Is the gravitational constant really a constant?

Scientists have been measuring the universal gravitational constant, G, for hundreds of years.  But, how accurate are they in their measurements?  Is G truly a constant?  It’s a question physicists and astronomers continue to debate.  Due to variations in experimentally obtained values for G, a number of postulates have been proposed which note that G may vary with time, and could be dependent on orientation, surrounding masses, even the curvature of space time!

Complicating matters, experimental error in the determination of G is typically estimated at 1%, even with modern measuring equipment.  Is G really a constant?  Does it vary within this +/- 1% window?  Is Newton’s Law of Universal Gravitation complete, or is there more to it?  Recent studies continue to explore and debate these questions.