Impossible frontier
Theunis Piersma’s article regarding the health issues of weightless space flight, while certainly correct about the biology (13 November, p 30) was incredibly pessimistic. Artificial gravity should solve all the physiological issues mentioned.
While the exact level of artificial gravity required to maintain health is unknown, Earth’s gravity would likely be the upper limit. Constant acceleration at 1 g may be beyond the capabilities of current propulsion techniques for an interplanetary journey, but 1 g centrifuges are a possibility. James Lackner and Paul DiZio showed that, by gradually increasing spin rates, humans can acclimatise to over 7 revolutions per minute without motion sickness (). Tether systems, in which one vehicle is rotated around another, could also be used to keep mass, costs and motion sickness down.
Why has so little effort has been put into space-based centrifuges? I know only of a brief tether experiment on Gemini 11, and a cancelled centrifuge for the International Space Station.
Regardless, accommodating human physiology should hardly be seen as an impenetrable barrier to crewed space flight: it is just an engineering hurdle.
From John O’Hara
When it comes to problems for crewed space flights, I was surprised Piersma made no mention of the ghastly problem of galactic radiation. This has been well described in New 杏吧原创 (19 September 2009, p 11), where it was pointed out that, while a Mars round trip would take 750 days, even in a spacecraft with 4-centimetre-thick aluminium shielding, NASA’s radiation exposure limit for the crew would be reached in less than 200 days.
Mount Waverley, Victoria, Australia
Animal empathy
I was disappointed that Douglas Fox’s otherwise enjoyable article on anthropomorphism left unexamined the empathy felt by people in hunter-gatherer societies for the animals they hunt (27 November, p 32).
In David Attenborough’s series The Life of Mammals, one episode focused on Kalahari bushmen and “persistence hunting”. This examined a hunter’s techniques and his increased efficacy from “thinking like the prey”, rather than thinking of the prey as human-like. In anthropological circles, this ancient form of hunting is widely considered central to the evolution of the modern human’s physique and ability to think up strategies and predetermine events.
It seems a reasonable conclusion that the most empathic hunters are the most effective hunters. From this, it seems possible that other predators have likewise developed a refined capacity for empathy.
In a domestic setting, dogs and cats have a rudimentary understanding of human behaviour, perhaps drawn from empathy developed as hunters, which has allowed them to adapt their own behaviour to effect beneficial interspecies cohabitation and cooperation. Without exception, these animals behave very differently in the wild, or with members of their own species.
Those decrying the assignment of “higher functions” to animals are themselves guilty of anthropomorphic conceit. Why this irrational insistence that humans alone are “special” in terms of possessing insight into the behaviour of others? The ability of any animal to anticipate the behaviour of another species seems to me to be an obvious survival trait favoured by evolutionary processes.
From Max Potter
Douglas Fox wrote an excellent article on anthropomorphism, but don’t you think the headline “Comet caught throwing snowballs” from the same issue (27 November, p 18) is taking it a bit far?
Aston, Oxfordshire, UK
Did the west win?
When explaining the effect of biology and geography on the supremacy of western science, Ian Morris writes: “People in Australia, Siberia or sub-Saharan Africa stuck with hunting and gathering” (30 October, p 32). With respect to sub-Saharan Africa, this is plainly wrong.
In his book The Civilizations of Africa: A history to 1800, Christopher Ehret reports that archaeological and linguistic evidence suggests agriculture, both arable and livestock-based, has been invented in Africa independently at least four times, in the regions of the Nile, Sudan and Ethiopia, perhaps as early as 10,000 BC.
The Neolithic technologies of agriculture, livestock breeding and pottery reached north-west Europe considerably later. Whatever caused the industrial revolution and western science to start there thousands of years later, it certainly has nothing to do with the Neolithic revolution.
It is also worth noting that Africans invented both copper and iron technology independent of the Middle East. The copper smelting and copper alloy technology of Africa that culminated in the marvellous bronzes of Benin and Ife goes back to an invention of copper smelting in Niger’s Air mountains, dated at 3000 to 2500 BC, from where copper technology spread over large parts of Africa. Iron smelting was invented in central Africa before 1000 BC and spread from there to western, eastern and southern Africa. Copper smelting was later reinvented by people in the copper belt in the Congo area.
