vaginal penetration (see Stephen Jay Gould, Bully for Brontosaurus,
Chapter 8 ‘Male nipples and clitoral ripples’, Hutchinson Radius, 1991).
As Gould points out, it is, after all, the clitoris not the vaginal
wall that has abundant sensory nerves and is the homologue of the penis.
This story seems all very strange; perhaps we will be enlightened further
at a later date.
Bill Breed University of Adelaide Australia
Letters: Fertile orgasms
I was very interested to read the article entitled ‘Ultrasound listens
to love in the lab’ by Peter Spinks and would love to know more details
of these experiments carried out at University Hospital, Copenhagen. The
results appeared to fly in the face of research such as the Hite Report
on women’s experience of sex.
Over the past decade or so it has become recognised that women have
a right to express their requirements as far as lovemaking is concerned,
and that this does not usually entail just being banged into from behind
with maximum penetration.
It has been well established that orgasms of mammoth proportions can
be produced from clitoral stimulation, without any need for penetration
by a penis at all. Was there any clitoral stimulation during the experiments
you quote?
If not, how long did it take before these women reached orgasm, as I
should think it would be longer than most men could manage.
If a women has already reached orgasm once then maybe I can believe
what the report says, but in that case there has been a crucial omission
in your account. If there’s no such omission then please, tell us how it’s
done.
Elizabeth Boothman Wolverhampton
Letters: Algal power
In their article on the carbon cycle (Inside Science, 2 November) Jonathan
Scurlock and David Hall mention using bioreactors growing single-celled
algae to take in carbon dioxide from the atmosphere, subsequently storing
them permanently or converting them to stable, useful products. Whilst we
applaud the latter idea, we are somewhat bemused at the former.
At Bristol Polytechnic, we have successfully run a diesel engine partially
fuelled on dried single-celled algae. Other workers have shown that the
use of carbon dioxide-rich exhaust gases greatly improve algal productivity;
we have calculated that the heat rejected by the diesel cycle is adequate
to prepare the algae for combustion.
First estimates for a solar power station based on this concept could,
even in the UK, produce electricity for about 6 pence a kilowatt hour.
On the other hand, if you cost the coal production, the subsequent gas
clean up, and the production and burial of the algae, we suspect that this
would be somewhat more expensive; literally digging holes and filling them
in.
Paul Jenkins and Stuart Shales Bristol Polytechnic
Letters: Mummy-longlegs
The letter of D. W. Ewer (21/28 December) has made me think over some
observations I made on the behaviour of daddy-longlegs (Tipula) on my back
lawn last year.
The adults emerged from the chrysalis only in the evening just before
dusk. The chrysalis is a thin, brown papery tube which is pushed vertically
to about 10 millimetres above ground level before the insect begins to emerge
from the upper end.
Once emerged, some daddy-longlegs sat about on the grass blades, quivering
occasionally. Others appeared to carry out a kind of random search.
This consisted of jumping about 20 to 30 centimetres horizontally in
a galumphing parabola. I think the latter were males searching for a female
(by sight or pheromones?).
Eventually one of the galumphers came across a sitter and mating took
place. Clearly, for this activity to be successful, the male (well, the
one on top) has to be able to position himself correctly while clinging
onto any handy grass blades: mummy’s long legs are essential for daddy,
too.
Egg-laying was seen to occur only in the early morning from dawn. Here
the real need for long legs became apparent.
The female held onto the grass blades (up to 8 centimetres high) and
used the legs as levers to position the abdomen vertically beneath her.
Probing the soil and pushing in the ovipositor was assisted by some back
and forth rotary movements along the long axis of the abdomen. Again, this
was facilitated by her long legs.
I think, therefore, that the female has a long abdomen and long legs
to enable her to lay eggs at spaced intervals (which she seems to do) in
a grassy habitat with the greatest economy of effort. Her elevation reduces
the mountaineering up and down the tussocks between laying-places.
A short abdomen and legs would necessitate much more clambering about
and might result in larger clutches of eggs at fewer sites. This would place
the larvae, once hatched, at a disadvantage in respect of feeding and predation
a starling finds one it finds them all).
If my supposition is correct, then leg length is related to the microhabitat,
mode and angle of egg laying by the female.
Daddy-longlegs is just built that way in order to carry out mating manoeuvres
successfully.
Anne Bonny Chertsey Surrey
Letters: Mummy-longlegs
Like any other organism, the design of daddy-longlegs is influenced
by fundamental physics.
If you are small and need very long legs to move about your environment
then it is no use having your body balanced on the tops of the limbs.
Humans have also found this out, the hard way, in the designs of many-wheeled
vehicles. If you were to be balanced like this then up goes the centre of
gravity and over you go.
It is a wonder the ‘Martians’ in Wells’s War of the Worlds driving around
in their tall machines were never toppled before they eventually succumbed
to the common cold.
Nature has beaten us again – this time in the design of underslung suspensions.
For stability, the body (or chassis) is mounted near the ground, attached
to long, bent limbs (or spring mountings and springs).
Not only does physics necessitate this stable design, but also the number
of limbs you have. Most arthropods have five, six or eight pairs of walking
legs simply because this is the optimum range of numbers of legs for ‘normal’
walking in animals of their size. Many species, in fact, use fewer legs
to move when they start running since it is physically more efficient to
do so.
Gerald Legg Booth Museum of Natural History Brighton