Chaotic aliens
Your article, “Symphony in chaos” (8 April), explaining how digital transmissions can be made with chaotic signals, was the insight of the decade. Eric Kostelich doesn’t say so, but applications to the search for extraterrestrial intelligence (SETI) are very appealing.
I’ve long wondered how mistaken the current drive to detect conventional pulsed signals might be. I think an extension of the work of Scott Hayes, Celso Grebogi and Edward Ott now provides the answer.
Don't tell
I would like to make two comments about Alan Slomson’s propositions about the National Lottery (Letters, 22 April).
Firstly, any pair of consecutive numbers above three will contain one multiple of two and therefore be non-prime. So, it is not possible to adhere to both propositions at once.
Secondly, publicising an “unpopular” choice is self-defeating. Proposition two will restrict the player to a set of 11 prime numbers leading to a choice of 462 combinations, which is far fewer than the number of readers of this illustrious publication. So, it would not take a large proportion of the readership to make the combinations in the set very popular.
Bird talk
D. W Ewer is mistaken when he proposes that a spoken language had a selective advantage when early humans wanted to communicate with companions who were out of sight in a tall grass savanna or a forest (Letters, 15 April).
When I surveyed chimpanzee paths in the rainforest in Eastern Zaire, accompanied by Mbuti Pygmies, I noticed that they used bird calls as a means of communication at a distance and avoided speaking. Their aim apparently was not to reveal the presence of human hunters to their game, mainly antelopes.
What do they know?
Your correspondent Adrian Bowyer (Letters, 1 April) suggests that the highly red-shifted objects known as quasars may in fact be interstellar spacecraft emitting large quantities of energy directly aft, and hence visible only from the rear.
I made this suggestion in my science fiction novel Hero! (Ballantine Books, New York, 1991). I doubt if I was the first to do so.
Unfortunately, it won’t work. In order to arrive at a destination, such ships would have to turn around and use their propulsion system to brake. Those emissions would appear to be blue-shifted.
Alternatively, of course, these advanced aliens are all heading away from us as fast as they can, as suggested by Graeme Pietersz (Letters, 29 April), and not one of them is planning to drop in. Could they know something that we don’t?
Letters to the Editor
Write to: Letters to the Editor, New 杏吧原创, King’s Reach Tower, Stamford Street, London SE1 9LS, or fax to 0171 261 6464.
Please include a daytime telephone number, and cite the date of the articles mentioned. We reserve the right to edit longer letters. Your letters may also be published in New 杏吧原创 newsletters.
Cheap point
“Too cheap to meter” was not “a slogan invented by supporters of nuclear power before the industry’s real cost had been worked out” (“Quest for the supershuttle”, 8 April).
In the 1930s, C. P. Steinmetz of the General Electric Company in the US declared that electricity would become “so cheap it is not going to pay to meter it”. This remark appears to have been the source of the claim by Lewis L. Strauss in 1954, then chairman of the US Atomic Energy Commission, that “it is not too much to expect that our children enjoy in their homes electrical energy too cheap to meter”. It was understood that Strauss, an eccentric financier with no technical training and a tendency to overstate his case, was referring to the cost of nuclear power.
Supporters of nuclear power have never claimed that nuclear power is “too cheap”; they know that no method of generation falls into that category. However, nor is nuclear power very expensive. The cost of electricity generation is a function primarily of the discount rate and the amortisation period. It is not primarily a function of the fuel used.
Testing the absolute
Julian Brown’s article “Faster than the speed of light” (1 April) has clearly highlighted the need to reconsider an important postulate of special relativity: that absolute speeds cannot exist. It is this feature which makes causality seem to be violated if messages travel faster than light. So do absolute speeds exist or not?
Use can be made of the fact that the Earth is a spinning sphere to answer this important question: if the Earth has its centre moving at some absolute speed, then a point on the surface, far from the poles, will have a speed which varies in daily cycles. Any clock placed there will consequently keep gaining and losing in daily cycles. Hence two clocks separated in longitude will cycle with a difference in phase.
Unfortunately, a very detailed mathematical study showed that it would be impossible to detect this phase-difference by signals bounced from satellites, whatever the orbiting height, because differences in signal-time delays cancel out the effect to a high degree of accuracy.
