Winter Soltice is nearly here. My dictionary defines soltice (be it Winter or Summer) as “when the sun is the greatest distance from the celestial equator.” Therefore, the first day of winter is when the northern part of the north/south axis is pointing furthest away from the sun. The occurs (give a day or two) on December 21.
Likewise a year is “the period of time in which the earth completes one revolution around the sun.” Therefore the earth is in relatively the same position to the sun on December 21
There are to be two phenomenons occuring at approximately the same time. The tilt of the North/South Axis and the relative position of the earth to the sun.
Are these two phenomenons occuring at exactly the same time?
And if they are occuring at the same: What is the reason? Is it purely coincidence?
If you meant that the Earth is in relatively the same position to the sun on December 21 as is was last year on December 21, you’d be right. But then again, that’s true of every date in a given year (except for 2/29, which of course happens only once every four years).
could you possibly mean- solstice
sol·stice (slsts, sl-, sôl-)
n.
Astronomy. Either of two times of the year when the sun is at its greatest distance from the celestial equator. The summer solstice in the Northern Hemisphere occurs about June 21, when the sun is in the zenith at the tropic of Cancer; the winter solstice occurs about December 21, when the sun is over the tropic of Capricorn. The summer solstice is the longest day of the year and the winter solstice is the shortest.
A highest point or culmination.
I still dont understand your questions… are you refering to how the earth rotates around the sun or how the earths axis rotates? Either way maybe this could explain.
A year is any (roughly) 365 1/4 day period that it takes for the Earth to orbit the sun. Our current calendar measures “the” year (the one with dates on it such as 2000 or 2001) from January 1 through December 31, adding an additional day every four years or so to make up that approximate quarter day.
Any event that repeats only once during a solar orbit will occur “once a year.” The reason that the calendar year begins and ends near the solstice is that the Romans from whom we borrowed our calendar (with modifications) did consider the period when the days were shortest to be the end and beginning of the year. Other cultures marked the year from spring planting to spring or from autumn harvest to autumn, but we got the version that used the short days and long nights.
The Encyclopædia Britannica: calendar and Encyclopædia Britannica: year each have sections dealing with these phenomena. It can be long, but it is interesting. Go to the bottom of the “calendar” article to find an index of related topics. Both articles have hyperlinks for further research.
I agree with the other responses. Something basic is missing from your question.
The Earth’s axis of rotation is tilted to the plane of its orbit around the sun. On the winter solstice, the northern hemisphere is facing away from the sun as much as it can (the sun appears lowest in the sky).
Are you wondering whether the position of the Earth in its orbit has something to do with winter? If so, it doesn’t really. Winter is due to the Earth’s tilt away from the sun. During the northern hemisphere’s winter, the Earth is actually closer to the sun than during summer. But summer is hotter because of the tilt toward the sun.
Perihelion, and its converse event Aphelion do not occur at the same time as the solstices. Well, at least they don’t do it every year. Currently Perihelion is happening on January the sixth, I think, or thereabouts. Both the solstices, and the exact time of the apical orbital positions are slightly variable. Over a period of many thousands of years, there will be some times when those events will coincide. Most of the time, they do not.
First, define “year”. There are at least three different definitions, two of which are important here. The tropical year is the time from one vernal equinox to the next (very nearly the same as from one winter solstice to the next), 365d,5h,48m,46s. The sidereal year is the time from any moment until the Earth is again in the same place with respect to the sun and the distant stars. For example, today the sun is in a certain point in Sagittarius. It will be in the same place one sidereal year from now, 365d,6h,9m,10s. This difference of about 20 minutes between the tropical and sidereal years leads to a cycle of about 26,000 years (the precession of the equinoxes). The cycle occurs because the earth is wobbling like a top, albeit very slowly. Now the axis points toward Polaris, in 13,000 years it will point toward Vega, and 13,000 years afte that, it will point toward Polaris again. If the year were wobbling a lot faster, say once every ten years instead of every 26,000 years, we would be much more likely to notice the discrepancy.
The solstice does not occur exactly at the time of perihelion. The third definition of year is the “anomalistic year”, the period from one perihelion to the next, 365d,6h,13m,53s. Since this is not exactly the same as the tropical year, the number of days between perihelion and the solstice is not constant. This cycle is much slower than the precession of the equinoxes, however, with a cycle of about 100,000 years, I think.
As I read the question, notfrommensa is asking if there is a connection or if it is coincidence that winter solstice occurs exactly once a year. Is there a connection between the axial tilt of Earth and the time it takes to orbit the sun once?
The answer to that is yes, there is a connection.
Assume that the Earth’s axis is constant, and doesn’t wobble. This is a good first order approximation. Look at the picture in the link provided by absoul. It shows how the axial tilt stays pointed in the same direction during the orbit, and how the seasons are defined by angle of sunlight. Notice that it is the location of the Earth around the Sun that defines the seasons, because that location is what defines the sun angle.
If the Earth were wobbling in orbit really quickly, such that the axis changed directions a lot, then the seasons would not be as systematic.
Note before I said assume constant direction. There is a small wobble, as explained by bibliophage. That wobble is miniscule in orientation and very slow, so it is almost negligible.
Today (January 4th 2001) is Perihelion. At approximately nine AM, Greenwich Meridian (Universal) Time, the Earth will pass through its closest approach to the Sun.