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Equinox. A solar equinox is a moment in time when the Sun crosses the Earth's equator, which is to say, appears directly above the equator, rather than north or south of the equator. On the day of the equinox, the Sun appears to rise "due east" and set "due west". This occurs twice each year, around 20 March and 23 September.
The winter solstice, also called the hibernal solstice, occurs when either of Earth 's poles reaches its maximum tilt away from the Sun. This happens twice yearly, once in each hemisphere (Northern and Southern). For that hemisphere, the winter solstice is the day with the shortest period of daylight and longest night of the year, and when the ...
21. 14:14. A solstice is the time when the Sun reaches its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around 20-22 June and 20-22 December. In many countries, the seasons of the year are defined by reference to the solstices and the equinoxes.
Illumination of Earth by the Sun on the day of an equinox. The March equinox[7][8] or northward equinox[9] is the equinox on the Earth when the subsolar point appears to leave the Southern Hemisphere and cross the celestial equator, heading northward as seen from Earth. The March equinox is known as the vernal equinox (spring equinox) in the ...
14:14. Earth during the summer solstice in June 2017. The summer solstice or estival solstice[i] occurs when one of Earth 's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere (Northern and Southern). For that hemisphere, the summer solstice is the day with the longest period of daylight and shortest ...
01:48. 22. 17:37. 21. 14:14. Illumination of Earth by the Sun on the day of the June solstice. The June solstice is the solstice on Earth that occurs annually between 20 and 22 June according to the Gregorian calendar. In the Northern Hemisphere, the June solstice is the summer solstice (the day with the longest period of daylight), while in ...
The Globe at Night project was launched as a NASA program in the United States. [1] The project quickly expanded internationally, and was part of the outreach effort of the International Year of Astronomy in 2009. [27] The size of the project (in terms of number of observations) expanded dramatically in that year.
Annual. Earth Day is an annual event on April 22 to demonstrate support for environmental protection. First held on April 22, 1970, it now includes a wide range of events coordinated globally by EARTHDAY.ORG (formerly Earth Day Network) [1] including 1 billion people in more than 193 countries. [2][1][3] In 1969 at a UNESCO Conference in San ...