In a study published in the journal Applied Optics, Rosa Weigand, professor of the department of optics of the Universidad Complutense de Madrid (UCM), and a team of researchers have attempted to reproduce the lighting conditions that occurred in this ancient Greek temple more than 2,000 years ago, using samples of the two types of marble that were used in the roof, thus reports the Archaeological News Network.

With a height of twelve metres and built from ivory and gold overlaid on a wooden frame, the statue of Zeus was considered one of the seven wonders of the ancient world. Located in the interior of a temple at Olympia in ancient Greece, it was crafted in the year 432 BC by the sculptor Pheidias.

Despite its large size, and the darkness of the temple, which had neither windows nor a door of great size, various classical sources describe the eyes and the hair of the god in detail, which would indicate some type of lighting by natural means. This natural lighting was sufficient for the statue to be perceived by any person when entering the temple, once their eyesight had become accustomed to the darkness.
According to Paul A. Garcia, co-author of the study and project collaborator from the Institute of Languages and Cultures of the Mediterranean and the Middle East (CSIC), whose doctoral dissertation is the basis of the research, the best light is transmitted by the Pentelic marble rather than the marble from Paros. This property of the marble could be one of the reasons that led the Greeks to replace the original material of the temple, brought from the island of Paros, with plates of Pentelic marble, although, as the authors say, this could also have been due to economic or commercial issues.
Jose Jacobo Storch of Grace, Professor of the Faculty of Geography and History of the UCM and director of the study says the researchers first became interested in the phenomenon because of the frequent descriptions of the hair and eyes:
"The reason that made us consider the lighting from the roof is that ancient sources place great emphasis on the eyes and hair when describing the Zeus of Olympia. The results [of our tests] reveal a high transmission area in the yellow-red end of the spectrum, which is suitable for illuminating an object made of ivory and gold."
In order to reach these conclusions, the researchers--among which are also experts from the Institute of optics of the CSIC--used a light meter, which estimated the transmittance (amount of light that passes through a body) of the samples, and a spectrophotometer, to measure the resulting spectrum and see what wavelengths are more efficient.
Unfortunately nothing remains of the sculpture today, except for representations on ancient coins and paintings on ceramics, in addition to detailed literary descriptions. Following the destruction of the temple in Olympia after several earthquakes, the statue moved to Constantinople (now Istanbul) where it was destroyed by fire in the year 475 A.D.