My office window is in a shadow created by the sun going behind a mountain. As we approach Dec 21 it occurs earlier and reaches maximim time before 2pm on the 21st. It has always been some time before 2pm (4pm Eastern). This year it occured after 2pm by a few minutes. I know the mountain did not get smaller, so I am guessing the axis is leaning more toward the sun cause the sun to appear higher in the sky. Looking up all I cound find on the movement of the earth, it appear the explanation is the Chandler woble.
Could someone more wiser then me confirm I am observing the effect of the Chandelr woble or direct me toward another explantion.
The Chandler wobble is a movement of a few feet in the Earth’s axis of rotation. The Earth is 8,000 miles in diameter. I assure you that you can’t notice the wobble from a window in your office.
One possibility is that you’re mistaken in remembering that the earliest “shadow time” occurred on the 21st of December. As discussed in this thread, the earliest sunset (or in your case, the earliest “shadow time”) occurs a couple of weeks before that. Perhaps you remembered that the earliest shadow occurred before 2 p.m., but forgot that this happened earlier in December.
Note that a year is not an exact number of days. So 365 or 366 days later the Earth is not going to be in the exact same spot of its orbit. Given the orbit is elliptical and all that, certain things like this vary from year to year.
The change is probably due to 2004 being a leap year. This year, the 21st came 366 days after the 21st in 2003. The last three years, the 21st came 265 days after the previous one. I suspect if you plotted the time over a long period, your times would show a small change for three years, and a jump every fourth year. Something like
