In this episode of Tiny Show and Tell Us, we get to the bottom of if glass is a liquid or a solid and why riboflavin makes milk fluorescent. Then we talk about the Laser Interferometer Space Antenna (LISA) — the first space-based observatory that NASA scientists and their collaborators are sending up into space to detect and study gravitational waves, better known as “ripples in spacetime.”
Transcript of this Episode
Sam Jones: Welcome to Tiny Show and Tell Us, the bonus series where you write in with your favorite science news or factoid, we read your email aloud and then we dive deeper. I'm Sam Jones and I'm here with my co-host Deboki Chakravarti.
Deboki Chakravarti: Hi Sam. Last time we went team wasp for the moment at least because they're great for biocontrol for pests. And then we also talked about the importance of iron and hemoglobin. And also a reminder for all of you that if you have a story you'd like for us to cover on Tiny Show and Tell Us, all you have to do is write us an email so you can email us at tinymatters@acs.org or fill out this form linked in the episode description.
Sam Jones: Cool. Deboki, you want to go first this time?
Deboki Chakravarti: I sure will. And I've got two for you because they're both kind of short, but they're also very fun. So I'm going to just tell you them both right off the top. The first is from listener Mary, who wrote, "Glass is technically a liquid," and the second is from listener Zoe, who wrote, "Milk is fluorescent due primarily to riboflavin."
Sam Jones: All right.
Deboki Chakravarti: So let's start with Mary and whether or not glass is technically a liquid, because it turns out it's not, but it's also not a solid really fully, it's something in between called an amorphous solid.
Sam Jones: Whoa. I actually feel like I should have known that, but I didn't, so I'm so glad Mary wrote in and it was like Mary was half right.
Deboki Chakravarti: Yeah, yeah, exactly.
Sam Jones: But it's so confusing.
Deboki Chakravarti: Right. And so one of the reasons that people sometimes think that glass is a liquid is because they might go to old cathedrals and you'll look at these window panes and sometimes they'll be thicker at the bottom so it looks like they've kind of melted. And yeah, I hadn't heard about this until I think this past year, I think we actually had a SciShow Tangents that was about glass and someone wrote in asking about this phenomenon. And so yeah, apparently it's something that people notice and I think it totally makes sense that you'd be like, "Oh, that makes sense that glass might be this liquid. And it's, over time, kind of melted downward and created this thicker window bottom."
So why is glass not a liquid though? So solids have an organized structure to them, right? Especially something like crystals, those are super organized, the atoms inside are laid out, very, very structure repeated kind of things. Liquids don't have that, and glass also doesn't have that super organized of a structure. So when you are making glass, you will melt it into a liquid, but when it cools down below its melting point, it doesn't solidify it, it becomes what's called a super cooled liquid. But then as it cools down more, it gets below what's called the glass transition temperature, and this is where the atoms in glass stop moving. And so at that point, it's not super organized like a crystal, but it's also still more ordered than a liquid. And amorphous solids can flow, but they can flow super slowly and eventually, I think we're probably talking on very long time scales, they might get into more of that crystal-ish kind of order within them in terms of those atoms and how they're arranged.
This still doesn't actually explain why you might see these windows that have these thick bottoms to them, because the temperature that those windows are at is still way below that glass transition temperature. So the article that I was reading from Scientific American on why glass windows might do this says that it might be more actually due to how those windows are made rather than them being liquidy. So yeah.
Sam Jones: That is so interesting.
Deboki Chakravarti: Yep. Categorizations are weird.
Sam Jones: Yeah, amorphous solid, you said?
Deboki Chakravarti: Yes, amorphous solid. When you see glass, that's what you're looking at.
Sam Jones: Okay.
Deboki Chakravarti: Let's get into fluorescent milk. This was also really cool. So just as a reminder, Zoe wrote, "Milk is fluorescent due primarily to riboflavin." Riboflavin is vitamin B12. It's in a lot of things like meat, green veggies, and yes, it's also in milk. We need it for our skin for the lining of our digestive tract. It's a thing that our body uses, and it's also fluorescent.
So for a quick reminder on what fluorescence is, this is what happens when certain chemicals that are out there, you shoot a light at them with one wavelength and they'll actually emit light at another wavelength. So with riboflavin, you can shoot a light that has a wavelength of 349 nanometers at it, which is in the ultraviolet range, and the riboflavin will then emit light at 532 nanometers, which is green. So yes, milk can actually glow this greenish yellow color when it's irradiated with ultraviolet light.
