The triple point of any substance is that temperature and pressure at which the material can coexist in all
three phases (solid, liquid and gas) in equilibrium.
Specifically the triple point of water is 273.16 K at 611.2 Pa
Answered by: Ryan Hitch, MPhys Physics, University of Hull
'The atomic bomb ... made the prospect of future war unendurable. It has led us up those last few steps to the mountain pass; and beyond there is different country.'