Exploring Bose-Einstein Condensate And Superfluids : Short Wave Sharpen your pencils. Get out your notebook. Today, we are unveiling a new series called "Back To School." In these episodes, we take a concept you were taught in school and go a little deeper with it. Short Wave reporter Emily Kwong and host Maddie Sofia explore OTHER states of matter — beyond solid, liquid, gas, and plasma. Have you heard of Bose-Einstein condensate superfluids? It's your lucky day!

Email us your Back-To-School ideas at shortwave@npr.org.

Ultracold Soup: Meet The 'Superfluid' States Of Matter

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Hey, everybody. Maddie Sofia here with Emily Kwong.

EMILY KWONG, BYLINE: Hey, Maddie. All right, we're going to mix it up today.


KWONG: Talk about something new by revisiting something old.

SOFIA: Is this a - is that some kind of riddle? Is this a riddle show now, Kwong?

KWONG: No. No, not quite. Today we are going back to school.

SOFIA: Ooh, our favorite place.

KWONG: Yes. Part of a new series we're launching today...

SOFIA: Whoop, whoop.

KWONG: ...Episodes where we take something you were taught in school, maybe something you thought you knew, and go a little deeper. And to kick things off, let me introduce you to Jorge Sigler Garcia, who pretty much inspired this episode. He remembers encountering science ed for the first time in his middle school chemistry class.

JORGE SIGLER GARCIA: I grew up in Cuba, and they called my classroom the cave because it lacked windows and had only one lightbulb.

KWONG: And Jorge has this distinct memory of one time, when their teacher...

SIGLER GARCIA: Ana Maria Farinas (ph) walked into the cave and started the class by writing the three basic states of matter on the chalkboard.

KWONG: The three basic states of matter - solid, liquid and gas. Their teacher then paused, turned and said, that's not all.

SOFIA: (Laughter).

KWONG: There are other states of matter not covered in the textbook.

SIGLER GARCIA: Her statement left us all with more questions. She just told us, there is still a lot to discover and that any of us could be the ones to make such discoveries.

KWONG: These are states of matter, Maddie, beyond our everyday comprehension. And this footnote, this glimpse into the world beyond the lesson plan, really caught Jorge's attention.

SIGLER GARCIA: Her words filled my young self with awe at how much there is to learn about our world and beyond, how even textbooks struggle to keep up with the new findings.

KWONG: Jorge sent me this voice memo from Palm Beach, Fla., where he works for the local school district and runs a marine conservation organization. And it really got me thinking about how much of what we learn in science class only scratches the surface of what science is truly about.

SOFIA: Yeah. And, I mean, that's because science is a process, right? It's a way of understanding. It's constantly changing to incorporate new information and observations. Like, you know, one paragraph in a science textbook can be a whole field of research people dedicate their lives to.

KWONG: Like states of matter. So for today's show, take a seat, sharpen those pencils - we're going to venture beyond the fundamental states of matter and consider what other states of matter are lurking in our universe.




SOFIA: All right, Kwong, I am ready to go back to school with you...

KWONG: Yes (laughter).

SOFIA: ...Which - honestly, a dream. We would be great.

KWONG: We would be good lab partners.

SOFIA: I don't know. We would be competitive. Yeah, we would be competitive, but we would be great together, I think. And so the science concept we're going to unpack today is states of matter - you know, some of those other states of matter you didn't learn about in science class.

KWONG: Right. So the physicist I called up to explain this is Martin Zwierlein at MIT. And what I find hilarious about Martin is he said when it comes to his own kid, he actually prefers to keep this particular science lesson pretty simple.

MARTIN ZWIERLEIN: To my son, I'm like, oh, yeah, you - they're gas, liquid, solid - bam, leave it at that. You know, he's 7.

KWONG: And states of matter is really just a way to describe how a group of particles - think atoms or molecules, etc. - move.

ZWIERLEIN: Which is sort of beautiful and collective and different from what you would guess by looking just at a single particle.

KWONG: And changes in temperature and pressure can cause those particles to move differently and change their behavior.

SOFIA: Right. We see this super easily with water.

KWONG: That's right. In the liquid phase, water molecules slip and slide past each other. But we humans quickly learned that if you lower the temperature, the particles slow down.

ZWIERLEIN: Bam - we see ice appear. And we build fridges, and we're very excited about that.


ZWIERLEIN: Actually, that was a huge deal a hundred years ago to make ice.

KWONG: And if we go in the opposite direction - heat water up - the particles move faster and farther apart, and eventually, the H2O molecules break away and dissipate into the air as water vapor.

SOFIA: Yeah, aka humidity.

KWONG: That's right.

ZWIERLEIN: It is already a miracle in itself, like, that water exists in these three different states and that we can see those states at temperatures that we can reach as humans in the kitchen.

KWONG: But here's the thing - we can only do so much in our kitchen, right?

SOFIA: Speak for yourself. Speak for yourself.

KWONG: (Laughter) But there's a limited range of temperature and pressure that even you can achieve in your kitchen, Maddie.

SOFIA: Sure.

KWONG: And there are states of matter beyond this. OK, like, do you remember plasma?

SOFIA: Ooh, yeah. Sometimes that's called the fourth state of matter, and it can happen when matter gets heated to a super high temperature. Like, electrons are ripped from atoms, which actually allows plasma to conduct electricity - super cool. Lightning is plasma. I mean, plasma is wild, Kwong.

KWONG: It is wild, yeah. And if we were to go in the other direction, to an extreme, if Martin's son were to ask, you know, Dad, what can happen at a temperature much cooler than ice?

