By the left
Q: Why is it that when two people walk together they often subconsciously
start to walk in a synchronised manner. Is this some natural instinct?
(continued)
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A: The next time you walk alongside somebody, walk out of step. Then try to
follow the conversation you are having. You will soon fall back into step,
because once you are in step with the other person, it is easier to watch where
you are walking and then turn to look at them. Communication is easier with
another person when you are in close proximity and when both faces are
relatively stable and not bobbing all over the place.
Hamish
by e-mail, no address supplied
A: Here is a more prosaic (less sociologically inclined) explanation. When
people walk they have a slight side-to-side sway. Two people walking together
and out of step would bump shoulders every second step.
Peter Verstappen
Kaleen, ACT
Stabbing pain
Q: Why is it that when someone mentions a personal gory accident such as a
deep cut with a knife, I feel a contraction in my testicles?
(continued)
A: Your correspondents seem to be suggesting that this is exclusively a male
experience. Let me assure them that there are certain similar circumstances in
which I feel my womb contract. This can hardly be anything to do with my
鈥渞etract(ing) the vulnerable appendages out of harm鈥檚 way when danger
threatens鈥�, as one of your correspondents suggests. My own vulnerable
protuberances are unaffected.
Elizabeth Young
London
Now wash
Q: Do normal hand soaps actually kill germs? We are always encouraged to wash
our hands after a visit to the toilet, but does this really make much
difference? I remember a biology experiment at school where we pressed our
fingers into a Petri dish and cultured the bacteria that were deposited there.
As I remember there was no difference between the two.
(continued)
A: The reason why you may not have been able to differentiate between the
cultures of bacteria from washed and unwashed hands could be because of the way
in which bacteria grow under conditions of limited resources. A graph of
population against time shows a sigmoidal shape. Initially, the population
increases in an exponential manner and then levels out as food and space begin
to run out. There may have been more bacteria from the unwashed hand but this
could not be determined because both populations eventually reached the limiting
maximum and appeared identical.
Adnaan Ali
by e-mail, no address supplied.
A: When I had a wart removed from my hand a few years ago my doctor told me
an interesting fact about the microbial risks of washing your hands. There is a
variety of wart which specialises in colonising wounds and can be recognised
because it is found in lines on skin that have been caused by grazes. The doctor
told me it is common in surgeons because they scrub up before operating.
David Frin
London
Fried potato
Q: Years ago I bought a 鈥減otato clock鈥�. This strange device made a circuit
with a digital clock attached by two wires to a potato (though it also worked
well with cola). The potato or cola could provide enough energy to run the clock
for a while. How did it work? I presume that if you used more or bigger potatoes
you could run something more powerful. Has anyone studied this phenomenon?
A: The energy powering the potato clock does not come from the potato, but
simply from the electrochemical properties of two different metals being placed
into a salt solution. As the questioner correctly notes, cola also works, as
does any simple salt solution鈥攖ry it with table salt. The potato acts as a
compact, slow-to-dry, salt bridge.
Nevertheless, plants routinely generate large electrical
potentials鈥攎uch greater, in fact, than those in animal cells. These
potentials are generated mainly by the activity of energy-consuming ion pumps
embedded in most plant cell membranes. The activity of these pumps leads to the
establishment of electrical field strengths of over 20 million volts per metre.
If only we could plug into this.
Mark Tester
Department of Plant Sciences
Cambridge University
A: This item took me back 18 years to the time when I was writing my PhD
thesis. I was working on electrochemistry, and looking for a quotation to go at
the start of the thesis. I found it in The Times: 鈥淢r Anthony Ashill, a
watch repairer of Kidderminster, Hereford-Worcester, has managed to keep a small
electric motor running day and night for the past five months powered by a
single lemon.
鈥業 connected two wires to a lemon with a piece of copper and a piece of zinc
and soldered them on to the motor. Although the lemon is now black and
shrivelled the motor is still going strong. If I can make my small motor run for
month after month on a single lemon, just imagine how much 鈥渏uice鈥� there must be
in a whole sackful鈥�, Mr Ashill said.鈥�
Interestingly, your correspondent makes exactly the same mistake as Mr
Ashill, though in less picturesque language鈥攖he lemon or potato is just
the electrolyte in a battery.
Roger Newman
by e-mail, no address supplied
This week鈥檚 questions
Perfect pitch: In musical circles it is often claimed that the key or pitch
of a piece can have a profound bearing on the mood conveyed. For example, if
played in the key of E major, the music may be considered bright and powerful
but in F major, peaceful or contemplative. This is surprising, given that all
keys contain similar intervals when played in equal temperament.
Few people have perfect pitch and the frequency shift in the above example is
only one semitone, just under 6 per cent. It seems unlikely therefore that such
an effect could be consistently experienced by a wide range of listeners.
Have any tests been conducted, perhaps by simply playing recordings at
different speeds and, if confirmed, what might be the physiological basis?
John Allsop
Rayleigh, Essex
It鈥檚 handy: Much of the rise of the human species up the evolutionary ladder
has been attributable to a palm, four fingers and an opposing thumb. The human
hand can manipulate a large range of tools and objects with a wide range of
sensitivity. Is there any other design, which might be able to occur naturally,
that would offer its owner the same level of dexterity and ability?
Gregory Mackenzie
Drummoyne, New South Wales
A similar question was asked by Stephen Saxon of Stockport,
Cheshire.