Chemical Factories Smaller than a Snowflake

In the warmer dust clouds (whose temperature is about 60 degrees above absolute zero, or minus 213 degrees Centigrade), the silicate grains are on the order of 1/100^th of a micron in size (recall that one micron is a thousandth of a millimeter), whereas in very cold dust clouds (20 degrees above absolute zero, or minus 253 degrees Centigrade), the sizes are typically 1/10^th of one micron, so they are minute indeed. A comparison may be helpful.

An ordinary snowfl ake — one of billions which may gently drift downward during winter — is 25 000 times larger — snowfl akes are typically of the order of 2500 microns across. A snow-fl ake is a veritable immensity compared to one grain of cold cosmic dust. Furthermore, the nucleus at the center of a snowfl ake measures one micron; the aerosols in the atmosphere around which a snowfl ake crystallizes measures 1/10^th of a micron. Cold grains in dusty Shrouds of the Night, 1/10^th of a micron in size, are truly like aerosols — the mists of a fog.