Muon detectors are elementary particles used by researchers to look inside ancient pyramids. Scientists from the University of Texas at Austin are using these detectors to explore the Mayan pyramids in Belize. Roy Schwitters, Professor of Science at U-T Austin, joins Hari Sreenivasan via Google Hangout.
A scientist explores the Mayan pyramids
Muon detectors are elementary particles used by researchers to look inside ancient pyramids.
Scientists from the University of Texas at Austin are using these detectors to explore the Mayan pyramids in Belize.
Roy Schwitters, professor of science at UT Austin, joins us via Google Hangout.
So, professor, how does a muon detector help me figure out what's inside a pyramid?
Make that connection for me.
What you want to find out is what's inside, as you say.
That's the question.
So you need to have something that gets inside and that you can track and then reconstruct an image of the material inside this huge space.
So we use subatomic particles called muons.
They're like heavy electrons.
They are found in cosmic rays and in particle-accelerator laboratories, and are used, actually, in these days, in many different technologies.
But they have the beautiful feature that penetrate deeply through dirt and mud and rock and all those things and yet can continue on a path through a huge object.
And we can detect them, and then they essentially tell us where they came from.
We can measure their direction, see where they came from, and basically reconstruct an image all along the path that they've taken through this material.
So these things are flying through the air all the time.
We just can't see them with our eyes, but we can -- How do we see that they actually are -- or what do they strike?
They actually go through the air and other materials around us, and they ionize it.
And so what that means is they leave a little track of ionized atoms, much like a jet airplane leaves a contrail in the high upper atmosphere.
So it's a very good analogy.
You can see the path of the airplane even if you can't see the airplane.
And so we do that by detecting the ionization, and that's done nowadays with a rather simple apparatus -- pieces of plastic, really, with a dye in them that emit light when the ionizing muons go by.
And so we can put a picket fence of plastic strips, and we watch as they go from one to the next, and we can reconstruct the path.
But I think the best analogy is a high-flying airplane, where you can't actually see the plane.
Okay, so, as they go through, do they change in direction or velocity when they bump into a harder object than when they are just going through something of the same consistency?
What they do is they lose energy to the ionization.
So as they go through a dense object, they lose more than they would've just going through air.
And the practical effect of that is some of them, by the time they get to our detector, don't make it.
They've lost all their energy.
And so they just -- they're AWOL.
They don't show up in our detector.
So the way we do this is we put the detector up on top of a building, say here on campus.
We measure what the open sky gives us in muons, and then we carry it down to a pyramid and look at the difference.
And, essentially, that tells us the amount of material that they've gone through.
So, if there's, say, a room or a cavernous area or something, what are you likely to see as the indicator of that?
It's almost like you're seeing the kind of shadow of where these muons hit and where they didn't.
We see those shadows, we look at them in many different directions through the pyramid, and we can reconstruct a three-dimensional image of where the mass, where the material is in that object that -- You know, the eye only sees -- In Belize, it's so interesting.
The eye only sees a jungle-covered hill.
You wouldn't even know there was a pyramid in there.
And yet we can then see the dense rock.
We can see by inference... We hope to find caverns and chambers and all kinds of stuff, but that's how it works.
You've worked on Belize so far.
Is this technology that can be used in, say, the pyramids of Egypt or other places that aren't pyramids?
Very much so.
In fact, the whole idea here came from a... My field is particle physics.
And some of us were sitting around talking about how we'd do quite a different problem -- how would you find out if someone was drilling into your vault in the basement of your bank?
I mean, that's a silly challenge -- not so silly.
There was a news article that day.
And we recognized that this technology, which was invented by Alvarez 50 years ago -- one of the heroes of our field -- with modern implementation is quite a practical way to set up, essentially, cameras that could see if someone were tunneling into your bank vault.
My interest in the beginning was to develop the technology with the much better tools available today than were available 50 years ago.
And in doing so, we proved the efficacy of this and realized we have colleagues here at the university with pyramids.
You know, not everybody has a pyramid in their backyard.
These people are really experts in the extremely fascinating problem of the Mayan culture.
And so here was a chance to contribute to their science with our technology.
And it was just a great opportunity.
So, what did you find in Belize?
[ Chuckles ] Well, we're finding that it's difficult to do high-energy experiments in the jungle.
So we're really testing our technology to the limit.
We find that we can X-ray Maya pyramids.
That's all established.
But these experiments take a long time.
They take weeks to months.
So we want to take a good, long exposure this spring, and then we open the box and see what's inside.
Roy Schwitters of UT Austin.
Thanks so much for joining us.
You're very welcome.
[ Keyboard clacking ]