Don't dig up the dump
You say that around half the aluminium cans thrown away are not recycled but end up in landfill (4 October, p 34). Then you describe plans to dig up landfill waste and sort it mechanically to separate out the contents for recycling. Why not simply take all waste material from homes and businesses to a separation facility to get as much useful material out of it as possible?
This would result in more waste being recycled than currently is. It would get rid of the sometimes confusing bi-weekly collections of various boxes, bags and bins that mean some people don’t bother recycling because it is too much trouble. It would also reduce the need for new landfill sites, while at the same time we could be reclaiming old ones. Is anyone considering doing this?
Renewable what?
Your features on renewable energy (11 October, p 28) made only a passing reference to water power. From my window, I can see the giant turbines of the country’s largest on-shore wind farm. They were made in Germany, taken to high moorland and erected at enormous cost. Yet in the valley below, the River Irwell, once described as the most overworked in the world, is ignored as a reliable source of energy. Two centuries ago, it drove a string of mills and helped to kick-start the industrial revolution.
In writing a book about water-driven textile factories, I spent 14 years tramping the Pennines and found hundred of sites that could easily be adapted to turn water turbines of various sizes. I have no doubt that many villages could become self-sufficient in electricity. Water can be stored in ponds and reservoirs and used both night and day. The monsters on the moor are still when there is no wind.
Water also flows endlessly through pipes from high ground to consumers throughout the country. Surely it could be passed through turbines.
From John Gummer
The established method of storing large quantities of electrical energy is via pumped storage. It has been used successfully for many years and, with the increasing amount of intermittent supply from renewables such as wind and solar, many new pumped storage stations are now under construction.
In your article you fail to mention hydro power. Hydro power is a premier source of renewable energy currently accounting for about 25 per cent of the world’s electrical generation. The hydro potential of many countries is still untapped but, with the current drive away from fossil fuels, large hydro is also experiencing a renaissance.
Rye, Victoria, Australia
Altruism and exhibitionism
The Hewlett-Packard researchers’ conclusion that contributors to websites are seeking personal glory rather than performing a public service (4 October, p 23) seems a very harsh and rather nihilistic interpretation of something that I see rather as another example of the altruism inherent in any healthy individual.
Most people continue to try to live their lives at a village or clan level, where there are obvious advantages to helping those around us, not least that a helpful person is more likely to receive help. It is entirely possible that those whose contributions are viewed more often interpret this as an indication that the contribution was considered to be valuable to the group. There would be no point in continuing to post videos or opinions that were ignored: this would be a rather strong indication that the group did not find them to be helpful.
Speed limiting cars
Brian Moss suggests that all cars should be electronically limited to the speed limit (11 October, p 20). Which country’s speed limit? Is he suggesting a dynamic speed limiter, based around either GPS or transponders? How confident is he that such a system would not suddenly suffer a glitch and lose the trailing zero from a 70-miles-per-hour limit? I would not like to be in a car which suddenly and incorrectly decided it was travelling at 10 times the speed limit.
Sceptical injection
A $200 gadget to give a 19 per cent boost to engine efficiency (4 October, p 23)? I can’t believe it, and if they reduced the claim to 5 per cent I would still be a sceptic. If it only gives a reliable 1 per cent improvement competition will ensure that it is fitted as standard in every new car, with garages everywhere specialising in retro-fitting the magic kit. If I am wrong I will give a grovelling apology a year from today 鈥� but I am not holding my breath.
Pigeon footing
You say that the case of the passenger pigeon in the US is a classic example of a decline of a species as a result of hunting (20 September, p 3). While hunting did play a part in its extinction, the elimination of suitable habitat due to the industrial expansion of the US was significant too.
Controlled hunting does two things to preserve a species. One is to limit the population to a given number so that the existing environmental circumstances can support it. The passenger pigeon might have been saved had this been done. The other is to prevent overpopulation encouraging disease that would ultimately result in a dramatic drop in population density.
Life's interstellar routes
I am disappointed that Stuart Clark answered the “Where did life come from?” question in your “Unknown Earth: Our planet’s seven biggest mysteries” article by immediately minimising the possibility that life arrived on Earth in any of the ways that the “panspermia” theories suggest (27 September, p 30).
