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I can slightly move the "useless" muscle that lets some people wiggle their ears. Of more interest is that I feel the muscle slightly twitch when someone/something approaches outside of my visual field. It feels almost like a sixth sense, but obviously it is linked to my auditory system picking up a sound I don't …

In fire-prone southern Australia, intentional burning to combat wildfire risk is controversial. These burns run for weeks every autumn and the smoke is a health and environmental hazard ( 1 February, p 12 ). The effect on wildlife and plants seems to be rarely taken into account. Fire does reduce fine, easily burned plant matter, …

Paul Friedlander says past colonisation has been a hunt for opportunities to trade or get rich, hence the same will apply to Mars. This leaves out one of the strongest drivers: curiosity/adventure. It is often assumed that billionaires are motivated by money, but if you look at Martian colony proponent Elon Musk's track record, he …

The same sentiment that "you will probably never own a personal quantum computer" was felt about conventional computers in the 1950s, 60s and 70s. Current quantum computers are still nothing but proofs of concept. But once commercially viable and useful ones become available to buy, the pressure will be on to make them more powerful …

As an engineering student decades ago, I was taught that a simple empirical formula that gave a "good enough" result was more useful than a perfect, correct analysis with too many variables ( 15 February, p 19 ). A case in point is the "best boiled egg" method you reported. It was fascinating and illuminating …

You report the idea that the use of crushed rock on agricultural land to capture carbon may also alter Earth's reflectivity. However, this geoengineering proposal isn't practical. A millimetre-thick layer of rock per hectare weighs around 20 tonnes. Extended to 1.5 billion hectares of cropped land in the world, and that is a lot of …

I wonder if any change in reflectivity due to spreading crushed rock on farmland would only occur where there was no crop cover. And would the rock deplete carbon dioxide where crop seedlings grow, reducing viability? I suspect this method would be only for areas with no plant cover.

The problem with recognition of alien intelligence raised in your review of Adrian Tchaikovsky's book Shroud was also tackled in a short sci-fi story from the 1970s, in which some humans get stuck on a very warm and humid planet where every artefact they have rapidly rusts or rots. Aliens arrive, assume they are indigenous …

While Filippo Tommaso Marinetti is said to have founded futurism in 1909, the word was actually created in 1904 by Catalan writer Gabriel Alomar at a Barcelona conference ( 8 February, p 22 ). His was an aesthetic movement, but also a political one, in a sense opposite to Marinetti's. Alomar was unequivocally democrat, Catalanist …

Beth Morrell makes the excellent point that the modern world is grossly mismatched to the one in which we evolved. The restraints of our evolution on our thinking are there to be seen in our actions. We continue to wreck the planet, render its air toxic, pollute rivers, destroy wildlife and slaughter our own kind. …