We’ve all heard something along the lines of mathematical physicist John Wheeler’s statement that “Spacetime tells matter how to move; matter tells spacetime how to curve.”  But what do these academics actually mean when they state that gravity warps spacetime?  

Do they mean that there is a substance called spacetime that is mechanically deformed by large aggregates of material?

Absolutely not.  

First, we have to understand what scientists are referring to when they drop the term ‘spacetime’.  Spacetime is a continuum of points with reference to an event: measurements of locations at some moment.  A point in spacetime is where and when something occurred.  So what they are actually saying when they say spacetime warped in the presence of material, is that the gravitational attraction intensified in that particular location.  Because the phenomenon of gravitational attraction equally affects both the motion of bodies as well as the motion of clocks, scientists say that the spacetime is affected, or warped.  

Unfortunately the term ‘warp’ is merely a poetic analogy adapted from mechanics to pseudo-physicalize the phenomenon of gravitational attraction.  In reality, while mathematicians since Lorentz, Einstein, and Poincare have been increasingly accurate in their descriptions of gravitational attraction, none have provided any mechanical explanations for what is apparent:  bodies and clocks are affected by the presence of nearby aggregates of material.  In Einstein’s own words, 

“Relativity declares that space and time would disappear with matter.” 

Indeed, without material there could be no distance between the material (space/location) nor any clocks (time). The lack of mechanism for observed gravitational effects is not news.  Since this process was first recognized as universal to all bodies by Newton, there has been little advancement.  The question as to what physical actors actually mediate the phenomenon of gravity remains open.  Newton himself in 1675 took to speculating that there may be a substance retaining atoms to bind one another and that the

”… gravitating attraction of the earth be caused by...something very thinly and subtilely diffused...perhaps of an unctuous or gummy, tenacious, and springy nature." 

Ultimately, Newton went to his grave convinced that the puzzle remained to be solved.  It seems a great dishonor to our venerable scientific predecessors that we should abandon the search for mechanism, in favor of congratulating ourselves for establishing increasingly accurate mathematical descriptions of the mysterious phenomenon.  Perhaps it would be wise to repeat Newton’s own admonition against such hubris:

“I desired you would not ascribe 'innate gravity' to me. That gravity should…act… without the mediation of anything else, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it.”