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View Full Version : Discussion: The Winter Solstice Approaches



Fraser
2004-Dec-10, 05:29 PM
SUMMARY: As the year winds down, observers in the Northern Hemisphere may notice the days growing steadily shorter; while observers in the Southern Hemisphere notice the days getting longer. In addition, in the north the days are getting colder and in the south the days are getting warmer. All this happens while Earth is moving toward a point in its orbit known as the Winter Solstice. But what is the Solstice anyway?

View full article (http://www.universetoday.com/am/publish/winter_solstice_approach.html)

What do you think about this story? Post your comments below.

Guest
2004-Dec-10, 07:44 PM
nice info :D

David, Dunedin
2004-Dec-11, 08:06 PM
A nice article, yes as we approach the SUMMER SOLSTICE, the days are gettings longer. This is one of those things where the answer is opposite but both answers are true.

The earth is moving to a point on its orbit known as winter solstice, BY YOU NOrtheners!

We in the best part of the world are looking toward Summer Solstice, we will enter Winter Solstice in 6 months.

In the orbit we have 2 solstices and 2 equinoxes.

Hail to RA in his height.

A southern Pagan.

Greg
2004-Dec-12, 06:15 AM
I am already glad to put the solstice behind me. The sun has been setting around 415pm (1615) lately and I am tired of turning my headlights on at 3pm on a cloudy day.

Guest
2004-Dec-12, 06:22 PM
Now here is an interesting question to ponder, if the earth were not tilted and we had no seasons, would we celebrate the holidays in the same way?"

Hmmm... Would/could life have developed if the earth were not tilted seems more interesting,
just my 2cents. <_<

Heidi
2004-Dec-13, 11:34 PM
It would seem to me that the northern Earth is colder at this time of year not only because the Sun is shining obliquely on us but also because the days are shorter. Right? But the tempature isn&#39;t what is of concern to me. What I&#39;m interested in is the length of the day - the number of seconds of sunshine. While I can "see" the picture from our point of view on the surface of the earth (the Sun being lower in the sky each day and the days getting shorter, then about the same height for a few days, and finally starting to get higher in the sky each day and the days beginning to get longer), I am having difficulty picturing what is actually happening to the relationship between the earth and the sun. The Earth is spinning (making day and night); it is traveling in an elliptical orbit around the sun (one full orbit in about 365 days, right?); it is tilted.

First, does the orbit form a plane or is the Earth moving "up and down" in its orbit relative to the Sun?

Second, does the Earth wobble? Is it tilted so that the north pole is always further from the Sun than the south pole? I&#39;m thinking that can&#39;t be right. So I&#39;m reasoning that the Earth does "wobble" and it is, in fact, this wobble that makes the days longer and then shorter. Am I on the right track?

Dave Mitsky
2004-Dec-14, 04:32 AM
Heidi,

The angle of incidence of sunlight and the duration of daylight are both a result of the same cause, namely the fact that the northern hemisphere is pointed less directly at the Sun in winter due to the axial tilt or obliquity of the Earth. The Sun traces a shallower arc across the sky and culminates at a lower altitude. This means fewer hours of daylight.

http://solar.physics.montana.edu/YPOP/Clas...als/winter.html (http://solar.physics.montana.edu/YPOP/Classroom/Lessons/Sundials/winter.html)

http://www.schoolsobservatory.org.uk/astro...hys/season2.htm (http://www.schoolsobservatory.org.uk/astro/textb/phys/season2.htm)

http://imagine.gsfc.nasa.gov/docs/ask_astr...rs/980211f.html (http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980211f.html)

The Earth does not travel "up" and "down" through the ecliptic plane, which is simply the plane of the Earth&#39;s orbit around the Sun. (The equatorial plane of the Earth is tilted with respect to the ecliptic by an angle of 23.5 degrees.) The Moon varies 5 degrees from its orbital plane, however. This is what makes solar and lunar eclipses fairly rare instead of being monthly events. The orbital inclination of most of the satellites (moons) in the solar system to the plane of their primaries (i.e., the planets that they orbit) is only about 1 degree.

http://www.mhhe.com/physsci/astronomy/fix/...ter9/09f04.html (http://www.mhhe.com/physsci/astronomy/fix/student/chapter9/09f04.html)

http://starryskies.com/The_sky/events/luna...3/eclipse2.html (http://starryskies.com/The_sky/events/lunar-2003/eclipse2.html)

The Earth does indeed wobble. This phenomenon is known as precession and is responsible for the change in pole stars and the precession of the equinoxes over a 25,800 year period.

http://csep10.phys.utk.edu/astr161/lect/ti...precession.html (http://csep10.phys.utk.edu/astr161/lect/time/precession.html)

Dave Mitsky

astromark
2004-Dec-14, 11:45 AM
Good on ya Dave... Just want to add that the wobble is very slow. 25800 years. So it is not responsable for your winter. That 23.5 degrees is what gives us the seasons, and at the moment we in the southern hemisphear are enjoying the worm weather and clearer skies.
If the solar system was indeed the perfect model we would not have the angle of inclanation. The sun would come up and go over the equater every day. The moon would follow the same path. We would have monthly eclipses of both the sun and moon. and our weather would be,...... diferent. Orbital machanics is complex so its the way it is. Do have a look at the links Dave suplied, it/they will help.

Cathy
2004-Dec-16, 06:15 PM
But was there a time when the earth didn&#39;t tilt? Back in the time when the world was lit only by fire, the observance of the movement of the sun, moon, stars etc was a part of life. If the earth was always tilted to the same degree, one would think that after a few years of observing that when the sun reached a certain point on the horizon- ie say a specific mountain peak, or the last in a series of stones used to mark the sun&#39;s progress in the absence of such landmarks as mountains, that it would be accepted as a natural occurance, so that the solstice would be a time of pure celebration as opposed to sympathetic magic. So why all the myths, (ie Persepone) & ritual? Is it possible that the earth wasn&#39;t always tilted to such a degree & something happened to change the tilt of the earth. Of course this would be much more cataclysmic & so disruptive to the psyche of anyone&#39;s mind - let alone the ancient mind. So the myth of Hades snatching Persepone from her mother, Demeter&#39;s care, and the subsequent previously unexperienced cold & darkness which would necessitate magic & ritual to return Persepone to the surface & so turn the sun&#39;s movement back in the "right" direction.
Or was the earth always at the same tilt but something like a volcanic eruption or meteor strike obscured the sun & brought the darkness & cold to previously temperate climes so that some kind of propitiatory action was deemed vital?
Anyhow, The upshot of what I am saying is that perhaps we shouldn&#39;t think the ancient mind quite so based on superstition, because in those times there was only time for things that worked & were necessary, & that perhaps something more unusual than the normal, observable movement of the sun took place to engender the myths & rituals associated with this time of the year.
And now a question for our friends in the Southern hemisphere- are there myths, etc associated with the solstices amongst the indigenous people of your areas?

Guest
2004-Dec-22, 09:31 AM
<_< Please excuse my ignorance, but can anyone tell me how much longer daytime we Northeners can expect each day now that the winter solstice has passed?

David

antoniseb
2004-Dec-22, 01:44 PM
Originally posted by Guest@Dec 22 2004, 09:31 AM
<_< Please excuse my ignorance, but can anyone tell me how much longer daytime we Northeners can expect each day now that the winter solstice has passed?

David
At first, almost none. Imagine that the annual graph of total minutes of sunlight per day is a sine-wave [It isn&#39;t, but it is close]. We are at that bottom trough. In a month or so, you will notice very obvious increases in daylight on a daily basis.