IRA FLATOW: This is Science Friday. I’m Ira Flatow. Later in the hour, the first data from the Parker Solar Probe has been collected and analyzed. And it shows surprising and unexpected behaviors of the sun. We’ll get into that.

But first, remember we talked a few weeks ago about how scientists are working to rebuild coral reefs by planting little nuggets of coral that are more resistant to warming or by plugging 3D-printed corals into degraded habitats to give reef-dwelling fish and urchins somewhere to live while the reef recovers? But how do you actually get all that marine life to return to a recovering reef? Well, you put on the soundtrack of a healthy reef.

[GURGLING]

[SNAPPING]

And when the fish hear that, they start coming and swimming back. And here to talk about the theory behind that tactic is my guest, Amy Nordrum, news editor at the IEEE Spectrum, joins us here in New York. Always welcome to have you back.

AMY NORDRUM: Hi, Ira.

IRA FLATOW: Amy. All right, tell us about this coral reef noise idea.

AMY NORDRUM: Yeah, who knew reefs were so noisy? And to be clear, that sound you just heard is sort of like a highlight reel or a greatest hits version of what you might hear. All those sounds wouldn’t occur at once necessarily in nature.

But this is a really interesting piece of work where scientists off of the coast of Australia built 33 artificial reefs and installed underwater loudspeakers on 11 of them. And then they played recordings throughout the night that they had collected prior to bleaching that had occurred in this area. Then they measured and saw which kinds of species and how many fish returned to each of the artificial reefs.

IRA FLATOW: Let’s listen to that again because it was so interesting.

[GURGLING]

[SNAPPING]

Wow. That is the best hits.

AMY NORDRUM: Yeah, there’s a lot of noises going on in there. There’s some snapping shrimp that snap their claws at each other. There’s some clownfish, which are really territorial and make noises sort of like a woodpecker at each other. Then there’s a couple mystery fish mixed in that the researchers couldn’t identify based on the noises.

But fish returned to the reefs with the loudspeakers more than the reefs that didn’t have loudspeakers. They actually attracted twice as many fish and 50% more species.

IRA FLATOW: And did they stay around?

AMY NORDRUM: They stuck around throughout the length of the study, which was about 40 days. And so they’re hoping that that will last. And this isn’t a silver bullet. You’d obviously need the restoration efforts along with it that you spoke about before. But at least the terms of getting the fish to know that the reef is available, they can hear this noise and then recognize it as a place that they might like to go.

IRA FLATOW: It almost sounds like there’s something unethical about tricking a fish to come back.

AMY NORDRUM: I asked about that. Is this like a bait and switch effort? But the scientist I spoke with, Tim Gordon, he was telling me that in practice, you would make this a pleasant place for the fish to live. And the sound would just be to attract them there in the beginning. And they’re working on putting this out in the real world in a project in Southeast Asia right now.

IRA FLATOW: And so it’s all experimental right now.

AMY NORDRUM: Yeah, this is a proof of concept. And now they’re hoping to roll it out.

IRA FLATOW: I can’t wait. All right, next up, you have a story about an innovative new way to transplant hearts– really interesting.

AMY NORDRUM: Yes, right now, you know hearts are recovered from donors typically after they’ve been declared brain dead and while the heart is still beating. But there’s a new technology being tested in a clinical trial that allows doctors to recover a heart from a donor after circulatory death. So these patients are never declared brain dead but are taken off of mechanical support for other reasons.

And typically, you wouldn’t be able to recover organs from these donors because there’s a period where the heart stops beating and isn’t receiving oxygen or blood flow. And instead of putting the hearts on ice to preserve them as is typical for these cases, Duke is testing out a new technology that helps to revive and rehabilitate the heart and circulate blood through and pump oxygen in until it’s ready to go into a recipient. And Duke researchers performed their first transplant using this technology just last Sunday.

