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Not long ago, I posed the following question to an online seminar: "The age of the universe is stated as 13.8 billion years, but in whose frame of reference is this true( 8 March, p 26 )?" It wasn't selected for discussion, but I know the standard answer is that time passes at the same …

The timescape hypothesis, said to explain the apparently increasing rate of expansion of the universe by assuming that the flow of time can vary spatially across the cosmos, raises another interesting question: is time a fixed constant during the life of the universe? If the speed of time could vary over the age of the …

There are interesting links between the timescape hypothesis and an earlier article published in New Scientist , "The past appears to run slower" ( 8 July 2023, p 11 ). The non-linear behaviour of the deep past suggests that assumptions about the age of the universe could be erroneous.

Much of the worry about "mirror life" seems to be predicated on the assumption that our immune system wouldn't recognise it. I'm not convinced. But we can test this since, as your story tells us, we can already synthesise proteins with a mirror-image structure to the ones in our bodies. It would be simple enough, …

Rather than just sometimes, futurism almost always prevents us from seeing what is actually coming next. No futurists predicted geosynchronous satellites, remote control mechanical manipulators, mainframe computers, handheld personal electronic assistants etc. Some current technologies – including all of my examples – were suggested by science fiction writers, but sci-fi isn't futurism ( 8 March, …

It struck me when reading your article "Hunting for the oldest code" that we may have found an excellent use for artificial intelligence. Can older coders who know the old programming languages pass their knowledge to AI systems before they depart this mortal coil? With the dependency on legacy systems you discussed, we would be …

Matthew Sparkes's evaluation of our reliance on old code is spot on. I imagine organisations ought to think about software support agreements they are paying for, as it is likely that some companies collecting annual fees no longer have the available expertise to solve any problems arising. All code is broken. When we are lucky, …

In the report on ancient building shape, there was no mention of the critical relationship between the roofs and walls. The roof of a rectangular structure provides strength to ensure the walls stay upright. Such a roof requires strong structural elements and robust materials such as timber or stone before it can be clad with …

Carl Zetie suggests we "send 100 million sperm and eggs, not 100,000 people" to colonise an alien planet, but leaves the story of raising the offspring to others ( Letters, 15 March ). You would need a machine to provide food, made in situ, for the resulting infants, and much more. They may see it …

The idea of mirror cells producing long-lived pharmaceuticals seems a bit too much like the creation of "forever chemicals" to me ( 1 March, p 34 ).