Science of the Summer Solstice


The word Solstice comes from the Latin solstitium, meaning “Sun, standing-still.” This year the Summer Solstice occurs on June 20 at 21:44 UTC, Coordinated Universal Time, or Zulu Time, or roughly Greenwich Mean Time. Greenwich, England, is the prime meridian — the zero point for longitude lines.

Why is UTC the abbreviation for Coordinated Universal Time? The acronym came about as a compromise between English and French speakers: Coordinated Universal Time would normally be abbreviated as CUT, and the French name, Temps Universel Coordonné, would be TUC.


Summer Time and the Summer Solstice

This is also known as the Northern Solstice because the Sun is positioned directly above the Tropic of Cancer in the Northern Hemisphere. This time of year is known as Midsummer, though the official Midsummer Day is actually celebrated on June 24, thanks to differences between the Julian and Gregorian calendars. Christian festivals during this time of year are related to the Birth of St. John the Baptist. In Bolivia and Peru, it’s called the Festival of San Juan.


The Solstice in Summer Solstice

Solstice2Earth enjoys different seasons because the planet is tilted 23 degrees and 27 minutes off the perpendicular to the plane of orbit. This means that the earth revolves like a tilted spinning top. The Summer Solstice is the longest day of sunlight as the Sun is at its highest arc in the sky, at least in the Northern Hemisphere.

The farther north one is from the Equator, the more pronounced this is in Summer. However, as the Earth continues its orbit, the hemisphere angled closest to the sun changes, and the seasons are reversed.

In the Northern Hemisphere, the sun appears at its highest point in the sky, and its noontime elevation appears to be the same for several days before and after the solstice so that it looks like the Sun is “standing still” until following the Summer Solstice, the days begin to grow shorter and the nights longer.


Summer Solstice Know-it-all Facts to impress your friends and neighbors:

  • The Summer Solstice is not the longest day of the year, only the one with the most daylight. The longest day (no relation to the movie) is in November when we “fall back” for Daylight Saving Time and pick up an extra hour in the day, making it 25 hours long.
  • The earth is actually farthest from the Sun on the Summer Solstice
  • Fairbanks, Alaska, gets almost 24 hours of sunlight on the Summer Solstice. They routinely have an annual midnight baseball game.


Bill Petro, your friendly neighborhood historian

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About billpetro

Bill Petro has been a technology sales enablement executive with extensive experience in Cloud Computing, Automation, Data Center, Information Storage, Big Data/Analytics, Mobile, and Social technologies.

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