The SG is capable of recording temporal gravity variations from seconds to years and thus the GGP has application to large number of scientific tasks. As indicated above, at long periods (months - years), we highly recommend the use of a SG supplemented by an Absolute Gravimeter to fully characterise secular trends in gravity. Many of the Earth parameters of critical interest in global dynamics are recoverable from gravimetric signals at or below the ambient noise level. This includes internal gravity waves in the fluid core, post-glacial uplift and plate motions. The SG has a stated sensitivity at the nanogal level and most signals of interest are expected to be in this range. Since the ambient gravity noise is usuallytwo to three orders of magnitude greater than this, global signals identified on the record of an individual instrument at the nanogal level cannot be considered reliable unless and until confirmed with similar signals from other instruments. Furthermore, these instruments must be distributed widely around the Earth because global gravimetric signals have theoretically predictable spatial and temporal global variations. 

Rapid access to worldwide gravimetric data is essential for progress in global geodynamics for several reasons. First, high resolution gravimetric data makes it possible to measure free oscillations of the Earth with unprecedented precision. In real-time, an array of SG instruments would provide a means for global detection of `silent earthquakes' (Beroza & Jordan, 1990). Second, sub-milliarcsecond orientation can be obtained through measurement by an SG network for space-based measurements such as Satellite Laser Ranging and the US-proposed GLRS project to position points on the Earth's surface to the sub-centimetre level through the use of Earth-based retro-reflectors and satellite-based lasers. Third, Earth models which incorporate core resonances require access to gravimetric data at the nanogal level to successfully account for motion in the deep interior in all of the orientation calculations. The proposed network of instruments and communication makes access to gravimetric data sufficiently rapid that all the above tasks can be accomplished. 

Lastly, a number of tectonics-related problems require global gravity field data for their resolution. In particular the problems of long-term secular changes in elevation, caused not only by post-glacial rebound and sea level changes but also by active plate-tectonic related deformation, need long-term gravity variations at continental scales. The long period behaviour of SG's is currently very variable, with the best instruments virtually drift-free at the level of about 1 microgal per year. If this level of stability can be maintained by even a small number of SG stations in the global network, particularly where confirmed with Absolute Gravimeters, then GGP will provide useful data for these tectonic problems. At shorter periods, the signatures of earthquake pre-cursor activity, the search for slow earthquakes and the precise monitoring of the normal modes following large earthquakes are all tasks for which the SG is particularly suited. 

In the past an individual with access to a computing service could make major progress in the solution of both analytical and data analysis problems. However, the complexity of presently extant problems in global geodynamics is such that measurements on a global scale are needed to make even minimum progress. Concerted effort by cooperating scientists is needed to make any significant advance. Without uniform high precision global data it will be impossible to move toward the solution of the problems of the Earth's deep interior. High quality continuous vertical gravity values need to have global coverage to answer a number of important geophysical questions. Due to the extremely weak gravity signals (some at the nanogal level) associated with many of these phenomena, it is essential that very high sensitivity ground based observations using SGs be undertaken.