It depends entirely on what you mean by knowledge.

Our theories for gravity and magnetism allow us to describe the essential physics of systems from nearly the size of the universe, to events at a scale of nearly 1 million times smaller than the nucleus of an atom. The latter phenomenon is explained by quantum electrodynamics which routinely makes predictions correct to 10 decimal places. For gravity, we can accurately describe systems as vast as the universe and its evolution, to the surfaces of black holes.

From a practical point of view we understand these two forces almost perfectly, and to our best current ability to measure. If you are asking a more metaphysical question about our knowledge, then we don't really understand ANYTHING about our physical world at the deepest level, such as why does gravity exist? Is it a quantum field? What is the nature of space-time?

In terms of the human sphere of activity, we understand enough about these two fields that we will never have much practical need for better theories than the ones we now have.

Copyright 1997 Dr. Sten Odenwald