Niels Bohr Nukes the Pudding

2017

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Saying the word “atomic” conjures the icon of electrons whirling in a circle about a nucleus. We can thank the great physicist Niels Bohr for proposing that image in 1913. Before his insight, many saw the atom as a “plum pudding”, an amorphous mixture with charged particles distributed throughout.

 

Then in 1911 Ernest Rutherford found something really, really hard down in an atom. Niels Bohr proposed that each atom had a dense, massive nucleus, surrounded by orbiting electrons at fixed distances. Aspects of his model explained much about chemistry and radiation. By the late 1920s, Bohr and others had made great advances in the new quantum physics, and the Bohr Model of the atom became obsolete. But the icon remains, an immortal symbol of the atomic world. Plum pudding has quietly retired to British television.

 

The sculpture highlights some aspects of the Bohr atom. The nucleus, small but central, remains motionless except for rotation. Electron orbits, shown as circles, orbit the nucleus in such a way that all points on each circle stay a fixed distance from the central nucleus, representing a fixed energy for each electron. The sculpture is an example of a spherical linkage mechanism. All rotation axes have their origins at the sphere’s center, so rotating parts attached to the axles keep a fixed distance from the sculpture’s center point.

 

For the nucleus, the radius is zero, hence its fixed aspect. The nucleus color? Just a taste of pudding.