For this week's Ask Ethan, Katia Moskovitch wants that cleared up:Could you one day write a story explaining to a lay person what the metric is in GR? It was this revelation, and the development to link this, mathematically, to the Minkowski-an concept of spacetime, that led to general relativity. Conceptually, the metric tensor defines how spacetime itself is curved. Physically, there are a number of different pieces that contribute to the Metric Tensor in general relativity. The metric tells us the relationship between all the matter/energy in the Universe and the curvature of spacetime itself.

Source: Forbes January 28, 2017 15:01 UTC