We had pouring freezing rain today, after some lovely powder then some very warm days (I use “warm” in the relative sense–40˚F around here and I ditch the heavy coat and pretend it’s spring). Walking up to the Observatory, the fields were covered in snow that had turned to ice, while water rushed from the higher hills to the ponds in the lower areas. The humidity was causing a white mist to form near the roots of the black trees.

We live on a planet where the temperatures and pressures are hover near the triple point of water. Some happy coincidence allows us to have solid, liquid, and gas dihydrogen monoxide, all within our reach.

Wouldn’t it be interesting to live on a planet at the triple point of some other molecule or element? Take Titan, for instance. Its surface is only a few degrees away from the triple point of methane and it is so cold such that methane rivers flow over solid water ice “rocks”. The aforementioned author, Henry Roe, spoke here a few weeks ago–his various techniques for probing the nature of Titan’s surface were fascinating. It’s amazing how you can find out so much about a moon that’s eight times further from the sun than Earth is, just by using huge pieces of glass to collect photons.

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