Weight and see
Richard Hemingway’s letter suggests there is a connection between obesity and global warming (10 August, p 31). Last year, Anna Gryka and colleagues at in Aberdeen, UK, calculated that if all obese and overweight people lost 10 kilograms, global carbon dioxide emissions would fall by 0.2 per cent ().
This does not seem a lot to me. And what if all these people live longer? Even worse, they might become more fertile.
On a related note, Mark Peplow’s look at how food affects your mind and body raised some interesting points (3 August, p 37). I have no issue with the idea that a high-fat diet tilts your metabolism towards obesity, and that PPAR-gamma and uncoupling protein-1 may be involved. The problem is not, however, that activation of PPAR-gamma reduces the amount of uncoupling protein-1. In fact, it increases the amount of the protein, but this is more than compensated for by a reduction in the protein’s level of activation. Reduced activation, rather than a reduced amount of uncoupling protein-1, may result in less fat being burned in fat cells.
Even this explanation is probably too simplistic. Mice that lack uncoupling protein-1 may actually be resistant to obesity induced by a high-fat diet, when you would expect them to be more prone to obesity.
Buckingham, UK
Driven to distraction
Anything that diverts attention from the road ahead, no matter how briefly, increases the risks when driving. So reader Andrew Lockley’s suggestion that texting is safe because it is quick and may avoid detours leaves me a little incredulous (3 August, p 30). How many texts are likely to be sent during a journey? Multiply by the number of drivers on the road and the risk increases significantly.
Isle of Arran, North Ayrshire, UK
Driven to distraction
You are quite right to highlight the danger of drivers being distracted, and the safety benefits of un-distractable autonomous self-driving cars (20 July, p 3). My all-time favourite distraction is a massive illuminated government sign, well off drivers’ normal eyeline, warning that “distracted drivers are dangerous drivers”.
Did someone let the work experience novice loose on the road-safety project?
Mackay, Queensland, Australia
Infinity and beyond
Amanda Gefter’s presentation of efforts to eliminate infinity was well written (17 August, p 32). It reminded me of the furore that greeted philosopher Ludwig Wittgenstein when he confronted the use of infinity and the infinite in mathematical propositions.
In dissecting Cantor’s theorem, Wittgenstein took a view that is eerily similar to the points made by current scientists such as Norman Wildberger, Max Tegmark and Doron Zeilberger, who Gefter quotes.
Wittgenstein was also brave enough and big enough to question the inconsistency that sits right at the heart of so much of the philosophy of mathematics. The inconsistency is that a system that demands so much rigour and empirically sustainable proof is willing to accept a concept such as infinity, which has defied any and all attempts at even the most approximate proof.
Cambridge, UK
Without intelligence
While the achievements of machine learning are impressive, it is too soon to call artificial intelligence a solved problem, despite Douglas Heaven’s optimism for new approaches (10 August, p 32).
When a computer finally scraped a win at chess over Gary Kasparov, no one mistook it for AI, and Kasparov was doing almost as well as the computer despite having vastly less computational power and working memory at his disposal.
It follows that not everything that humans need intelligence to perform necessarily requires intelligence: so a computer performing these tasks is not necessarily a demonstration of AI.
For example, while humans need to understand all but the simplest passages in order to translate them, evidently computers do not.
Machine learning may yet produce intelligence, but it could instead fall foul of the law of diminishing returns, just as the first generation of “AI” did.
Irvington, New York, US
Shaman marketing
Anil Ananthaswamy mentions the world’s oldest temple at G枚bekli Tepe being perhaps linked to the sudden appearance of Sirius, the dog star, at about the same time (17 August, p 14). I suggest an expansion of this view.
Almost all hunter-gatherer societies have a religious specialist, often called a shaman. These might plausibly maintain loose links over hundreds of miles, and see religious significance in the stars.
It would not take great astronomical knowledge to realise that the zone in which this bright star was visible was moving north. So the local shaman could make this prediction 鈥� and be triumphantly vindicated. That could be enough for them to evolve into a local priesthood.
Peterborough, Cambridgeshire, UK
Flight of fancy
Tim Birkhead’s Instant Expert on avian senses was excellent (3 August). His discussion of navigation made me wonder what happens to migratory birds when Earth’s magnetic field flips.
