Final answer:
When a small pebble is placed on the rubber sheet, it causes a slight distortion and alters the ant's path slightly. However, when a paperweight with more mass is placed on the sheet, it causes a significant distortion and forces the ant to follow a curved path. This demonstrates how mass can affect the curvature of space.
Step-by-step explanation:
When the ant is placed on an empty rubber sheet, it walks in a straight line from one side to the other. When a small grain of sand is placed on the sheet, it causes a tiny distortion that the ant doesn't notice and can continue walking in a straight line. However, when a small pebble is placed on the sheet, it causes a slight distortion and the ant's path is slightly altered, deviating from a straight line. Finally, when a paperweight with more mass is placed on the sheet, it causes a significant distortion and forces the ant to follow a curved path to reach the other side of the sheet.