Live From The American Association For The Advancement of Science

20 February 2005

Interview with

Dr Chris Smith, in Washington


Chris - I'm in Washington this week for the AAAS, which stands for the American Association for the Advancement of Science. I'm getting to meet lots of people doing some amazing research over here in America. This evening, I'm going to tell some rather worrying information about whales; talk about work in Mexico where scientists are effectively x-raying a pyramid; some news about avian flu; and how a new type of fishing line might put an end to 'the one that got away' stories.

Kat - So what's the deal with the whales?

Chris - Whales are very much auditory creatures. They communicate using infra - sound, which is very low frequency sound waves that travel well through water and can be heard by other whales thousands of miles away. I spoke to researcher Dr Christopher Clark from Cornell University. He's finding evidence that the noise mankind is making in the environment is causing major havoc for whales. Historically, whales were able to find mates hundreds of miles away, just by listening out for them. Now their dating game is restricted to perhaps twenty to a hundred miles because the racket we're making in the sea means that it's much more difficult for them to hear each other.

I asked him whether whales have changed their behaviour in order to compensate for this because birds living in cities have been shown to increase the frequency of the notes in their songs to compensate for all the noise around them. Apparently whales have done the same thing, but by lowering their voices by an octave to an octave and a half. But they are already at the extent of their voice range, meaning that they won't be able to change much more. This is a bad thing, because whales not only use their voices for the mating game, but also to tell others where food is and when predators are nearby. This might cause their numbers to go into further decline.

Helen - Whales are also declining because of hunting. Hearing a whale sing under water is the most amazing thing, and so I really hope there isn't too much more bad news for them.

Kat - What about the pyramids?

Chris - Well it relies on a cosmic particle called a muon. When the earth is bathed and bombarded with radiation coming in from outer space, which happens on a second by second basis, the cosmic radiation strikes our protective magnetic field and most of it gets removed so that it doesn't come into the earth's atmosphere. This is why you get the Northern Lights. However, some particles get through, interact with our atmosphere and produce something a bit like a giant electron. This charged particle is called a muon. It doesn't live for very long; literally just millionths of a second, but it moves incredibly fast and is very penetrating.

X - rays work by passing high energy light waves through the body. When they hit something dense like bone, they are absorbed. But when they hit soft tissue, they pass through more easily. This lets you build up a picture of the internal structure of the body. Muons can be used to do exactly the same thing, but for rocks! In other words, they can pass straight through buildings and other dense things, but some are mopped up on the way. So, just like an x-ray, they can be used to to work out what's inside dense structures like pyramids.

In this story really centres on Mexico. There is a structure in Mexico, which is actually Mexico's leading tourist attraction, called the Pyramid of the Sun. It dates back about 2000 years, but that's pretty much all we know about it. When the Aztecs arrived the pyramid had already been there about 600 years, but it was built by a civilisation that we known nothing about. The people who lived there left no written record of their activities; just pyramids. No-one knows what's inside the Pyramid of the Sun, but owing to its archaeological significance, it's also not appropriate to dig it up. But if we could find out what's inside, we might discover something about the people that built it.

So scientists have decided to give it an x-ray, with muons. Conveniently, there is a natural tunnel underneath the pyramid. By placing a detector in the tunnel, muons from the atmosphere which pass through the pyramid can be counted and used to build up a profile of the inside of the pyramid.

for instance, if the pyramid is solid, then you will collect far fewer muons than if it's got holes in it. Scientists can work out what's inside the pyramid by looking at where the muons have come from and their respective scatter patterns, meaning that scientists don't have to dig it up. If there is something inside, researchers can work out what it is, and where it is, without having to do devastating damage to the structure.

Mandy - What are they hoping to find? Is there any indication of what might be inside there?

Chris - There is a bit of information, because there's another pyramid just down the road called the Pyramid of the Moon and this one has been excavated. Inside, they found a burial chamber. As we don't know much about these people, if we could identify the burial chamber, we could potentially extract DNA if the occupants are well enough preserved. This could be used to work out where these people came from, who they were, what kind of diseases they might have suffered from, and also where they may have ended up. It would also help us to track down where mankind were spreading to at this point in history.

Kat - Is there anything else we can do with muons?

Chris - Yes, there is. America is worried about people trying to attack them. They are trying to work out how they can use muons to find out what is hidden in the backs of lorries. People are worried about the shipping of radioactive isotopes, as they could be used to make bombs. Obviously, there needs to be a way of stopping the lorry driver from being fried, so if someone is trying to transport radioactive isotopes, they will want to keep it in a heavy container made of something like lead. Muons can't pass through lead either, so the detectors will pin point any things in the lorry that are particularly dense or heavy. These could potentially be containers holding radioactive materials. Mandy - So this could potentially revolutionise security.

Chris - I'm just hoping that it won't slow down customs any more!

Kat - So what's this final story on fishing tackle?

Chris - 'The one that got away' graces every fishing story down the pub, and anglers often blame their equipment, but this could soon be a thing of the past. A research group from Ohio that have come up with a new polymer that can be incorporated into fishing line to pin point weak spots. The idea is that when your fishing line becomes stretched or distorted, it glows bright green. The only slight downside is that you need a UV (ultraviolet) lamp to see it glowing! The effect is produced by a chemical called phenylene-ethylene-oligomer, which is incorporated into the fishing line. As the chemical structure of the line becomes distorted by stress or tension, the optical properties change, and the line fluoresces under UV. The team are now working on another way to make the line glow in day light, helping fisherman to know when it is time to change their tackle. It could also be used to make tamper-proof coverings. If you have a sealed product and are not too sure if someone has injected something into it, if you shone a UV light over this material, any needle puncture points would glow green. So it has a non-fishing use too.


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