Sam Jones: I guess I've just never looked at milk under UV light.
Deboki Chakravarti: Right, yeah. I've never thought, "That seems like something I want to do." But there are actually really good reasons to do it. That's what I found really fascinating when I looked into this, riboflavin is not the only molecule that can fluorescent milk. And what scientists have realized is that they can actually use fluorescent spectroscopy to test the quality of dairy products. And it's a great technique because it's fast, it's sensitive, and you don't have to destroy any of the milk to do it, you can just shine a light at it and see, is it fluorescing?
So one really, really interesting application is if you want to know if your milk is from grass-fed cows, you can use fluorescent spectroscopy because when cows are grass fed as opposed to cows that are eating grain, they'll actually have chlorophyll that'll show up in their milk because that's one of the byproducts of them metabolizing the grass. And chlorophyll also fluoresces, so you can use spectroscopy to figure out how much chlorophyll is in the milk. And that's just one example, there were a lot of other ways that I found you can use fluorescence to figure out where the milk is from geographically, there's just all of these different applications for figuring out the quality of milk from how it fluoresces.
Sam Jones: That is so interesting. I had no idea. And of course, it's not just when you're trying to figure out is it chlorophyll, is it something else, it's not just shining a UV light or something, right? It takes a lot more, but you could still in a chemistry lab, you could find out a lot about that milk.
Deboki Chakravarti: For sure, yeah.
Sam Jones: Oh, so cool, I love that. All right, well, my Tiny Show and Tell Us is from listener Joshua, and it is a very in-depth one, very well explained. So I'm going to stop at a couple points, but mostly just go through what he's sharing.
Deboki Chakravarti: Okay.
Sam Jones: So Joshua wrote in saying, "Today I would like to share a not so tiny matter, which would be well worth telling your audience about! For my master's research I worked for NASA Goddard Space Flight Center modeling the very fascinating topic of the gravitational waves emitted from a special black hole binary called extreme mass ratio inspirals, EMRIs."
Deboki Chakravarti: Oh.
Sam Jones: Yes. So let's talk about this. Continuing with Joshua's email, "At the center of every galaxy, we believe there exists a very massive black hole, which can be millions to billions of times the mass of our sun. Around these massive black holes, we could find a group of stars, which could contain a much smaller black hole with a mass comparable to the sun. If this group of stars falls toward the massive black hole, then the stars would likely be torn apart by the force of gravity and contribute to the swirling vortex of hot plasma called the accretion disk." By the way, Joshua, I think you did a really good job of explaining this.
Deboki Chakravarti: Yeah. This is very vivid.
Sam Jones: It's very vivid. And then Joshua writes, "However, that much smaller black hole, if the conditions are just right, will not be torn apart. Instead, this smaller black hole will slowly fall into the massive black hole, kind of like a marble slowly spiraling down a well," which great visual.
Deboki Chakravarti: Joshua, I have a question. How do you go about your daily life knowing this? This is something that you think about all the time, and then also you go buy groceries.
Sam Jones: I know.
Deboki Chakravarti: Are you thinking about how somewhere out there is a tiny black hole sinking into another?
Sam Jones: Into a larger one?
Deboki Chakravarti: Yeah, I just feel like that would just be... I would not be able to think about anything else.
Sam Jones: Yeah, no, it's wild. Okay, so Joshua has that marble slowly spiraling down, a well visual, and then writes, "Due to the very stark differences in these two black hole’s masses, we call this system an extreme mass ratio inspiral." So that's what that is. All right. Joshua continues, "As the marble falls down the well, it creates wiggles and wobbles in the fabric of space-time that we characterize in the scientific community as gravitational waves." Love that. "Encoded within these signals is rich information, which can aid us in addressing many unanswered questions within the field of astrophysics that we hope to answer. The future of gravity wave detection will be made with the laser interferometer space antenna, or LISA, which is set to launch in the mid 2030s. This detector can be described as a series of three satellites projecting laser beams in an equilateral triangle so big that you can inscribe the sun inside of it. This triangular satellite constellation will cartwheel in a coalescent orbit, which trails the earth around the sun." Okay.
