An attribute of three-dimensional space which is crucial for life and Mind is that only in three dimensions does the gravitational force permit masses to move in stable orbits. If the space of our universe was of a higher dimensionality, our earth and the other planets could not maintain a stable orbit about the sun: they would either spiral into it, or move away from it due to asteroid or meteor impacts. A planetary orbit with long-term stability during the 3.7 billion years that has elapsed since life emerged on earth has been, and continues to be, absolutely necessary for the existence of life and Mind.

The first investigator to successfully develop mathematical models of planetary orbits was the German astronomer Johannes Kepler. He had worked under the Danish astronomer Tycho Brahe, who during 1570-1601 had supervised the making and recording of a large accurate collection of naked-eye astronomical observations, including the movement among the fixed stars of the six planets then known.(30) Using Tycho's data, Kepler was able to calculate the stable orbits of the planets around the sun, and construct three models of their motions, which he published in 1609(31) and 1619.(32)

Kepler's models showed that the orbit of a planet is an ellipse with the sun in one focus, and described the planets' orbital speeds and periods. In 1687, the British mathematician and physicist Isaac Newton published his model of the gravitational force(33), which subsumed Kepler's models of orbital stability in a more comprehensive explanation of the motions of astronomical bodies. Later, in 1916, the German-American physicist Albert Einstein published his new model of the gravitational force, based on four-dimensional space-time and the equivalence or symmetry of all possible frames of reference, as set forth in his principle of General Relativity.(34) Einstein's model also predicted stable planetary orbits.

During 1917-1920 the Austrian physicist Paul Ehrenfest carried out an investigation of the Newtonian model of gravitational stability of planetary orbits in spaces of different dimensions.(35) He found that for three-dimensional space, planetary orbits are stable, and if they are disrupted in some way, say by the impact of a large meteor on the planet, they will always move to another stable nearby orbit if the force is not too large, He also showed that this same orbital stability extends to curved non-Euclidian three-dimensional spaces, such as were predicted by Einstein's gravitational model. But Ehrenfest found that for spaces of four dimensions and higher, even the smallest impact on a planet would immediately cause it to either spiral inward into the central body, or outward towards infinity.

In 1963, the American physicist, Frank Tangherlini extended the investigations of the gravitational stability of planetary orbits using Einstein's General Relativity gravitational model, called the Schwarzchild field, adapting it to spaces of higher dimensionality than three.(36) He demonstrated that, for this more general case, the same conditions of stability for orbits are found only in three dimensional space, as Ehrenfest had shown. Given our earth's long history of asteroid and meteor impacts, the stability of orbits allowed by our three-dimensional space is essential to life and Mind.

This column celebrates the stability of gravitational orbits which is possible only in our three-dimensional space. The space-time path, or "world line", of a stable orbit can be represented by a helix, where the horizontal axes show the spatial rotation of the body, and the vertical axis shows the dimension of time. The term "world line" was introduced by the Polish-German mathematician Hermann Minkowski in his model of four-dimensional space-time published in 1908.(37) The central cylindrical shaft of the column is symbolically ornamented by two orbital world line helices, one right-handed and the other left-handed, placed tangent to each other, supported by rods at their tangent points. At the capital of the column, each helix starts at a ring of slightly larger orbital diameter, from which it transitions into the stable orbit which is maintained to the column base plate. The column was executed in formed and welded stainless steel.