Spring arrives this week in the form of the vernal equinox. This marks the moment when day and night are of approximately equal length. From here on, there will be more daylight hours in the northern hemisphere than night time ones. This situation continues until the next equinox (in October) when the situation reverses. The moment of the equinox takes place at 21:58 GMT on 20 March and by coincidence the moon reaches full illumination approximately four hours later at 01:43 GMT on 21 March. Also by coincidence, this moon is a “supermoon”. A supermoon takes place when the full moon occurs close to the moon’s perigee, its closest approach to Earth. In the early hours of 21 March, the moon will be 224,173 miles or 360,772km away, roughly 20,000km closer than average. Although the difference in the moon’s appearance will be unnoticeable to the naked eye, it will raise the tides a few inches higher than usual in most places. The full moon marks the mid-point of the lunar cycle. Earth is now between the moon and the sun, and so we see the visible surface of the moon fully illuminated.
