Amber alert
David Holzman reported that exposure to blue light at night can restrict levels of melatonin (7 May, p 44), with possibly serious effects on the body clock and health.
I first heard about this in 2007 during the European Symposium for the Protection of the Night Sky, in Bled, Slovenia. It was suggested that lamps could be fitted with a filter to remove blue light, perhaps using amber stage-lighting gel sheets.
My upstairs lights are covered with such sheets, and the blue-rich bedside LED reading lights have a double layer. We are healthy and sleep very well; better, I think, than before the lights were changed.
You could use the same thing over your computer screen if you must go online at bedtime.
What worries me is that people who have slept for years with an old-fashioned, low-pressure sodium street light illuminating their bedroom with almost monochromatic orange light, may suffer 鈥� perhaps through cancer, years from now 鈥� as a result of that system being changed to produce new-fashioned white light.
In any case, street lighting should light the street, not our living space.
鈥� The editor writes:
The capacity of light at night to suppress melatonin depends on both its wavelength and intensity. So while blue light has the strongest effect, other wavelengths can also affect our circadian cycle.
Worldwide waste
Your rather wonderful feature “The next wave” (14 May, p 30) listed technologies predicted to be big in the next decade and suggested what a “lexicon of tomorrow” might contain.
How about shifting your suggestion of “digital litter” to the lexicon of today, as a useful term for the many websites that can be accessed long after the businesses, societies or clubs that created them have become defunct and their contact details obsolete.
Just now I checked and, sure enough, a personal website created by an old acquaintance is still running 10 years after he died, with no mention of the fact that its creator is not going to be answering any emails.
Given that many older websites had unchanging static content, the code and files that create the pages are so small that many internet service providers cannot be bothered to clear them out, and free services such as Facebook are also unlikely to remove pages unless someone tells them that they are now just digital litter.
鈥� The editor writes:
Of course, one man’s litter could be another’s legacy, as mentioned in Sumit Paul-Choudhury’s recent look at efforts to archive the digital records of those no longer with us (23 April, p 41).
Schr枚dinger spat
Your article “Cruelty-free quantum probes” (30 April, p 8) invoked Schr枚dinger’s famous thought experiment involving a cat in a closed box which also contains a booby trap with a quantum trigger. The cat is both dead and alive until it is observed, raising the question as to whether a conscious observation is required to determine its fate.
Some have taken this idea so far as to say never mind the wretched cat 鈥� according to Niels Bohr’s Copenhagen interpretation of quantum mechanics, the whole universe only exists because humans observe it. This is deifying humanity.
I believe Bohr was satisfied that any “unconscious” measurement by some form of detector , and the cat would certainly be a sufficient detector long before the box was opened.
If conscious observation were really required, virtually all undergraduate textbooks would exist only in a superposition of states.
From David Prichard
The Schr枚dinger’s cat paradox could perhaps be solved in an easier way than by placing a tiny vibrating wire into the closed box, as you reported.
If a microphone and transmitter, in a “superposition” of two states, were first placed in the box, the sound of the cat’s breathing would suggest it was alive. If it were absent, it would be reasonable to assume it was dead.
If, on the other hand, the sound of purring were transmitted, it would present another imponderable, insofar as the cat might either be alive in the box or dead, having arrived at its Shangri-La.
Bluff Point, Western Australia
No long-term fix
Creating nitrogen-fixing, non-leguminous crops (7 May, p 8) to boost food supply could support an increased human population, only to have it face the “end” of mineral nutrients extracted from the earth, such as phosphorus and potassium.
Nitrogen is an atmospheric plant nutrient, along with carbon, oxygen and hydrogen. We are not at risk of running out of atmospheric nutrients as the atmosphere rapidly cycles them.
Nutrients from the rocks and soil of the lithosphere are only cycled at geological speed. The current approach of mining them and then using them, often inefficiently, to boost crop yields before they are washed away on what, in human timescales, is effectively a one-way trip to the oceans, is foolhardy.
