I hurt, therefore I am
How do I know I exist (23 July, p 36)? 1. Sit at desk. 2. Open drawer. 3. Put fingers in drawer. 4. Slam drawer shut.
Yep, I exist.
From Ian Stewart, Mathematics Institute, University of Warwick
Central to answering the question “Am I a hologram?” (23 July, p 31) is the holographic principle, which states that there is a one-to-one correspondence between quantum states within a domain and states of a related set of equations on its boundary. This has numerous precedents in classical physics, such as the flow of a fluid inside a domain, which is uniquely determined by the boundary conditions. No one suggests that a fluid is really a hologram, and it is equally silly to suggest that we are.
Mathematically, our world can be modelled in several equivalent ways. Physically, they all describe the same thing.
Coventry, West Midlands, UK
From Anthony Hammond
I was struck by a number of questions when reading about the idea that we may be holograms. What are the deeper implications of us being holographic entities? Is consciousness itself holographic? Indeed, are my questions here only illusory, having been generated billions of light years away on a 2D surface?
Manchester, UK
Alzheimer's insight
Andy Coghlan reported the latest evidence that Alzheimer’s is, in part, a cell cycle disease that generates neurons and other cells with abnormal numbers of chromosomes (14 May, p 8).
We would like to supplement this story by pointing out that the vast majority of abnormal neurons and other cells in people with Alzheimer’s show less than double the number of chromosomes. They are monosomic or trisomic, containing just one or three copies of various chromosomes. This is a cell state known as aneuploidy, which is evidence for a general chromosome mis-segregation defect rather than merely a problem with DNA replication and uncompleted cell division.
Many of those cells have three copies of chromosome 21, a defect known as trisomy 21, which is seen in all the cells of people with Down’s syndrome. Thus people with Alzheimer’s essentially become mosaic Down’s syndrome individuals 鈥� that is with some, rather than all, cells affected.
Chromosome 21 also encodes the Alzheimer amyloid precursor protein gene. All people with Down’s develop Alzheimer’s pathology by the age of 20, and most develop dementia by 50. Furthermore, mothers of most people with Down’s are often mosaic for trisomy 21, are prone to chromosome mis-segregation and at greater risk of developing Alzheimer’s.
Unbreakable net
The internet will never become the “splinternet” (16 July, p 42). To understand why, remember that there were splinternets before the internet. It was the internet that swept them aside, not the other way around.
The importance of the internet lies in its connectivity, not content, despite what some corporations fondly believe. There were proprietary online services before the internet, like CompuServe, the original form of AOL, BIX and others. They had access to valuable “premium” content that the internet could not offer, and had promotional budgets that the early internet service providers could not afford. Yet the internet still prevailed, as it was the best way for people to find each other.
In short, I don’t see the internet reverting to old, closed ways of doing things. On the contrary, I see more and more of those old, closed ways being made obsolete by the internet.
Chimp tests
In her article on the mental lives of animals, Emma Young wrote, “Chimps… just don’t get abstract physical concepts, like weight, gravity and the transfer of force” (2 July, p 41). She cited work by Daniel Povinelli, in which a group of orphaned, institutionalised chimpanzees often failed to select a tool with the correct properties to retrieve food.
Yet when this same task was given to chimpanzees kept in unusually enriched captive circumstances 鈥� either raised as part of a human family or in very close association with people 鈥� they performed very well (). More generally, apes that experience enriched captive rearing environments perform well in tool-using tasks requiring sophisticated manipulations of weight, gravity and force ().
Wild chimpanzees use tools to crack nuts, spear animals, probe termite mounds and soak up liquids, all of which require the application of abstract physical concepts during tool preparation. It is therefore absurd to use the behaviour of those subjected to institutionalisation as a generalisation of all chimps.
It has been demonstrated that orphaned children brought up in institutions experience severe cognitive delays. Moreover, the longer they spend in these settings, the worse the impact (). Why would chimpanzees be any different?
