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Susannah Fisher's take on the COP30 negotiations in Brazil is hopeful, but I can't share her faith in relying on government or corporations to do anything meaningful. The common feature of most administrations is the setting of short-term goals, because democratic governments don't want to plan for a future for which they won't get credit, …

Robert Kuhn deserves praise for compiling a comprehensive catalogue of theories of consciousness. There is a problem, however. Science progresses by proposals of hypotheses that generate testable predictions. If the predictions generated by a hypothesis are disconfirmed, then that hypothesis is discarded and we can move on to better ones( 25 October, p 36 ). …

It seems to me that consciousness isn't a state or quality, but something the brain does. Two observations that I think support this conclusion: one, we manipulate conscious experience by ingesting certain substances. Two, anaesthetics reduce conscious experience to about as close to zero as is likely possible. The above implies that the proper question …

When I did A-level biology, a species was a group of individuals whose members could interbreed to form fertile offspring. Since then it seems there has been meaning creep, especially in the hominins ( 8 November, p 40 ). There is good evidence for hybridisation between all the "species" derived from Homo erectus . We …

With regard to Jonathan Goodman's article on how "survival of the nicest" makes no sense when seen in evolutionary terms, one can see the frustration in those who try to seek explanations in terms only of an individual's genes and consequent behaviour ( 15 November, p 19 ). For most of human history we have …

I agree with Annalee Newitz that we live in a great era, when quality education of the highest level can be accessed without physically attending an institution. However, people need jobs, as no other model of earning one's own means is really available for most of us. This implies that to be truly valuable, these …

We can learn much about when to give up from the natural world. When a bee is collecting pollen, there is an optimal time to give up expending increasing amounts of energy, and deliver the pollen to the hive ( 15 November, p 28 ). Charnov's marginal value theorem states that if there are diminishing …

There have been a number of articles about geoengineering as a means of averting catastrophic climate change. It isn't so much a scientific problem but a political one. All solutions require global cooperation – something that remains elusive. However, guerrilla approaches can work! For example, we know shrinking icecaps mean less radiation is reflected back. …

Robin Asby misunderstands the essential difference between quantum and classical. In a quantum equivalent of his observation that his cat is sleeping in one of a number of possible places when he gets home, the quantum "cat" is in none of the locations until he observes it (or all of them, depending on which interpretation …

The answer to the second part of BrainTwister #97 is 67