This leaves only a single option. A mobile atomic clock needs to travel from a fixed master clock and return for recheck a few hours later. A gain directly proportional to the product of longitude change and absolute speed of the Earth’s centre is predicted 鈥� when other things are fixed.
I discovered that the National Physical Laboratory uses a caesium clock, carried by car, to take the time (literally) to other clocks. They kindly supplied me with eight sets of data so I was able to carry out a preliminary analysis of the time gains (T) caused by longitude changes of 0.7 to 0.9 degrees for about 6-hour intervals between checks.
I found that the apparently random ▵T errors could be roughly halved if the Sun was assumed to move with absolute speeds between 30 and 60 kilometres per second as compared with zero speed.
A final check is needed since a mere halving of error is unconvincing. A run along the M4 from Teddington to Downend (Bristol turn-off) and back is planned on either 7 July or 5 November when checks are made against the master at 9.30 am and 4.30 pm. If values between about plus or minus 15 nanoseconds appear, then the errors are random and absolute speeds will have been proved nonexistent. I can provide car and batteries if somebody can provide the funding for clock hire and insurance, estimated by the NPL at 拢600. Is anybody interested in joining in?
Perhaps the photons leaving the barrier in Raymond Chiao’s experiments are not the same ones that entered. Within the barrier the entering photons interact with others already existing and captured, for example by electrons, inside. The interaction is a transfer of frequency and phase from the entering photon to the captured photon. On completion of the interaction, the entering photon has been captured and the captured photon released 鈥� with the same outward indentity carried onward.
This process is repeated across the barrier as a cascade only if conditions are right. If the interaction takes less time than the entering photon takes to cross half of the physical size of the captured photon, then the released photon will effectively leave early and the passage of the identity of the original photon will appear to be faster than light speed. If the interaction takes more time than crossing half the photon, then the apparent speed will be less than light speed.
The right conditions within the barrier to allow a cascade would be where the photons “collide” precisely enough to transfer all momentum and energy. Anything other than precise collision would result in reflected photons, not transmitted photons. The probability of precise collisions decreases exponentially with distance into the barrier.
So G眉nter Nimtz has transmitted Mozart’s 40th symphony through space at 4.7 times the velocity of light? The length of the concert hall was 12 centimetres? And the performance lasted (say) 1500 seconds? Normally that means that, using sound waves, it would take 1500.0004 seconds from the time the conductor brings down his baton to the time the audience starts applauding.
But it is rather old hat to convert the sound into an electromagnetic signal. That cuts the time to 1500.0000000004 seconds. Now Nimtz, by making the signal tunnel through (or is it round or under?) a barrier, has cut it down to 1500.0000000001 seconds? How long before I can buy one of these barriers and install it in my hi-fi? I should so like to pick up Classic FM a millisecond or two before my neighbours.
Your article is another demonstration of fallacies arising through describing light as particles. Einstein’s error, in uncharacteristically reverting to Newtonian light corpuscles to explain photoelectron emissions, now being used to logically contradict the maximum velocity concept, is a twist that the old genius would surely have appreciated.
Heavy thrust
I am puzzled by the account of a racing car that can accelerate to 225 kilometres per hour and brake to a standstill in a total of 6 seconds (“May the best driver win”, 25 March).
This corresponds, according to my calculations (and I am only a simple pure mathematician) to an average acceleration of about 2.12 g followed by an average deceleration of 鈭�2.12 g (assuming, for simplicity, a symmetry). Now, I recall dimly, from my unregenerate days at school, that even given a friction coefficient of unity, the maximum horizontal thrust attainable on a horizontal plane is equal to g. And this would be, to some extent, countered by aerodynamic drag.
It seems that the only way of increasing the frictional thrust is by increasing the apparent weight of the car by aerodynamic downthrust. But, since this will be zero, or near-zero, when the car is starting from rest, it implies that towards the end of the acceleration phase there must be an aerodynamic downthrust of more than twice the weight of the car. Can this be true? Or have I missed some other, more esoteric, explanation?
