In this demonstration, we see an example of how Conservation of Energy is true even when it appears to be wrong. This example shows how a bowling ball pendulum swings a smaller distance back and forth as time goes on. It appears to have lost energy over time!
In reality, while the kinetic energy has decreased, no energy is lost. The decrease in Kinetic Energy that we can see is due to the fact that some of that energy is being transferred as Heat due to Friction. This friction is created by the loop at the top of the cable rubbing against the hook it is hanging from as the ball swings.
Thus, some of the kinetic energy is being used to heat up the hook and loop and there is less energy to keep the bowling ball swinging. Therefore, energy changes but is not lost. This is an example of the law of Conservation of Energy.