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You report work on brain circuits involved in the fear of being high off the ground, an evolved reaction almost everyone has ( 17 June, p 19 ). There does seem to be an exception to this for a lot of people. I think I have an average fear of being on high structures, but …

Bob Denmark's description of humankind as prone to violent conflict and conquest could equally apply to any alien we communicate with. Intelligence doesn't rule out the predatory instinct, and in-species warring could be a lot more common in the galaxy than we anticipate ( Letters, 17 June ). Having advanced technology doesn't necessarily mean violent …

We seem to always imagine alien civilisations will be homogenous, and hence unlike us. That is possibly because pretty much every sci-fi story I can think of, from H. G Wells and his Earth-invading Martians to the Dan Dare tales in the Eagle comic, portrays aliens as single planetary cultures.

James Wong describes the detrimental effects of caffeine on plants as a result of putting used coffee grounds on the soil of one's garden. I place my used grounds on the compost heap and have noticed that, when I lift some of the decomposing vegetable matter and dig into the heap, there are sometimes dense …

Fighting cancer with bacteria predates even William Coley's work of the late 1800s. Around 2600 BC, Imhotep (an Ancient Egyptian polymath) noted that making incisions into tumours and applying a poultice to induce an infection could cause them to shrink ( 24 June, p 40 ).

Each year, the UK imports around half its food and animal feed plus millions of tonnes of timber and finished timber products. Not only is agriculture highly polluting of atmosphere, land and watercourses here, but we are also responsible for an equally polluting effect in the nations supplying our shortfall. In addition, animal farming and …

Madeleine Cuff reports that over the past few decades, "pressure from supermarkets to provide plentiful food at low prices has pushed farmers to boost livestock numbers, use more fertilisers and pesticides" etc. These are the very attributes that make intensive farming, intensive. This may have been a welcome policy in terms of people's wallets, but …

The real problem with the concept of net zero is that by taking as much carbon dioxide out of the air as we put in, we maintain the amount of this greenhouse gas present when net zero takes effect. Hence the CO 2 level, while not increasing, remains high. That means continued warming, ice melt …

Packing in stuff to make best use of available space – the subject of your recent maths column – isn't always the best approach when it comes to unpacking, as seen in the Falklands war ( 10 June, p 44 ). The rapid loading of rations, ammunition, helicopters and other vehicles into all sorts of …

Jason Arunn Murugesu reports on why you can stay focused on conversations in a noisy room. This made me wonder why people, if you gather more than, say, 10 in a room, start raising their voices ( 17 June, p 13 ). If everyone spoke at a normal level, no one would have to shout. …