Letter
The notion that a moving solar sail can pick up energy from light because of the Doppler shift makes no sense. From the frame of reference of the moving sail, incoming light is already Doppler-shifted to the lower energy that a stationary observer sees reflected from the sail. In other words, the sail does not experience any Doppler shift in its frame of reference, and therefore there cannot be a difference in energy between the light that arrives and the light that is reflected.
The Doppler shift cannot explain solar sailing because it is irrelevant to the problem.
A snip of danger?
The article on masturbation and prostate cancer has highlighted a concern that I and many other men who have had a vasectomy will find worrying (19 July, p 15).
Having had the snip, our seminal fluids are now absorbed into our bodies instead of being ejected. Does this mean that we are now more susceptible to a variety of different cancers?
Coley's comeback
Sylvia Pag谩n Westphal’s article on how the anti-cancer drug Genasense may work (19 July, p 32) reminded me of another New 杏吧原创 article on William Coley (2 November 2002, p 54).
Coley tried to treat cancer with a home brew of dead streptococcal bacteria. If Genasense works by provoking an immune response to CpG gene bases usually found in bacteria and viruses, then it is possible that Coley’s toxins worked in the same way.
The bad news, if true, is that many doctors have been ignoring useful treatments for over 100 years. Millions of dollars have been invested to replicate the effect of poor hospital hygiene. How embarrassing.
Fishing compassion
James Hamilton-Paterson’s letter argues against Fred Pearce’s assertion that local communities “should work harder to police fishing” and correctly explains that no amount of argument will make a difference to fishing in poor countries unless poverty is addressed (12 July, p 22).
Misguided policing has malignant effects. The Australian government imprisons Indonesians who fish in Australian waters, even though these have been their traditional fishing grounds for millennia. The Indonesians do far less damage to fish stocks than large fishing fleets with modern equipment. Those imprisoned in Australia leave behind families who have no recourse to social security and who have to repay large loans taken out for the rent of the fishermen’s boats, which are burnt by Australian authorities.
I propose that the Australian government bring some compassion to fishing laws in its northern waters, as these laws have a devastating effect on the lives of so many who are already among the poorest in the region. They do nothing for the environment, since Australian trawlers are still allowed to fish these areas.
Exhaustive test
The technique of extracting drinking water from vehicle exhausts was pioneered in the UK during the second world war by a team led by Neville Shute Norway during his time with the Admiralty Department of Miscellaneous Weapon Development (19 July, p 17).
They conducted a successful 5000-mile run around Britain in a Bedford truck, recovering around 1 gallon of water for each gallon of fuel burnt. It was never used in action, as by then the army had moved from the North African desert to Italy, where there was no shortage of water.
Smoke in peace
The only thing criminal about cannabis is the fact that it’s illegal in the first place. Why waste all this expensive DNA technology chasing people who just want a smoke in peace (12 July, p 7)?
The US should learn from its prohibition mistake and grow up.
Unconvincing win
I still do not subscribe to the view that Gary Kasparov lost to the computer Deep Blue (12 July, p 40). He was playing against a team of computer programmers with plenty of time at their disposal. He lost once out of one game. Had he lost 9 out of 10 games then a significant conclusion could be drawn.
Your interview with Kasparov gives a most interesting insight into his mind, but the most significant fact is the statement in the box on p 42 that IBM hastened to dismantle Deep Blue once it had defeated Kasparov.
Nostalgia for nostalgia
Stephanie Pain vividly portrays the 17th-century disease of homesickness, but she errs in saying “nostalgia was consigned to history” after the American civil war (19 July, p 48).
As a “contagious disorder” that might “spread with the speed of an epidemic” through army induction centres, nostalgia figured during the second world war on the US surgeon general’s list of dreaded maladies. As late as 1946 an eminent social scientist termed it a possibly fatal “psycho-physiological complaint”.
Homesickness was a typical student affliction, treated alongside flu and hepatitis at university health centres. From the 1970s, as shown in my book The Past is a Foreign Country, nostalgic yearning, focused on past time rather than past place, became endemic in western culture.
So extensive was the regression, so obsessive the pull of the past, that the historian Jay Anderson feared “we are entering a future in which people may again die of nostalgia”.
But nostalgia isn’t what it used to be. Under the healing hand of the marketplace it has morphed into a mainstay of tourism. Nowadays we feel nostalgic for nostalgia. “Remember nostalgia?” wrote George Trow. “Remember remembering your first kiss鈥our first prom?鈥es, you remembered it all in the 70s, the Golden Age of Nostalgia.”
