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Name: Tanya
Status: student
Age: 18 
Location: N/A
Country: N/A
Date: 1999 - 2000


Question:
What are the interconnected cyclic patterns and associated phenoma of our solar system, and how might they influence our lives?

What I need to know is, What are the interconnected cyclic patterns and associated phenoma of our solar system. Which is well, cyclic patterns can be things like day and night. That is a cyclic pattern it goes around in a cycle. And associated phenoma is what causes this to happen eg.day and night is caused by the earths rotation around the sun. This affects our lives by giving us a new day after every night because every 7 days there's a week every 4 weeks there is a month, every 12 months there is a year, and so on.

This is just one example I can think of. Can you help me with some others?


Replies:
I thought this was a very interesting question. I knew that the answer was rather complicated so I took the liberty of asking an expert. I sent the question to the U.S. Naval Observatory, "ask and astronomer" web page. Credit for the answer belongs to:

James L. Hilton jhilton@aa.usno.navy.mil
Astronomical Applications Dept., U. S. Naval Observatory

Vince Calder

This is a difficult question to answer because there are many forces acting on the Earth and there are many different ways of dividing them up. Some of these forces are also poorly understood. What I will give you will cover all of the major forces and most of the minor ones.

1. The Sun on the Earth's center of mass - responsible for the yearly orbit of the Earth around the Sun.

2. The Moon on the Earth's center of mass - responsible for a monthly motion about the center of mass or the Earth-Moon system (the center of mass of the Earth-Moon system is about 3/4 of the radius of the Earth away from the Earth's center).

3. The perturbations of the planets on the Earth's center of mass - responbile for small, long term changes in the orbit of the Earth.

4. The rotation of the Earth (forceless) - responible for the day night cycle.

5. The Moon, Sun, and planets on the asymmetric bulk of the Earth - responsible for precession (a 26,000 yr. motion of the pole of the Earth in a small circle about the pole of the Earth's orbit) and nutation (a long series of smaller wobble in the Earth's pole with periods from two days to 18.6 years).

6. The Chandler wobble an approx. 450 motion of the Earth's pole caused by the fact that the axis of rotation does not exactly coincide with one of the Earth's principal axes of inertia (forceless).

7. The Nearly Diurnal Free Wobble caused by friction between the mantle and the core because the have slightly different shapes and hence want to nutate at different rates.

8. Tidal drag of the Moon and Sun on the Earth - responsible for a slowing down in the rate at which the Earth turns on its axis.

9. Post glacial rebound (a change in the shape of the Earth) - responsible for changes in the rate of the Earth's rotation, the exact postition of the Earth's rotation axis, and the principal axes of inertia.

10. Yearly movement of water on the surface of the Earth - responsible for changes in the rate of the Earth's rotation, the exact postition of the Earth's rotation axis, and the principal axes of inertia.

11. Friction between the Earth and its atmosphere and oceans - responsible for changes in the rate of the Earth's rotation and the exact postition of the Earth's rotation axis.

Many of these processes (especially the last three) are stochastic, so they cannot be predicted for more than a short period of time (usuually several days to a few months).

Astronomical Applications Dept.
U.S. Naval Observatory
http://aa.usno.navy.mil/AA/



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