APOD: A Sundial that Shows Solstice (2017 Jun 21)

Comments and questions about the APOD on the main view screen.
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APOD Robot
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APOD: A Sundial that Shows Solstice (2017 Jun 21)

Post by APOD Robot » Wed Jun 21, 2017 4:08 am

Image A Sundial that Shows Solstice

Explanation: What day is it? If the day -- and time -- are right, this sundial will tell you: SOLSTICE. Only then will our Sun be located just right for sunlight to stream through openings and spell out the term for the longest and shortest days of the year. But this will happen today (and again in December). The sundial was constructed by Jean Salins in 1980 and is situated at the Ecole Sup�rieure des Mines de Paris in Valbonne Sophia Antipolis of south-eastern France. On two other days of the year, watchers of this sundial might get to see it produce another word: EQUINOXE.

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LMMT

Re: APOD: A Sundial that Shows Solstice (2017 Jun 21)

Post by LMMT » Wed Jun 21, 2017 6:34 am

Wow, it is a truly genuine sundial. I am planning for next equinox (hopefuly, a sunny day).

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Re: APOD: A Sundial that Shows Solstice (2017 Jun 21)

Post by Boomer12k » Wed Jun 21, 2017 7:47 am

That is so cool....

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heehaw

Re: APOD: A Sundial that Shows Solstice (2017 Jun 21)

Post by heehaw » Wed Jun 21, 2017 9:37 am

Nice sundial, but not much of a wabe!

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Re: APOD: A Sundial that Shows Solstice (2017 Jun 21)

Post by Fred the Cat » Wed Jun 21, 2017 3:41 pm

Society has known how to use the sun’s position to tell the time of year and the time of day but we haven’t passed on how to portray the memory of time.
IMG_5845.JPG
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To remember all, we’d have to think faster than thought. But I don’t think I'll have enough time to figure that one out. :wink:
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Re: APOD: A Sundial that Shows Solstice (2017 Jun 21)

Post by neufer » Wed Jun 21, 2017 5:20 pm

heehaw wrote:
Nice sundial, but not much of a wabe!
  • Don't go all mimsy on us.
https://en.wikipedia.org/wiki/Potrzebie wrote:
<<In issue 33, Mad published a partial table of the "Potrzebie System of Weights and Measures", developed by 19-year-old Donald E. Knuth, later a famed computer scientist. According to Knuth, the basis of this new revolutionary system is the potrzebie, which equals the thickness of Mad issue 26, or 2.263348517438173216473 mm. A standardization in terms of the wavelength of the red line of the emission spectrum of cadmium is also given, which if the 1927 definition of the Ångstrom is taken for the value of that wavelength, would equal 2.263347539605392 mm.

Volume was measured in ngogn (equal to 1000 cubic potrzebies), mass in blintz (equal to the mass of 1 ngogn of halavah, which is "a form of pie [with] a specific gravity of 3.1416 and a specific heat of .31416"), and time in seven named units (decimal powers of the average earth rotation, equal to 1 "clarke"). The system also features such units as whatmeworry, cowznofski, vreeble, hoo and hah.

According to the "Date" system in Knuth's article, which substitutes a 10-clarke "mingo" for a month and a 100-clarke "cowznofski", for a year, the date of October 29, 2007, is rendered as "Cal 7, 201 C. M." (for Cowznofsko Madi, or "in the Cowznofski of our MAD"). The dates are calculated from October 1, 1952, the date MAD was first published. Dates before this point are referred to, tongue-in-cheek, as "B.M." ("Before MAD.") The ten "Mingoes" are: Tales (Tal.) Calculated (Cal.) To (To) Drive (Dri.) You (You) Humor (Hum.) In (In) A (A) Jugular (Jug.) Vein (Vei.)

Google's calculator and Wolfram Alpha can perform conversions between potrzebies and other units.>>
Last edited by neufer on Wed Jun 21, 2017 10:19 pm, edited 2 times in total.
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Re: APOD: A Sundial that Shows Solstice (2017 Jun 21)

Post by geoffrey.landis » Wed Jun 21, 2017 7:01 pm

Charming.
The signature of the solstice, however, is that the sun has (temporarily) stopped changing position from day to day. So the sun is in pretty much the same position the few days before and the few days after.
So it's hard to see that a sundial that reads "solstice" on the solstice won't also read the same the day before and the day after.

Tekija

Re: APOD: A Sundial that Shows Solstice (2017 Jun 21)

Post by Tekija » Wed Jun 21, 2017 10:02 pm

geoffrey.landis wrote:Charming.
The signature of the solstice, however, is that the sun has (temporarily) stopped changing position from day to day. So the sun is in pretty much the same position the few days before and the few days after.
So it's hard to see that a sundial that reads "solstice" on the solstice won't also read the same the day before and the day after.
Indeed! For solstice, the text can be read for about 20 min a day for up to two months, for equinox, less than two weeks. And the Sunday itself look quite a bit different in reality than in the fish eye APOD photo.

http://www.cadrans-solaires.fr/cadran-mines-2.html#2006

http://www.cadrans-solaires.fr/cadran-mines.html

Image