Letter
“Throughdoors” would be useful next to doors marked “Keep closed at all times”.
Present future
Time travel is not only enjoyed by the Scottish nation (22 November, p 35). May I bring to the attention of the world that we (the Swansea Valley Welsh) quite often address tasks “Now, in a minute” or “I’ll do that tomorrow now”. Case proven.
For the record
鈥� In “The fly that shouldn’t be able to” (29 November, p 14) we said the insects were collected in the Amazon. That should have been Arizona.
Just for us
Maybe it is not such an “accident that the moon is 400 times smaller than the sun and also 400 times closer”, as you state in your The Word piece about umbraphiles (1 November, p 51). Perhaps it is merely one further component of the anthropic principle that Leonard Susskind describes so thoroughly in the same issue (p 34).
If the discs of the sun and moon had not fitted so well, and eclipses had been “much less spectacular”, perhaps our ancestors would not have been so panicked into anticipating future occurrences. Perhaps our technology to build large structures, such as stone circles and mathematics, owes more than we realise to this motivation.
Spam tsunami
Your article on stopping spam mentions that “over a third of incoming email at New 杏吧原创 is now spam” (29 November, p 20).
For a period of one week between Sunday 26 October 2003, 21:11:24 hours (GMT) and Sunday 2 November 2003, 21:14:25 hours, we decided to log the number of emails that were sent to our Kite News and Information website.
In total, we received 984 spam or unsolicited emails, an average of 140 per day. Altogether, 97.4 per cent of our emails were junk. Unfortunately, this was a typical week.
Overbridges
Feedback is generally so well informed and is right to make fun of the various obscure, badly worded and illiterate notices that appear in the public realm. However, in attacking the use of the word “overbridge” Feedback shows a lack of engineering knowledge.
The terms “overbridge” and “underbridge” have been used on the railways since the 19th century to indicate the difference between those bridges where the road or footway is carried over the railway line and those where the railway line is carried over the road. Both words appear in the Oxford English Dictionary.
Letter
Talking of overbridges, Feedback’s predecessor, Ariadne, used to have an obsession with foot pedals. And a few days ago I saw another example of whatever phenomenon this is, which Feedback has unfortunately not yet coined a word for. A restaurant advised me that tables should be reserved in advance. I suppose at least that means it wasn’t the restaurant at the end of the universe where time travellers could reserve their tables afterwards.
Letter
One reason why time should stay based on atomic clocks is space exploration. For the solar system, relativistic effects must be tiny between planets, and it is absurd to change the standard because the Earth’s orbit has palpitations. Far better to count seconds from an arbitrary baseline and let each planet define its own days and years.
Risky radio
While the picture of Raymond Chiao’s gravity radio is reminiscent of Douglas Adams’s infinite improbability drive (8 November, p 38), Chiao’s thoughts on electromagnetic to gravitational wave conversion at anywhere near 100 per cent immediately reminded me of Terry Pratchett’s character Leonard de Quirm, whose combination of scientific brilliance and worldly naivety are considered so dangerous that he has to be locked away in seclusion not only for his own safety, but for the safety of the world.
The strongest indication of any significant success by Chiao will undoubtedly be the complete disappearance of the whole topic from open discussion 鈥� because the Pentagon will have grabbed the results, silenced Chiao and be working on perfecting a weapon capable of destroying armies and cities without chemical, biological or radioactive contamination.
We have named gravitational waves correctly
Computer co-pilots
May I correct a mistake in your article about drive-by-wire cars (8 November, p 28)?
Duncan Graham-Rowe states: “Pilots still operate cockpit controls similar to the old stick and rudder, but their commands are fed through 150 on-board computers before being translated into action.”
In fact, although the total number of computer boxes on board the A320 aircraft is around 150, most of them control less critical functions than moving the primary flight control surfaces (the ailerons, spoilers, elevators and rudder). Some, for example, control the water supply to the lavatories.
The flight control system consists of only five computer boxes. Two of these boxes, the elevator and aileron computers (ELAC), are duplicates of each other. ELAC2 controls the system in normal operation, with ELAC1 as “hot standby” in case ELAC2 fails.
