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Sub-atomic Particles Used To Map Pyramid
firegate writes "Yahoo News is reporting on a pyramid-mapping project focusing on an ancient Aztec site in Teotihuacan, Mexico. Scientists are attempting to map an ancient pyramid by detecting muons - sub-atomic particles which are left as remnants of ancient cosmic rays. A similar method was used to scan Egypt's Khephren Pyramid in the 1960's."
It detects the amount of shielding that the walls provide. I = I_0 * 10 ^ (- x/ x_1/10), where I is the intensity measured, I_0 is the unshielded intensity, x is the thickness of material, and x_1/10 is the tenth thickness of attenuation for that material (i.e. the amount of material required for the intensity to drop to 1/10 of its original value). All they have to do is solve for x. Obviously, if x drops somewhere there is 'missing' shielding.
This *looks* like a normal decay equation which assumes that the number of particles decaying/getting anhiliated at any time is a fraction of those present.
The article says "Since there are fewer muons in an empty space than in solid rock or earth.."
So, if we assume muons are formed when the cosmic rays pass through the walls(which is what the article sasy) and assume that empty space offers lesser resistance to the rays than, say a brick wall(sounds reasonable), there would be lesser muons in empty space than in a wall.
If we pass some rays which lose energy when they hit a muon (which could happen if the muons resonate at this freq), and calculate the energy of the rays when they come out of the other end of the pyramid. If the energy is more than what we expect it to be, then its possible that there is a chamber somewhere inside.
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I believe in freedom of thought. I have no other choice.
This was on my Physics undergraduate course; a rather nice technique. Releated resources from my lecture notes give:
An abstract, a presentation on applying similar techniques to volcanoes, a citation [L. Alvarez et al, Science 167, 832 (1970)] (accessible only to subscribers of Science, I'm afraid), a Physics Today article, a useful paper.
is the conference where the experiment was originally proposed.
It's even mentioned in the article the editor cites. *sigh*
The culture of Teotihuacan predates the Aztecs by a few hundred years. It climaxed around 500, went under around 600 (my sources say 700). The so-called Aztecs arived around 1200 and gave the site its name, but that's the only Aztec connection to Teotihuacan.
The system works a lot like a CAT scanner, where the absorption of penetrating radiation is measured over a variety of different paths through the object to be scanned. The only real difference is that the radiation is muons rather than X-rays (less easily absorbed, thus able to provide detectable signals through a hundred meters of rock - you should see what Fermilab uses to absorb muons so they can do neutrino experiments) and the source is natural. If you had enough money you could make your own muon source and scan the thing yourself, but when nature has been so obliging there's really no great need.
Time is Nature's way of keeping everything from happening at once... the bitch.
Muons are created high above the earth when cosmic rays interact with matter up there. They shoot out from those reactions at velocities near light speed. Because they are traveling at such high velocities, their lifetimes are extended as predicted by special relativity. Instead of nearly all decaying within a tiny fraction of a second, many of the muons exist long enough to travel down and reach us. They are a few seconds old--I think it is a few seconds; it might be less--when they reach us. They pass through objects on the surface of the earth at about the rate 1 / second / cm^2.
Muons can react with matter, but such interaction is very unlikely. If the matter is denser, such as stone, they are more likely to interact. By placing detectors inside the pyramid and counting muons coming from overhead for a long time, the scientists can estimate how much matter. They have another estimate of the matter is there by comparing to the number they would expect if they had passed through air. If that experimental estimate of the matter present is somewhat less than the expected amount based on the thickness and density of the pyramid above the detector and the density of the stone, there much be less stone than expected, possibly due to a secret chamber.
The author of the story was misleading. Muons are created in the atmosphere in high energy cosmic ray to atmosphere interactions. While the equation looks like a decay rate equation, that is not the case. If (- x / x_(1/10) ) were replaced by ( - t / t _(1/10) ) (normally shown as t_(1/2), but there is no reason you can't measure tenth-lives vice half-lives) it would be *a* decay rate equation. The shielding eqaution has a similar concept (exponential decay), so it takes a similar form. Everything has a tenth-thickness of attenuation to a different degree for different types of radiation (for example an opaque substance will have an almost zero tenth thickness for some frequencies, but a window will have a very large tenth thickness for some frequencies).
There's a similar project at the University of Texas at Austin. It aims to image Mayan pyramids in Belize.
They have a fairly sparse website, but there's a quite good PDF of a slides from a talk that Roy Schwitters (former director of the Superconducting Supercollider) gave.
Well to scan in a reasonable time, say 10 sec or less you would need much more than the background level of muons from cosmic rays.
Generating muons would require a particle accelerator. This is already pushing the cost beyond that of standard x-ray gear.
Then you have to consider the interaction of muons with the human body. They are penetrating ionizing radiation, and they decay into more fast ionizing particles once they are inside the body. Not something you really want.
Best to stick with metal detectors at airports I think.
They already have terahertz frequency scanners in the works as an airport security imaging solution, pretty much exactly like Total Recall.
The basic concept is similar, except our detectors use modern HEP technology. Our detector is smaller and more versatile than the one in the article. The smaller detector will permit us to use it in a harsh enviroment. We plan to use it in a unexplored pyramid (still buried) in La Milpa, Belize. Read: in the middle of the jungle, as opposed to a well studied pyramid. It is going to be exciting!
"There is no teacher but the enemy."-Mazer Rackham
Quite contrary, it did work, but the results weren't interesting. Nothing new was found in the pyramid. Go read the paper.
"There is no teacher but the enemy."-Mazer Rackham
"Teotihuacan is up there with Rome, one of the biggest pre-industrial cities in the world. Constantinople is also maybe there but no Chinese city was of this magnitude. Egypt didn't even have cities," Manzanilla said.
Rome had over a million inhabitants at its peak in antiquity, and Constantinople just about the same by the time of Justinian according to most sources, and even those who lowball the populations of both places put them no lower than 400,000. Even classical Athens had 300,000 residents, and second-century Xi'an in China had at least 400,000 during the time Teotihuacan was inhabited with 150,000 according to the article.
Yes, it's a very large city for antiquity, but it's far from the largest.
Incidentally, one might quibble with the definition of a "city", but Memphis in Old Kingdom Egypt had a population of 30,000, which was the largest settlement in the world at the time. I think we can safely call that an Egyptian city.
And the brethren went away edified.