Max Wallis and N. Chandra Wickramasinghe,
Could life have arrived in our solar system aboard an interstellar meteorite? While meteorites from Mars reach other bodies in our solar system, any solar system meteorites similarly dispatched to other planetary systems hurtle through at 10 kilometres per second or more. They have an insignificant chance of being caught by direct impact or by a planet’s gravitation 鈥� so how might they transport seeds of life from one system to another?
You report Edward Belbruno and colleagues at Princeton University showing that the early solar system, when it was in a young, densely packed cluster of similar systems, could throw out catchable rocks at slower relative speeds (6 September, p 21). But this applies only to the solar system’s first 10 million years or so, when the terrestrial planets had hardly condensed. Even if these were seeded with life from the start, evolution would barely have progressed: any life forms they dispatched on meteorites would scarcely differ from those they received.
We have addressed, instead, the key problem for spreading life through the galaxy (panspermia), namely how solar system meteorites could deliver seeds of our life to a distant planetary system in formation. Its pre-planetary cloud contains large amounts of solid millimetre-sized grains, which fragment centimetre-sized meteorites explosively on collision. The system’s new protoplanets readily capture some fragments, along with any viable spores (see ).
Primitive life forms that spread through one planetary system evolve adaptively with that system. The environmental diversity and extended timescales allow galaxy-scale evolution to higher levels of genome complexity than is achievable on a single planet.
Cardiff, UK
Albatross of ill omen
I was surprised to discover a new, super-heavy 22-kilogram breed of albatross exists (4 October, p 10). I have worked with southern royal albatrosses, which are generally around 9 kilograms. These have a hard time taking off and landing, so I can’t imagine how the 22-kg monsters avoid crashing!
I recall a Mars probe crashing due to a mix-up between metric and imperial units. A large albatross would be about 22 pounds. The researchers aren’t ex-NASA employees, are they?
The editor writes:
鈥� It should have been clearer that we intended to refer to the period when albatrosses are at their heaviest, which would be when a .
For the record
鈥� We said that “levels of carbon dioxide in the atmosphere need to be cut by 80 per cent by the middle of the century” (11 October, p 3); we meant to say that the rate of CO2 emissions needed to be cut by 80 per cent.
鈥� We said that the Royal Naval Air Station Milltown, where three planes “fell out of the sky” one day (not night) in the 1940s, was in Aberdeenshire (11 October, p 20). It was in Morayshire.
Limited improbability
Tony Budd is right to criticise the kind of thinking that says, “this high-rise block of flats is designed to withstand a wind speed unlikely to be exceeded more than once in 100 years, so since its design life is 60 years, we have got 40 years to spare” (18 October, p 20). But he is wrong to say that “the correct interpretation would be that there is a 1 per cent chance that the maximum wind speed will be exceeded in any given year, or a 60 per cent chance in the building’s lifetime”. That would include the odds of the building blowing down twice or more.
If the risk is 1 per cent in any given year, then the risk in the building’s lifetime is (1 鈥� (99 per cent)60), which is just over 45 per cent. I too find that understanding of this kind of issue is rare, even among engineers. It’s nuclear engineers I worry about.
Infinite improbability
Thank you for the great article “Tools maketh the monkey” (11 October, p 42). It seems that Douglas Adams was, again, right in The Hitchhiker’s Guide to the Galaxy, where it is written: “a news report brought to you here on the Sub-Etha waveband, broadcasting around the galaxy, around the clock; we’ll be saying a big hello to all intelligent life forms everywhere, and to everyone else out there, the secret is to bang the rocks together”. It is particularly fitting that the article was published on page 42.
HIV origins
New techniques to track HIV infection in Africa show that the virus crossed from chimps to humans as early as 1908, at a time of rapid growth in the major cities in colonised sub-Saharan Africa (4 October, p 10). David Worobey notes the likelihood that high-risk sexual behaviours found in cities allowed the virus “a toehold in the human population”.
An equally plausible explanation for this toehold was the widespread use of injections in African cities beginning in the early decades of the 20th century. The use of bismuth injections to treat the yaws infection 鈥� even an incomplete dose eliminated visible symptoms 鈥� led to a belief in the healing power of the injection and its popular use as a cure for all complaints.
