### Happy Kepler Day

At 0608 Zulu time today, if our calculations are correct, the sun will cease it's apparent drift to the south and begin moving northwards again, lengthening the day. If this doesn't happen, then Kepler (and quite possibly Copernicus) were wrong. Kepler's laws were the first step towards seeing the physical universe in terms of conservation laws (and hence symmetries). In fact if this doesn't occur we can pretty much drop almost all of physics since Aristotle. Thankfully the celestial dynamics have not altered since (at least) 1605 when Kepler discovered his three elegantly stated laws of planetary motion.

This is why, every winter on this special day (and a few days either side usually), people of all countries, faiths, cultures and opinions about loop quantum gravity celebrate **Kepler Day**. Kepler day is a celebration of the fact that the earth's entire orbit last year has gone as planned - no black holes, inflationary scalar fields, casimir forces, wandering MACHOs or anything have contrived to make Newtonian mechanics a bad approximation. We're still moving elliptically around the big shiny thing.

If you can, take a moment to wish a happy Kepler Day to your friends, family, colleagues and random confused druids this year. The druids tend to think it's some sort of fertility festival - one track minds, you know how druids are.