Brighten clouds to modify climate, but do it carefully
You report that spraying salt water into the atmosphere over the Pacific to brighten clouds for nine months a year for 30 years to save California from extreme heat could eventually cause dire temperature increases in Europe as a side effect (29 June, p 11).
However, other studies are more hopeful about such geoengineering. Some suggest , moved seasonally and controlled by an international team to safeguard the interests of all countries. Another found would give up to 20 per cent more rain in north-west Africa and Pakistan, and maybe 10 per cent more in the Sahara, South Africa, Saudi Arabia, India, Australia and Central America. These models made small changes in parameters to get great effects, which shows we need trials where we can make adjustments as we go.
For cosmic significance, size doesn't really matter
The idea of our cosmic insignificance is a matter of emotion rather than reason. We all feel it, but it does, after all, involve equating physical size with significance. This is absurd, as we don’t say an elephant is more significant than a human, or a mountain than an elephant. What happens is that, when a certain point of absolute size is reached, our imaginations kick in and we turn mere statistics and quantities into a quality: the awesome (29 June, p 36).
The cosmos is overpoweringly great only because we are here to see it that way 鈥� in a sense, it owes its greatness to us. In this and other ways, the vastness of the cosmos points to us rather than away from us. The cosmos is a great wonder, but a still greater and more central wonder is the human mind and spirit.
This is how the universe has become conscious
When it comes to our “cosmic perspective”, there is one aspect of our existence that I find deeply significant. We are composed of matter and energy that has become capable of thinking about and describing matter and energy. Thus, through us and any other technologically advanced beings that may exist, matter/energy 鈥� and, by extension, the universe 鈥� has become consciously aware of itself. I find this very profound (29 June, p 30).
The young are becoming consumeristic sheep
The article “Digital damage?” misses the real danger to children from screen time 鈥� the extremely sophisticated marketing that sucks them into ruthless games that have no socially redeeming value. They are being purposely led deeper and deeper into a highly cloistered digital environment and away from being able to develop discrimination regarding how they spend the limited time we have on this beautiful Earth (22 June, p 31).
In order to be healthy, we need to develop a traditional relationship with nature and read the printed word, such as books. Unless parents and society take a stand on this, the end result is certainly increasingly larger new generations of easily manipulated consumeristic sheep.
Surely physical reality won't tolerate infinity
You write about the singularity, the “infinitesimal point of infinite density” within a black hole. The concepts of infinitesimally small and infinitely large are extremely powerful in pure mathematics. But is their use acceptable in trying to model the physical universe? (15 June, p 32)
At the centre of a black hole, the wave-like particles are fighting against the gravitational forces that are trying to compress them to a point. And if there really are such singularities, then by definition they can’t be modelled and can’t carry detailed information. Surely I am not the only person to question the use of these extreme mathematical concepts in trying to understand our physical universe.
Beautiful image also highlights ugly truth
What a magnificent photograph of the Milky Way seemingly emerging from the summit of Aoraki/Mount Cook in Aotearoa/New Zealand. In it, our galaxy also seems to be looking down on the rapidly retreating terminus of the Hooker glacier and the equally rapidly expanding Hooker Lake. By 2016, this lake had lengthened from nothing to 2.5 kilometres. It has continued to fill up the valley it occupies and will probably stop when it stretches for 4 kilometres. The base of the glacier will then be above the lake surface (15 June, p 26).
I wonder whether there are civilisations up there wondering why we have so far completely failed to end global warming.
Mixing it up is great for runners too
You outline research showing how varying stride length while walking helps burn more calories. However, it does more than that. It enhances muscle tone and overall fitness. This is the idea behind fartlek, a training method for runners. Practitioners vary their pace (and thus their stride length) while running through woodland or open country, switching from a gentle jog to a race-pace run to an all-out sprint and repeat (22 June, p 8).
Adherents develop muscles better suited for distance racing. You burn more calories and also enhance your racing potential.
On the drive to tackle the obesity epidemic (1)
You raise the idea of paying people to lose weight. Use of financial incentives isn’t new. American football player William “The Refrigerator” Perry had a clause in his contract with the Chicago Bears stating he would be penalised if his body weight went above a certain level (29 June, p 12).
On the drive to tackle the obesity epidemic (2)
When it comes to obesity, some people claim healthy food costs more. This is false. I cook all my food, mostly vegan, and it costs just a fraction of what most people spend on their unhealthy food.
For the record
There is one vagus nerve on each side of the human neck (29 June, p 19).