Deboki Chakravarti: Sorry, I just want to make sure I'm picturing this right. So there's going to be these satellites and they are following us as we go around the sun, but they're also really, really big, it's bigger than the sun too?
Sam Jones: Yeah. So before I get into the last bit of what Joshua sent, I'm going to just talk a little bit about LISA, the laser interferometer space antenna, because it's also very new to me. So like Joshua said, LISA is a space probe. It's going to detect and measure gravitational waves, which are sometimes referred to as ripples in the fabric of space-time, which is just the best visual ever. So what's cool about LISA is that it will be the first space-based gravitational wave observatory.
Deboki Chakravarti: That we know of.
Sam Jones: Yeah, right. Okay, so LISA is made up of three spacecrafts that are separated by millions of miles, trailing many millions of miles behind earth as we orbit the sun. So according to NASA, I'm quoting NASA because I think this is a really good explanation and this is-
Deboki Chakravarti: The same way that we're quoting Joshua, you guys, you know how to explain this stuff.
Sam Jones: Yeah, exactly. So according to NASA, "These three spacecraft relay laser beams back and forth between the different spacecraft and the signals are combined to search for gravitational wave signatures that come from distortions of space-time. We need a giant detector the size of the sun to catch gravitational waves from orbiting black holes that are millions of times more massive than our sun." Why do they need it to be so big? This is me now, the quote is done, so why do they need it to be quite so big? I don't know for sure, but I assume that you would need a very large amount of area that's covered to really be able to detect something like a gravitational wave. And this is in partnership, I'll say, with the European Space Agency, and it's scheduled to launch in the mid 2030s, which Joshua mentioned.
Deboki Chakravarti: Yeah, I wonder, I mean, when I'm thinking of a gravitational wave, I'm picturing it like an actual wave in an ocean, and so I wonder if you don't capture a large enough area, you're just not going to see as much of the wave to make it look like a wave. Like if you zoom in too close on a wave…
Sam Jones: You have no idea what it is.
Deboki Chakravarti: It's just going to look like an even terrain.
Sam Jones: It's just water.
Deboki Chakravarti: Yeah.
Sam Jones: Yeah, totally, I think that's definitely a part of it. And also, I'm going to link to a great little video that's on loop from NASA, because I think that that will help people visualize what the heck is going on here with LISA.
Deboki Chakravarti: I'm going to take a quick look. Oh, wow. It's just going. I like this animation because it makes it look so, not simple, but it feels like so straightforward, but it's like there's so much that's happening.
Sam Jones: Yeah.
Deboki Chakravarti: How precise does it need to be? I have so many questions.
Sam Jones: I think quite.
Deboki Chakravarti: Yeah. And it has to be an equilateral triangle, is that really important?
Sam Jones: Yeah, it seems like it.
Deboki Chakravarti: Oh, man.
Sam Jones: Yeah. So this is just a little looping video that I'll link to where you have this big LISA detector trailing behind Earth as earth is going around the sun and hopefully picking up on gravitational waves.
Okay. So going back to Joshua, last thing that Joshua wrote, "Before LISA comes online, we need to model these gravity wave signals using theoretical models, mathematical techniques to find solutions to these equations and computers to crunch the numbers. My master's research focused on building gravitational wave signals for EMRIs, now considering the effects of a massive black hole that spins. The road ahead for understanding the elusive nature of black holes among many other adjacent fields is incredibly exciting with the prospect of gravity wave observations with LISA. Stay tuned!"
Deboki Chakravarti: We sure will.
Sam Jones: We will. But yeah, thank you so much, Joshua, this was great. As I was reading it, I had to keep stopping every sentence to just visualize what was going on, but you did a great job of using just some excellent examples and very descriptive language that helped it make more sense.
Deboki Chakravarti: Right, yeah. I think, like I said, it's just wild to me that we can think about the universe in this way and that people do that and then go live their normal lives knowing this about the universe.
Sam Jones: I know, it is wild.
Deboki Chakravarti: Yeah. Well, thanks to Mary, Zoe and Joshua for submitting to Tiny Show and Tell Us, a bonus episode from Tiny Matters created by the American Chemical Society and produced by Multitude.
Sam Jones: You can send us an email to be featured in a future Tiny Show and Tell Us episode at tinymatters@acs.org, or you can fill out this form that's linked in the episode description. We'll see you next time.
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