The massive problem of trying to fully explain what mass actually is

LAST month, I wrote concerning the problem of explaining space-time. To give folks a sense for what I imply once I say that space-time is curved, generally I speak about a rubber sheet with a ball sitting on it. I level out that the ball causes the sheet to curve and the curvature of the sheet actually shapes the place the ball will roll. I say we are able to consider this as an analogy for our native star – the solar – curving space-time round it. How is the solar in a position to do that? Because it has mass.

Increasingly, I feel it …