Sunrises and sunsets reach their extreme northerly and southerly positions
on the solstices; and occur due east and due west on the equinoxes.
On the solstices:
- The Sun rises at an extreme northerly or southerly limit (about 23.5 degrees
north or south as seen from the equator; the range is far greater in America,
at Stonehenge, or toward the poles).
- "Solstice" derives from Latin, "Sol" = Sun; "sisto, sistere, stiti,
statum" = "stand still."
- Solstice refers to the position the Sun occupies in the sky when it
rises at a northerly or southerly extreme against the horizon. On the
day or moment of a solstice, the location of the Sun's rising or setting
"stands still" on the horizon at its most northerly or southerly extreme
before turning back, or beginning to shift each day in the reverse direction.
- Daylight and nighttime are of extremely unequal length (longest days, shortest
nights; or longest nights, shortest days).
- The sunrise and sunset locations are shifting very slowly, perhaps as little
as one-tenth of a solar diameter in four days.
There are two solstices each year:
- Summer solstice:
- Occurs around June 21 or 22, when the Sun reaches its most northerly
- The day of longest daylight and shortest night, and the first day of
summer, in the northern hemisphere.
- The Sun is located directly overhead at noon on the Tropic of Cancer.
- The Sun never sets above the Arctic Circle; never rises above the Antarctic
- Winter solstice:
- Occurs around December 21 or 22, when the Sun reaches its most southerly
- The day of longest nighttime and shortest daylight, and the first day
of winter, in the northern hemisphere.
- The Sun is located directly overhead at noon on the Tropic of Capricorn.
- The Sun never rises above the Arctic Circle; never sets above the Antarctic
Did you know?
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. Prior to its setting, the Sun will
have been located above the horizon throughout the summer, for a total of 186
days, reaching 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