ZWIERLEIN: Is there something else? I might start telling him about these superfluid states of matter.

KWONG: Which is exactly what Martin studies at MIT - these superfluid states of matter that were long predicted but not easily observed in nature.

SOFIA: So how many states of matter are out there?

KWONG: Well, we don't actually know. Martin didn't want to even commit to a number. When I asked him this question, he actually said, ouch.

ZWIERLEIN: There is apparently no end to the series of interesting new twists that nature gives us to find new states of matter. We just are digging - as we speak, we are digging into this all the time.

KWONG: And that's because in theoretical physics, you can use math to predict things that experimental physicists haven't observed yet. And I say yet because in the last few decades, scientists have successfully coaxed atoms under extreme laboratory conditions to enter other states of matter, states that could have useful applications for future technologies.

SOFIA: Awesome. OK, OK. Let's get into this, Emily. Like, how do they do this? What kind of lab conditions had to exist for these other states of matter to emerge?

KWONG: I'm so glad you asked.

SOFIA: (Laughter).

KWONG: They had to get cold, ultracold.

ZWIERLEIN: We worked in the nanokelvin regime for breakfast.

SOFIA: Nanokelvin.

ZWIERLEIN: So you might ask, what on Earth? So that's actually very cold (laughter). It's a billion times colder than interstellar space.

SOFIA: That's too cold, Kwong. That's just - it's too cold, you know?

KWONG: Honestly, these ultracold labs are some of the coldest places in the known universe - just chilling at MIT.


KWONG: And at these chillingly low temperatures, Martin and his colleagues can see atoms start to lose their kind of individualistic nature.

SOFIA: So start to kind of lose energy because, you know, atoms are notorious for kind of doing their own thing. Like, I picture, like, a crowd of people kind of bumping elbows as they move around.

KWONG: Yeah, and these ultracold temperatures you can achieve in a lab, scientists have been able to cool down gases of atoms to within a hair of absolute zero.

SOFIA: The lowest temperature theoretically possible.

KWONG: Right. And it's so cold that the atoms kind of appear as a glowing cloud.

SOFIA: Ooh. And then what happens?

KWONG: There is a dramatic transformation. The atoms start to lose their individual identity.

SOFIA: (Laughter).

KWONG: Quantum mechanics kicks in - that's the science of really small particles. So instead of this crowd of people jostling against one another, the atoms come together and move in lockstep...

SOFIA: Cool.

KWONG: ...And form what's called a Bose-Einstein condensate...


KWONG: ...A brand-spanking-new state of matter called BEC for short. And what's really remarkable about BEC is that it doesn't behave like any states of matter you may be familiar with. It's got moves that you've never seen.

SOFIA: I'm so into this right now.

KWONG: Yeah.

SOFIA: What kind of moves are we talking about?

KWONG: Well, if I were to pour myself a stiff, cold glass of BEC and stir it and remove the spoon, it would form a whirlpool that would never stop.

ZWIERLEIN: It will develop not one but many, many microscopic...

SOFIA: Wild.

ZWIERLEIN: ...Spinning whirlpools.

KWONG: And it flows without any resistance. So the condensate would spill over the walls of the cup and out any tiny holes that exist at the bottom. It would flow through a wire or capillary tube without stopping.

ZWIERLEIN: We call it superfluid. It flows through any cracks, and there's no dissipation.

KWONG: No dissipation of heat. It's this frictionless quantum soup.

ZWIERLEIN: I mean, I can't even picture a state of matter like - like, I'm trying. It's very oozy (ph) in my mind. It's kind of got an ooze-like quality, you know?

KWONG: Yeah. It's really complicated to imagine, but these states of matter - scientists think they do exist in nature. But for us humans to create and study them ourselves, we need extreme laboratory conditions. And Martin is able to create those and then take pictures of the superfluid behavior, the many whirlpools, directly with a camera.

ZWIERLEIN: We can take pictures of these atoms and atom clouds. And, in fact, we are very visual. I'm actually a very visual guy. I need to see this stuff to believe it (laughter). And, luckily, we have techniques to actually take rather beautiful pictures of this quantum soup, of these whirlpools, of individual atoms doing funny many-body physics to try to take it out of this invisible realm and make it very real, touchable.

SOFIA: What a time to be alive, Kwong, you know?

KWONG: Yeah, right?

SOFIA: That's wild. OK, OK. So this is under extreme laboratory settings. It's not like these condensates are going to start showing up, like, in my lightbulbs.

KWONG: No, no. But, you know, one generation's playing around with quantum matter is another generation's technological breakthrough...

SOFIA: (Laughter).

KWONG: ...In computing or circuitry or precision measurement. And as a first step, Martin would love nothing more than to see some of these pictures or these videos tucked into a modern science textbook.

ZWIERLEIN: Because why not? You know, it can only help to learn that the world is a bit different from what you see at the surface.

SOFIA: Well, Emily Kwong, what a delight. Thank you for this first episode in our Back to School series. What a time.

KWONG: Yeah, you are so welcome, Maddie. And, also, if any of you listening have ideas for this Back to School series, please email the show.

SOFIA: You can email us at shortwave@npr.org.


SOFIA: This episode was produced by Thomas Lu, edited by Viet Le and fact-checked by Ariela Zebede.

KWONG: I'm Emily Kwong.

SOFIA: And I'm Maddie Sofia.

KWONG: And this is SHORT WAVE from NPR.


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