Equinoxes

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Sunrises and sunsets reach their extreme northerly and southerly positions on the solstices; and occur due east and due west on the equinoxes.

"Equi-" = same; "nox" = night. Equinox = "equal night."

On the equinoxes, and only on the equinoxes:

There are only two equinoxes each year:


Did you know?

If the Earth were not tilted, every day would be an equinox and there would be no seasons. However, the path of the Sun against the background of fixed stars (the "ecliptic") is tilted with respect to the celestial equator and intersects the celestial equator in only two points (the equinox positions).

At the North Pole, the Sun sets on the September equinox, the first sunset since the March equinox. The Sun has been located above the horizon throughout the summer, for a total of 186 days, and reached its highest altitude above the horizon on the summer solstice. Once the Sun sets on the September equinox, it will not rise again until the March equinox; there will be 179 days of nighttime at the North Pole. Question: You are an astronomer and wish to book some time using a telescope at the South Pole. What time of year should you go? How many hours a day could you observe the stars?

When the Sun rises due east, it makes an angle to the horizon equal to 90 minus your latitude. Therefore, at 35 degrees north latitude in Oklahoma, the Sun will rise at an angle of 55 degrees to the horizon.