IRA FLATOW: This is Science Friday. I’m Ira Flatow. A bit later in the hour, we’re going to talk about the structure of dark matter and how we’re going to get the very first picture of a black hole. It’s going to be something.

But first, you’ve probably heard the story of the lost city of Atlantis, the ancient Greek city that was swept into the sea overnight. Atlantis, of course, was just a story created by Plato. But that doesn’t stop people from searching.

Scuba divers stumbled– or I guess they rather swam across what they thought looked like submerged ancient cities off of Greece. Maybe is Atlantis, this city? It turned out to be something quite different. Rachel Feltman is here to uncover that story and other selected short subjects in science. She’s editor of the “Speaking of Science” blog for the Washington Post.

Always good to see you, Rachel.

RACHEL FELTMAN: Great to see you too, Ira.

IRA FLATOW: What does this city, so to speak, look like?

RACHEL FELTMAN: So you can’t blame the snorkelers who found it for thinking it was a lost city. It really does look like one. There are what look like cobblestone streets; and these interesting pillars; and these very symmetrical, kind of fountain-like structures.

But researchers knew as soon as they went down there that it probably wasn’t man-made, because they couldn’t find the pottery or coins you’d expect from an ancient Greek plaza. And they analyzed the makeup of these structures, and they found that they’ve actually been made by bacteria and were probably made around 5 million years ago, so way before humans were around to build cities.

Basically, when bacteria start to feed off of methane vents in the ocean, they excrete this calcium that then combines with the methane to form a cement-like substance called dolomite. And because the bacteria are crowding around in this very symmetrical way, they’ll form these super symmetrical structures of dolomite around jets of methane. Or if there’s kind of a spread out ooze of methane gas, they’ll make these things that look like cobblestone.

And these structures are pretty common in the ocean, but usually found deeper because that’s where we tend to see methane leaks today. So, you know, snorkelers aren’t used to finding these so close to the coast, but they’re actually a pretty common phenomenon.

IRA FLATOW: So sort of, it’s cement poop that bacteria–

RACHEL FELTMAN: Yeah, it’s basically bacteria poop– really beautiful bacteria poop.

[IRA LAUGHS]

IRA FLATOW: Well, how long does it take the bacteria to sort of build this kingdom? How old are they, these structures? Do we know?

RACHEL FELTMAN: You know, we don’t know how many years it took for them to build up. But I would say it would probably take some time. But these particular ones, they think are between 2 to 5 million years old.

IRA FLATOW: Wow. And so it’s common. They’re found everywhere.

RACHEL FELTMAN: Yeah– or–

IRA FLATOW: Usually in deeper water as you say.

RACHEL FELTMAN: Right, where the methane leaks are. And, you know, there is no methane in this area off the coast of the Greek isles right now, but there must have been at some time.

IRA FLATOW: That’s good news for those who want to keep looking for the lost city.

Let’s talk about new evidence for the origin of our hobbit cousins the Homo floresiensis. I think I got that right.

RACHEL FELTMAN: (LAUGHING) Yeah. So the Indonesian island of Flores is home to these early humans that are often referred to as hobbits, because they were just 3 and 1/2 feet tall– which is the same stature as human relatives that were living some 2 million years ago.

But these guys, the hobbits, lived just a few tens of thousands of years ago. So they caused a lot of controversy when they were first discovered. Some people thought that they were children or individuals with congenital abnormalities. But lately, researchers have been pretty confident that these are indeed their own human species, and that they did indeed live just a few tens of thousands of years ago.

And now they’ve found some really exciting evidence that might help point us towards their origins. They’ve found some 700,000-year-old fossils that are more similar to Homo erectus. They’re more what we would expect for an early human from that period.

IRA FLATOW: And that’s some branch that developed on its own, like the other theory said.

RACHEL FELTMAN: Right. So they know that human relatives lived on this island starting around a million years ago at least because there are tools that old.

So what they think is that these humans similar to Homo erectus were kind of washed on to this island during a storm. And there is some, like, historical precedence for that– just groups of people getting water logged, thrown onto an isolated island. And then they started to evolve in this isolated area and experienced island dwarfism, where– because resources are scarce– to be successful, a species has to get smaller and smaller.

The cool thing is that these 700,000-year-old fossils had tools with them that were significantly smaller than the 1 million-year-old tools. So it kind of creates this nice narrative of these humans getting washed up on this island; progressively getting smaller and smaller; and eventually, a few tens of thousands of years ago, being the hobbits that we think probably went extinct after interacting with modern humans when they showed up on the island.

IRA FLATOW: You know, just when you think you have the human evolution figured out, another piece of evidence comes in and–

RACHEL FELTMAN: It’s a very complicated family tree.

IRA FLATOW: It is.

And finally, a fish. Now, this is a fish that has learned– this is amazing– learned how to spit at the human face?

[RACHEL LAUGHS]

RACHEL FELTMAN: Well, archerfish could already spit at human faces if they wanted to. They’re considered some of the only fish to use tools, because they use these high-powered jets of spit to hit prey, like insects. And you can train them to spit at particular objects. But what’s really exciting is that researchers taught them to recognize individual human faces and spit at those faces as opposed to some 40 other human faces.

