Letter
There is an easily verifiable proof that time travel is impossible, which I was able to demonstrate only the other night in The Angel pub in London’s St Giles High Street.
I took several sheets of blank paper and at the top of the first I wrote “Plans For Time Machine”. Under this I wrote “漏 Rex Anderson 2003”. Then I wrote: “As soon as this time machine is constructed, I or whoever takes up the challenge after me will return to this bar at [this time] on [this date] and complete the plan.”
I then pinned the sheets of paper to the darts notice board and, to avoid any space/time anomaly of my having to meet myself, my friends and I adjourned to the other bar. We are still waiting.
Solar cost
Jeremy Leggett’s article promoting solar power contains several statements, unfortunately not backed by facts, that imply that solar power is relatively cheap and that economists are conspiring to make it sound expensive (6 September, p 23).
As an exercise I costed a system that would take my house off the grid. Last month I used 1800 kilowatt-hours which cost an average of 10 cents per kilowatt hour. Using an average number of hours sunshine per day for Florida and a reasonable efficiency I calculate that I would need a 10-kilowatt photovoltaic array to meet my power needs. A quick internet search shows that PV arrays can cost up to $5 per watt, although I did find a supplier at $3 per watt. That is $30,000 for the PV cells alone. This does not take into account the charging system, batteries and inverters as well as structural materials.
Even ignoring those costs and just factoring in the arrays, it would take over 13 years to recoup the cost of the system assuming no maintenance or depreciation. It also assumes the cost of money is zero.
Leggett correctly accuses grid suppliers of not factoring in environmental costs and therefore hiding the true cost of power. But in conveniently ignoring the upfront cost of money, as well as the ongoing maintenance and degradation of PV arrays, Leggett is guilty of the same fudging. While I applaud Leggett in his desire for renewable power we must deal with the world as it is and not as we might wish it to be.
Your own fault
I’m afraid I have to disagree with John Fisher and Tony Woodhouse’s opinions on the spread of viruses (20 September, p 26). The most common cause of viral infection is human error. Opening an email which is from either an unknown sender, or has a subject which seems less than genuine, spreads viruses by the bucket load.
Windows now comes with its own firewall. Even a free firewall downloaded from the internet will solve the problem. There are few excuses. To suggest that people move away from a common operating system is madness. We use computers as a common ground to make communication easier between people and companies. To move away from such compatibility would cause more problems than it solves.
The simplest way to avoid viruses? Common sense, a firewall and a good virus checker.
Copyright copies
Peter Wienand’s response to Tony Straka raises doubts about the authority of the Bridgeman vs Corel case and argues for copyright associated with photographic reproductions of art works in the public domain (20 September, p 26).
While some may disagree with the finding of the case, many others agree with it as being consistent with the general principle that, while hard work can be respected, it nevertheless is not sufficient grounds for granting copyright. No one is doubting the technical skill and hard work of photographers, but copyright is only granted for originality. Making a good copy of someone else’s work is hardly creative or original.
People running museums and art galleries undoubtedly disagree with the finding, as it has financial implications for them. However, copyright must expire at some point otherwise we will all be the poorer for the deprivation of the public domain, a point which has escaped the US Congress to date.
Factor five
Graham Lawton exaggerates the virtues of the five-factor model in his article on personality (13 September, p 30). He states that “the score you get on one [factor] has no bearing on the others”.
I am afraid that this is not so. In the manual of their revised NEO Personality Inventory, Paul Costa and Robert McCrae provide a chart of the cross-correlations between the five factors and their various facets. While many of the cross-correlation coefficients are low, those between neuroticism and conscientiousness are much higher.
I am quite an enthusiast for the five-factor model, as is Lawton, but there is no point in gilding the lily. Assuming that the genetic basis of these factors is eventually established, we may find that some of the genes responsible for positioning someone along one dimension also to some extent position that person along another.
Letter
I am confused by the assertion in your article on personality that agriculture emerged as part of radical technological advances 40,000 ago, and that it affected our genes. While certain genes may have been changing, it would not have been anything to do with farming, as this did not appear until at least 30,000 years later.