Yes, it is true. According to Williams, the maximum downthrust generated would allow the car to drive upside down along the roof of a tunnel, for example 鈥� Ed
Helium's no help
Having been responsible for using a large quantity of helium over the years due to working in the saturation diving industry, I read your article on the gas with interest (Forum, 8 April). Sadly, the one mention of its use in diving was wrong.
By breathing helium and oxygen mixtures, divers do not “avoid the bends”. The bends (or decompression sickness) is caused by bubbles of inert gas forming in the blood and tissues of the body due to reduced solubility as the pressure is reduced on ascent (Henry’s Law). Any physiologist will tell you that a bubble of helium is just as bad as a bubble of nitrogen (from air) if a diver is decompressed incorrectly.
Helium is used as a replacement for nitrogen for two main reasons. Firstly, whereas the narcotic potency of helium is very low, nitrogen is highly narcotic if breathed at pressures of more than about 0.4 bar absolute, and secondly, helium, being a lighter gas, is easier to breathe at increased pressures.
Helium was not used as a refrigerant for hydrogen and oxygen fuels in the Apollo moon lander, for the very good reason that the lander didn’t use such fuels, for safety reasons. Hydrogen and oxygen need complicated (and therefore unreliable) turbopumps to pump them into the combustion chamber of a rocket. They then need a spark to ignite them (at considerable risk of explosion), and the mixture control has to be exact. Get it wrong one way, and there’s an explosion, get it wrong the other way, and there’s no ignition.
The Apollo lunar module had to take off from the moon alone, without sophisticated launch facilities, fuel control and monitoring, back-up systems, service crews, and so on. And if the ascent rocket didn’t ignite, the crew would be stranded. For all these reasons the Apollo LM did not use hydrogen and oxygen as rocket fuels. Instead, it used hypergolic fuels, which do not need refrigeration, and which ignite on contact with each other. These fuels are of the nitrogen tetroxide/monomethyl hydrazine family. Incidentally, they were first used in the Messerschmitt Komet rocket fighter in the Second World War, and are used for the Orbital Maneuvering System in the Shuttle.
These fuels were, for reliability and light weight, not pumped by mechanical pumps into the rocket chamber, but were simply driven in by pressurised gas 鈥� yes, helium 鈥� which was stored on board.
Starting the ascent rocket was: then simply a matter of turning on the taps. The pressurised helium drove the hyperbolic fuels into the rocket, where they ignited on contact.
Only administrate
While I have every sympathy with Rachel Allen regarding her frustrated attempts to obtain “summer science work placements” (Letters, 22 April), I suspect that this has very little to do with her gender and a great deal to do with a general scarcity of employment opportunities within science.
Despite current rhetoric which implies a shortage of scientists and engineers, my own experience indicates just the opposite. For example:
I obtained 3 As and a B at A level, followed by a BEng (1st) and a PhD in Engineering Mathematics. Despite 15 months of applications to advertisements, speculative applications, applications to employment agencies and resulting interviews (47, 62, 6 and 14 respectively) I had no success whatsoever in obtaining employment. That is, until very recently, when in desperation, I have begun to apply for positions in the administration of science, in addition to my usual “research” or “R&D” type applications.
Although I have only made three such applications, the result has been three interviews and three job offers. While this has somewhat allayed my fears that I might somehow be so repulsive in personality that no one would want to employ me (after so many rejections, one’s self-confidence takes a bit of a nasty knock), it has only strengthened my belief that we scientists/engineers are two a penny. Friends with whom I went to university have had similar experiences. And, in my new job as an administrator, I have heard the same story over and over again from other scientists turned administrators: “no opportunities in research, had to eat, hope the situation improves soon and I don’t become unemployable”.
What I would like to know is, where exactly is this supposed shortage? Which company doesn’t have over 250 applications to every advertised position? And why, if we scientists and engineers are in such short supply, can the relevant industries not be a bit more flexible in their requirements? Why is the first question from every personnel officer and every employment agency, “What industrial experience do you have?”
