Here in Oz (and the Southern Hemisphere), it is the longest night of the year. Over in the Northern Hemisphere it is the longest day of the year. The Bad Astronomer
have nice mediations and links on this. Of course, although the days are getting longer after this, it will still get colder. This is due to the heat budget of the earth, the planet has cooled off, and it will take a while to re-heat it. Exactly what part of the Earth is responsible is not clear. This site
claims the oceans, this one
seems to claim the entire planet. Anyone know which is right (or a better soruce for an explanation?).