# Why mornings get darker after the Winter solstice



## Brian G Turner (Dec 21, 2014)

Found this interesting:
http://www.bbc.co.uk/news/magazine-30549149



> There are two reasons why the length of the solar day varies, the first being the fact that the axis of the Earth's rotation is tilted - 23.5 degrees from vertical - and second, the Earth's speed varies because it moves in an elliptical orbit around the sun, accelerating when it is closer to the star's gravitational pull and decelerating when it is further away.
> 
> The sun therefore in effect lags behind the clock for part of the year, then speeds ahead of it for another.
> 
> ...


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## Venusian Broon (Dec 21, 2014)

Brian Turner said:


> Found this interesting:
> http://www.bbc.co.uk/news/magazine-30549149



Well, that actually took me a few readings to understand. Not the orbital stuff, but how the solar day - standard time mismatch produces the earliest sunset on the 10th and mornings getting darker a few weeks after the 21st. Finally caved in and drew a diagram. Pictures are a thousand words sometimes!


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## Anne Spackman (Apr 1, 2015)

Fascinating.  I wonder who first figured this out. I guess no ancient astronomers ever guessed why the seasons occur.  Most didn't even guess that the Earth was round and that it orbited the sun, a basic knowledge of which would be necessary to understand how the seasons occur.  I looked up information about this, but it seems none of the ancient astronomers knew much about the Earth's shape, orbit, or why we have seasons:
https://explorable.com/greek-astronomy

I used to read a lot of Greek myths, and Hades' abduction of Persephone was one of the first stories I read.  When Demeter mourns the loss of her daughter Persphone in the underworld, the world turns to cold winter.  When Persephone returns to her mother, it is spring again. I wonder what other ancient cultures thought of the seasons and why we have them, and even what was thought about this in the time between the fall of Rome and Copernicus?


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## Ray McCarthy (Apr 1, 2015)

Anne Spackman said:


> ancient astronomers ever guessed why the seasons occur


I think both Babylonians and possibly Chinese did.

Newgrange was built 3200 BC, that's over FIVE THOUSAND TWO HUNDRED years ago. We have no idea who the builders were. But immense effort was required and it shows that they knew about the Winter Solstice.  We don't know if they knew what caused the seasons though.
https://en.wikipedia.org/wiki/Newgrange

The idea that anyone ever that thought about it much, thought the Earth WASN'T round was a myth created in the Victorian age.

http://en.wikipedia.org/wiki/Myth_of_the_Flat_Earth

http://www.medievalists.net/2013/11/21/ironing-out-the-myth-of-the-flat-earth/

also
http://www.medievalists.net/2014/06/27/15-myths-middle-ages/

http://en.wikipedia.org/wiki/Babylonian_astronomy


> The history of astronomy in Mesopotamia, and the world, begins with the Sumerians who developed the earliest writing system—known as cuneiform—around 3500–3200 BC. The Sumerians developed a form of astronomy that had an important influence on the sophisticated astronomy of the Babylonians. Astrolatry, which gave planetary gods an important role in Mesopotamian mythology and religion, began with the Sumerians. They also used a sexagesimal (base 60) place-value number system, which simplified the task of recording very great and very small numbers. The modern practice of dividing a circle into 360 degrees, of 60 minutes each hour, began with the Sumerians.
> 
> During the 8th and 7th centuries BCE, Babylonian astronomers developed a new empirical approach to astronomy. They began studying philosophy dealing with the ideal nature of the universe and began employing an internal logic within their predictive planetary systems. This was an important contribution to astronomy and the philosophy of science, and some scholars have thus referred to this new approach as the first scientific revolution.[2] This new approach to astronomy was adopted and further developed in Greek and Hellenistic astronomy. Classical Greek and Latin sources frequently use the term Chaldeans for the astronomers of Mesopotamia, who were, in reality, priest-scribes specializing in astrology and other forms of divination.



I have a book, from one to zero and later revision in several volumes that covers this. Georges Ifrah.
The Universal History of Numbers Georges Ifrah

Also
http://www.livius.org/k/kidinnu/kidinnu.htm


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## Dennis E. Taylor (Apr 1, 2015)

The analemma on globes http://en.wikipedia.org/wiki/Analemma is a representation of how the sun varies in relation to a fixed point over the course of the year.


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