• A hidden corridor, 9 m longand roughly 2 m wide, has been unearthed by scientists close to the main entrance of the 4,500-year-old Great Pyramid of Giza. Egyptian antiquities officials confirmed the discovery on 2 March 2023, Reuters reported.
• The discovery was originally made by the ScanPyramids project in 2016using a non-invasive technique called cosmic-ray muon radiography, the BBC reported. Since then, scientists have carried out a dedicated study of the discovered structure using multiple methods, the results of which were published in Nature journal on 2 March 2023.
• “We’re going to continue our scanning so we will see what we can do…to figure out what we can find out beneath it, or just by the end of this corridor,” Mostafa Waziri, head of Egypt’s Supreme Council of Antiquities, told reporters in a press conference in front of the pyramid.

The greatest pyramid

• The Great Pyramid of Gizais the largest of the three pyramids in Giza, originally standing roughly 147 m above the Giza plateau. Construction was started in circa 2550 BC, during the reign of Khufu, often considered the greatest pharaoh of Egypt’s old kingdom. It is estimated that the pyramid was built using 2.5 million stone blocks, each weighing between 2.5 and 15 tonnes according to The National Geographic.
• Building the Great Pyramidwas a feat of engineering unmatched for thousands of years. Of note is not only the scale of the building – it was the tallest structure on the planet until the main spire of the Lincoln Cathedral in the United Kingdom overtook it in 1400 AD – but also its symmetry and perfect alignment to the four cardinal directions (the error is less than 1/15th of a degree).
• Thus, over the years, the structure has been an object of fascination for many. Greek historian Herodotuswrote about it glowingly in the 5th century BC, Arab travellers in the middle ages described and measured the structure with remarkable accuracy, and Napoleon Bonaparte, during his Nile expedition of 1798, spent days at Giza with a team of scholars and scientists, ostensibly starting the modern field of Egyptology as we know it.

The inside of the Great Pyramid

• But as interesting as the Great Pyramid’s towering presence is, perhaps of even greater fascination are its inner secrets– passages and chambers hiding many mysteries, some still untouched, others found and long forgotten, and many currently accessible.
• According to the Smithsonian Magazine, Khufu’s pyramidcontains “by far the most elaborate system of passages and chambers concealed within any pyramid”. His is the only one of the 35 such tombs constructed between 2630 and 1750 BC to contain tunnels and vaults well above ground level – most others either have a chamber at the ground level or well below it with the structures being completely solid inside.
• This has meant that the Great Pyramid hides withinit a world unto itself which has attracted treasure hunters and scholars of Egypt’s antiquity alike. While there is no consensus on who first entered the tomb after it was sealed in about 2566 BC, accounts as far back as that of Herodotus (445 BC) imply that at least some passages inside the pyramid had already been opened and explored in antiquity itself.
• There are two distinct tunnel systems insidethe Great Pyramid – the Descending Passage (described by Greeks like Herodotus) and the Ascending Passage (more hidden, opened by the Arabs as recently as the 9th century).

The latest discovery and the technology used

• The tourists’ entranceused today is the passage dug by the Abbasid Caliph al-Ma’mun’s men in the Middle Ages, located at the intersection of the Descending and Ascending Corridors.
• Scientists detected an empty space behind the northern face of the Great Pyramid, about 7 m above this entrance. Marked on the outside with a stone slab with a gabled chevron structure, scientists have now confirmed the presence of a hidden corridor behind it.
• The initial discovery of a voidwas made using a imaging technique known as cosmic-ray muon radiography. This method uses the penetrative power of cosmic subatomic particles called muons to scan large structures.
• A muon detectortracks the number of muons going through the object from different directions, to form a three-dimensional image. Subsequently, this picture is compared with a muon image of the “free sky” – indicating how many muons have been blocked. The final picture is essentially a shadow of the object, in the light of cosmic muons.
• Further tests were then carried out with radar and ultrasoundbefore a 6 mm-wide (0.24 in) endoscope was fed through a tiny joint between the stones that make up the chevrons, the BBC reported. The footage from this camera was unveiled during Waziri’s news conference.

The importance of the discovery

• ScanPyramids, initiated in 2015, is an international projectthat uses various high-tech instruments employing non-invasive infrared thermography, ultrasound, 3D simulations and cosmic-ray radiography to study the structures. For the longest time, experts have known that many secrets hide behind the thick walls in often physically inaccessible places.
• Christoph Grosseof the Technical University of Munich, a leading member of the ScanPyramids project, told DW that he hopes to uncover still more hidden secrets. Speaking of the newly discovered corridor, he said, “There are two large limestones at the end of the chamber, and now the question is what’s behind those stones and below the chamber?”
• Waziri suggested the corridormay have been designed to redistribute weight above the main entrance or around another as yet undiscovered chamber, the DW report said. Waziri also said that it might help reveal whether the burial chamber of King Khufu still existed inside the pyramid, according to the BBC.
• The salience of the discovery lies not in the newly discovered corridor itself, but in the various implications of the finding, which can help answer longstanding questions around the Great Pyramid, including how it was constructed more than 4500 years ago, using the technology and wherewithal available at the time.