Your letters
Saving our figures and the planet too
4 May, p 28
From Grace Bedell, Toronto, Canada
You review a new book on weight loss drugs that are taking off. Could these hold more promise than just reducing waistlines, one related to the link between food production and its impact on our planet? While many hope the drugs will make them slim, one side-effect could be that sales of fast food, highly processed food and snacks drop, assuming a lower appetite means fewer cravings for them.
If so, then perhaps this will also lead to less clearing of the biosphere for resource-greedy monocultures, plus the reduced production of tree pulp or fabrication of plastics from fossil fuels, both of which are used to package processed foods.
Direct air capture is just a drop in the ocean
25 May, p 12
From Keith Parkin, Sheffield, UK
In coverage of the direct air capture industry, you mention a plant being built to remove half a million tonnes of carbon dioxide per year from the atmosphere. This apparently impressive figure needs context.
In my youth, the colliery in my village was producing a million tonnes of coal per year, and within 20 miles were at least another eight similarly prolific mines. The current plans for carbon capture are frighteningly inadequate. I await, without holding my breath, any mention of this in the pledges for the forthcoming UK election.
Born to run? More like born to use our brains
18 May, p 11
From Geoff Harding, Sydney, Australia
It isn’t surprising that there has been criticism of the idea that humans evolved to chase down prey over large distances. The need to do this regularly would suggest an inability to hunt strategically or co-operate with others, which is somewhat insulting to the developing human intelligence.
Sensible strategies would have involved the use of hunting weapons and traps or driving an animal a short distance towards an ambush by fellow hunters, with factors such as wind direction considered to avoid detection by scent. This would have been highly energy efficient and both men and women would have participated.
Why aliens probably won’t bother with Dyson spheres
18 May, p 12
From Alan Worsley, Hull, East Yorkshire, UK
How feasible are Dyson spheres, signs of which may have cropped up in a survey of 5 million stars in our galaxy? The basic engineering logic behind these proposed alien structures that encircle a star to capture all its energy isn’t obvious.
It makes sense that you would start building in certain ways. A narrow equatorial belt – akin to the asteroid belt or Saturn’s rings – would have a degree of orbital stability for siting parts of such a structure, and components could be joined in their existing orbits. However, as soon as the structure is extended towards the poles of a sphere, this stabi
