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Cyclic Patterns and the Solar System
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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Update: June 2012
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