We first make the comparison with the way an architect draws a house and its implementation by a builder. The architect may not bother with the thickness of his lines when making the drawing. But the builder must also consider the fine resolution of the lines, which will be enlarged to centimeters or decimeters in practice. In the same way, Special Relativity (SR) will need to be complemented by the introduction of a fine-structure given by the thickness of particle time-sheets, which replace the notion of geometrical time in the form of infinitely thin light-rays used heretofore. Only by making this extension to SR will it be possible to extend General Relativity (GR) from a static picture of the curved space-time to a dynamic theory which includes cause and effect.
