It’s that time of year again when the sun is at its maximum declination and passes overhead at noon for all observers at latitude 23.5 degrees.
As the Earth orbits the sun, in a slightly eccentric orbit and inclined at an angle of 23.5 degrees with respect to its orbital path, it passes through two maximal points of declination – the angular distance of a point north or south of the celestial equator.
Tomorrow – June 21st – we will be passing through one of those points of maximal declination, which in tomorrow’s case will be at 23.5 degrees north. The Earth will be inclined TOWARDS the Sun at an angle of 23.5 degrees and thus the northern hemisphere will receive the longest duration of sunlight – this is known as the summer solstice and will happen at 10:08 UTC (Coordinated Universal Time – the successor to Greenwich Mean Time).
However, for the southern hemisphere, this point of maximal declination will mark the shortest duration of daylight. For them, the longest duration of daylight is experienced at the second point of maximal declination, 23.5 degrees South, when the Earth is inclined AWAY from the Sun – which for us up here in the North is the shortest duration of daylight and is thus known as the winter solstice.
For many, in the northern hemisphere at least, this marks the first day of summer.
Amira Val Baker