So, when exactly is the solstice? I felt a little dumb cause I couldn't remember if it was Dec. 21 or 22. Turns out it changes. This year, the solstice was today at 1:07am.
Hermetic Systems Offers a way to calculate the solstice:
To calculate the date and approximate time of the vernal and autumnal equinoxes and of the summer and winter solstices you can use this online calculator. This is based upon the formulas given by Jean Meeus in his Astronomical Algorithms but without corrections for perturbations, so that the times may differ from the true times by up to 20 minutes.So who is Jean Meeus? Wikipedia says:
Jean Meeus (born 1928) is a Belgian astronomer specializing in celestial mechanics. He is sometimes known as Jan Meeus. The asteroid 2213 Meeus is named after him.
Jean Meeus studied mathematics at the University of Leuven in Belgium, where he received the Degree of Licentiate in 1953 . From then until his retirement in 1993 , he was a meteorologist at Brussels Airport.
His area of interest is spherical and mathematical astronomy.
In 1986 he won the Amateur Achievement Award of the Astronomical Society of the Pacific.
The Willmann Bell Publisher site has this on Meeus' book Astronomical Algorithms:
Meeus, 6.00" by 9.00", 477 pages, hardbound, 2nd Edition published 1999, 2 Lbs. 6 Ozs. ship wt., $29.95..
Errata: 1st Edition
Errata: 2nd Edition
Note: We are currently shipping the June 2005 printing which incorporates all knowcorrections to that date.
In the field of celestial calculations, Jean Meeus has enjoyed wide acclaim and respect since long before microcomputers and pocket calculators appeared on the market. When he brought out his Astronomical Formulae for Calculators in 1979, it was practically the only book of its genre. It quickly became the "source among sources," even for other writers in the field. Many of them have warmly acknowledged their debt (or should have), citing the unparalleled clarity of his instructions and the rigor of his methods.
Start year and End year specify the range of years you're interested in. Only years in the range -100 CE through 4000 CE can be used with this calculator. (c) 2001-2007 Sunlit Design www.sunlit-design.com Sat, 22 Dec 2007 03:20:22 PM +700 gives UT You can click the publisher link above for the rest of this.
And Sunlit Designs a site for Understanding and Designing Sundials writes:
Jean Meeus has provided a bridge text for dedicated amateurs interested in astronomical and solar event calculations.Programming the calculations provided by Meeus is possible using any modern programming language. Meeus covers a wide range of astronomical areas.
If your interest is in the motion of the sun, you do not need to program his algorithms yourself ... it has already been done in The Sun API.
Someone named Raoul posted to habitiblezone.com 12/10/2007 9:09:17 AM
A very well known mathematician (I once spent some time at his home) Jean (for John) Meeus calculated when did that happen before and when in the future: 1612, 1615, 1632, 1668, 2007, 2022, 2059, 2078, 2191. [I would think John is for Jean myself]I mention this only because there is a John F. Meeus who is the Belgian Consul to Liverpool, England. Is this the same man? I don't know how common a name Meeus is and I don't think it is worth it emailing him.
The point of all this is: We can thank, apparently, Jean Meuss for knowing exactly when the solstice is.
Last year I put up some pictures that showed the winter and summer solstices - here's a link to that post
I'd thought it was yesterday-- so tomorrow I will be happy that we get a few extra minutes of sunshine! I have been looking forward to this since November when the driving got really difficult for me and i was trying to get home before it got black outside. I am happy knowing that in one month from now that I will start to really feel it.
ReplyDeleteOh, Steve-- what happened at 1:07 AM?
ReplyDeleteI think last year's post will be of more interest to you. Click the link at the end of the post.
ReplyDeleteAs I understand it, at 1:07am we got to the spot where the north pole's tilt away from the sun begins to shift back to tilting toward the sun. See the diagram, though it needs some thinking about. The pictures of the world have China at the top so bear that in mind when you look at it. The south pole can be seen in the pictures, but not the north. There's a white icon on China that shows the direction the earth revolves. Let your kids explain it to you. :)
The old post has a chart showing how much daylight we gain for the ten days around the solstice. Last year on Dec. 22 we gained 5 seconds after losing 7 seconds on Dec. 21, but in less than a week we will gain a little over a minute.
It was at 1:08 a.m. Eastern time Saturday, which was 9:08 p.m. Friday Alaska time.
ReplyDeleteYay, the days will be getting longer! My favorite time of the year!
Ish is correct. Best article on this, one I try to re-read every five or ten years, is found in The American Practical Navigator.
ReplyDeleteIf you go to:
http://en.wikisource.org/wiki/
The_American_Practical_Navigator/
Chapter_15
and scroll down to 1.2.6 1521 - Time and the Calendar, you get a glimpse at how mathematicians deal with this.
The graph I keep on promising myself to make is one that shows how the number of additional seconds and minutes of light or darkness change from day to day, and also shows the rate of change to the change itself.
Don't you mean equinox? Solstice is in March and October I think.
ReplyDeleteno, you were right I always mix equinox, solstice and the date when we change the time.
ReplyDeleteThanks all for the comments. I'm treading on thin ice here since this is something I don't know well at all, and neither of my physics major children have offered help here.
ReplyDeleteIsh, I didn't even think about it being ESTime, and wonder why it wouldn't be Greenwich Time for that matter. And from what I read the calculations, depending on how you calculate and whether you take all the various factors into consideration, could be off by as much as 20 minutes.
Philip, last year's post did a little of what you are talking about if I understand correctly. And congrats on your blog's mention in the Ear today.
Ropi, the way I remember the difference between solstice and equinox is the equi = equal, and on the equinox everyone around the world has an equal amount of daylight and dark.
So in one month, we won't be were we were with day light one month ago? I take it that it's not equal. . . this is no fun. I just want daylight back.
ReplyDeleteI remember living up in Fairbanks in the 1970's and playing outside int he dark with lights lighting up our 2:15 recess as Christmas came. I walked home, about a half mile from my bus stop to the house, on snow packed roads that were more designed for snow machines than my mother's Datsun. (She always got it to go where she needed to!) I needed a flashlight "to let the cars know where you are." The schools sent home 3' of reflective tape for dark jackets that mothers sewed on to the kids' jackets if they needed it.
ReplyDeleteI forgot all about that until you got onto the solstice and how it works. My dad even got a globe to explain it and I asked him what he brought us up to Alaska when the sun was so far away.
Great topic and thanks for explaining it again!