Ever wonder where the sun is?
June 10, 2006 4:33 PM   Subscribe

June 21st, the day of the summer solstice is the longest day of the year. Where in the central time zone, (or any time zone for that matter) is the sun directly over head at exactly midday?

Every year I am amazed at where the sun is in the horizon at sunrise on the winter solstice compared to the sunrise of the summer solstice. So I am wondering how far north does the sun come. (I realize that the earth is moving and not the sun.)

So this is the scenario, I have a perfectly straight pole projecting out of the earth one hundred feet straight up. Perfectly plumb! Where in (insert your time zone) would there be NO SHADOW, WHATSOEVER at exactly midway between sunrise and sunset on June 21st, 2006?
posted by ok to Science & Nature (3 answers total) 1 user marked this as a favorite
 
The inclination of the Earth is 23.45 degrees, which means the sun cannot perfectly overhead at any latitude greater than that.

The "Tropic of Cancer" and "Tropic of Capricorn" are the names given to the northernmost and southernmost latitudes where what you describe is possible to observe.

Your question is an interesting one because it has historical significance. It permitted Eratosthenes to measure the diameter of the earth.
posted by Steven C. Den Beste at 4:47 PM on June 10, 2006


On every day of the year, there is a circle of latitude along which the sun will appear directly overhead. June 21st is remarkable because it is the day on which this circle lies farthest north.

On that day, the sun may be seen directly overhead anywhere along this red line. North of that line, the sun's apex will be to your south, south of that line, it will be to your north.

Up to June 21st, this circle moves north toward the Tropic of Cancer. After that day, it will start moving south, passing over the Equator on the autumnal equinox (Sept 23rd), and reaching the Tropic of Capricorn on Dec 22nd.

Anyway, looking at the dotted line on this map, you'd need to make a trip to Cabo San Lucas or somewhere in Central Mexico on June 21st to see your shadow directly below you at noon.
posted by driveler at 5:40 PM on June 10, 2006


Also, note that there's a difference between standard time and solar time. Every time zone comprises (roughly) 15 degrees of longitude, and the time for each time zone is set so that clock noon is equivalent to solar noon at some reference longitude. In the case of the Central Time Zone, that reference longitude is 90°W, so if you want to have the sun overhead when the clock strikes twelve, you'd have to go to 23°26' N, 90° W, which might not be so feasible.
posted by Johnny Assay at 7:51 PM on June 10, 2006


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