Â鶹´«Ã½

Chris Eve wonders how much more heat burning a kilogram of petrol generates through the greenhouse effect than it does through the energy of combustion (Letters, 23 March ). He calls this a "gearing ratio", the name for the proportion of debt to capital used in finance. With colleagues, I estimated this , though we …

They'll be saying this about Earth in a few decades Lesley Wise expands on the news that Venus may have had a climate suitable for life billions of years ago ( 6 April, p 10 )

Bob Holmes discusses the idea of Earth as a superorganism featuring selection by persistence ( 23 March, p 34 ). This is intriguing and quite convincing. We should, however, make clear what we know about the actual process of evolution: namely, that the processes of natural selection, drift and other drivers of evolution operate at …

Jason Barlow applauds electric cars for personal transport entering the mainstream ( 23 March, p 24 ). Of course, getting rid of fossil-fuel-powered vehicles is a step in the right direction. But even if electrically powered, a car conveying one person to and from work five days a week is hugely inefficient. Our road networks …

Barlow asks what would make people switch to a pure electric car. I would switch when they are as practical and affordable as standard vehicles. A serious impediment is charging the batteries, but not because of the "range anxiety" that Barlow mentions. Like many people in the UK, I have to park my car on …

I nominate Richard Webb for a prize for bringing science to the rescue of humans beset by political imbroglios ( 9 March, p 30 ). His account of "the original Brexit" offers proof that humour survives in the UK and is perhaps the most effective defence, at least of our equilibrium.

Webb mentions the headline "Fog in Channel: Continent Cut Off". It isn't just apocryphal, but one of the great misquotations. "Fog in Channel: Continent Isolated" appeared in a cartoon by Russell Brockbank in Round the Bend with Brockbank in 1948.

John van Someren asks for the match of colour and function in indicator lights to be standardised (Letters, 9 March ). On behalf of the many millions who are red-green colour blind, could we please never use red and green LEDs for off and on.

I would suggest getting rid of indicator lights . What is the point of wasting energy on an indicator to tell you that the TV is on?

• A sweeter cube: mathematician Louis Mordell's question is whether each integer can be expressed as the sum of the cubes of three integers ( 23 March, p 16 ). • Looking for alignment of black holes' spins is one way to find out what brings them together; there may be others ( 30 March, …