Furthermore, the idea of a massive jump in technology at around 40,000 ago (the “human revolution”) is increasingly being challenged by evidence of modern behaviour and technology from the African Middle Stone Age. This occurred from between 160,000 and 120,000 years ago to between 50,000 and 30,000 years ago, and during this period we find the use of bone, composite tools and blades, and microlithic technology, as well as systematic use of pigments. This counters the traditional Eurocentric view that modern behaviour equals the Upper Palaeolithic.
Feet in the air
When a person feels faint, or has indeed fainted, first aiders are trained to raise that person’s legs so as to increase the blood flow to the brain 鈥� and the recovery is quite dramatic. While an inflatable “shock sheet” sounds like a good idea (13 September, p 24), would there also be some benefit in simply raising a persons legs whilst administering CPR?
Mark Wilson writes:
鈥� There has been some research into raising the legs or tilting the bed during CPR. This increases venous return (blood coming back from the extremities) but does not increase your systemic vascular resistance, so blood still flows in the arteries, since they are high-pressure vessels and are not compressed. Therefore, it doesn’t help divert arterial blood to the head and heart.
Tired phones
I was surprised by the complexity of the idea of linking several cell phones to gather the last remnants of available battery power for emergency calls (13 September, p 22).
If cellphones already have technology to shut them down before all battery power is entirely drained, wouldn’t it make much more sense to program them to always save up enough power for one last call, which would only be accessible by dialling the number of the emergency services?
Many lasers
Your correspondent Ian McKinley points out that 1013 years would be required to transmute the iodine using a laser (20 September, p 27). This is obviously a ridiculous proposition. 杏吧原创s are intelligent people, and would accomplish the task in just one year, using 1013 lasers.
For the record
鈥� In our editorial on contaminated cell lines (20 September, p 5) we mistakenly called Walter Nelson Rees “William” Nelson Rees.
Climate control
Philip Stott quotes two recent papers as supposedly implying that carbon emissions should not be reduced. However, neither of the papers quoted support that position (20 September, p 25).
The first paper, by J谩n Veizer and Nir Shaviv, is a speculative study on climate forcings over hundreds of millions of years, for which we do not have enough information about CO2 levels to be able to claim that the gas played no role. Even if the study were correct, it says nothing about the role of CO2 in recent or future climate change.
The other paper, by Willie Soon and Sallie Baliunas, reviews all the criticisms they could find about climate models and lumps them together. All positive conclusions about climate modelling in those same papers are ignored in favour of negative-sounding caveats. The suggestion that changes in the shape of the Earth have had an impact on recent climate change is laughable.
The facts remain that CO2 levels are increasing due to human activities. This has a demonstrable impact on radiation of heat from the planet, and despite uncertainties, all climate model simulations show that this will lead to increased global warming. Stott’s continual attempts to confuse the issue are neither useful nor illuminating.
Letter
Stott claims that the paper by Shaviv and Veizer is important science that did not get enough attention from media and policy makers. The opposite is true: it received a disproportionate amount of media coverage due to the strong but unfounded claims the authors made in their press releases.
Shaviv and Veizer claim to have found a correlation between cosmic ray flux and temperature. Even if we accept their (questionable) data, it should be noted that this correlation was constructed by arbitrarily stretching the timescale to shift the maxima of cosmic ray flux by up to 20 million years, to make them coincide with temperature minima. The unadulterated data show no significant correlation 鈥� we have checked this. Shaviv and Veizer then proceed to estimate the climate sensitivity to a doubling of CO2 concentration through regression analysis, which for a number of reasons is not possible.
If it were, far better data is available for this analysis: the Antarctic ice core data. It is much more accurate, shows variations on more relevant timescales and closer to present CO2 levels, and applies to the present-day configuration of continents. Such an analysis would yield a climate sensitivity exceeding 10 掳C, but no climatologist would suggest this is a viable method.
Just in time
The paradoxes referred to when time travel is discussed always seem to involve sentient beings (20 September, p 28). Someone goes back in time and alters the time line or carries information back with them.
Is it possible to specify a significant paradox involving only non-sentient objects 鈥� say a rock, or an electron? Come to that, since all electrons are identical, would it mean anything to say that a particular electron had been sent back in time?