Nov. 2 (UPI) -- With the help of cosmic rays, scientists have identified a secret chamber inside the Great Pyramid of Giza.
The chamber lies above a cathedral-like corridor known as the Grand Gallery. Both share similar dimensions. It's purpose is unknown.
"All we know is that we have a void, we have a cavity, and it's huge, which means possibly intentional and certainly worthy of further exploration," Peter Der Manuelian, an Egyptologist at Harvard University who did not assist the latest research, told NPR.
The discovery was made using technology normally deployed in particle physics labs.
Cosmic rays are high-energy particles that stream through space. When they collide with Earth's atmosphere, they trigger another high-energy particle called a muon.
Muons can penetrate rock, but they lose energy as they do. Their absorption rates can reveal the density of the rocky medium through which the electron particles are traveling. To map the insides of the pyramid, scientists surrounded it with muon detectors.
The system is rather simple.
"If there is more mass, fewer muons get to that detector," Christopher Morris, a researcher at Los Alamos National Laboratory, told New Scientist. "When there is less mass, more muons get to the detector."
Researchers with the Scan Pyramids Mission were able to use the data picked up by the muon detectors -- how many muons were detected and at what angles -- to detail the dimensions of several chambers within the pyramid.
Their analysis revealed the three known chambers, the King's Chamber, the Queen's Chamber and an underground chamber. The two main chambers are connected by the Grand Gallery, above which lies the fourth -- and previously unknown -- chamber.
To confirm their findings, researchers conducted two more slightly different muon-detection experiments, setting their instruments up in different locations and allowing long exposure times.
"The good news is the void is there. Now we are sure that there is a void. We know that this void is big," Mehdi Tayoubi, with the HIP Institute in Paris, the group leading the scanning mission, told NPR. "I don't know what it could be. I think it's now time for Egyptologists and specialists in ancient Egypt architecture to collaborate with us, to provide us with some hypotheses."
The scientists detailed their discovery of the new chamber in a paper published this week in the journal Nature.