Stiff structure
About half of the population are more personally familiar with a “hydrostatically stiffened structure against which muscles can pull” than they are with a sea anemone or elephant’s trunk (19 July, p 17). The other half are probably also aware of the organ in question.
For the record
鈥� Our article “The sun catcher” said that NASA’s Genesis spacecraft went on a 3-month journey to a region 1.5 kilometres from Earth (26 July, p 26). It should, of course, have read 1.5 million kilometres.
Gun lore
Roger Taylor trots out the old saw that the only way to reduce gun crime is to arm every citizen (26 July, p 24).
That is like saying the only way to avoid automobile accidents is to let everyone drive very fast so they all get where they are going before any accidents can occur.
The fact is that in the UK the level of gun crime, though on the rise, is a tiny fraction of gun crime in just one city in the US, where the gun is almost ubiquitous. The main reason for this disparity is, I think, that access to weaponry is far easier in the US than in the UK, simply because there are so many more guns in the US.
According to pundits like Taylor, gun crime should be astronomical in the UK, where few people own guns legally and villains can arm themselves at will. But since the opposite is true 鈥� the level of gun crime is many orders of magnitude lower in the UK than in the US 鈥� the argument is without foundation.
Arming every citizen can only increase the level of gun crime. That’s not rocket science 鈥� it’s simple common sense.
Letter
Your correspondents are of the opinion that gun safety can only come from the user. If so, why do guns have safety catches? I have never heard of a gun having its safety catch removed 鈥� because users, legitimate or otherwise, understand them.
T. Martel likened “safe” gun technology to a desktop PC. I think that the technology would be much better compared to ABS brakes on a car, which are widely accepted even though they could prevent the driver from stopping if they malfunctioned. The widespread use of this technology implies that it has been reliable.
Your correspondents seem to rubbish the idea of investigating any extra gun safety because of problems, real or perceived, in some proposed safety devices. Safety devices should be researched, even though not all will be incorporated.
Deluded computers
In his article on computers and consciousness, Igor Aleksander was quite wrong to say that “Susan Blackmore鈥� implies that constructing a machine that is conscious like us would be impossible” (19 July, p 40).
I do indeed claim that consciousness is an illusion. This is because it feels to us humans as though there is a continuous flow of experiences happening to an inner self, when in fact, there is no such inner self. Computers have no inner self either, but if ever they start thinking they do they will become deluded like us, and hence conscious like us. And that day is surely not far off.
We humans can sometimes wake up from our delusion, through intellectual insight or through practices like meditation. Maybe future computers will teach us a thing or two about waking up from illusion.
Letter
The arguments for or against the notion of consciousness emerging from machines overlook an important fact. Human beings differ from machines in one very important way: machines break down or are switched off, while human beings die.
This is an important distinction and it raises the question: does death play a role in consciousness formation? That is, does consciousness evolve because we are going to die? If so, how could you program a machine to die? Somehow, it would have to be ever aware of this inevitability.
One could argue that our drives and our sexuality are all fuelled by the presence of death, however unconsciously. It determines what we do and motivates our need to “leave something behind” when we die. In the absence of this dimension of death, researchers will end up only imitating consciousness, and not getting any closer to understanding it.
Impossible sails
My thanks for having the nerve to publish something so far removed from the majority opinion on solar sailing (5 July, p 16).
In response to your correspondents (19 July, p 26), let me make clear that I am not saying radiation pressure does not exist or that it does not act in many other circumstances. I’m only saying that a mirror will have no radiation pressure exerted on it.
As your article stresses, one cannot hope to overcome the laws of thermodynamics regarding the transfer of heat to mechanical energy by turning the heat first into radiation. If heat cannot be transferred to free energy, likewise free energy cannot be created from heat via radiation.
Also, I am not suggesting the solar wind will not exert a force on the sails. Charged particles in the solar wind will exert the usual forces of gas dynamics. However, solar sails were thought to be a much better solution than merely depending on the solar wind because the radiation pressure that is proposed to come from light would be far greater. It is this light pressure that I believe does not exist.
Many correspondents thought that the Doppler effect would allow a degradation of the energy to take place for energy to be transferred to the mirror. But if you work out the exact amount of energy transmitted in a pulse of energy and received with a certain Doppler shift, the total energy arriving due to that pulse will still be exactly the same. The only thing that happens is that the pulse will take a longer or shorter time to arrive. Its total energy will be unchanged, and therefore, leave no energy to be given to the mirror.