Jupiter is back in the evening sky again. It made me realise that it is a bit later this year - I was looking at it in the same place in early October last year. It takes Jupiter 12 years to go round the Sun. In the year that it takes the Earth to go round the Sun, Jupiter has also moved on round its orbit so we have to go round our orbit for more than 12 months to catch up with it again. Jupiter advances by 1/12 of its orbit in an Earth-year which works out as an extra month for us - hence I'm seeing in early November what I saw in early October last year.
