Letters archive

John Hastings suggests that scientists who claim that we have no free will cannot be trusted because they themselves have no free will and were bound to come to that conclusion (Letters, 14 May). While I believe it is true that our thoughts and decisions are dependent on everything that makes us what we are, …

The main problem with free will is terminology. The freedom to "will" things suggests a power over the universe to set the options – and that is not the same as choosing between them, which is the limited power we have. I suggest that freedom of will is a misleading term and what we actually …

You suggest that health gurus should be held to higher standards (21 May, p 5). May I suggest that a law requiring all public figures and profit-seekers to tell the truth, and correct mistakes if they make them, would be a good start? It is claimed that oil companies have known about climate change since …

Thanks for 'it's the first this has been seen in other animals ' – yes, we're animals too Elisa Drass appreciates the precision of our online video on killer whale "culture" shaping their evolution ( bit.ly/NS_whales )

Cheap renewable energy is not inherently the dangerous myth that Michael Le Page suggests ( 21 May, p 19 ). It may be, as long as its production remains subject to "free market" rules. If you separate renewable energy production from economic forces, transforming it into a common good, the issue disappears. This comes at …

Le Page is too pessimistic. Industries that use the excess cheap but intermittent energy will evolve – for example, the production of metals by electrolysis. There is a double benefit if the metal being won is now produced by means that emit carbon dioxide.

Le Page makes a valid point concerning the operation of the electricity market. It is clearly true that when solar, wind and nuclear generation reaches a certain level, further investment in any of these will bring a lesser return. But he says "we can't keep subsidising forever" – when that is exactly what we have …

Olive Hefferman indicates that plant growth is "increased with extra CO 2 and temperature" and this is of course true (7 May, p 20). More than 20 years ago, the Royal Agricultural Society ran tests in geodesic domes at Kenilworth with different temperatures and carbon dioxide levels. As expected, plant growth was enormous in the …

Dustin Grinnell reports Adam Zeman's interesting suggestion that people who believe they have no "mind's eye" may nevertheless be using visual imagery at an unconscious level ( 23 April, p 34 ). Surely the contrary is equally plausible – that some people who claim to possess a mind's eye may be mistaken? It is notoriously …

Like many others, I already drive a car that the manufacturers regard as a "guardian angel" (14 May, p 22). It has automatic emergency braking that allows it to stop itself if a collision is imminent. The designers seem to have an odd vision of the dangers posed by different collisions. A bird flew in …

I am still not certain what happens if a person stands in front of a driverless car and refuses to move. Can it back off and try to drive round the person?

There has recently been a great deal of discussion about a coming revolution in self-driving vehicles. This often focuses on anticipated reductions in road deaths. Most of that will be in developed countries where many customers can afford the new autonomous vehicles – and which already have relatively very low levels of road death. They …

You report that memory isn't arranged in alphabetical order, and indeed I am sure mine isn't (7 May, p 15). However, why is it that when I fruitlessly attempt to remember something, I often remember only the initial letter, which subsequently proves to have been correct?

Reader R. T. Lewis notes that I say that "persistent drones could sit on buildings or trees and keep watch indefinitely" and asks: "When is a drone that sits in wait for its victim not a military mine?" (Letters, 28 May). If there is a human operator in the loop controlling the drone, it does …

Do we want every foreign policy issue to be settled by sending in the drones, asks David Hambling (16 April, p 18). No foreign policy issue has been settled by sending in drones. In the future, as today, they are more likely to raise issues than settle them.

Tim Stevenson writes that at the distance of the Oort Cloud, the sun could not be obscured by a pinhead, since the dilated pupil of the eye would be bigger than a pinhead (Letters, 14 May). This is surely a misconception. The lens in the viewer's eye will focus the image of the sun and …

I read with great interest your report linking the bankruptcy of Peabody Energy to China burning less coal and inroads of renewable energy (23 April, p 7). I suggest that the bankruptcy is rooted in a low coal price, related to an extended depression in oil and gas prices. Thermal coal prices declined from US$142 …