Winter Solstice is worth observing

The summer and winter solstices mark a special time in our calendar. When the sun is over the Tropic of Capricorn this is the peak of summer in the southern hemisphere, the longest day of the year and it predictably occurs on 21 December. When the sun is over the Tropic of Cancer, this signals the shortest day of the year, and, predictably, it is always on 21 June. On this day the southern hemisphere is leaning away from the Sun at its greatest angle. Use this link for an informative and amusing series of diagrams by Dr Nick Lomb illustrating these phenomena.

Building monuments which align with the solstices has been a challenge for architects, engineers and astronomers for centuries. One of this year's Sydney City Skywatcher talks by astrophysicist Brenan Dew featured his research into the alignment of ancient Egyptian sites in Karnak with the solstice.

In Sydney the beautiful house designed by John Verge for scientist Alexander Macleay in Elizabeth Bay during the early 1830s has recently been identified as being directly aligned with the rising sun on the winter solstice. This results in an amazing effect of the Sun streaming right through the building to the back of the courtyard. Each year Sydney Observatory's astronomy curator has collaborated with the Sydney Living Museum on an early morning sunrise event to let visitors experience this phenomenon. This year Dr Andrew Jacob will again lead the enquiry into whether this building is purposefully aligned.

There is an early morning event again this year on 21 and 22 June which you must book in through the Sydney Living Museums website.