OPOD - A year of sunsets, Greece

A year of sunsets

The previous OPOD showed the sunset point moving appreciably northwards in only one day near the spring equinox. Here we see sunset movements over a whole year.

Anastasios Nezis captured sunsets every two weeks from the Greek Island of Salamis near Athens. See them also in video (science videos)

Sunset almost due west at the spring equinox starts the sequence. Then, joyously, the sunset point creeps northwards reaching its maximum travel at the summer solstice. There the days are long.

Then we sadden as, each day, the sunset is that much further south and each day is a little shorter. Daily changes are most rapid near the autumnal equinox and they slow again towards the maximum travel southwards marking the winter solstice.

At Salamis's latitude of 38�N the sunset point moves 30� northwards between the spring equinox and summer solstice. Then it slides 60� south to the winter solstice. The midsummer day is nearly 15 hours long but only nine and a half hours at midwinter.

These are mild seasonal changes compared to those further north and especially in the Arctic where midsummer sunlight is endless but in midwinter nonexistent .
Images ©Anastasios Nezis, shown with permission

Earth's axis is tilted ~23.5° to the plane of its path around the sun. At the equinox the sun rises near exactly in the east and sets at west. In the northern hemisphere the sunrise and sunset points creep northwards as spring advances making each day slightly longer. The changes are most rapid at the equinox and slow to zero at the summer solstice.