Einstein's General Relativity Through Systemic Functional Linguistics

Gribbin (1989: 78-9):

[The ideas of General Relativity] envisage what we think of in everyday terms as empty space as something almost tangible, a continuum of in four dimensions (three of space and one of time) that can be bent and distorted by the presence of material objects.  It is those bends and distortions that provide the "force" of gravity.

Forget about the four dimensions of space-time for a moment and think of a two-dimension elastic surface.  Imagine a rubber sheet stretched tightly across a frame to make a flat surface.  That is a "model" of Einstein's version of empty space.  Now imagine dumping a heavy bowling ball in the middle of the sheet.  It bends.  That is Einstein's "model" of the way space distorts near a large lump of matter.  When you roll marbles across the flat rubber sheet, they travel in straight lines.  But when the sheet is distorted by the bowling ball, any marble you roll near the ball follows a curved trajectory around the depression in the rubber sheet.  That, said Einstein in effect, is where the "force" of gravity comes from.  There really isn''t any force.  Objects are simply following a path of least resistance, the equivalent of a straight line, through a curved portion of space, or space-time.  The object can be a marble, a planet, or a beam of light.  The effect is the same.  When it moves near a large mass — through a gravitational field of force, on the old picture — it gets bent.

Blogger Comments:

From the perspective of Systemic Functional Linguistic Theory, the term 'empty space' confuses the circumstantial dimension ('space') with a quality of the participant ('empty') being measured.  The same category error occurs when the circumstantial dimension of time is confused with the process (such as the ticking of a clock) being measured.

If space-time is understood in Einstein's terms, as a four-dimensional grid, then gravity is the gradual contraction of space intervals (and expansion of time intervals) with increasing proximity to a material object.  It is the gradual contraction of space intervals that accounts for the curved trajectory of other objects in their vicinity.  This is because, other things being equal, a moving body takes the shortest path between two points, a geodesic, and the increasingly contracted space intervals with proximity to a massive body means that the shortest path is increasingly toward that object.

On the "rubber sheet" model, the increasing depth of the depression in the rubber sheet near a massive body actually correlates with the increasing contraction of space intervals with increasing proximity to the object.

Where gravity is the relative contraction of space intervals (and expansion of time intervals), the cosmological expansion is the relative expansion of space intervals (and contraction of time intervals).