Classical Lithium


Ben Whitaker

Classical Lithium is a proposal for a mobile sculpture in which three spinning tops in gimbal mounts are used to represent the entangled motion of the three electrons in a lithium atom. In the mobile the total angular momentum of the three spinning tops is conserved so as they orbit around a common centre of mass they rotate in their gimbals in an intricate dance. The electrons in the inner 1s orbital of a real lithium atom are indistinguishable and, unlike the spinning tops, their individual paths cannot be followed. They are quantum mechanically entangled; if one were to measure the direction of spin of one of them then the other would always be found to be spinning in the opposite direction. This quantum correlation between the spins can’t be replicated in a classical object like a spinning top because the direction of its spin is always known but, nonetheless, the classical correlation causes two gyroscopes coupled together in a larger gimbal to move in such a way that there axes of rotation are always anti-correlated, rather like the inner shell electrons in lithium. At present “Classical Lithium” only exists as an in-silicon simulation in which Newton’s equations are used to predict the trajectories of the spinning tops and produce a short loop video. A few component parts have also been manufactured.


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