Stockport, Cheshire, UK
Flight of fancy
My wife and I looked after two gulls with incurably broken wings for 16 years. We usually fed them relatively expensive cat food, but once I threw them a cheap brand.
The gulls dashed towards it, then stopped 2 metres away and went to the back of the garden. At the time we were puzzled, as they had not even tasted the food.
Thanks to Birkhead, I now realise they probably detected the awful odour, just as we did.
Withernsea, East Yorkshire, UK
Gloves off!
John Hardy’s call to ban boxing (10 August, p 26) inadvertently suggests a less dictatorial solution: a ban on boxing gloves.
These were originally introduced to protect the faces of rich young men who would pay to go a few rounds with the champions of the day.
As gloves became heavier, boxers began defending their heads by holding the glove a short distance away and stiffening the arm. Some of the power of the incoming punch is still received, but most is absorbed by the defending glove.
In bare-knuckle boxing, fighters would either move their head out of the way or deflect an incoming punch with their forearms. They would avoid every one they could, making the sport a safer one.
London, UK
Metamagically
Surely your report on cryptography and quantum entanglement is quoting a key law of sympathetic magic, as set out by James Frazer in : things once in contact continue to interact at a distance (20 July, p 15). And Jacob Aron’s piece in the same issue on levitating particles that move to music (p 10) reminds me that Merlin was once credited with moving Stonehenge from Ireland to England by means of music.
How far does physics have to go before it meets magic coming round the corner?
Chesham, Buckinghamshire, UK
Now ear this
Linda Geddes’s article on the medical potential of manipulating the vagus nerve (17 August, p 12) brought to mind something I learned as a student in 1960. The auricular branch of the vagus nerve is also known as the Alderman’s nerve.
This is apparently because the nerve’s role in encouraging peristalsis 鈥� the movement of food through the digestive tract 鈥� was well-known a couple of hundred years ago. Aldermen, towards the end of lavish banquets, would stimulate the lobe of the ear with rose water to make room for yet more goodies.
Cracoe, North Yorkshire, UK
Radio days
Feedback and reader Roger Christie were correct when discussing the relativity of a 55-minute BBC Science Hour radio show (20 July), contrary to Jay Pasachoff’s letter (17 August, p 31).
A radio listener moving in space will have to constantly retune their radio, if they are moving relative to the transmitter and even if it is not accelerating, because space is constantly expanding between them and the transmitter.
Diggle, Lancashire, UK
Heat pump measure
Steve Elliott was surprised to learn that heat pumps can “operate at 300 to 400 per cent efficiency” (Feedback, 20 July), but was reassured by reader Barry Manor (10 August, p 31). However, what Manor describes is the coefficient of performance, a measure of the efficacy, not the efficiency, of the heat pump.
Pollen莽a, Mallorca, Spain
Never say never
I can’t see much call for a beefburger made from lab-grown meat that costs 拢250,000 (10 August, p 10), but I can see a demand for more exotic varieties.
How about mammoth burgers created from a single preserved stem cell? And, taking it to extremes, with a single stem cell donated by a celebrity: anyone for Bieber burgers?
Lenham, Kent, UK
<i>From Erik Foxcroft</i>
If alternative sources of protein such as synthetic meat can offer significant environmental benefits over more direct ways of exploiting vegetable protein, then they may be worth further investigation.
If not, perhaps people such as Sergey Brin of Google fame, who funded the lab-grown burger, would be better off putting their money and talents into promoting vegetarianism.
St Albans, Hertfordshire, UK
For the record
鈥� Our report on Icarus Interstellar’s Starship Congress went into a bit of a spin (24 August, p 8). The organisation was founded in 2011; Philip Lubin’s calculations refer to a 100-kilogram, not a 10-kilogram craft; and a radioisotope thermoelectric generator is a power source, not a fuel source.
鈥� As beneficiaries of hindsight, we now see that Mariana Mazzucato proposed that if the beneficiaries of a grant make a certain profit, a contribution will be made back to the benefactors, not the other way around (24 August, p 26).