In defence of raising meat on pasture land
Daniel Benetti suggests that land used for cattle raising should be converted to cropland to feed fish (Letters, 21 October). This misses the point. Cattle can be raised on pasture, usually unsuited for the production of annual crops. Light rocky soils erode rapidly under cultivation and are best left in permanent cover. Cattle are ecological converters. They eat coarse vegetation and convert it into products that we can use.
For the record
• Not so fast: a suggested prototype of a plasma oxygen generator for Mars would use 150 to 200 watts for four hours a day to produce 80 to 160 grams (28 October, p 10).
A test for artificial intelligence, right here
So AlphaGo Zero is the best Go-playing AI (21 October, p 9). But how good is AI at understanding the rest of reality? For that, I propose the Letters test: getting more letters in 快猫短视频 than anyone else. So far, I humbly observe that I am doing better at that than all the AIs put together.
So does nothing have a mass after all, then?
I am a keen reader of 快猫短视频 but admit that I am no physicist and the apparent facts about the quantum world blow my mind. That said, may I ask a question?
I read that “As far as we can tell, electrons are points with precisely zero size” (9 September, p 38). Further on, I read that muons and tau particles are 207 and 3400 times the mass of an electron respectively.
Do I understand from this that something with zero size can still have a mass?
These dinosaurs may be accidental piscivores
You report that hadrosaurs that were thought to be vegetarian also ate the odd bit of shellfish (30 September, p 19). They had duck-like bills, suggesting that they fed on aquatic plants, and so perhaps crabs were an inadvertent bycatch.
Water as well as energy from evaporating water
You report hopes that energy from evaporating water could rival wind and solar (7 October, p 19). Can solar distillation of salt water for irrigation be carried out economically using polytunnels in a hot climate near the sea – for example, in North Africa?
If not, perhaps it could be made economical in conjunction with a scheme producing energy from evaporating water.
Where first: Mars, the Moon or our own Earth?
So the European Space Agency is “pushing for a permanent sustainable human presence on the moon“. Would it not be a good idea to push for one on Planet Earth first?
Where first: Mars, the Moon or our own Earth?
Paul Marks's comment proposing a base on the moon before trying for Mars was a welcome breath of reality (21 October, p 24). By focussing on a more achievable target as a preparatory step we will also develop the necessary recycling and conservation technologies to improve our situation here on Earth. It's the news that many science and science fiction fans have been eagerly awaiting since 1969.
Ethical chicken and self-driving morals
Giving passengers control over the ethical decisions of a self-driving car may lead to problems, because our ethical decisions are fallible. The car in question will sometimes have driven itself into a lethal situation. How infallible is that? Such an ethical setting will reflect only the user's confidence in the vehicle, not their actual ethics. Moreover, if it is variable it can be hacked, which is not a pleasant prospect. Best admit that systems are not perfect either, and steer well clear.
Ethical chicken and self-driving morals
The roads might soon be filled with driverless cars, programmed to stop or swerve to avoid hitting any pedestrian in the way (21 October, p 11). What could be more fun than to play chicken with these cars? The miscreants will soon work out just how to time it, and with hoods pulled well down to hide their faces from the dashcams, they will be off the scene before the passengers know what's happened. Of course, if the “ethical knob” has been set to “full egoist” it would be more hazardous for the joker.
Editor's pick: Focusing attention by waggling eardrums
Aylin Woodward reports research finding that our eardrums coordinate with our eyes to shift our hearing in the direction we are looking (29 July, p 12). Pauline Keyne asks whether our eyes are in fact following our ears (Letters, 30 September). This set me thinking. Since I experimented with two turntables playing the same record, one to each ear, I have been fascinated by the way the brain detects the location of a source sound partly through minute differences in its arrival time at each ear.
The left and right eardrums both moving to the right would, by changing the sound arrival times at each eardrum, tend to make a sound appear to come from further to the right. A sound coming from the left might then appear to come from directly in front of the listener. Coordinating this change with an eye movement to the left would therefore make a sound from the left appear to be coming from the centre of view. Is the brain making it easier to identify sound sources by moving them to the middle of our vision, perhaps?
A chance to research "young blood" effects
As a person in my late 50s I was fascinated by Sally Adee's report on the use of “young blood” in rejuvenation efforts (30 September, p 39). I was intrigued by the suggestion that simply removing “bad blood” might be the prime mechanism. As a chemical engineer I am well aware of the need for a purge stream in any closed-loop cycle.
Surely there is a population of blood donors who have donated every couple of months for more than 40 years. Do they have a longer lifespan or otherwise indicate a younger “biological age”? Has anyone examined that?
No shark fishery has ever been sustainable
Lesley Evans Ogden's Comment piece opposes a ban on selling shark fin in the US (14 October, p 24). It draws on arguing that this would undermine sustainable shark fisheries. But no shark fishery has ever been shown to be sustainable. The Walt Disney Company found this out at great expense some years ago and finally banned shark fin soup from its menu in Hong Kong (22 July 2005, p 6).
Remember pioneering surgeon Harold Gillies
Ellie Grigsby seeks support for a memorial to the veterans with facial injuries treated at Queen Mary's Hospital, Sidcup, UK (Signal Boost, 21 October). I would like also to remember , the pioneer of plastic surgery who masterminded the whole operation there. He assembled a multidisciplinary team to carry out groundbreaking work. In 1930 he persuaded his cousin Archibald McIndoe to join his practice and they both continued the work during the second world war.
In 1946 he carried out the first sex reassignment operation in the UK. I cannot understand why he is not more widely known.
Reasons to ban smacking, part two
Jessica Hamzelou argues that all countries should ban smacking (28 October, p 25). Having been to a school run by the infamous , may I point out a “benefit” of corporal punishment that she did not mention? Adults enjoy handing it out. That is another reason for banning it.
History is never just one story, but a rambling tale
Phillip Ball's piece asking whether a religious revolt created science was excellent (28 October, p 32). It reminds us that history is never just one story, but a disparate collection rambling ambiguously into the future.
Believing that science will eventually prevail over vested denial may be comforting for historians, but is problematic for those who live and die during times when it doesn't, such as environmentalists in the US now.
Big Brother is sniffing your mobile device data
You say a billboard in London's Piccadilly Circus that displays adverts on the basis of what cars are passing “will mitigate any dystopian overtones by providing free Wi-Fi, too” (21 October, p 4). That sounds suspiciously like a way to extract useful metadata from passers-by, rather than an altruistic gesture.
First class post
With funding and good cooperation between nation states, yes, this can help rhinos Jess asking whether an international convention promising to protect sharks will help (4 November, p 4)
Body cameras and the view from above
Alice Klein asks whether body-worn cameras are defusing tense situations (21 October, p 22). What about closed-circuit television? This gives what fluid mechanics calls “” data – collected from a fixed point overseeing a predetermined space. Body cams, meanwhile, record “Lagrangian” data – a flow of events befalling one “particle” or participant. Has any work been done on the effect of events being recorded from these two points of view?