Just as a merry-go-round spins faster when the kids riding it draw their legs in close, so every northern hemisphere Autumn when the trees drop their leaves the Earth spins a little faster. We are only talking fractions of a second, but still it is measurable apparently. Most of the land mass of Earth, and therefore most of the trees, lie in the northern hemisphere. When the deciduous trees drop their leaves the weight of this discarded foliage is then about 30 metres closer to the centre of the Earth, speeding the rotation. And in spring the converse occurs: fresh new leaves, plump with water, shift the weight away from the centre and the planet slows down.

But here’s the weird bit for us in New Zealand. Because most of the southern hemisphere is ocean (no trees), we don’t get to influence this phenomenon. In our Autumn the planet slows down and in our Spring it speeds up. So when Spring is just around the corner get ready for the ride!