An optical table is a platform that is used to support systems used for optics experiments and engineering. The surfaces of these tables are designed to be very rigid so that the alignment of optical elements remains stable over time. Many optical systems require that vibration of optical elements be kept small. As a result, optical tables are typically very heavy and incorporate vibration-damping features in their structure. Many use pneumatic bearings that act as a low-pass filter to vibrations, preventing high-frequency vibrations in the floor from reaching the tabletop.