Khafre pyramid much less dense than believed, researchers say：The Asahi Shimbun

http://www.asahi.com/ajw/articles/AJ201604240016.html

Khafre pyramid much less dense than believed, researchers say

By NOBUTARO KAJI/ Staff Writer

April 24, 2016 at 11:05 JST

The pyramid of Khafre in Giza, Egypt (Asahi Shimbun file photo)

The pyramid of Khafre, a symbol of the ancient world in Giza outside Cairo and one of three such huge structures there, is not quite as massive as it appears to be, according to Japanese researchers.

They say it is 30 percent less heavy than has long been accepted, based on a re-evaluation of data taken nearly half a century ago that suggests the density of the pyramid's interior is actually that much lower.

"Our study shows the blocks of stone that had to be transported were relatively light for their size," said Michinori Oshiro, a professor of Egyptology at Komazawa University in Tokyo, who was part of a study team that includes Hiroyuki Tanaka, a professor of particle physics at the University of Tokyo's Earthquake Research Institute.

"That could change part of the established theory, such as how long it took to build it," Oshiro said.

The pyramid, which reaches a height of 136 meters, is believed to be the tomb of Khafre, a pharaoh of the Fourth Dynasty (around 2613 B.C. to 2494 B.C).

While the surface consists of limestone blocks, it has not been determined what material was used for the interior.

The structure's weight, based on the volume and the densities of typical building stone materials, such as marble and granite, has been estimated at 5.5 million tons.

The researchers focused on a paper written by a group of U.S. scientists who, in 1968, observed cosmic ray muons that had penetrated the pyramid. The earlier study was done to check for the presence of hidden chambers, and its authors concluded that the pyramid contains no sizable cavities or chambers.

The Japanese scientists took a new look at that data and inferred the pyramid's interior density from how muons had decreased in number. As a result, the interior density was estimated at about 1.8 grams per cubic centimeter, or only 70 percent of the conventional estimate, and the entire structure was estimated to weigh 3.98 million tons.

The interior is likely made of remarkably lightweight limestone that is produced in surrounding areas, the researchers said.