A Leaning Tower, A Jumping Spider, And Missing Plutonium

6:42 minutes

leaning tower of pisa
Credit: jamal via Pexels

The famous Leaning Tower of Pisa has been tipping for centuries, but has managed to withstand weather, wars, and earthquakes. And while it has been stabilized over the years, it turns out that there’s another contributor to its longevity—the soil beneath it. In a study scheduled to be presented at the 16th European Conference in Earthquake Engineering in Greece, researchers from the University of Bristol, UK reported that the height and stiffness of the Tower combined with the softness of the foundation soil beneath it damps out vibrations from seismic activity.

[Explore bioacoustics by tuning your ears to the sound waves of burps.]

Sophie Bushwick, senior editor at Popular Science, joins Ira to talk about the tower’s lean and other selected stories from the week in science, including the case of some missing plutonium,  a Russian (cuckoo) invasion, and a trained jumping spider.

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Segment Guests

Sophie Bushwick

Sophie Bushwick is a Senior Editor at Popular Science in New York, New York.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. A bit later in the hour, we’ll be talking about the volcanic eruptions in Hawaii, and the strange species of bacteria that can eat antibiotics. But first, the Leaning Tower of Pisa has been tipping for centuries. You knew that, and you know it’s managed to withstand weather, and wars, and earthquakes. And well over the years, engineers have taken action to stabilize it. Turns out, there’s another contributor to its longevity. And that is the soil beneath it. Joining me to talk about that and other selected short subjects in science is Sophie Bushwick, Senior Editor at Popular Science. Welcome to Science Friday.


IRA FLATOW: I have to note that congratulations are in order, because the Pop Sci team was victorious at our sci-fi trivia night earlier this week.

SOPHIE BUSHWICK: It was a tough battle. We were really excited to win.

IRA FLATOW: Two years in a row.

SOPHIE BUSHWICK: Two years in a row.

IRA FLATOW: Consecutive. Well, we’ll have to see what happens next year.

SOPHIE BUSHWICK: We’ll aim for a three-peat.

IRA FLATOW: [LAUGHS] All right. Let’s talk about the news. What’s this Leaning Tower of Pisa story? What’s the secret here?

SOPHIE BUSHWICK: Right, so the Leaning Tower of Pisa– one of the reasons it’s leaning, is because the soil in the region is very soft. In fact, there’s a couple of other towers that are also leaning, although not as much. Pisa, that tower, is leaning at about a four degree angle right now, and at its greatest, it was at closer to a 5 and 1/2 degree angle. So you would think that this really unstable tower would be really in bad shape when earthquakes strike, and at least four major earthquakes have hit the area since the construction of the tower, but it’s withstood them. So this latest study looked at the relationship between the soil and the tower, and they found that one of the reasons it’s been able to withstand the earthquakes is because interaction between that soft soil– the same soil that makes it lean, and this tall, rigid tower has sort of balanced out, and so it doesn’t vibrate when the ground vibrates the same way other buildings do.

IRA FLATOW: So the soil is sort of squishy and absorbs the vibration?

SOPHIE BUSHWICK: Exactly, it has to do with the interaction between that squishy soil and the tower itself.

IRA FLATOW: All right, now I want to move on to this really interesting story, not that that wasn’t. There’s some missing plutonium somewhere?

SOPHIE BUSHWICK: Right, so Idaho State University was just fined over $8,000 by the Nuclear Regulatory Commission because they had a missing amount of plutonium– weapons-grade plutonium. But the amount is about 1/30 of an ounce, so think something the size of a quarter.

IRA FLATOW: Do they have any idea where? Where do you hide, or where it went? Do you lose it? You drop a quarter in the subway?

SOPHIE BUSHWICK: [LAUGHS] We think the culprit is paperwork, actually. So apparently, back in about 2003, there’s some paperwork showing that the university was trying to get rid of just that amount of plutonium. But someone didn’t fill out the rest of the paperwork showing it had been properly disposed of, so then there’s like, a blank in the records. And they’ve been fined for it, and they’ve had to– in fact, the university has established new processes of taking their inventory and to try to prevent that error from happening in the future.

