Archaeologists use high-tech eyes
By Chika Ishikawa / Yomiuri Shimbun Staff Writer"An unprecedented grand plan." This is how Egypt's State Ministry for Antiquities describes the large-scale survey of pyramids that started in November last year. Using the latest technologies, a reexamination is being carried out on a number of pyramids, including the Great Pyramid of Pharaoh Khufu, said to be the largest in Egypt. The centerpiece of the survey is a Japanese team's operation to look through the pyramids using elementary muon particles (see below). In archaeology, the number of surveys using this type of technology is increasing.
The Great Pyramid for Pharaoh Khufu, located in Giza, outside Cairo, is 146 meters high and weighs 5 million tons. It is believed that the pyramid was built more than 4,000 years ago over a period of about 25 years. However, the construction methods remain a mystery. If new hidden rooms are discovered, they may provide hints about how the builders managed to stack the enormous stones.
Participating in the survey from Japan is a team led by Kunihiro Morishima, a research assistant professor at Nagoya University. Morishima, who specializes in particle physics and astrophysics, worked to determine the position of the nuclear fuel that melted down at reactors at the Fukushima No. 1 nuclear power plant using muons that bombard the Earth from space.
Morishima explained that "the penetration rate of muons changes depending on factors such as an object's density. If there are any undiscovered empty spaces in the pyramids, those areas will have greater penetration rates than their immediate surroundings."
The principle used to look through the pyramids is the same as that used in X-ray photography. Pieces of special film, known as nuclear emulsion plates, are installed in rooms within the pyramids and left for several months. The film turns black in the areas that are hit by muons. It is said that when these films are analyzed in detail, the direction from which the muons came can be determined. This means the team may be able to infer not only the presence or absence of hidden rooms but also their general shape.
Teams from France and other countries are searching for clues using methods such as examining air pathways through the pyramids by using infrared cameras to measure surface temperatures, and taking detailed measurements of surface irregularities with small, unmanned drones.
Morishima says: "I am looking forward to finding out to what extent our technology works. Using the results in combination with those of the other teams, I want to reveal unknown parts." The survey is scheduled to continue for about one year.
A survey to look through the pyramids using muons was previously attempted by an American physicist in the late 1960s. Although that survey did not find any hidden chambers due to a lack of data, Morishima read the research paper when he was a student and thought he would like to try the same kind of survey one day.
Although he claims that it became possible to implement the survey this time "because the paths of the right people happened to cross," it is more likely that the tenacity and passion with which he pursued his dream is what made it happen.
3-D scanner and GPS
The amount of high-tech research in archaeology is increasing every year. Last summer, a team led by Prof. Masato Sakai, a specialist in Andean archaeology from Yamagata University, conducted research on the UNESCO World Heritage site Nazca Lines (see below) in Peru. The team announced the discovery of 24 new geoglyphs depicting objects including a llama, a common animal in the country.
The discovery demonstrated the power of a surveying instrument known as the 3-D laser scanner. It is capable of detecting to an accuracy of a few centimeters subtle irregularities on the surface of the ground that are difficult to discern with the naked eye.
Sakai's team conducted a field survey based on satellite photos, using the scanner to measure unnatural surface depressions before analyzing the data on a computer. As a result, they were able to find faded and weathered geoglyphs.
"There are still fresh discoveries of the geoglyphs. We'd like to think about conservation methods in cooperation with the locals," Sakai added.
Last summer, a team led by archaeology specialist Prof. Yoshifumi Ikeda from the University of the Ryukyus announced that a shipwreck discovered off the coast of Nagasaki Prefecture had been identified as part of the 13th-century Mongolian fleet sent to invade Japan in an incident known as Genko. The ship had been buried under 1.5 meters of sand, which inhibited decay and preserved the wooden hull of the ship.
By combining the latest underwater sonic probe with a global positioning system (GPS), the team was able to produce an accurate chart based on the locations of signals picked up from materials not normally found on the seabed, such as ceramics and tiles, leading to divers being able to accurately investigate.
"We were able to establish an underwater archaeology technique," Ikeda said.
■ Muon particle
One of 12 elementary particles that make up matter. The Earth's surface is constantly bombarded by muons that are generated when cosmic radiation hits the Earth's atmosphere. The rate at which these muons bombard the planet is one per second on an area roughly the size of a human palm. Muons easily pass through matter, and can even pass through bedrock several kilometers thick. Tomographic technologies that utilize this property have been used to monitor nuclear materials and in volcano research.
■ Nazca Lines
Discovered in 1939 by an American archaeologist in the Nazca Plateau of southern Peru. They were created by utilizing the color difference between the dark surface rocks and the lighter-colored underlying ground. The geoglyphs have varying designs, such as monkeys, hummingbirds and geometric patterns. With some exceeding 300 meters in length, there is a theory that the Nazca people, who had no writing system, created them as signposts to connect their villages or as a record of their rituals. They were designated a UNESCO World Cultural Heritage site in 1994.
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