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But if you draw one-inch and two-inch circles on the surface of a sphere, the bigger circle will have less than four times the area of the smaller one. This is because it is more curved by the sphere than the little circle, and is therefore more curled in upon itself.
Now, says Robertson, add a dimension. Take a deep breath and consider spheres instead of circles. In freshman solid geometry (which deals with ordinary "flat" space), a two-inch sphere has eight times the volume of a one-inch sphere. But if space is curved (a la Einstein), the two-inch sphere (curling in upon itself in space) will have less than eight times the volume of the one-inch sphere.
Spheres in the realm of the nebulae may behave in the same way. When Hubble looks out into a billion-light-year sphere of space with the 200-inch's doubled range of penetration, he may not find eight times as many nebulae as in the 500-million-light-year sphere of the 100-inch. Since the nebulae are apparently pretty evenly distributed, will this mean that the larger sphere has actually less than eight times the volumes of the smaller one? If so, perhaps space is really curved—and Hubble will be the first man to "see" its majestic curvature.
If space is really curved, then the universe must be "finite," of limited (though perhaps expanding) size'. One "model of the universe" (Einstein's) gives the "circumference of space" (the path which a beam of light would cover as it circles around finite space and back to its starting place) as about 300 billion lightyears.
If the nebula-dotted universe is finite, what lies beyond it? Robertson does not know. Perhaps, he admits, there may exist, far off in some medium that is thinner than space, still other universes. But each, presumably, is sealed in its own bubble of space, the light from its stars circulating endlessly, never escaping to reach our astronomers' telescopes. Scientists, briskly dusting their hands of other universes, say that if they exist, they must be penetrated by "nonphysical means."
Historic Night. Palomar's 200-inch telescope is all but complete now, with the big mirror in place. There is still much tinkering to be done. The mirror, slightly flexible, is supported by 36 complicated gadgets to keep it accurately in shape as the telescope changes its position. Each support contains 1,100 parts, and each will need expert adjustments before it works correctly. So will other mechanisms.
But its creators are sure by now that all will be well. Soon, Hubble will take his first photograph of the depths of space. It will be a historic night — an extra-clear night with the sky velvety black and the stars, though bright, twinkling hardly at all. Hubble will go into the observatory after dusk, rise to the big round telescope chamber in a push-button elevator.
He will be carried up inside the dome on a cleverly moving platform to the observer's cage, a cylindrical chamber, six feet in diameter, right in the muzzle of the telescope tube. He will climb into the cage, sit down in a seat which moves as the telescope swings.