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Good to hear that the largest-known prime number has been found – but at what cost in terms of energy consumption? Rather than rewarding the finder with $3000, perhaps that money would be better spent on carbon offsetting ( 2 November, p 19 ).

Your story on how the Neanderthals really died amid the rise of Homo sapiens , based on regional occupation, sounds like a perpetual hunt/war between the two groups. It would have started with Neanderthals hunting invasive "weak" humans until our species got smarter and tried to eliminate them ( 12 October, p 36 ). Those …

Despite its name, Barnard's star isn't in Barnard's galaxy ( 26 October, p 30 ). A new type of energy storage device that could be used on Mars is a supercapacitor ( 2 November, p 12 ). In our look at precision nutrition, we misattributed a quote to Regan Bailey ( 2 November, p 38 …

Kelly and Zach Weinersmith consider challenges to living on Mars. Fictional futures sometimes improve the Martian climate by moving the planet closer to the sun, but the more I learn, the less plausible these scenarios seem ( 16 November, p 48 ). Back-of-the-envelope calculations suggest that moving Mars into Earth's orbit would require energy equivalent …

I fear Mars would be a dreadful destination for colonising for all the reasons stated, plus the planet-wide dust storms that would kill any hope of photosynthesis for periods and interrupt solar power. And what about surviving the maddening isolation? At least on the ISS one can look out of the window at the beauty …

Neither your article on the impact of food production on the planet nor the editorial that accompanied it mentions the health and maintenance of the largest biome bar the ocean: soil. It is unlikely that wheat yields could increase by 18 per cent by 2100 if farmers keep doing what they are doing unless you …

As a myope and optometrist, I find the term "disease" for myopia misleading. Axial length of the eye is a continuum; people whose eyes don't grow long enough have hypermetropia/long-sight. No one says this is a disease, but it also requires spectacle correction ( 16 November, p 40 ).

When it comes to myopia, there is a mystery that has long plagued me. After illness kept me at home for a few days, I returned to school to find I could no longer make out writing on the blackboard. A lifetime of spectacles and contact lenses to correct "short-sightedness" ensued. My mother always insisted …

Myopia isn't all bad news. Reading small print or seeing fine detail is easy even as an adult, when this acuity can otherwise fade. Perhaps an evolutionary advantage arose after fine craftsmanship became an essential survival skill.

For most of my life, my brain rendered the moon as a flat disc or crescent in the diamond-studded canvas of the night sky. However, I discovered that if I think of the moon as spherical while I look at it, it pops out that way. Instead of a flat object, I see it for …