My research into HIV transmission in Chiang Mai, Thailand, in 1996 and 1997 documented how Thailand’s successful response to the epidemic was dependent on major efforts to extend health infrastructure. This effectively eliminated unsafe injections arising from a lack of resources, as well as injections by traditional lay healers.
From Andreas Keller
Debora MacKenzie discusses a possible link between the origin of the AIDS epidemic and “central Africa’s first-ever cities”. But the cities mentioned in the article were not the first in central Africa. Around 1550, there were already M’banza-Kongo, capital of the Kongo kingdom, and Loango, capital of the Loango kingdom.
Olfert Dapper’s Description of Africa, published in 1668, includes a panorama of Loango, showing a city comparable in size to many contemporary European cities.
Cologne, Germany
Debora MacKenzie writes:
鈥� Those earlier cities apparently did not allow HIV to persist, perhaps because they were too small or socially stable, or because their inhabitants didn’t have sex with people who ate chimps. Or perhaps they did support occasional spread of HIV, but it died out without travelling abroad. What struck the researchers about the emergence of HIV around 1908 is that this coincided with rapid, violent social change and urbanisation under the rule of King Leopold II of the Belgians and his ilk.
How green are we?
I really enjoy reading your magazine, but I am curious to know how much Virgin paid for the full page advert for “Upper Class” service (18 October, p 4). It seems to me that in an issue about the folly of growth (18 October, p 40) to advertise a hugely carbon expensive means of travel for the business travellers who fuel this growth is a bit wrong.
In the same issue (of the UK edition) are adverts for cars, laptops and BP. The one that made me laugh most was for Land Rover. It is made green, apparently, because they have built a couple of wind turbines to power the Dagenham factory 鈥� while the top urban fuel consumption given at the bottom of the ad is a whopping 22.4 litres per 100 kilometres.
Given New 杏吧原创‘s standing and position, wouldn’t it be a good idea only to advertise those companies that are really enabling a greener world?
And while we are on the subject, why are you still printing and distributing paper copies, rather then being fully online? What is the carbon cost of transporting these copies to those people who read it in the far-flung corners of the world?
Sorry, but all this just seems like common sense to me, and I’m only 13.
Renewable what?
Your special issue on renewable energy implied that its objective is to generate electricity (11 October, p 28). In fact, the primary purpose is to reduce the discharge of carbon dioxide. The generation of electricity from renewable sources does have merit, as even the best fossil-fuelled power stations convert only half the fuel energy into usable power. A renewable energy source that delivers electricity compatible with grid distribution is therefore doubly effective in reducing CO2.
The snag is that it is difficult to maintain a balance between the energy available from a renewable source and the demand for electricity at that time. The need to supply electricity compatible with the grid 鈥� at the right voltage and frequency 鈥� means that wind turbines operate only above a cut-in speed, typically a wind speed of 3 metres per second. The average wind speed over the UK’s lowlands is about 4 m/s. At high wind speeds energy output must be restricted.
A typical UK dwelling spends about five times as much on heating as on electricity. There is a demand for domestic hot water throughout the year, so an obvious solution is to equip homes with wind generators that deliver heat, replicating the energy conversion system that the physicist James Prescott Joule used to establish the relationship between mechanical energy and heat: paddles rotating in water.
From David Rose
You refer on the cover to “guilt-free energy” (11 October). What is guilt-free about growing and burning biofuels, placing barrages across every suitable estuary, and gigantic windmills coast-to-coast and out to sea? The power generation industry, including nuclear power, should be given a chance to put across its case in your pages. A study of how the French are managing with 80 per cent of their electricity generation coming from nuclear power would be most interesting.
Any more editorials like this (11 October, p 3) and readers will start to think of the magazine as Green 杏吧原创.
Enderby, Leicestershire, UK
From Anthony Higham
You say: “a large, 10-megawatt wind turbine should produce at least 10,000 megawatt-hours of energy in a year” (11 October, p 29). Where are these monsters going to be located? Constructing one of these 鈥� bigger in diameter than an Airbus A380 wingspan 鈥� for every 1000 homes sounds more like a nightmare than a dream.
Edenbridge, Kent, UK
The editor writes:
鈥� These large turbines are mostly designed for installation off-shore, where the wind is stronger and more predictable.