From Paul Hield, Bristol, UK
I had to chuckle while reading the section “Does space-time commute?” in your feature on quantum reality (5 February, p 38). The example for classical space being commutative is that it doesn’t matter if you travel 5 kilometres south and then 3 kilometres west or vice versa, you end up in the same place. But, of course, that falls apart when you are near a pole and is only approximately true elsewhere, although the error quickly becomes very small the further from a pole you are. In a sense, this makes the point perfectly: what we hold to be self-evident in fact doesn’t work under extreme conditions, with proximity to a pole or at the very small scales of the quantum world.
