Editor's pick: When force of habit is derailed
Those who, like myself, have experienced brain illness or injury as adults become aware of how habit impairment can play a key role in interrupting the patterns of normal life that habits used to sustain (16 January, p 30).
Depending on the site of brain damage, one's habits may either be disrupted or may persist but with disruption to the cognitive capabilities on which their “automated” behaviours depend. In either case the old habits are no longer effective; indeed, in the latter they can even be counterproductive, as when habits induce behaviours a person is no longer capable of, resulting in confusion or risk.
For an adult, rehabilitation into “normal” life requires the re-creation of a set of habits that has been built up over a lifetime. For example, I had to re-establish basic life-skills originally acquired as a toddler, such as rapid arithmetic, time-keeping and road-crossing.
When tasks of daily living, including those previously catered for by habits, require full attention, the state of mental exhaustion that is often apparent following brain injury is exacerbated. If it can take a person of uncompromised neurological capability a year to acquire a single new habit, then one can appreciate why it can take a person in such a disordered state many years to reacquire a full set of habits.
Odds of finding extraterrestrials
Your article about detecting alien civilisations may underestimate the difficulty (16 January, p 38). As beings become more advanced they may become more ethical. (If not, then they may not survive long enough to leave a mark.)
One principle that might be adopted by ET, an Ethical Thing, is that of making as small an impact on the universe as they can. The green movement on Earth is already advocating this.
The Ethical Things may then live, develop and grow in their understanding of the universe while being careful to leave as little sign of their presence as possible. This would extend to deleting any signs of historic pollution. They might be invisible not because they are hiding, but because they don't want to make a fuss or leave any mess.
Odds of finding extraterrestrials
The visible, detectable universe isn't infinite. It seems to me very unlikely that life would start on any given Earth-like planet, let alone give rise to self-aware animals like us. So we have a very small probability multiplying a very large number of planets. We have no idea how small the product is. The fact that we exist doesn't help answer the question.
Odds of finding extraterrestrials
We invented radio about 120 years ago. Within 60 years or so we have invented efficient compression (to increase data bandwidth), good error correction (to increase reliability) and good encryption (to prevent eavesdropping). All of these make our transmissions look like randomised noise without any order. On top of that, our communications are progressively going “dark”, using wires, fibres and lasers that leak very little information. Other technological civilisations would probably do the same. So there would be a vanishingly small window in the history of any technological civilisation in which eavesdropping could detect an unambiguously intelligent signal.
If I were sending a signal to make contact I would tailor it to be easily detected and understood – but only by a civilisation that could respond. A space-based solar-powered laser might be the most energy-efficient method. Once life had been detected in a star system, perhaps from its planets' emission spectra, I might pulse out a message to it for a year, every 10,000 years or so.
First class post
I hope it wasn't the result of humans screwing up these beautiful whales' sonar
Beth Kattleman's over beached wales in eastern England (newscientist.com/article/2075274).
Entropy and typical universes
I am surprised that your article describing how time might flow backwards (16 January, p 8) makes no mention of the 2014 paper “Identification of a gravitational arrow of time” (), nor of the 2015 post “Entropy and the typicality of universes” (). In these my collaborators and I published very similar ideas.
The model created by Sean Carroll and Alan Guth that your article describes is simply that of our 2014 paper with gravitational interaction removed: we already presented that simplification in our 2015 arXiv post.
I do not dispute that more than a decade ago Carroll , with Jennifer Chen, the possibility of what we call a universe with one past and two futures, nor that Carroll expanded on this in his recent book . However, this had none of the mathematical results my team published. We are grateful to Carroll for his support as a referee in the publication of our paper. His comment on our 2014 paper, referring to his earlier intuition, was “I would personally count this work as an explicit example demonstrating that intuition”. This is why I am so puzzled you made no mention of our work.
