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31 July 2019
From Butch Dalrymple Smith, La Ciotat, France
Over and over, we hear that one of the solutions to global warming is to plant trees ( 20 July, p 20 ). Certainly, these magnificent means of pulling carbon dioxide out of the atmosphere are an essential part of our response to climate change. But it is equally important to do something with the …
31 July 2019
From Scott McNeil, Banstead, Surrey, UK
Electric cars are in the news again ( 13 July, p 18 ). Over the past few years, I have become concerned that people often treat battery-powered electric vehicles as a panacea. I see many problems with this. If demand for cobalt, nickel and lithium for batteries can be met, it will cause environmental damage …
31 July 2019
From Hillary J. Shaw, Newport, Shropshire, UK
Chris Stokel-Walker reports that ransomware attacks are on the rise ( 13 July, p 9 ). Surely these can almost always be defeated by backing up all data securely to a computer that has no internet access? Can't we design software that will do this automatically, as often as every 5 minutes if necessary? Its …
31 July 2019
From Peter Basford, Potters Bar, Hertfordshire, UK
Guy Cox suggests that the inability to make a decision proves free will exists (Letters, 6 July ). A deterministic decision-making process can find the weights of multiple options to be equal and so be unable to decide. It doesn't follow that because I can't decide whether to have an extra pint before I go …
31 July 2019
From Chris Brausch, Thames, New Zealand
It seems that lost wallets with more money inside are more likely to be returned than those with smaller sums ( 29 June, p 17 ). Someone who finds one will probably consider the amount of trouble they would have to go to in order to return it compared with the benefit to the person …
31 July 2019
From Anne Sproule, Ottawa, Canada
I wonder why Ruth Searle writes of surprise that cat owners were found to be more adventurous and unconventional than dog people ( 6 July, p 43 ). Just last year, you reported that many cat owners are infected with Toxoplasma gondii , a parasite carried by cats that makes infected animals, including humans, more …
31 July 2019
• Cold facts: An Arctic fox travelled 3506 kilometres during a 76-day polar marathon ( 6 July, p 16 ). • We're shaken: The epicentre of an earthquake is on Earth's surface above its focus ( 13 July, p 7 ).
7 August 2019
From Frank Dawson, Liverpool, UK
The juxtaposition of your articles on the moon landing ( 13 July, p 36 ) and news of Arctic wildfires ( 13 July, p 14 ) was interesting . You imagine a moon base in 2069 producing textiles and art that command high prices back on our planet. And on Earth today, one of the …
7 August 2019
From Keith Ross, Villembits, France
Michael Brooks writes that hot liquid iron rises towards the exterior of Earth's outer core, then cools, becomes more dense and descends ( 29 June, p 34 ). This implies, as do most textbooks, that hot stuff somehow rises spontaneously. It is gravity pulling harder on the denser material that starts things off, with the …
7 August 2019
From Ben Haller, Ithaca, New York, US
The ability of seals to recall what they have just done and repeat it on command doesn't suggest awareness or mean they have "a degree of consciousness" ( 13 July, p 16 ). My computer can remember what it does and undo and redo those actions. But that is no reason to think it is …
