Einstein's general relativity tells us that matter and energy bend spacetime. One of the best examples of this can be seen with "gravitational lensing." Lensing occurs when the path of light from a source (or in this case a grid of point sources) travels near a massive or energetic object, called a "lens," and bends due to the mass/energy of the lens. In this Demonstration the massive object is an infinitely small point of variable mass, marked with a brown dot.
