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Lara Williams supports the UK ban on e-cigarettes on public transport and in workplaces ( 1 September, p 22 ). But how do we know what the health effects of keeping or ending the ban would be? I would like to propose a clinical trial to test the effect of passive vaping. It will not …

Oh please... I'm tired and depressed even without gluten Colin ( @diabloamp47 ) has nothing to fear from news that eating gluten could make you tired and depressed ( 22 September, p 15 )

Michael Le Page reports that air conditioning could warm Paris by an extra 2°C and that it is expensive to install and run ( 4 August, p 18 ). Do not overlook absorption and adsorption cooling systems. In these, energy is required only to circulate the fluid being cooled through the evaporator. Such systems can …

You observed that our inboxes were full of pleading emails because of the European Union's new data rules ( 26 May, p 22 ). Now, every website asks for our consent to set cookies and so on. Has anyone estimated how many hundreds of millions of extra mouse clicks have been caused by the General …

I much enjoy the ongoing discussion of consciousness in your pages (for example, Letters, 21 July ). It seems to me that one cannot just be conscious: you have to be conscious of something, whether it is the scent of a rose, the internal feeling of being happy or sad, or the words you are …

• Land of the rolling wheel, still: Japan's bullet trains do not levitate (Feedback, 8 September ).

You ask what kind of force is evolution (Leader, 1 September ). Evolution isn't a force. It is a description of the process by which species change over time in response to their environments. And it makes no sense to see it as either malevolent or beneficial, although you may like or dislike the results …

You announce your report on ways to outwit evolution ( 1 September, p 28 ) by saying on your cover : "Nature used to decide how life turned out. Now we do". But we are products of nature's evolution and everything we do is part of the evolutionary process. If our attempts to be smart …

Michael Le Page quotes Stephen Palumbi describing triple drug therapy for HIV as "one of the first truly evolutionary treatment strategies". Much the same strategy was used 60 years ago in the early days of antibiotic treatment for tuberculosis. Streptomycin, the first anti-TB antibiotic, became available in the UK in 1948. When the country's Medical …

Fred Pearce says that Croll's ideas were only revived by Milutin Milankovic in the 1930s. However, Robert Ball , Royal Astronomer of Ireland and a notable populariser of astronomy, gave talks on ice ages in 1886 acknowledging Croll's work. In 1890, he published The Cause of an Ice Age . My copy was originally presented …