At this time of year the night sky is beginning to fill with the winter constellations. Orion the Hunter, the Diary's favourite, still isn't visible at 11 in the evening, but two others, Andromeda and Cassiopeia, are.
Cassiopeia is fairly easy to find, a slightly lop-sided W high in the sky. Andromeda is a disappointment, lying below Cassiopeia - yet this constellation holds something which fills the Diary with awe. To find this wonder, locate the W of Cassiopeia and move about 2/3 the distance to Andromeda and, if you're lucky and the night is clear, you should find a faint smudge of light.
This is the Andromeda Galaxy, M31, a spiral galaxy like the Milky Way, the galaxy we live in. M31 contains an estimated 1,000,000,000,000 stars but, what is more important, it's close enough to see with the naked eye - and even better if you have binoculars or a telescope.
'Close' in astronomy doesn't mean any such thing, since 'closeness' is measured in light years - the distance light travels in a year. M31 is a mere 2.2 light years away - and that is what is so wonderful. Because, if you think about it, this means that the light you are seeing is 2.2 million years old, so the image you see is 2.2 million years old. You're looking back in time. You're time travelling to the days when the population of West Ardnamurchan was zero, and our ancestors were being eaten by sabre-toothed lions on the savanna plains of Africa.