From Andrew Gray
I read with interest your article on a “snowball” Earth
(6 November, p 28),
in which Gabrielle Walker states that “with the mercury barely topping –40
°C, only a few living things survive”.
This snowball Earth must have been a strange place indeed. In today’s world,
the mercury would have solidified at −39 °C.
Gairloch, Ross-shire