Three further boxes, the spoiler and elevator computers (SEC), control different pairs of spoilers in normal operation, but can reconfigure themselves to take over some of the function of the ELAC if both ELAC boxes fail.
Setting the clocks
It’s amazing that a small bug in one particular GPS receiver with few, if any, practical consequences is mentioned in a New 杏吧原创 feature about measuring time (22 November, p 30).
I would like to correct some points. The responsibility for establishing international atomic time from some 200 atomic clocks worldwide rests with the Bureau International des Poids et Mesures, and not the International Telecommunication Union. The ITU is only the regulatory body that established the procedure for adding or removing leap seconds in the 1970s.
In recent years there have been a lot of discussions about the future of universal coordinated time (UTC), culminating in the meeting in Turin mentioned in the article. But, the only question submitted to the audience for a show of hands was: “Do you think the present system is adequate for the next 30 to 50 years?” Though the verdict was no, the majority for this was quite small.
The advantages of making a change are not clear. First, any change that is not backed up by a strong technical rationale is likely to create more havoc than it corrects, as the latest software bug shows. Secondly, the great majority of problems with the present system are caused by errors or intentional intervention by humans, and this will remain true even with perfect regulations.
Expanding fast
Marcus Chown says that the universe was 18 million light years across when it was 760,000 years old (1 November, p 16). If a light year is the distance travelled by light in one year, and if the universe expanded uniformly from a point at the speed of light, it should have been only 1.52 million light years across. Which of the above assumptions is incorrect, and what does a “light year” mean if something is travelling faster than the speed of light?
Marcus Chown writes:
鈥� It is perfectly true that Einstein’s special theory of relativity forbids material bodies travelling faster than light. But in 1915 special relativity was superseded by the general theory of relativity. Applied to the whole universe, this puts no limit on the rate at which the fabric of space 鈥� the backdrop against which the cosmic drama is played out 鈥� can expand. As general relativity pictures it, the galaxies are not moving; they are nailed to the fabric of space, which is expanding. And space can expand at any rate it likes 鈥� even faster than light, which it most certainly did in the earliest moments of the universe.
Non-violent biology
Your article on alternatives to antibiotics in the control of bacteria raises a question of wide significance (29 November, p 34).
In effect, the approach accepts the existence of potentially harmful organisms and, rather than attempting to exterminate them, seeks to discourage their activity in specific locations or to reduce their virulence.
This bears a strong resemblance to the unexpected finding earlier last month by the UK government’s trials assessing the effectiveness of exterminating badgers as a means of controlling tuberculosis in cattle. The trials showed that exterminating colonies in areas where TB is rife has the paradoxical effect of increasing badger activity, and that control might best be established by non-lethal means.
A species’ paramount need to survive requires its members to find ways of resisting extermination at any cost. In less threatening situations the same need requires it to conserve energy, making it amenable to gentler controls. Does this suggest an evolutionary basis for non-violence as the most effective response to threats at any level?
Matching irises
The assertion by Simon Davies that iris recognition generates high rates of false matches will probably now become gospel, and it may set policy, even though it completely contradicts all published scientific studies of this technology (22 November, p 13). In fact, those studies have reported no false matches even after millions, and even hundreds of millions, of comparisons between different iris patterns. (A bibliography of test reports can be found at ).
In the largest national deployment of iris recognition to date, the United Arab Emirates (UAE) Ministry of Interior requires iris recognition tests on all passengers entering the UAE from all 17 air, land and sea ports. Via internet links each passenger is compared against each of 293,406 former expellees (foreign nationals expelled for visa and work-permit violations) whose iris codes were registered in a central database during an amnesty. The time required for an exhaustive search is 2 seconds.
So far 1,011,876 exhaustive searches against that database have been done. Something in the order of 100 billion iris comparisons have been performed. A total of 3684 matches against this watch list have been found by these iris algorithms. According to the UAE Ministry of Interior, none of these matches has been disputed, and all have ultimately been confirmed by other records.
If Davies’s assertion that iris recognition has a false match rate of 1 per cent were correct, then those 100 billion iris comparisons should have generated 1 billion false matches, instead of zero.