![]() The subsolar point crosses the equator moving northward at the March equinox and southward at the September equinox. In other words, the equinoxes are the only times when the subsolar point is on the equator, meaning that the Sun is exactly overhead at a point on the equatorial line. ![]() Also in 2021, sunrise on the South Pole is 20 September 16:08 UTC, and sunset on the North Pole is 24 September 22:30 UTC. For example, in 2021 sunrise on the North Pole is 18 March 07:09 UTC, and sunset on the South Pole is 22 March 13:08 UTC. For a brief period lasting approximately four days, both North and South Poles are in daylight. As a result, the northern and southern hemispheres are equally illuminated.įor the same reason, this is also the time when the Sun rises for an observer at one of Earth's rotational poles and sets at the other. ![]() The equinoxes are the only times when the solar terminator (the "edge" between night and day) is perpendicular to the equator. ĭiagram of the Earth's seasons as seen from the south. The Antikythera mechanism predicts the equinoxes and solstices. Ancient Greek calendars too had the beginning of the year either at the autumnal or vernal equinox and some at solstices. In the northern hemisphere, the vernal equinox (March) conventionally marks the beginning of spring in most cultures and is considered the start of the New Year in the Assyrian calendar, Hindu, and the Persian or Iranian calendars, while the autumnal equinox (September) marks the beginning of autumn. Later it was realized that this happens on a day when the duration of the day and the night are practically equal and the word "equinox" comes from Latin aequus, meaning "equal", and nox, meaning "night". Systematically observing the sunrise, people discovered that it occurs between two extreme locations at the horizon and eventually noted the midpoint between the two.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |