Chamber of secrets

ATEAM of scientists, led by Kunihiro Morishima of the Nagoya University in Japan, recently used tiny particles called muons to unlock a secret of the Great Pyramid at Giza in Egypt.

Also known as the Pyramid of Khufu, or alternatively the Pyramid of Cheops, the Great Pyramid is now suspected to contain an extra chamber — and it is all thanks to these particles, which are arriving at the Earth’s surface all the time, and which occur naturally.

Digressing somewhat, it can be quite amazing to contemplate the extent to which astronomy is involved in our everyday lives, and in some of the discoveries we make.

Probably the most wellknown connection is navigation. Explorers made great use of the directions of objects in the sky when deducing their positions on Earth.

There are many other examples. In the 19th century, the element helium was discovered in the sun before it was found on Earth. Indeed, it is named after Helios, the Greek personification of the sun.

Another use of astronomy, of course, has been the apparent passage of the sun across the daytime sky, resulting in shadows pointing in different directions. Much use of this has been made in the construction of sundials, which are no longer an important way of telling the time but are still found all over the world, and are quite educational.

Let’s get back to the muons. They are subatomic particles that are less massive than neutrons and the positively charged protons — the two main components of the atomic nucleus — but much more massive than electrons, which, in the classical model of an atom, are the negatively charged particles often depicted as being “in orbit’’ around the nucleus.

Muons are produced in high-energy events, and an important one for astronomy is the collision of cosmic ray particles with our atmosphere. Most cosmic “rays’’ are protons. They travel at great speeds through space, and when they reach our atmosphere their collision releases a cascade of particles, including muons.

The University of Tasmania has made extensive cosmic-ray studies using purpose-built muon detectors in various places in the state, obtaining a wealth of data on them.

One of the detectors is on display in the Southern Skies exhibition at the Queen Victoria Museum in Launceston, adjacent to the Planetarium.

Muons can penetrate a long way, with the higher-energy ones being able to travel deep underground. Indeed, some Tasmanian detectors were used below ground level. It is this capability of passing through matter, but nevertheless being at least partly absorbed during that passage, that is the key to the recent research performed on the Great Pyramid.

By carefully measuring the number of muons passing through the pyramid in different directions, the researchers have been able to deduce that there is a previously unknown empty volume inside the pyramid, just above the space known as the Grand Gallery, which connects the King’s and Queen’s Chambers.

The principle is called muon radiography and it is relatively simple: the more matter through which the muons try to pass, the fewer get through.

This method of probing is not new, and indeed it has been attempted on the Great Pyramid before. However, in that 1970 attempt, the new “void’’ within the pyramid was not noticed.

However, despite the excitement, it is not certain that this is a chamber that was part of the deliberate construction of the pyramid. It could have been formed by an internal collapse. The way to find out is to drill through to the cavity and send a camera in. It will be very interesting to see the result.