Introducing our Advent Calendar – here’s the twenty-first post in a cultural countdown to Christmas. Today: Light painting and the longest night.

There’s a whole series of light-related events going on at MOSI right up until 4 January 2015, including Circuit City (13.40pm-14.10pm daily), an interactive show that puts crazy electrical inventions to the test, and a workshop exploring the wonders of glowsticks in MOSI’s new Pi space (3pm-4.30pm daily). If you’re quick off the mark, you might be able to bag a place on their Light Painting workshop at 11am today – it’s free, but you need to book and be ready with a camera, tripod and empty memory card. Alternatively, drop into the regular Secret in the Sky sessions until 4 January (11am, 12pm, 2.30pm and 1.30pm daily).

Do more. One of our favourite ways to spend an evening is back: In the Dark Radio return to The Castle Hotel this evening to celebrate the Winter Solstice. It’s an hour of superbly curated radio extracts, all under the theme of “The Long Dark”. Find out more about shadows, loneliness and the colours of darkness in this brilliant event from some truly innovative radio producers. The Castle Hotel, 7.30pm. Tickets £3 on the door.