91av

In his article "What's inside a black hole?", Stuart Clark is troubled at the thought of conceding that "the universe is not entirely ruled by physics"( 4 October, p 28 ). As a physicist, I am content to think that the universe is always ruled by physics, and in fact that is a tautologous statement. …

Stuart Clark doesn't mention Carlo Rovelli's idea that singularities can exist only in the future. In his book White Holes , he says that because time slows down in a strong gravitational field, a point of infinite density with infinitely strong gravity would take an infinite amount of time to form. So, from our point …

Are gravastars, electroweak stars, boson stars and fuzzballs really needed to do away with singularities? From our perspective, standing beyond the black hole, gravitational time dilation means that anything that falls into it slows down as it approaches the event horizon and takes an infinite amount of time to actually reach it. So, from the …

I always understood that time grinds to a halt at a black hole's event horizon. If so, it is surely nonsensical to ask what is inside a black hole, and by implication, whether at this moment it contains a singularity. So if I were to fly my spaceship across the event horizon of a black …

As a lover of "mouldy" cheeses, I very much enjoyed Graham Lawton's article on fermented foods, though I would have to dispute that all blue cheeses taste the same – perhaps we can lure him out to Australia to sample some of our offerings( 4 October, p 32 ). But you list fish sauce – …

The artefacts associated with newly discovered rock art in Saudi Arabia indicate links with Pre-Pottery Neolithic people in the Levant (11 October, p 16).

James Wong describes the use of chilli powder to deter wildlife from eating plants in the home garden. I too thought it was a good idea when ring-tailed possums discovered my rhubarb patch. Yet they seemed to enjoy the treat even more. It seems Australian wildlife is tougher than those European wimps. I moved the …

The short article by Caroline Williams about the selective detection of sounds was of particular interest to me as one who depends significantly on hearing aids( 11 October, p 20 ). The problem is that in, say, the dining area of a pub, the aids will selectively home in on what happens to be the …

Vincent Flood, in Illinois, US, pins inordinate faith on geoengineering to keep our planet in a habitable state – partly, it seems, because you can't "tell people in low-income countries they can't have air conditioning or cars...". But people in low-income countries currently aren't the biggest problem. The people who do have to be forced …

Graham Lawton writes about the conspiracy theory that bad actors are using aircraft contrails to poison us. I have experienced the discomfort caused by ham acting in the theatre, but was surprised that bad actors could poison the upper atmosphere as well( 11 October, p 26 ).