IRA FLATOW: But that’s not enough to worry anybody– that you could make a bomb, if it really were missing.

SOPHIE BUSHWICK: Well you couldn’t make an explosive nuclear bomb, but you could make a dirty bomb, which is something that spreads radioactive contamination. So any amount of plutonium is enough to make the Nuclear Regulatory Commission kind of nervous and want to make sure that they know they can account for all of it.

IRA FLATOW: Yeah, let’s hope that it is something in the paperwork.


IRA FLATOW: Now, I understand there’s an invasion from Russia into Alaska, oh no. But these are cuckoo birds?

SOPHIE BUSHWICK: Right. So it might sound innocuous, but cuckoo birds are these– they’re called broad parasites. Basically, cuckoo parents won’t make their own nests. They’ll lay their eggs in another species’ nest, and when the young cuckoo hatches, it kicks out the new hatchlings, or eggs that are there. And the parents devote all their resources to the cuckoo baby, and then they don’t raise their own chicks. And this can actually have a big impact on native species.

IRA FLATOW: And so why do we think this is happening now?

SOPHIE BUSHWICK: So, because of climate change, the region in which these cuckoos can live has kind of expanded. And so bird watchers have noticed greater numbers of them in Siberia, and also in Alaska. But researchers wanted to know how the native birds would respond to the cuckoos, so they made 3D printed eggs and put them in nests in Alaska and in Siberia. And what they found was that in Siberia, the birds were onto the cuckoos and they knew their tricks, and they kicked out the 3D printed eggs often. But in Alaska, only one out of 96 eggs got booted out of the nest. And so, the Alaskan birds are more gullible, which means they could be a lot more vulnerable to cuckoos.

IRA FLATOW: So this is why, I guess, in other parts of the country or world, that these birds know already to expect the cuckoos coming, and you’d better be careful.

SOPHIE BUSHWICK: Yeah, other birds have adapted, so some of them will mob cuckoos, some of them will knock those cuckoo eggs out of the nest, and some of them have adapted to just have very distinctive-looking eggs, so they can easily tell when one of the eggs in the nest isn’t their own.

IRA FLATOW: Wow. Up, up, up. Next, there’s a train-jumping spider. I needed to know that today on Friday. Why would you train– why– get into that, please.

SOPHIE BUSHWICK: Well how else are you going to make an army of tiny spider robots?

IRA FLATOW: Absolutely. [LAUGHS] Know that.

SOPHIE BUSHWICK: So basically, jumping spiders can jump horizontally about six times their body length, which is a huge amount. Humans can only jump– from a standing start, can only jump about one and 1/2 times our body lengths. So this is an amazing feat, and researchers thought, we want to mimic it to make robots. Tiny robots that move more easily. So they were looking at a regal jumping spider, they’re about the weight of a raindrop, so they’re very tiny. About 15 millimeters long. And basically, they were trying to get these spiders to– they bought them at a pet shop, and they wanted to get them to jump around an obstacle course that would force them to make different kinds of leaps. But only one of them would do it. And so, this is a spider named Kim, and they filmed her at very high speeds making these different leaps, and that way they could analyze her motion.

IRA FLATOW: How do you train a spider to leap when you want it to?

SOPHIE BUSHWICK: Right. It’s really difficult, because this is the only one of the spiders that would do it. I’m thinking they use some reward-based motivation to get these spiders to jump around this obstacle course. But even Kim wouldn’t do all the jumps, the biggest jump that Kim would do was a 60 millimeter one, and they think it was because she couldn’t see much farther than that. They have keen eyesight, but it only goes so far.

IRA FLATOW: I’m sure somewhere in Hollywood, you know, where they train all those animals, they have a jumping spider that’s trained. They could have loaned it them.

SOPHIE BUSHWICK: Yeah, a movie star spider.

IRA FLATOW: Sophie Bushwick, Senior Editor at Popular Science. Congratulations again.


IRA FLATOW: Always a pleasure to have you.

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