The response to the shortage of experienced scientists and engineers seems to have been to encourage people to obtain more of the qualifications that employers deem so inadequate in the first place. Why can the policy-makers and bureaucrats (and journalists?) not see that there are already thousands of us with academic qualifications, but little or no work experience? If anything, those with influence should be steering people away from academic qualifications and doing more to create employment within the science base.
Passive peril
Your article on Stanton Glantz and William Parmley’s review of the evidence on cardiovascular disease and second-hand smoking (This Week, 15 April) mentions that the tobacco industry resents the fact that the review did not take into account studies “sponsored by The Tobacco Institute”. There are two other, very recent studies not mentioned in that review in the Journal of the American Medical Association, but which the industry did not complain about being omitted by Glantz and Parmley.
A recent report in Preventative Medicine (vol 24, p 48) looked at carotid artery intimal-medial wall thickness “as an indicator of carotid atherosclerosis” and using data about people’s past and present second-hand smoking discovered that “both past and current passive smoking are associated with increased carotid intimal-medial wall thickness”.
Research carried out in Scotland revealed a “gradient of diagnosed coronary heart disease with both self-reported exposure [to tobacco-smoke pollution] and serum cotinine”, a metabolite of nicotine (Journal of Epidemiological Community Health, vol 49, p 139). This finding was “surprisingly strong, statistically significant, and unexplained by other factors”. We do not need scientific research to understand why the tobacco industry did not cite these two studies as being left out of the review in JAMA.
This current medical research is certainly of interest to more than just the scientific community. The British Government’s Scientific Committee on Tobacco and Health is supposed to come out with a statement on second-hand smoking later this year. Since this will be the first major government report in Europe to review the evidence on second-hand smoking since the firming up of the evidence on cardiovascular disease, the tobacco industry has a lot to lose if the committee essentially agrees with Glantz and Parmley.
Nor will the committee be rushing to judgement if it reaches the conclusion that passive smoking causes heart disease. By the late nineteenth century leading doctors were already suggesting the possible link between heart problems and breathing other people’s tobacco smoke. For some reason, the tobacco industry does not remind us that physicians have suspected the truth about second-hand smoking and heart disease for about a hundred years.
Fudging on fishing
Your editorial puts the blame for overfishing of the world’s fish stocks on fishery scientists, saying “scientists have said that more could be caught than turned out to be supportable by the fish populations” (Comment, 8 April). I am surprised that a journal of New 杏吧原创’s reputation should take such an antiscience stand when the fault is not at all with the scientists but rather with those responsible for applying science 鈥� the politicians and policy-makers.
A good example is provided with the European Union’s stand against Canada. Canada wants a limit of 27 000 tonnes for the Blue Whiting catch in international waters and has offered the EU half of this. Yet the EU Commissioner for Fisheries says this is not enough and if there is no agreement signed between the EU and Canada then the EU will go it alone and fish 18 500 tonnes. This is decidedly not what the fisheries scientists are recommending.
The EU’s so-called fisheries policy has always led to quotas being set in the North Sea which are above those recommended by fisheries scientists. What should the scientists do 鈥� recommend quotas half those they estimate as sustainable, knowing that the politicians will negotiate them upwards?
Up to now I have always been positive towards the EU, but the recent public outbursts of the EU Commissioner for Fisheries convinces me that the EU’s fisheries policy is more interested in sustaining fishermen than sustaining fish.
Sadly, it would not be practical to cancel out overfishing by simply adding iron to the oceans (Letters, 22 April). Rhodri Powell has misunderstood the significance of the iron enrichment experiments which he mentions.
These were aimed at mid-ocean areas which appear to have nutrients available (nitrate, phosphate and silicate) but do not support high phytoplankton populations. In such situations, it seems very possible that addition of iron increases the growth rate of phytoplankton.
However, the main fisheries occur in shallow seas and at shelf edges, where run-off from land and mixing from below supply plenty of nutrients, including iron.
Wrecks may attract fish, but the reason is not that phytoplankton bloom on the iron dissolving away. The effect occurs even in the deep ocean, where no light is available for phytoplankton growth. It is more probably to do with shelter, and with the availability of food from fixed organisms growing on the wreck.
It remains true that the way to conserve fish stock is to stop overfishing: there are no other “technological fixes”.