Thermal scans of the Great Pyramid of Giza have revealed an "impressive" anomaly in the rock -- a change in temperature that could indicate something behind the 4,500-year-old walls.
"This anomaly is really quite impressive and it’s just in front of us, at the ground level," said Mehdi Tayoubi, founder of the Paris-based Heritage Innovation Preservation Institute that is conducting the Scan Pyramids experiments using a mix of infrared thermography, muon radiography and 3D reconstruction.
The anomaly is located on the eastern side of the pyramid, also known as the pyramid of Khufu, as can be seen in this image provided by the organization:
The scans were conducted at different times of the day and night; temperatures were measured as the stones grew warmer and cooled off. While the temperature differences between most adjacent stones typically varied by between 0.1 degrees and 0.5 degrees, this one particular segment had a 6-degree variation, as can be seen in the thermal scans:
"We have several hypotheses but no conclusion for the moment," said Tayoubi.
Egyptian Antiquities Minister Mamdouh el-Damaty said he also had several hypotheses, but wanted to do more research before revealing them.
“It could be void spaces, fissures or passages," he told Ahram Online. "So far, I do not know."
El-Damaty told The Associated Press that closer inspection of the site found what appeared to be "a small passage in the ground" on the eastern side leading up to the area with the temperature change.
Egyptologist Beth Ann Judas said it makes sense that the anomaly is on the eastern side of the pyramid as that was in many ways the "focal point" of the pyramid, with several major temples and tombs located on that side.
"The Nile was to the east of the pyramid, and most everyone would have approached from the east," she said. "Pyramids also have a connection to the solar aspect, and the cult of the god Ra, in ancient Egyptian religion."
Judas, who has done several seasons of fieldwork in Egypt, said the Khufu pyramid contains the most complex series of passages of any of the pyramids and may have had several design changes during construction.
The original burial chamber, for example, is below ground. However, the eventual final resting place of the pharaoh was the "King's Chamber" located near the top of the pyramid.
Judas said whatever is responsible for the anomaly could be connected to the earliest phases of the construction and that first burial chamber.
"At the very least, this anomaly will shed additional light on the construction techniques of the 4th dynasty Egyptians," said Judas. "It's rather exciting actually. Over the past few years, archaeologists have been learning more about the workmen and officials who are connected to the pyramids, and this gives us more information about their work."
Several other anomalies found at the Khufu pyramid, as well as on other monuments, will be examined as the Scan Pyramids project continues through 2016.
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