IRA FLATOW: So they had to make a special box to put the heart in. Not an ice box, but the heart is beating in a box. It’s circulating blood through it.

AMY NORDRUM: Exactly. It’s created by this company. It’s known as the TransMedics OCS system. The system is already approved for use in other parts of the world. But it’s currently in a clinical trial here in the US. And that’s what the Duke researchers were participating in.

IRA FLATOW: Imagine how many people’s lives could be saved now with this technique.

AMY NORDRUM: Yeah, the doctor I spoke with said one of his colleagues did a calculation that it could expand the donor pool by 30%.

IRA FLATOW: Wow, that’s a lot of hearts. Your next couple of stories are about space. Let’s talk about first a mission to deflect an asteroid.

AMY NORDRUM: Yes, this is a collaboration between NASA and the European Space Agency. And it has two parts. The first part is an independent NASA mission called DART, where they’re sending a very simple spacecraft out to an asteroid called Didymos B. And it’s orbiting, actually, around another asteroid. And NASA spacecraft is going to ram into that asteroid and attempt to change its orbit.

And then last week, the second part of this collaboration, called the Hera Mission, was approved by the European Space Agency. And they’ll be sending a spacecraft out a few years after the DART impact to study both asteroids in the system in more detail.

IRA FLATOW: I would imagine you have to be very careful which way you nudge that asteroid, right?

AMY NORDRUM: Yes. Fortunately, NASA is pretty careful about these things. The sense that I asked them, could you possibly redirect it in the wrong way? And they are specifically targeting this asteroid system. It’s actually got two asteroids in it. And I didn’t know this, but a lot of asteroids come in pairs or threes or fours.

IRA FLATOW: Is that right? I didn’t know that.

AMY NORDRUM: Yeah, so it’s a big asteroid and a tiny asteroid orbiting around the big one. And they’re targeting the tiny one. And the spacecraft that are going to slam into it isn’t really big enough to knock the tiny one out of its whole orbit around the big one. It’s just big enough to hopefully just change the orbit slightly. So that’s one reason they chose this specific system is because it lowers that possibility.

IRA FLATOW: Another proof of concept idea.

AMY NORDRUM: Exactly.

IRA FLATOW: And then there’s a new Chinese experiment to listen to the cosmic dawn and the cosmic dark ages. You got me intrigued already.

AMY NORDRUM: [LAUGHS] Right. Well, if you look at the up at the moon tonight, you can’t see it. But there’s a satellite right now on the opposite side of the moon. Its main job is to relay messages between Earth and a lander on the moon’s surface that was placed there by China’s space agency.

But it also has a secondary mission, which is to turn itself into a radio telescope that peers out into the rest of the universe and listens for signals that are so low frequency we couldn’t detect them here on Earth because of interference in the ionosphere. And just in the last couple of weeks, antennas for that experiment were deployed on the satellite and are starting to collect data.

IRA FLATOW: And finally, you brought us a mystery of shrinking songbirds– not of songbird populations, but the birds themselves.

AMY NORDRUM: The birds themselves, yes. There is an incredible collection of songbirds, migratory birds, at the Chicago Field Museum, a huge collection built up by a man named David Willard, who collected and measured by hand birds that had flown into high-rise buildings and been killed in Chicago. And this city took a look at more than 70,000 specimens from that collection from 52 different species and measured how they changed over the years that this collection was amassed, about 40 years.

And they found that as temperatures became warmer, the body size of the birds actually got smaller. And the wings became longer. So we think about climate change and how animals might respond, and they might shift their range or change the timing of behaviors like reproduction. Well, now we know with these birds, they’re also already changing their morphology.

IRA FLATOW: Unexpected consequences.

AMY NORDRUM: Yes.

IRA FLATOW: Wow. Thank you, Amy.

AMY NORDRUM: Thanks.

IRA FLATOW: Amy Nordrum, the news editor at the IEEE Spectrum here in New York.

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