From Summertide by Charles Sheffield:
ARTIFACT: LENS.
UAC#: 1023
Galactic Coordinates: 29,334.229/18,339.895/-831.22
Name: Lens Star/planet association: None, free space entity
Bose Access Node:em> 108 Estimated age: 9.138 ± 0.56 Megayears
Exploration History: The full history of Lens may never be known. Lying as it does in the clade of the Zardalu Communion, all early records were lost with the collapse of the Zardalu Empire. However, given the preoccupation of the Zardalu with biological science and their relative indifference to physical ones, it is most unlikely that any systematic exploration of Lens was ever attempted by them.
The recorded history of Lens begins with its observation in E. 122, but it was long assumed to be extragalactic. The local nature, as part of the spiral arm, was discovered in E. 388 from parallax effects. The Lens was approached directly in E. 2101 by Kusra (one-way journey), but no physical evidence for material existence could be obtained. Paperl and Ula H'sagta (E. 2377) measured a polarization change of beamed lasers passed through the region of the Lens, confirmed its location, and mapped its extent.
Physical Description: The Lens is a focusing region of space, 0.23 light-years in diameter and of apparently zero thickness (grazing incidence measurements have been made down to one micrometer). Focusing is performed only for light with wavelength range 0.110 to 2.335 micrometers, approaching within 0.077 radians of normal incidence to the plane surface of the Lens. There is, however, weak evidence of interaction with radiation of wavelength in excess of 0.1 light-years (the low energy of such radiation makes its separation from cosmic background of debatable validity). All other light, all particles or solid objects, and all gravity waves pass through the Lens apparently unaffected. Radiation focusing appears to be perfectly achromatic for all wavelengths in the stated range. In that range, the Lens performs as a diffraction-limited focusing device of 0.22 light-years effective aperture and 427 light-years focal length. With its aid, planetary details have been observed in galaxies more than one hundred million parsecs distant.
Physical Nature: This must unfortunately comprise an eliminative list of what the Lens is not. Today's science and technology can provide no tenable suggestion as to what it is.
The Lens is not built of any particles known to today's inhabitants of the spiral arm. It is not a form of space-time singularity, since such a singularity cannot affect light of certain wavelengths and leave all other forms of matter and radiation untouched. For the same reason, it cannot be an assembly of bound gravitons. It cannot possess a superstring or superloop structure, since no spontaneous or induced emission is observed.
Intended Purpose: Unknown. The Lens represents macroengineering by the Builders at its largest and most mysterious. The specific wavelength range has, however, induced some students of the artifact to speculate that this range corresponds to the spectral sensitivity range of Builder eyes. Since there is no evidence that the Builders possessed anything equivalent to eyes in human or Hymenopt terms, the conjecture is of passing interest only.
It has also been conjectured that the Lens performs modulation of the light passing through it, in a way not understood. If so, its function as a focusing lens would be no more than an accidental by-product of the structure's true purpose.
Excerpt from Summertide by Charles Sheffield, ©1990 Charles Sheffield.
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