Floating Ball is a 2nd generation exhibit. The original was done by the Exploratorium in San Francisco. The exhibit is about feedback. A small metal globe floats in the air. It is held up by an electromagnet. It is exactly balanced by the feedback look between the electromagnet and an optical sensor. As the globe drops slightly, more light is picked up by the sensor which in turn causes the electromagnet to increase its force which brings the ball up again. This feedback is happening very quickly so the globe appears very stable. The first generation exhibit was a great starting point, one of our favourite exhibits. The Mystus version has made several enhancements. First, the new circuitry and sensors have allowed us to use an electromagnet that dissipates a minimal amount of heat. The coil can easily be held by hand without any safety risk; there is actually no feeling of heat. We do, however, cover the coil to prevent inadvertent damage. In the original exhibit it was a little difficult to grasp the meaning of the exhibit - feedback. In our enhanced version we have added some features to give the visitor further insight into the nature of feedback. Even though the globe appears stable, there are actually very small fluctuations in its position due to wind currents, floor vibration etc. These variations are in the range of 40-100 Hz. We hooked up a speaker so you can hear them. We also allow the visitor to alter the gain in the circuit to discover the upper and lower boundaries. In approaching these boundaries the increasing instability can be seen, and heard. We also allow the visitor to introduce delay into the feedback loop and see/hear the resulting instability.