A quantum view of the past, present and future
With reference to the interesting article by Ciar谩n Gilligan-Lee on quantum cause and effect, I would point out something that I have often noted, but that is always overlooked (29 November, p 36).
History can be understood in quantum terms. The future is nothing but a series of probabilities, the present is where we “measure” them by experiencing them, the past is things that have already been measured. No observer is necessary to make these “measurements” 鈥� they would happen even if no life had ever existed. Each present of each individual entity exists independently and relative to all the others (in its own causal bubble), but all are consistent and fit into one coherent whole. And what drives the course of history except cause and effect?
Reality as we experience it, and the reality of the quantum world, are often typified as different. In fact, we have a parallel classical world and quantum reality always around us and observable at every moment of our lives.
The yin and yang of human evolution
Jonathan R. Goodman argues that the selfish gene view of evolution is correct and bemoans the “old and tired” debate on whether niceness and group selection trump that. It is this binary thinking that is old and tired. Evidence for each view exists and must be synthesised into a 360-degree view. Competition and cooperation are the yin and yang of evolution. Their interaction is the endless dance of behaviour and adaptation we call life (15 November, p 19).
Hearing aids that know which way you're facing
Richard Black asks if a hearing aid can be designed with software to selectively amplify sounds coming from the direction you are facing. I can tell him that my hearing aid does exactly that (Letters, 22 November).
Instead of picking up all the sounds entering the ear and amplifying select frequencies, my hearing aid software can be set for “Conversation in Loud Noise”. In theory, I can sit facing my wife in a crowded restaurant and forward-facing microphones amplify what she is saying, so I can hear her. In practice, they don’t work quite like that. Yes, I can hear what she says, but I can better hear the ladies who are lunching a couple of tables behind her.
A counterpoint on biomass carbon capture
David Flint says biomass carbon capture would require too much land area. He favours using chemical plants to capture carbon dioxide from the air. I would like to point out that, every year, about 440 gigatonnes of carbon dioxide enter the atmosphere from rotting vegetation, whereas we have about 1100 gigatonnes more carbon dioxide in the atmosphere than in pre-industrial times. In other words, if we could store all the biomass that rots, we could solve global warming in a couple of years. The problem isn’t land area, it is how to collect and store vast quantities of biomass, and how to incentivise this (Letters, 22 November).
A response to our review of Mars documentary
As a contributor to the documentary Blue Planet Red, I would like to address the criticism in Simon Ings’s review that xenon-129’s presence in the Martian atmosphere implies ancient nuclear conflict only if you ignore the well-understood process by which a now-extinct isotope, iodine-129, would have decayed to xenon-129 in Mars’s rapidly cooling lithosphere (11 October, p 32).
When Mars and Earth formed 4.5 billion years ago, they contained both iodine-129, source of xenon-129, and plutonium-244, source of xenon-132. The half-lives of both isotopes are comparable in geologic timescales and their decay products should have both outgassed by now.
On Earth, these isotopes are approximately equal in abundance in the atmosphere, but on Mars, there is 2.5 times more xenon-129 than xenon-132. The mystery is why the iodine-129 decay product shows up, but there is less of the plutonium-244 decay product.
Supernova and thermonuclear weapons both produce iodine-129 preferentially over plutonium-244. Mars didn’t experience a supernova, hence I propose that the xenon-129 excess, along with other evidence, is explained by a thermonuclear holocaust.
Mystery still surrounds the dawn chorus
You report that a study by Satoshi Kojima and his colleagues may have solved the mystery of why birds sing at dawn, suggesting singing is suppressed by darkness, leading to a build-up of motivation that is released when the dawn breaks. This may explain the mechanism that mediates the diurnal pattern of singing, but it hardly explains why dawn singing has evolved (1 November, p 7). Other behaviours are also suppressed by darkness, so why, for example, do songbirds not respond to the daybreak with a burst of intensive feeding or some other behaviour?
Admiration for ancient cave paintings
Regarding the feature Songs from the caves, the Lascaux cave paintings in France include a star map of the Taurus region of the sky with a bull painted around the Hyades, just as the constellation is depicted today (22 November, p 34). Dated at 17,000 years old, surely this is the oldest provable human concept? After viewing this cave art, Pablo Picasso proclaimed: “We have learned nothing in 12,000 years.”
Why it's futile to chase after perfection
On the discussion of knowing when to give up on your goals, I contend that longing for perfection of oneself is an exercise in futility and frustration. Why? Because none of us is perfect and, despite our best efforts, alas, none of us will ever be perfect. Let’s all relax a little and not set ourselves unachievable goals (15 November, p 28).
For the record
The Torino scale assigns asteroids a score of 0 to 10 based on their size, energy and probability of hitting Earth (15 November, p 38).