Contrail cooling
Reading how contrails from second world war bombers changed the weather (16 July, p 14) brought to mind the flight marking the 10th anniversary of the wartime 1000 bomber raids by the UK’s Royal Air Force.
I was living in west London, near Northolt airfield, and the weather was fine, clear and very warm. A huge band of aircraft appeared, probably higher than the original 8000 feet used for the raids.
They covered the sky as far as you could see, leaving a “carpet” of contrails which soon merged. It immediately became noticeably chillier, and as far as I remember the temperature did not recover for many hours, if at all, that day.
Focus on stability
South Africa’s efforts to increase its scientific capabilities should be applauded (16 July, p 25). However, the decision on siting the Square Kilometre Array (SKA), the world’s biggest radio telescope, should be made in the best interests of science, not to foster scientific development in any one region.
Whilst South Africa is a stable and democratic nation, other potential host nations for some of the thousands of antennae needed are not. The distances involved would make protecting the entire SKA almost impossible.
Australia, the other potential host, also has vast, sparsely populated areas, with limited or no radio interference, as well as being in an appropriate location in astronomy terms. The difference between the two bids would seem to be that Australia has political stability.
For a project with the potential to make ground-breaking discoveries of global impact, this should be paramount.
Millions and billions
In “Unsung elements” (18 June, p 36) James Mitchell Crow states they “make up a few parts per billion of Earth’s crust”. While correct for one of the nine 鈥� tellurium is about 1 part per billion (ppb) 鈥� he is way out with the others.
With reasonable confidence, their crustal abundances are: indium 200 ppb; terbium 1000 ppb; europium 2000 ppb; dysprosium 6000 ppb; yttrium 30,000 ppb; neodymium 35,000 ppb; lanthanum 35,000 ppb; and cerium 60,000 ppb.
Baby talk
After reading of the connections between words and sensory perceptions and possible links to the emergence of language (16 July, p 30), I suspect that “the ancestral genius who invented the first words” was female.
I can see language developing out of a game played by mothers and their babbling, curious children, with mothers remembering and developing the children’s words, encouraging more, inventing connections and spreading the results. As the hunting males returned, they would have joined in.
From Colin Day
Contrary to what was written in your article “Language’s missing link”, in linguistics a “b” sound is not a continuant 鈥� a sound made with an incomplete closure of the vocal tract. Like the “k” sound, it is a stop, breaking the airflow. The difference is that “b” is a voiced bilabial stop and “k” is a voiceless velar stop.
Leyburn, North Yorkshire, UK
Faking it
The real fault with lie detectors (25 June, p 46) is the assumption that lying is stressful. It is for most of us, but for sociopaths lying is no problem. Career non-sociopathic criminals are another matter, though they soon learn tricks, like a drawing pin inside the shoe.
In the 1980s, my colleagues and I used polygraphs to teach students cardiovascular physiology. On quiet days we wired ourselves up and played games, seeing who could raise and lower their heart rate the best.
We evoked images that engaged the autonomic nervous system to change our physiology. Beating polygraphs would have been child’s play for us.
Men vs women
I was delighted to read Alan White’s thoughts on why being male is so bad for health (18 June, p 31). I have been irritated by the way feminist social scientists, among whom I count myself, often explain women’s higher rates of illness in terms of social factors, but men’s higher rates of mortality in terms of biology.
If the tendency of men to die early were biologically programmed then we would expect similar differences in all countries. In most societies for which we have records, men do die earlier than women, but the difference ranges from one year in Japan to 15 in pre-1980s Finland.
There are even a few societies where women die earlier, such as Afghanistan.
Tau's day
There appears to be a backlash against calls to replace pi with tau (9 July, p 5). After reading The Tau Manifesto by Michael Hartl (), I took the document’s advice and did a review, looking back through my engineering and physics books.
I was dumbfounded at how often 2pi showed up 鈥� nearly every time 鈥� and in cases where pi was alone or with another factor, such as 4pi, it was actually enlightening to replace pi with tau. Pi has always been one of my favourite numbers. Despite that, I agree tau is the winner.