The affairs of tides
Hans van Haren correctly points out that tidal flow is not likely to meet all our energy needs, but his suggestion that it is therefore not worth trying to exploit this energy source is wrong (3 April, p 20).
No single resource can ever provide all our energy. “Only” 20 per cent of our electricity needs would be a very substantial contribution to replacing fossil fuel, equivalent to the world’s installed hydroelectric capacity.
He is also wrong when he says there are only 20 suitable sites for extracting tidal stream energy around the world. There are more than that number of sites around the UK alone.
We have the world’s first commercial-scale tidal turbinein Strangford narrows in Northern Ireland. It is subject to a pioneering independent environmental impact monitoring programme, and the operating licence specifies that it will be shut down if it causes any significant environmental damage. Killing fish would clearly be within that category.
Perhaps van Haren could explain in what ways extracting a fraction of the energy in a tide race using slowly rotating turbine rotors can cause environmental damage. No explanation is needed of why failure to develop clean sources of energy will cause disastrous environmental damage 鈥� further acidification of the sea in particular.
Green economists
Your catalogue of efforts to reduce the wholesale rape and pillage of our precious planet was fascinating (13 March, p 34). However, you make no mention of the motivation behind these disparate initiatives and I would love to know more.
Economists traditionally insist that effects on the planet are “externalities”, which is to say that they will be ignored by business unless they are incorporated into prices via taxes. Could it be that economists have got yet another thing wildly wrong, and if so, what are the driving forces of these endeavours?
After the flood
Your interview with Joel Morgan, environment minister of the Seychelles, helped me understand something that had been puzzling me about the Copenhagen climate change summit last December (27 March, p 25). Why were Tuvalu and other small, low-lying island states treated with such hostility by the big players when they insisted on strong, binding measures against their countries disappearing?
If these island states wholly or partially disappear, then the hundreds of thousands of square kilometres of exclusive economic zones around their myriad islands will also disappear. Where these countries used to be, huge areas of shallow ocean would become freely exploitable for seabed minerals. All their fishing grounds would also be available.
It won’t be other small island states that exploit these new opportunities, but we know who can and will.
Road rationality
Nic Fleming’s article on semi-autonomous vehicles was far more rational than most of us are when it comes to our cars (3 April, p 34).
Presumably a semi-autonomous vehicle would be programmed to keep to the legal speed limit. But how many of us want to do that consistently? Those who oppose speed cameras on irrational grounds will surely be just as irrational when it comes to automated speed control.
And do drivers really want to travel in convoy? There are clearly some drivers who simply want to be ahead of the vehicle in front, and will do whatever it takes to get there.
In all this technical development, what psychological studies have been carried out by the car-makers to determine the acceptability of automated systems? And how will motorists be persuaded to adopt them?
From Peter Wicks
I was surprised to be reminded of a Beezer comic from the 1960s by Nic Fleming’s article on driverless cars. In a story called “The Year of Bedlam”, a driver would habitually take his car under manual control from his house down to the road, where he handed over control to a series of beacons alongside the road. There was no fail-safe written into the system, though, so when the electrics went down it failed, resulting in urban carnage and devastation.
One hopes developers of hands-off driving systems will take note.
Bulford, Wiltshire, UK
Cause or correlation?
Jared Diamond and James Robinson argue that “natural experiments are not inferior, second-class science” (27 March, p 28). I disagree: natural experiments are not experiments at all but observational studies.
In the case of the historical epidemiological study discussed, John Snow thought the cholera outbreak in London was due to a water-borne disease. To find out, he compared the health of people who drank water from the well closest to the cholera outbreak with that of men who worked at the brewery, and who drank only beer. He turned out to be right, but that does not mean it was these observations that clinched it.
There are many possible explanations for differences in the disease rates in the two groups. For example, the brewery employees were all male and had different socio-economic status (through employment, alcohol intake and so on) to the population who drank from the well.
In medicine there are numerous examples of observational studies giving the wrong answer. For instance, observational studies repeatedly showed cardioprotection for women on hormone replacement therapy. Controlled trials have since shown this to be false, and that there is actually a small adverse cardiac risk.
Fat offset
Peter Aldhous reports that test subjects who make green choices subsequently exhibit a greater tendency to lie and that people who improve their homes’ energy efficiency thereafter use their heating more (27 March, p 11).
Is this a general facet of human nature that also exhibits itself in dietary choices? Does ordering a skinny latte result in a greater propensity to buy a slice of cake or a doughnut?
The prevalence of low-fat products could, therefore, cause weight gain, by giving one a licence to indulge in a fatty treat. I doubt that the fat in milk has a significant effect on a person’s waistline, but I’m pretty sure cakes and doughnuts do.
Anty literature
E. O. Wilson says, of his new novel Anthill: “This is the first time anyone has written about the lives of ants from their point of view” (10 April, p 38).
Wilson seems unfamiliar with the works of the French science-fiction writer, Bernard Werber. In the 1990s, Werber wrote the trilogy Les Fourmis (The Ants), about the lives of ants from their point of view. His books have been translated into 30 languages, including English.
Accidental origins
Bob Holmes reports on evolutionary biologist Mark Pagel’s theory that speciation is best explained as a consequence of single accidental events rather than by the gradual changes caused by natural selection (13 March, p 30).
This resonates with Nassim Taleb’s suggestion in his book The Black Swan: The impact of the highly improbable (reviewed 7 April 2007, p 52) that the structure of modern society is due to the impact of sudden extreme events, from the cause of the first world war to the creation of the internet. Taleb also suggests that the Gaussian normal curve, the recognisable bell-shaped graph used to represent normal distribution, should be replaced by fractal representations that work on the basis of power law distributions of events, which is a far better statistical measure for both science and economics.
Key to safety
Nic Fleming’s article on the safety issues arising from the increasing computerisation of cars (27 March, p 20) put me in mind of a safety solution based on a close call I once had.
Driving at about 80 kilometres per hour in a snowstorm, I became suddenly aware that the throttle pedal was no longer working and I couldn’t slow down. My options were to force the gear lever into neutral, which would cause the engine to over-rev and perhaps disintegrate, to attempt to use the brakes (if they were working) to stall the car, or to switch off the ignition.
I chose the last option, and managed to coast the car to a halt on the hard shoulder, where I discovered that snow had packed itself behind the throttle lever, preventing it from closing.
Clearly, any of my options would be preferable to the high-speed crashes mentioned in your article. It seems to me that a hard-wired ignition switch is the cheapest and most practical fail-safe for cars that increasingly rely on complicated computer hardware and software.
Plant a dead donkey
I was pleased upon reading Linda Geddes’s piece on changes in vegetation around animal graves (10 April, p 18) to see another example of folklore being vindicated by science. In the part of rural Somerset in the UK where I grew up, nobody would dream of planting an asparagus patch without first inserting a dead donkey into the underlying soil. The patience shown in waiting for the long-lived animal to die, along with the determination required to dig a hole large enough to park a donkey in, was unfailingly rewarded with much improved yields.
Presumably, these flourishing fields would be observable from the air with the right spectroscopic kit.
For the record
鈥� RNA-based viruses replicate in the host cell’s cytoplasm. The mimivirus, on which we reported, joins the poxviruses as the only DNA-based viruses to do so (10 April, p 10).
鈥� The research we reported in our article on carnivorous plants and heavy metals was carried out by Iain Green and Christopher Moody (10 April, p 7).
鈥� Steve Haake is a sports scientist at Sheffield Hallam University, UK (3 April, p 15).