Problem 1: What are key physical constants related to gravitation and the gravity field of a planet and how well are these known? 
The Universal Gravity Constant (G) is 6.67x10^-11 m3/kg*s, Although this number has been researched for 300 years there are still large uncertainties. The mass of the Earth (Me) is another such constant whose value is 5.97x10^24 and it is well known. 
Problem 2: Name and characterize the main equations related to the gravity potential. 
Problem 3: How large are the deviations of the geoid from the reference ellipsoid and how are these deviations explained? The reference ellipsoid is the mathematical interpretation of a smooth oblate sphere which most accurately represents the earth. The geoid is a surface of equipotential gravity which occurs on earth. The geoid is most closely associated with sea level. The deviations between the reference ellipsoid and the geoid occur because while the geoid can vary its height, the reference ellipsoid remains constant
Problem 4: Explain in simple words the origin of tides. 
The tides are caused by revolution without rotation around the barycenter of the earth and moon. The difference between the centrifugal and gravitational forces is the tidal force.
Problem 5: Why do we see ocean tides? 
We see ocean tides because of a mixture of forces. As the earth rotates it creates a centrifugal force which creates tidal motion. The moon also exerts a gravitational force on earth which is represented in the tides. 
Problem 6: Why are the amplitude and phases of semidiurnal and diurnal tides varying irregularly in space? The semidiurnal tides have an m=2 and periods of 12 hours. The diurnal tides have an m=1 with a period of 24 hours. 
Problem 7: How large is the largest equilibrium tide on Earth? 
The largest equilibrium tides is the long-period constituent tide which last up to 18.6 years.
Problem 8: Why does the Moon keep the same face toward the Earth? The moon takes exactly one month to complete its rotation, which is also the same amount of time it takes the moon to orbit the earth. It is because of this that the moon always keeps the same face towards the earth.
Problem 9: How large is the tidal bulge of the Moon? 
Problem 10: What are the main rotational eigenmodes of the Earth and to which parts of the Earth are they mainly attributed? 
The Chandler Wobble is the first rotational Eigen mode of the earth is with a period close to 433 days, it is associated with polar motion. The Nearly Diurnal Free Wobble and free core nutation is the second rotational Eigen mode of the earth and has a period of 460 days. The period depends on the ellipicity of the core mantle boundary. The third rotational Eigen mode is the free inner core nutation and it is associated with interactions between the inner and outer core. 
　
　
　


--- On Tue, 4/26/11, hpplag@unr.edu <hpplag@unr.edu> wrote:

From: hpplag@unr.edu <hpplag@unr.edu>
Subject: Geology 495/695: Environmental Geodesy
To: "Armand Rodrigues" <aj007rod@yahoo.com>
Date: Tuesday, April 26, 2011, 7:22 AM
Armand,

Attached the first assignment with my comments.

I noticed that I still don't have your results for the second assignment. Could you please submit this as soon as possible?

Thanks,

Hans-Peter Plag


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Geodesy hw 2.wps