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With reference to the interesting article by Ciarán 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 …

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 …

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 …

As an ordinary reader trying to make sense of the universe before breakfast, I was delighted by your feature on quantum causality. The idea of "causal bubbles" gave me a way to picture the quantum world without feeling out of my depth ( 29 November, p 36 ). By chance, I had just finished your …

The article on causality in quantum theory reminds us that, until an observer takes a measurement, we are confronted by a fog of possible alternatives and that the measurement will cause these distributions to "collapse" to finally reveal definite properties. These quantum scenarios appear less weird if we liken them to every point in space …

Your feature explores the issue that nothing seems to be fixed until it is measured. Measurement can be an observation. What quantum theory doesn't explain is that it all depends on who is observing an object. That is why, after I have failed to find a particular object in the fridge, when my wife then …

I cannot agree more with Anthony Laverty's article on the need to curb the trend towards big cars. Not only are they more lethal in a crash, they are also more likely to be involved in accidents because of larger blind spots and longer braking distances. I call for regulations to inconvenience big car owners …

Laverty perfectly sums up what can only be described as the biggest environmental crisis ever to hit UK roads, and beyond. Let's hope this subject gathers much-needed momentum.

In reference to Claudia Canavan's article, "Time for a new you", I have been applying the Myers-Briggs Type Indicator – which categorises people into 16 personality types – for over 30 years ( 27 September, p 23 ). Despite often being dismissed, it has always "said" everyone is both an extrovert and introvert (just not …

Your article on giving up on your ambitions put me in mind of a passage from P. G. Wodehouse that has stayed with me since I read it over 30 years ago ( 15 November, p 28 ). In it, he succinctly summarises the gist of the article: " 'Well, well,' he said, 'if I …