South Newington, Oxfordshire, UK
Chimeras' benefits and a forensic flaw
Apparently fetal cells transferred across the placenta and retained in the mother can repair damage to the mother's heart muscle and other organs (9 January, p 26). Could this explain why women have a longer lifespan than men?
Chimeras' benefits and a forensic flaw
Where does the presence of cells from other people leave DNA fingerprinting?
Reasons to invest in electric cars
Peter Shand is right about electric cars (Letters, 23 January). Suppose we were to replace the UK's fleet of petrol and diesel cars with electric vehicles, using electricity from gas-fired thermal power stations. Back-of-the-envelope calculations suggest that carbon emissions from these cars would be between 30 and 50 per cent lower than from the present fleet.
Essentially, this is because burning fossil fuel in large power stations is more efficient than burning it in millions of little piston engines. Even after losses in transmission and charging you get at least a third more useful energy at the wheel rims.
Electric cars would also reduce the particulate pollution that is a major cause of poor air quality in cities. It is easier to control pollution at a few large power stations than from those millions of car exhausts.
Here in the UK, politicians want to spend upwards of £100 billion on replacing obsolete nuclear missiles. If the money were invested in electrifying the UK's car fleet this would create and protect far more high-skilled jobs, kick-start an essential change in technology and do something beneficial for the planet and all of humanity instead of contributing to global insecurity, paranoia and terror.
Grow shy microbes, pair by pair
Cynthia Graber's report on work by Slava Epstein and others on growing recalcitrant microbes was fascinating (2 January, p 36). I suggest a further experiment: dilute the microbes spread on the iChip growing apparatus so that there are two or three per cell. The aim would be to start to reveal the symbiotic existence of some of them, if that is as likely as I expect.
Some simple maths would be able to make predictions for behaviour with and without symbiosis. Pinpointing the symbiotic relationships would be more tricky, but rewarding.
Shipham, Somerset, UK
Slava Epstein writes:
• I have been thinking about microbial symbioses, in terms of cultivation and otherwise. One issue is that some such consortia of microbes are “uncultivable” as a whole – not only their individual members, but the entire group resists being grown.
Clarity in the face of science's doubts
Chris Ford suggests that climate scientists will connect better with the media if, instead of saying “It's impossible to say whether a particular flood event is or isn't caused by climate change”, they answered “climate change will bring more storms like this” (Letters, 9 January). But reality has already caught up and moved on. Confident assertions by respected scientists about probable future climate disasters have become increasingly common. Sadly, this isn't enough to counteract public doubts about uncertain future scenarios. A better response would be “climate change is bringing more storms like this”.
Hungry plants flower more
Researcher Robert Margolskee speculates that taste receptors in the testes might detect nutritional status to avoid wasting valuable energy making sperm when food is scarce (8 August 2015, p 38). This suggestion is anthropocentric.
Many a gardener has observed lack of flowering in pampered plants. Flowering and sperm production are a means of perpetuating the species, so are more likely to be favoured when food is scarce. Or are humans an exception to the rule?
Exponential growth in reverse
The article on exponential growth (12 December 2015, p 34) reminded me of a 1940s Lloyd's Log Problem Book puzzle. It described a lily that doubles in size every day, taking 36 days to completely cover a pond, and asks: how long does it take to half fill the pond? For some reason, having to think about it this way around seems more challenging for many people.
For the Record
• A study of the health effects of cuts to UK disability allowance found that 725,000 more prescriptions for antidepressants were issued (21 November 2015, p 7).
• World concrete production to date has been about 500 billion tonnes, which is enough to deliver 1 kilogram to every square metre of Earth (16 January, p 14).
• A brain in a warmer vat: maverick surgeon Sergio Canavero reports cooling a monkey's head only to 15 °C before transplant (23 January, p 6).
• Whoops. The curves showing the numbers of people not having relapses of schizophrenia, with standard drug treatment and with minimal treatment, were reversed (8 February 2014, p 32).