Ian Morris writes:
鈥� You are justified in criticising what I wrote for being too sweeping (and oversimplifying). Nonetheless, hunter-gatherer lifestyles dominated sub-Saharan Africa even in the 2nd millennium AD because of Africa’s geography, rather than because of cultural or genetic differences between Africans and people in Europe or Asia.
From Richard Cragg
Surely there is a simpler explanation for western science conquering the world than Morris’s idea that it is all down to the geography of Europe.
Western society developed a culture in which making money through innovation was not frowned upon as in ancient Greece; made uneconomic by slave labour (ancient Rome); or feared as disrupting social harmony, as in medieval and early modern China. Thanks to Magna Carta and European revolutions it was less subject to interference from autocrats.
Geography did not prevent China conducting extensive maritime trade from the 10th century onwards, not only with Korea, Indochina and the Malay peninsula but also with much of the Arab world. Until the late 16th century these areas were more culturally advanced than the European colonies in the Americas.
Unfortunately China chose to withdraw from the stimulus of the outside world after 1421, and forced its merchants to do the same. This would have been hard to enforce in Britain.
I share the author’s concerns about the future, but more because the US and UK are heavily dependent on attracting foreign PhD students to do research. As China and India improve their universities and research base, this supply will dry up.
Kingston, Surrey, UK
From Geoffrey Smith
Having recently read Simon Winchester’s Bomb, Book and Compass and consequently dipped into Joseph Needham’s multi-volume epic Science and Civilisation in China, I was surprised that Morris failed to mention the many areas of science in which Chinese discoveries clearly came earlier than similar western ones.
Canberra, ACT, Australia
Robotic semantics
I read Colin Barras’s article on literacy in robots with interest as well as some amusement, given the quirks and vagaries of the English language (27 November, p 22). It is easy to envision a robot-owner presenting his digital charge with a task list consisting of: dust the floors; prepare two rabbits for tonight’s dinner.
A few hours later the robot files its report: all floors have been covered with exactly 5 millimetres of dust; both rabbits were bathed, but it was necessary to borrow two small frocks from your daughter’s doll set so they will be presentable at dinner.
The editor writes:
鈥� Thank goodness for semantics software. By programming the robot to query online databases and dictionaries, such domestic calamities may be averted.
Flipping navigation
Reading about the mechanisms by which animals use magnetism for navigation (27 November, p 42) prompted me to wonder how they cope when the Earth’s magnetic poles reverse, which happens on average every 300,000 years.
Not only would the poles reverse, but the field strength would weaken during the time of change, perhaps being close to zero for a period of time. Such events would presumably cause mayhem for migrating birds, marine life and insects. Is there any evidence of this?
The editor writes:
鈥� Rather than relying on the polarity of the magnetic field, birds and other animals have inclination compasses. These reveal the angle of the magnetic field relative to Earth: parallel to the ground at the equator, and at right angles at the magnetic poles. For this reason, birds cannot use their compass to determine whether they are flying north in the northern hemisphere or south in the southern hemisphere. When birds cross the equator, they have to recalibrate their compasses by 180 degrees, so it may be they could do the same when the magnetic field reverses.
Bounding into the air
Mark Schrope’s interesting article on electric aeroplanes (6 November, p 40) did not mention the possibility of using cables or catapults to launch or assist planes into the sky. To an outsider, it seems that such a technique could reduce kerosene usage because the fuel used would not have to be lifted into the sky.
Quantum patricide
Why is the grandfather paradox so named (20 November, p 34)? Surely the same effect would be achieved and the same paradox would result if you travelled back in time and killed one of your parents before they met. Why not call it the father paradox or the mother paradox?
Yours, a nervous grandfather.
For the record
鈥� We misspelled the name of Eberhart Zrenner in our article on retinal implants (6 November, p 10).
鈥� In our diagram showing the human and Neanderthal evolutionary tree, the label for present-day humans should have read “H. sapiens with up to 4% Neanderthal genes” (4 December, p 32).