Phosphorus , in the next 50 to 100 years. Others will follow, such as .
There are no known practical means of recycling lithospheric nutrients from the oceans back to farmland and, unlike energy, for which there are alternatives to fossil fuels, there are no substitutes for these elements.
Nitrogen-fixing crops would only be setting humanity up for an even bigger fall.
Humans first
Learning to talk to dolphins is a charming, romantic notion, but it seems a big jump from the researchers using their software to analyse footage of sign-language and gym routines (7 May, p 23). Unnecessarily big.
Wouldn’t it have made more sense to try it with some obscure human languages first? The investigators and their software might learn things that would then be useful in inter-species communication.
Higgs no-show
The story about another hint of the elusive Higgs boson amounting to nothing (7 May, p 6) set me thinking. As a 16-year-old physics student, I find myself enraptured every time its tentative discovery is reported. Most times, I am disappointed.
However, the longer the Higgs remains elusive, the greater my hope grows that we, in fact, never discover it, effectively forcing physicists to rewrite the standard model from scratch.
Missing memory
I was fascinated by “Our forgotten years”, your article on childhood memory (30 April, p 42). I have a distinct early memory but the events are incomplete and I have always thought the full version must be buried in my brain. Now I realise it might not be.
I was about 3 and wearing a blue velvet-trimmed coat, so I am fairly certain of my age as, in post-war austerity, I only had one coat at a time and it appears in photos.
My mother parks my pushchair in our hallway, then lifts me out. My father is in the kitchen washing something in the sink and has wet hands. I run down the hall wanting him to pick me up. He smiles and calls out, “But I’m all wet!” I see his dripping hands and the memory ends abruptly. Did he pick me up?
Although it is of no real consequence, I would love to know what happened next, and still hope that one day something will spark the rest of the memory. It is disappointing to realise it may never happen.
Cold killer
In the story on dangerous ice build-up on aircraft (30 April, p 17), Paul Marks stated that “as ice accretes on the wings and tail, it changes their shape, creating drag. That, in turn, reduces the airspeed which is needed to generate lift 鈥� leaving the aircraft at risk of stalling”.
This wasn’t quite right. Ice build-up does increase drag, which slows the aircraft, while also raising the airspeed at which a stall occurs, thus creating a double whammy resulting in increased stall risk.
Beyond control
The description of three levels of technological complexity in “We’ve made a world we cannot control” (14 May, p 28), to describe function, network interactions and, lastly, an unfathomable interplay with the wider world, seems a very useful idea. Maybe we can take it further by giving them descriptive names: level 1 = stand-alone, level 2 = connected, level 3 = ecological.
We never had more than a very limited amount of control over the world. What we have plenty of is the illusion of it.
Outlook good?
BBC environment analyst Roger Harrabin’s plan to publicly (7 May, p 28) is to be applauded. Next, could someone do something similar for economic forecasts?
Sun-powered rocket
The “lightcraft” and the heat-exchanger rockets in “Beam riders” (30 April, p 38) may succeed in launching the next generation of spacecraft, but why bother with lasers and microwave generators?
A large could collect the reflected sunlight from an array of mirrors covering several thousand square metres, and focus it into a narrow beam. On a clear day in a sunny desert, this ought to generate sufficient concentrated radiant energy to power a plasma engine.
Launching a satellite with solar power alone could be highly cost-effective, as well as an inspiring application of green technology.
From Michael Kellock
Reading “Beam riders” coincided with a nostalgic journey through the Buck Rogers comic strips of 1931. In , Buck and Wilma set off in their “gyrocosmically stabilised” rocket ship, which bears an uncanny resemblance to your diagram depicting Leik Myrabo’s “lightcraft”, but with an added partial skirt for stability on landing.
Clearly, these early comic-book efforts are worthy of research.
Foster, Victoria, Australia
For the record
鈥� In the diagram in our solar systems feature (14 May, p 46) the four outer planets were mislabelled. From left to right, they should have been Jupiter, Saturn, Uranus and Neptune.