Do you have a hard time understanding some of the latest scientific discoveries? Often, I do, too. And I’m a scientist.
Good science communication is challenging. In this blog I’ll explain in simplest terms what scientists have learned recently about the Great Pyramid of Giza—and how they did it. As a bonus, I’ll toss in how this discovery relates directly to CT scans, one of the great medical inventions of modern times.
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What do the Great Pyramids, cosmic rays, and CT scans have in common?
Answer: READ ON!
An article in the scientific journal Nature (Nov. 2, 2017) describes how a team of physicists, supervised by the Egyptian Ministry of Antiquities, began collecting data last year with some highly specialized instrumentation placed inside and outside one of “Seven Wonders of the Ancient World.”
Analysis of the data revealed a 100 foot long empty space (chamber or tunnel?) located somewhere in the middle of the Great Pyramid of Giza.
How on earth did the scientists figure that out?
Well, for starters, the answer didn’t come from somewhere “on earth.”
The scientific team took advantage of the fact that particles from outer space—known as cosmic rays—constantly bombard the earth’s upper atmosphere, creating a stream of invisible particles that physicists have named muons.
Focus on the muons hitting the earth’s surface!
Wait a minute. What are muons?
Muons are elementary particles similar to electrons, although much heavier. They rain down upon us from the sky (a hundred or so pass through our body harmlessly each second).
But there’s a lot more to these invisible muons than you think!
Muons are like x-rays on steroids. They ram though almost everything without taking the time say “Hello.” Let me rephrase that: the muons generally pass straight through matter without interacting with any of the atoms that make up the matter. One big exception: massive works of stone, like pyramids, can STOP AND ABSORB some of the muons as they travel through.
Now think of muons bombarding the Great Pyramid of Giza from all directions. The researchers placed high-tech muon detectors outside the pyramid and inside various parts of it, e.g., the Queen’s Chamber and the Grand Gallery.
Then they found a PROBLEM.
The physicists discovered that some detectors inside the pyramid picked up more muons than expected. The simplest explanation is that there is a large empty space (the team called it a “void”), roughly in about the middle of the structure. If that empty space had not been there, all of the detectors would have picked up about the same frequency of hits, after taking into count the amount of stone the muons would have to pass through before detection.
Here’s another way to think about the science of what we might call “muon mapping.”
Suppose you are lost in a dense forest at night. A search party comes looking for you, each member carrying a bright flashlight. They shine their light beams (think muon beams) ahead to try to spot you. (Yes, they’re calling out your name, too, I know. Don’t let that cloud your thinking right now. Keep it simple.)
You can see the beams of light shining at you from the distance. Now and then a light beam (again, think muon beam) or two or three disappear because the searchers are behind a tree or are partially obstructed by a clump of bushes or whatever.
SWITCH BACK TO YOU: Eventually, you spot beams of light way out there—let’s say to your left. That’s the Big Gap in the woods you go running for! You have used your eyes—that most sensitive light detector—to map out at night the structure of the surrounding terrain because of the collection of light beams coming at you from all around. (Remember, it’s a large search party because you are very important!)
So, what might be hidden away in that most mysterious empty spot within the Great Pyramid of Giza?
No doubt that will be archeological fodder for many years to come.
Wait a minute! What the heck does any of this have to do with a medical CT scan?
Using muons in the fashion described above is similar to what we do with x-rays in a diagnostic CT machine at a medical clinic. The rotating head of the CT instrument allows x-rays to pass through the body or a particular organ from all around us as we lie there. X-ray detectors pick up varying amounts of the x-rays transmitted through the body. Some x-rays pass through unimpeded while some are absorbed within the tissue and that varies as the x-ray generating head rotates around the body.
The variation in x-ray detection occurs because the tissue structure changes with the path the beam takes: at one moment mostly blood vessels perhaps, the next moment mostly bone, and then maybe the x-rays pass through a structure that is predominantly a solid clump of dense tissue.
In this fashion, a sophisticated mathematical program can reconstruct a three dimensional image of the underlying anatomical features, revealing normal structure or—unfortunately at times—that solid lump of dense tissue: a tumor.
Whether speaking of muons bombarding pyramids or x-rays scanning our body, we refer to the methods described here as “tomography.” In fact, CT stands for computerized tomography.
So now you know how the Great Pyramid of Giza, CT scans, and cosmic rays can all be connected!
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James Marshall Smith is a physicist and novelist. His debut thriller was an Amazon best seller: Silent Source. You can find him at www.JamesMarshallSmith.com