Each galaxy lives within its own three-dimensional halo of dark matter whose gravitational field corrals the stars within it. Without the stars, the halo would still be there, albeit invisible to our eyes; but if the halo vanished, the stars would scatter into the depths of the universe – just as a Christmas tree remains a tree with or without the pretty lights. Whereas without the tree, the lights would merely be a puddle of colour on the snowy ground.

If you're a teacher, what's your ambition? It's got to be better to watch your students chase their dreams than, when they come to tell the story of their success, be remembered as the person who said they couldn't do it.

Unlike almost any other form of transport, regular cycling leaves you fitter and healthier than sitting in a car, or a bus or a train. Not only that, Auckland's best cycle paths run through parks and incorporate a series of stunning bridges, so you are likely to arrive at work with a smile on your face.

Auckland's 2017 Bike Challenge winds up today; February may be the shortest month, but it is prime cycling season in Auckland, with decent weather and long evenings.