91É«ÇéƬ

Laura Spinney's informative article on the isolation of ancient DNA (aDNA) from soil raises an intriguing consideration. Soil collected by NASA's Mars Perseverance rover will return to Earth as part of the Mars Sample Return mission, probably some time in the 2030s. I suspect I am not the only person now eagerly awaiting the analysis …

Why even discuss "time" travel outside fiction? We have no concept of what "time" is or if it even exists, just measurements of events compared with each other, the decay of atoms, the movement of the stars, etc ( 14/21 December 2024, p 54 ).

Reader views on the colonisation of Mars, varied as they have been, have missed the most important point of all. Historically, colonisation was driven by a search for opportunities to trade and get rich. Perhaps, with Elon Musk as one of the chief proponents, we are missing the elephant in the room. Rather than debating …

"Bursting the bubble", about quantum ideas that could do away with the multiverse, was excellent, but it is troubling that theorists still consider Schrödinger's cat and Wigner's friend to be valid thought experiments. They assume that a human observer is required for quantum collapse, which is absurd ( 11 January, p 32 ). How did …

If quantum computers are accessing the multiverse, as Hartmut Neven suggests, then we must assume that aliens in parallel universes could also have quantum computers. They must also be aware of their making use of other universes' quantum computers. Could this make us lab rats for their experiments( 4 January, p 40 )?

The report that blinking gives your brain a break by taking pauses while reading reminds me of the views of Hollywood film editor Walter Murch in his 1992 book In the Blink of an Eye ( 11 January, p 17 ). He says the difference between a good actor and a bad one is in …

As an energy/carbon engineer for over 35 years, I fully support the "defossilisation" of production of goods. However, why the fixation on capturing carbon from the flue gas of blast furnaces or other hot and highly polluted sources( 4 January, p 22 )? In my career, I have encountered many manufacturing processes, including acid neutralisation …

Name/address withheld on request When it comes to optimism, I am a glass-half-empty person and know why. I now recognise that my mother experienced extreme anxiety, particularly in relation to travel. As a child, holidays and trips would be planned, only to be cancelled at the last moment. I learned to temper my excited anticipation. …

As I understand it, "Backwards computing" asserted that the bulk of heat emitted by computers arises from changes to information in the process of doing calculations. Does this apply to other media? How about a sheet of paper on which difficult sums had been written( 28 December 2024, p 38 )?

Gremlins got into our bumper word search grid (14/21 December 2024, p 37), with Cetus, gray, Puppis, Crux, Lynx, lux, stratus and naledi affected. In computing, AND gates are logic gates that output the product of their inputs ( 28 December 2024, p 38 ).