Imager Credit: http://www.telegraph.co.uk/news/science |

Due to the inclination of the Earth's axis, and the fact that the axis of the Earth points at the same direction in the sky, as the Earth orbits the sun through out the year, the apparent motion of the sun follows a path in the sky called the ecliptic. On a star chart the ecliptic forms a sine wave. The December Solstice occurs when the apparent motion of the sun reaches the most southern point on that sine wave. At that point the sun is directly over the Tropic of Capricorn.

As such the solstice doesn't happen on a date per se like new year's day, it happens at a specific moment in time. That moment of time usually happens on the 21st or 22nd of December, but it can vary out to the 20th to the 23rd although rarely.

So the question comes to mind, how long does the solstice last? The ancients would have declared hours if not days. The apparent motion of the sun as it reaches it most southern point becomes difficult to discern and it appears to stop moving...always a source of concern. However everything is moving and if you consider the solstice to be defined as when the precise center of the disk of the sun is over the precise line of the Tropic of Capricorn then the theoretical time of transit is an infinitely short instant. The center of the sun has no dimension nor does imaginary line of the Tropic of Capricorn. They are mathematical entities of points and lines with no physical dimensions and as such there is no transit time.

Max Planck 1858 - 1947 The Father of Quantum Mechanics Image Credit: Wikipedia |

Ahhh but in our universe, there is no infinitely short instant. If you had a fine enough stopwatch, it would register the Solstice lasting one Jiffy...a slang physics term for Planck's time. Now if the Tropic of Capricorn was a painted line exactly 6 inches wide, the there would be a transit time. The exacter center of the sun would pass over the 6 inch line, well actually 3 inch line because we would have to assume that the painted line was centered over the theoretical line which has no dimension. So three inches of the painted line would be south of the actual Tropic. So in a theoretical sense the moment is infinitely short. In a real sense it lasts a Jiffy a discreet chunk of time.

Planck's time which is the amount of time it takes a photon traveling at the speed of light to travel the length of Planck's length. Plank's length is the shortest possible distance in our Universe. We would like to think that we could take a ruler and start cutting it in half. Twelve inches cut into 6, then cut 6 into 3, 1 1/2, 3/4, 3/8, 3/16.........3/ ...that is keep cutting in half forever. But you can't. When you get down to Planck's length, a further cut smaller and you are out of the Universe and into the quantum foam.

So this moment, the Jiffy, is the shortest measurable time in our universe, any shorter and you are again out of the universe and into the quantum foam. I have no idea how Planck figured this out, or even if he did. But anyhow the fabric of the universe has discreet chunks, it is not a uniform fabric that gets progressively smaller the finer you look and like wise the clock has specific tics that you can't get any shorter. So the solstice lasts exactly one Planck's width. How long is that? From

**Wikipedia**- Just round that off to 5.4 times ten to the minus forty-fourth power of a second. No use getting lost in the details.

- So anyhow the Solstice is going to happen at a moment and that moment is tonight on the 21st somewhere around 11:49 PM in EST. The reason Google says it is on the 22 is that they are using universal coordinated time, which when you are asked what time is it on the planet Earth, this is the time you use. It is virtually the same thing as the old Greenwich Mean Time except it has atomic clocks applying leap second corrections every now and again. The term Greenwich Mean Time now only applies to the time zone that surrounds the Prime Meridian going through Greenwich England. It is no longer the label for the universal standard.

- I don't know if anyone actually knows the precise moment...measured out to some fraction of a second, but according the website
**TIME AND DATE:** - December Solstice in Universal Coordinated Time is on
**Tuesday, December 22, 2015 at 04:49 UTC****I**would also think from a practical sense that you could say the the solstice lasts as long as a typical sunset into the ocean. That is allowing for the radius of the sun to pass over the tropic line stop and then reverse direction and pass back. It should be roughly the amount of time for the diameter of the sun to slip past a horizon. - Regardless of how long the it takes, it is happening tonight at either 11:48 or 11:49 PM Eastern Standard Time in the US. So go out and build a bon fire dance and howl at the moon and welcome the first day of winter and the return of Sol.
- For an excellent article see:
*T***he Telegraph,****When is the 2015 winter solstice? Everything you need to know about the shortest day of the year**

I don't know about all that mathematical mumbo jumbo, but the start of lengthening daylight is reason enough to celebrate. I recommend dancing around a roaring bonfire and chanting to the heavens.

