Humanity's cradle
While reading the many elaborate schemes discussed by Jim Giles for mitigating our effect on the climate (3 April, p 6), I was struck by two salient points about the human condition. First, how innately ingenious and creative we are, and secondly, how unable we are to notice the obvious.
Space-based light reflectors, cloud seeding and artificial trees are all very exciting, but why do we miss, or choose to ignore, the low risk, low cost and middling effectiveness of reforestation? It appeared on the accompanying chart, but was notably absent in the text.
Humans are profoundly childlike in outlook. Perhaps it is time we grew up and did the mundane chores, like planting trees globally.
No-brainer
As part of your “Nine big brain questions” special (3 April, p 26), Celeste Biever made a reference to the familiar problem that we “have no way of proving we are not the only self-aware individuals in a world of unaware ‘zombies'”. I have often wondered why this doubt persists when there is a cogent argument for accepting the consciousness of others.
The only knowledge we have of the nature of consciousness is our own direct personal experience of it. A zombie, lacking consciousness, could not have any comprehension of conscious experience, in the same way that a person blind from birth supposedly has no understanding of colour. This would mean that a zombie would be unable to discuss the subject with a conscious entity.
Since we discuss consciousness with other people, we have good reason to believe that they are as conscious as we are.
From Anna Wood
The link between the mind and body is interesting and complex, but Linda Geddes should take care when asserting that the wise doctor should “probe the mental state of a patient whose symptoms are hard to explain physically”. In fact, it is an arrogant doctor who will do this without being mindful of the deficiencies in medical knowledge.
It is naive to believe that we understand everything about the human body, and unacceptable that an absence of certain physical symptoms automatically makes the patient mentally ill. In the past, people with multiple sclerosis and diabetes have been wrongly given a psychological diagnosis, simply because doctors could not find anything physically wrong with them. Today it is patients with ME (myalgic encephalitis) who suffer this mistreatment.
Rather than assuming a diagnosis of mental illness, the wise doctor will diagnose both physical and psychological illness according to available evidence 鈥� and be prepared to admit that he or she does not know the answer when the necessary evidence is lacking.
Glasgow, UK
Multiversal mirror
If I read Amanda Gefter’s fascinating article right, for observers outside a black hole all information about stuff that has been sucked through the event horizon is smeared across the surface of the horizon (6 March, p 28). It’s a hologram. Thus the holographic principle: that the surface of every volume, including the infinite multiverse, contains all information within the volume.
Now, although we may not be able to access the multiverse, the boundary between it and us will contain all multiverse information, so if we can access the boundary we can make predictions about the multiverse and test them, observing and interacting with information about it.
Or does this overlook a huge difference between information in black holes and in the multiverse? Everything passing into a black hole started out in our domain, but nothing in the multiverse did. Or did it?
Atheist selection
Your editorial “Time to accept that atheism, not god, is odd” makes the case that since atheists are a minority group, they should be considered abnormal (6 March, p 3). However, almost every belief system has a history of stamping out non-believers, whereas there are, to my knowledge, no recorded instances of the reverse, so there is a definite selective pressure against atheism. Calling atheism abnormal is then no more logical than calling left-handedness abnormal.
Wonderful water
Marcus Chown reports on James Brownridge’s theory that the reason hot water freezes faster than cold 鈥� the Mpemba effect 鈥� is a consequence of supercooling in the water that started off cold (27 March, p 10). However, after many years of getting my student teachers to investigate the phenomenon, the neatest explanation I have found centres on the role of convection.
We often compared two samples, one of which started hotter than the other, and found that the hot water contained more ice than the cold. Crucially, they were both partly frozen. This discounts the supercooling explanation because once the first ice crystals had appeared in the supercooled water it would have quickly formed more ice than had formed in the hot water.
A better explanation relates to the rates at which heat can be transferred away from the water. We postulated that when placed in a freezer, cold water would quickly separate into three layers: water at 4 掳C at the bottom of the flask, 0 掳C ice at the top and room temperature water in between. This separation would leave conduction as the only method available for further heat loss.
In the hot water system, however, convection currents would persist, preventing this static phase from establishing and allowing a much faster heat transfer to the freezer.
It would be an interesting check on hypotheses about the Mpemba effect if the test were to be carried out under zero gravity, which would result in suppression of thermal convection.
Convection conviction
Scott Turner and Rupert Soar suggest that the circulation of air in termite nests is driven by wind blowing across the mounds rather than by convection currents within them (20 February, p 35). This may be so in the mounds they studied in Namibia 鈥� although it does not explain why the nest does not overheat and the termites suffocate on windless days 鈥� but it is not the case everywhere.
I have observed that the Macrotermes nests in Sudan and east Africa, and the Odontotermes nests in India use convection currents, as previously suggested by entomologist Martin L眉scher. You can tell by placing your hand over the top of a mound chimney: you should feel the warm, moist air coming out. It is possible to distinguish live termite nests from abandoned ones in this way.
A more dramatic demonstration is achieved by dusting talcum powder at the base of the mound. After about 30 seconds a plume of talc erupts from the top of the chimney.
Sugaring the pill
Colin Jacobson’s letter on homeopathy (20 March, p 25) annoyed me.
First, he argues that homeopathy is good because it costs less than conventional medicine. Of course, water and sugar should be cheaper than clinically tested drugs, but that does not make it useful.
He then argues that homeopathy satisfies a real demand in healthcare, to the inconvenience of big drug companies, ignoring the fact that selling water and sugar to people is of great convenience to the big homeopathy companies.
Next, Jacobsen suggests that the author of the original article on homeopathy, Martin Robbins, should take into consideration the anecdotal evidence of his miraculously cured dog, disregarding the importance of the scientific method.
Finally, he rounds off by stating that homeopathy is “cheap, effective and safe”. There are cheaper placebos on the market, more effective ways to treat people and there are safer, more reliable ways to run a healthcare system.
The day we found out we could give sweets to educated adults to make them feel better was the day we should have realised that people really are fools unto themselves, and that fools and their money are soon parted.
Glass flowing over
In his article about persistent observations and the sometimes slow pace of science (19 December 2009, p 58), Stephen Battersby suggests that “a carefully controlled 10,000-year experiment should do the trick” of seeing whether “any form of silica glass is fluid at room temperature”.
That experiment has already been started. I recently saw the exhibition Molten Colour: Glassmaking in Antiquity at the Getty Villa in Pacific Palisades, California. On display are beautiful glass vessels dating from 2500 BC, which makes them almost halfway through the time span Battersby calls for.
The vessels are all standing upright, showing no sign of either flow or sag.
For the record
鈥� We mistakenly illustrated a story about “pointillist graphics” for computers (3 April, p 18) with a standard polygon image; had it been pointillist it would have been less blocky.
鈥� The physicist Eugene Wigner was Hungarian, not German (10 April, p 28). He studied in Germany until 1930 and became a US citizen in 1937.
鈥� We misspelled Kerri Moloughney’s surname in our article on aerial detection of grave sites (10 April, p 18).
鈥� The statement “Shakespeare’s prose would have a higher entropy than Egyptian hieroglyphs or Morse code” had low information content (10 April, p 11). Shakespeare coded in Morse and in Roman script would have the same entropy, higher than that of, say, a laundry list, as it is less predictable and less “ordered”.