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The Big Room : Having trouble contemplating the structure of the universe and your place in it? Welcome to the club.

Just looking at our monthly gatefold star chart, you wouldn't necessarily figure we perceive the sky as a dome. The map flattens the sky, and our mind's eye has to transform the circular frame into a horizon and the center point into the zenith high overhead.

I still recall that childhood revelation of a celestial vault. Reclining on our front lawn in suburban Chicago, I realized the blue sky looked like an overturned bowl. Suddenly the world was more than a floor plan. It had architecture. Although that ceiling at night is filled with stars, we're still not cued to the depth of space. The stars are too far to inform us of their differing distances. Instead they persuade us they are attached to the inner surface of the same great dome that roofs the landscape by day.

The illusion of a hemispherical celestial ceiling, echoed in the modern planetarium theater, is a notion that originated with the ancient Greeks. The earliest reliably documented reference to a spherical cosmos belongs to Parmenides, a pre-Socratic philosopher who lived in Elea, a Greek settlement on Italy's southwestern coast, in the fifth century B.C.

Many other ancient and traditional images of the sky, however, do not rely on spherical geometry. The Warao Indians of Venezuela's Orinoco delta, for example, attribute a bell shape to the sky, and the roundhouses built by their upriver Yekuana neighbors mimic this profile in conical roofs that symbolize the sky. The Yakuts of northeast Siberia saw the sky as a tent made of overlapping tightly stretched skins, and the Buryats of southern Siberia recognized in the Milky Way a seam where the primordial celestial canopy was stitched together. A more permanent cosmic shelter is mentioned in hieroglyphic inscriptions carved 1,300 years ago at Palenque, a Maya ceremonial center in southern Mexico. For the Maya, the cosmos was a house constructed at the time of creation by First Father, and the sky was its roof.

According to Gaston-Camille-Charles Maspero, a 19th-century Egyptologist, the ancient Egyptians pictured the Earth as the bottom of a rectangular box. Walled by mountains, its lid was an iron plate. Stars were suspended from that flat metal sky like lamps from a ceiling, and the ceiling was supported by four world-trees or high peaks at the cardinal directions.

All of these archaic images of the universe are easy to visualize, but they all prompt us to think outside the box, to wonder what is beyond the tent. The pre-Socratic philosophers who figured the universe was infinite bypassed that problem. Even Plato and Aristotle, who eventually decided there was no "outside" - no Big Room in which the finite cosmos sits - described the universe as if there were.

By the fourth century B.C., Plato had adapted the Pythagorean model of a cosmos bounded by the sphere of fixed stars to his understanding of the physical world. He still left room beyond the stars for something like a Big Room in Phaedrus, one of his earliest dialogues. When immortal souls reached "the summit of the Heaven," they could "go outside and stand on the roof . . . and behold the things which are outside the Heaven." In the Republic, still appreciating what sounds like a scenic view on the transcendental highway, Plato described the world system. His metaphorical landscape is ambiguous, however. Although his Spindle of Necessity - the cosmic axis - is viewed from the territory of the Three Fates, who keep it turning, the details are confusing.

Later, in Timaeus, Plato avoids these contradictions by telling us that, for all practical purposes, there is no Big Room in which the cosmos is on display even for exalted, divine souls. The "proper and natural" figure of the universe, he informs us, is "on the outside round about, a surface perfectly finished and smooth," and "nothing visible was left outside it." Because nothing else exists, there is no outside. Nevertheless, he depicts it from an outside perspective.

Aristotle also circumscribed the cosmos with the sphere of fixed stars. He credited its motion to the Prime Mover - a divine, intangible, eternal, unmoved, dimensionless first cause, and there is nothing beyond it - no space, no void, no nothing. Aristotle, like Plato, however, described the universe as if it were a mechanical device housed within some greater parlor, and he relied on the geometric system devised by Eudoxus of Cnidus in the fourth century B.C. Eudoxus handled this set of concentric spheres as a mathematical device, not as a physical reality. With them, he attempted to duplicate the observed behavior of heavenly bodies. Historian of astronomy D. R. Dicks calls him "the first Greek astronomer of whom we have definite evidence that he worked with and fully understood the concept of the celestial sphere, and the first to have attempted the construction of a mathematically based system that would explain the apparent irregularities in the motions of the sun, moon, and planets as seen from the earth."

The modern planetarium projector now demonstrates what Eudoxus could only calculate. With technology invented in Jena, Germany, in 1923 by Walter Bauersfeld at the Carl Zeiss Co., this device accurately duplicates the appearance and the movements of celestial objects and the starry sky.

There is no evidence Eudoxus had any kind of mechanical device that made an operating model out of an abstract theory, but he did have a celestial globe that let him delineate the constellations. His treatises on the heavens - Mirror and Phaenomena - have not survived, but Aratus of Soli versified and popularized Phaenomena in the third or fourth century B.C. Studies of the poem's information on the risings and settings of stars and on the placement of the constellations suggest the data were extracted from a star globe.

We have no working celestial globes from Graeco-Roman antiquity, but the next-best thing - Atlante Farnese - is exhibited in the National Archaeological Museum in Naples, Italy. This marble statue of Atlas holding a celestial globe was probably sculpted around A.D. 150. It is a Roman copy of a Greek original, probably from the second century B.C., and the globe illustrates the Aratean constellations as figures, not star patterns.

Early in the seventh century B.C., the Greek poet Hesiod explained what Atlas is doing with that globe. Atlas was one of the Titans, the generation of divinities that preceded the Olympian gods, and the broad sky rests on the Titan's "head and tireless hands." Atlas supported and stabilized the cosmos, and the Farnese Atlas symbolizes the cosmos with a sphere of constellations.

At times Atlas was a stand-in for the north celestial pole and world axis. In other contexts, he symbolized the north pole of the planetary system centered on the Earth. He could, in yet another sense, be regarded as one of the world directions that stabilizes and organizes the sky. In any case, he was a metaphor for an anchored, stable, and therefore hospitable cosmos. So the Farnese Atlas telegraphed an important message about the Hellenistic universe. It was essentially stable. Although mortals achieve this understanding beneath the sky, on the surface of the Earth, this statue provided a view from outside the sphere. The constellations are correctly inverted for this perspective out in the Big Room Aristotle argued could not exist. We see the universe from the realm the medieval scholars populated with saints, angels, and God.

The Farnese Atlas is not ancient research equipment. It is a piece of public sculpture. It was intended to convey, economically and with impact, an abstract idea about the nature of the world. With a concrete and visual image, it accelerated assimilation of a complex concept. Neither the audience nor the artist had to transcend the everyday world of three- dimensional space to get the picture. They could step into the Big Room.

We live in an expanding universe of curved space-time, and we really haven't found a visual metaphor that encapsulates the fundamental principles of this relativistic landscape. There is no center and no edge, and we don't quite know how to draw that. Like Plato and Aristotle, we can't let go of the Big Room. We still think of the universe as if it were happening there, something staged in a box. We liken the expanding universe to a rising raisin cake or an inflating balloon. These bubbles of space-time are charming but not accurate. As long as we imagine the Big Bang is exploding in a Big Room, we may as well stick with Atlas. He's standing on the floor of the Big Room, and he hasn't got a leg to stand on.

E.C. Krupp has a room with a view at Griffith Observatory.
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Author:Krupp, E. C.
Publication:Sky & Telescope
Date:Jan 1, 2000
Words:1447
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