ReplyDeleteThe mathematical mumbo jumbo is just a bunch of hogwash. It's me being me, ranting about stuff for which I have little understanding and ergo find fascinating. You are right, dancing about a bonfire and chanting to the heavens is far more productive than worrying about in which Jiffy did the Solstice take place.

DeleteOlga always an honor, thanks for stopping by and commenting.

Well all I know is that's the shortest day of the year right? And because it's the shortest, that day is a tribute to short girls everywhere (I don't know why men aren't included, probably because it's not as great an asset for men to be petite as it is for women). So as such that was a special day for me measuring in at 5 foot 1 1/2 inches!

ReplyDeleteSo if the December Solstice (you have to watch winter and summer when speaking globally) is a "tribute to short girls everywhere", is the June Solstice a tribute to tall girls? And what of the southern hemisphere?

DeleteGlad you had your special day, sounds like a good excuse to have a glass of wine if not a margarita! Thanks for stopping by and commenting Alicia!

"there is no infinitely short instant.”

ReplyDeleteIs it not true that if you divide either time or distance into small enough parts that you will never get to the end of them since every unit of measurement could itself be halved?

In mathematics, the quantum foam, and super-space you are theoretically correct. Just keep slicing. There is a bit of a difficulty in the quantum foam and super-space in that time and space do not exist, so what exactly is it that you are slicing? The other problem is that we have no real assurances that math exists, ergo once you are outside the boundaries of the Universe there may simply be no math to rely on, everything is then an absurdity far beyond dividing by zero. So the answer to your question may very well be only in mathematics, and only when you are doing the problem while being extant in this particular Universe.

DeleteA far better answer but one not nearly as bullshitingly fun is that I don't have a clue. To the best of my knowledge space-time is a fabric that does not go down finer and finer forever. It has discreet chunks and discreet ticks. The best rule that Starrett can theoretically make is marked off in Plank's length, and the finest Rolex Oyster ticks in jiffies. Any finer and not only are you no longer in the universe, space, time, mathematics, and you no longer exist. We think of the edge of the universe as being way out there, but really it is right in the palm of your hand! I find it ironic that the only way to do this problem is with finite beings using flawed mathematics in a shit hole of a Universe that is going to fall apart or crunch itself into a black hole.

But to be on the safe side, let's stick with I don't know. I really should write a private journal and spare the world the babblings of a simple minded old man. It does keep me off the street.

“a shit hole of a Universe that is going to fall apart or crunch itself into a black hole.”

DeleteI thought it was supposed to expand forever. Is that what you mean by “fall apart”?

I haven't kept up with the latest theories but not too long ago, it was felt that the universe would either keep expanding and cooling and suffer what was then called heat death, equilibrium through the second law of thermodynamics. That and the natural decay of protons (average life 10^40 years) would be the falling apart, also the pessimistic view. Kaput!

DeleteThe optimistic view was that with enough mass, the expansion would slow, stop, then reverse into contraction due to gravity. It would speed up and eventually collapse into a singularity. The optimism was then it may Big Bang out again and off we go again.... The extremely optimistic believing that they will see another day in the sun. The big crunch...big bang...crunch ...bang forever. So perhaps we shall chat again in 105 billion years.

Hello Sextant, missing you lately? You OK? By the way, do you enjoy "The Big Bang Theory" (TV). Do they talk scientific rubbish? I love it though.

ReplyDeleteFiftyodd, I have never seen the show. Couldn't say if it has any accuracy or not.

DeleteI am OK, just a bit busy at the present.

Thanks for stopping by and commenting.