And this is very uncommon. A few animals have been shown to recognize human faces. But most of that work has been on birds that actually share the same brain structure that humans are thought to use for facial recognition and then some domesticated animals where it would make sense for them to have gotten better at recognizing humans. And bees are the wild card. Nobody really knows why bees can be trained to recognize human faces. But now we add archerfish to that group.

IRA FLATOW: Have any idea how they trained them to do this? Was it like Pavlovian? Do they get rewards?

RACHEL FELTMAN: Apparently, it’s as easy as training a dog. You just give them food pellets when they spit at the right thing. And we already knew that they could be trained to spit at random objects like colors and shapes, but now we know that you can do the same with human faces. And human faces are thought to be a particularly complicated object to recognize for most animals that aren’t human, so it kind of indicates that maybe this skill isn’t as difficult to come across in the animal kingdom as we think.

IRA FLATOW: Now we need one of those shoot-at-the-clown contests between the fish.

RACHEL FELTMAN: Yeah, that would be pretty good.

IRA FLATOW: Here now, who can fill up the little clown face at the circus?

[IRA AND RACHEL LAUGH]

You go to the arcades, and you have to shoot the water gun at the clown.

RACHEL FELTMAN: I’m sure someone is working on that study.

IRA FLATOW: (LAUGHING) I’m sure. All right, Rachel, thank you. Thanks again for such wonderful stuff.

RACHEL FELTMAN: Thanks for having me.

IRA FLATOW: Rachel Feltman is the editor of “Speaking of Science” blog for the Washington Post.

And now it’s time to play Good Thing/Bad Thing.

[MUSIC PLAYING]

Because every story has a flip side.

Now if you saw the movie Contact, you remember? You might remember that the telescope that is a backdrop for much of the beginning of the story– that big, white dish set in the crater in the jungle? That’s the Arecibo Observatory in Puerto Rico, the world’s largest radio telescope. And it has a rich history of real science, playing a role in the SETI project, the hunt for neutron stars, near-Earth asteroids, Nobel-winning research on pulsars, and more.

But now, the National Science Foundation– the NSF– is questioning whether to continue funding it at all. My next guest explains why, breaks down the potential consequences of shutting down Arecibo.

Nadia Drake is a science journalist for National Geographic. You can read her story on the National Geographic blog, “No Place Like Home”. Welcome to Science Friday.

NADIA DRAKE: Hi, it’s good to be here.

IRA FLATOW: Give us a good thing, if you can call it, about shutting down Arecibo.

[NADIA LAUGHS]

NADIA DRAKE: Well, fundamentally, the problem is that NSF doesn’t have enough money to fund all the science it wants to. So if it can pull money from Arecibo, it might be able to give that to something else. But that is really about it.

The trouble is that NSF’s budget is basically flatlined, and the agency needs to figure out where to spend its limited resources. So to do that, NSF relies on the input and recommendations of external review panels and committees, many of which have over the last decade suggested reducing funding for Arecibo or closing the observatory entirely.

IRA FLATOW: So how much money are we talking about here?

NADIA DRAKE: NSF funds a little bit more than $8 million of the observatory’s annual budget, which is around $12 million per year.

The rest of that money comes from NASA, which is funding the work that the telescope’s planetary radar does. And that work is incredibly important because that’s what we’re using to characterize what we call near-Earth objects, or asteroids and comets that are on potentially Earth-crossing orbits and could one day perhaps cause a very bad day on this planet.

IRA FLATOW: That doesn’t seem like a lot of money, you know. Some of these–

NADIA DRAKE: It doesn’t.

IRA FLATOW: –billionaires write out a little check every year, you know.

NADIA DRAKE: It is kind of like pocket change in some schemes, yes.

IRA FLATOW: It’s a 50-year-old instrument. What more can it contribute to science, you know, that newer facilities cannot?

NADIA DRAKE: Well there’s actually two things I want to point out here. One is that Arecibo could be the next facility to directly detect gravitational waves, those ripples in the fabric of space/time that were only directly detected for the first time within the last year. Gravitational waves are produced by the most violent and energetic events in the universe, and we can use them to study things that are powerful enough to jiggle space/time– such as colliding, supermassive black holes at the centers of galaxies.

There’s an experiment that’s using Arecibo to detect gravitational waves, and it’s called NANOGrav. And it’s looking for waves that are produced by colliding, supermassive black holes and galactic centers. And so that would be a huge deal if NANOGrav could make that detection.

IRA FLATOW: Now one of the things that you talk about in your piece is the telescope’s value to Puerto Rico. I don’t think people really realize that– that it’s an important part of the Puerto Rican economy.

NADIA DRAKE: It is. So something like 100,000 tourists come to visit the observatory every year, And? So that certainly contributes to the local economy. But aside from that, it also plays a huge role in inspiring local students to pursue careers in science and technology.

So one of the programs at the observatory is called the Arecibo Observatory Space Academy, and it offers a hands-on research experience to pre-college kids. And many of the students who’ve come through the Space Academy were speaking at the two public meetings in Puerto Rico earlier this week about how having that experience has inspired them to continue studying science. So I don’t think we can in any way overstate the value of that.

IRA FLATOW: Nadia, thank you very much for taking the time to be with us today.

NADIA DRAKE: Thank you.

IRA FLATOW: Nadia Drake is a science journalist for National Geographic.

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