Water doesn’t like being liquid. It much prefers its other forms — the ice of a comet or its vapour trail. Water flips through a single change of state at indeterminate temperature, and changes back again at will.
But the Earth with its gravity has ripped the tails off a hundred comets or swallowed them whole, and water under pressure of rock or atmosphere squeezes into a new and smaller form, dissolving other substances and giving medium to life.
In our gravity and atmosphere, water condenses out of air at somewhere near 100 ℃ and drips off ice at somewhere around zero. Under the pressure of heavy glaciers or skaters’ blades, cold ice will shrink briefly into lubricative liquid; under the crust of Earth, vapour lies pressed into liquid form at over 200. But pure water flows liquid at sea-level only within a narrow band of 100 degrees — the oceans of our world held in place by the air above them.
This is one of the reasons I’ve never wished to be an astronaut: Fifty-five percent of my body really wants to be ice or vapour — out among the asteroids and comets.
Fiona Jones lives in Scotland, a country with more than its fair share of water in liquid form.