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Tropical Sun: Newsletter Challenge (February 2017)

Posted January 31, 2017 5:01 PM
Pathfinder Tags: challenge questions tropics

This month's Challenge Question: Specs & Techs from IEEE Engineering360:

The Tropics of Cancer and Capricorn are circles of latitude corresponding to the northernmost and southernmost points where the Sun can still be found directly overhead (on the solstices). Those latitudes are 23.43709°N(S) and are considered the delineation between the temperate zones and subtropical zones. Why are they named “Cancer” and “Capricorn?”

And the answer is:

Cancer and Capricorn were the constellations of the zodiac in which the Sun rose on the days of the summer and winter solstices when the tropics were named 2000 years ago. The solstices are the days when the Sun is directly overhead at the respective Tropics, thus the naming convention. It is interesting to note that due to Precession of the Equinoxes, if the Tropics were named in modern times they would be the Tropic of Taurus and Tropic of Sagittarius. Also worth noting is the term Tropic, which is derived from the Greek “trope,” means “turn back” or “change of direction,” which is what happens to the Sun’s northern or southern latitude advancement on the solstices.

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Re: Tropical Sun: Newsletter Challenge (February 2017)

01/31/2017 5:49 PM

"When the lines were named 2000 years ago, the Sun was in the constellation of Capricorn during the winter solstice and Cancer during the summer solstice (hence the names). Now due to the precession of the equinoxes the Sun is no longer in these constellations during these times, but the names remain."

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Re: Tropical Sun: Newsletter Challenge (February 2017)

02/02/2017 5:39 AM

Highlighted in red: Cancer, Capricorn and ±23°

Highlighted in green1: Libra and Taurus.

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Re: Tropical Sun: Newsletter Challenge (February 2017)

01/31/2017 5:50 PM

The answer is that The Tropic of Cancer was named because at the time of its naming, the sun was positioned in the Cancer constellation during the June solstice. Likewise, the Tropic of Capricorn was named because the sun was in the constellation Capricorn during the December solstice. The naming took place about 2000 years ago and the sun is no longer in those constellations. At present-day, at the June solstice the sun is in Taurus and, at the December solstice, the sun is in Sagittarius.

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Re: Tropical Sun: Newsletter Challenge (February 2017)

01/31/2017 8:48 PM

But when the moon is in the Seventh House . . .

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Re: Tropical Sun: Newsletter Challenge (February 2017)

01/31/2017 6:07 PM

It has to do with which constellation the sun is in at the summer solstice in the northern and southern hemisphere.

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Re: Tropical Sun: Newsletter Challenge (February 2017)

02/03/2017 2:03 PM

Because Cancer is the constellation visible in the Northern Hemisphere, and Capricorn is the constellation visible in the Southern Hemisphere. Could it also be that the constellations also pass directly overhead (at night) on the night before the solstice?

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