Could dark energy be more dynamic than we thought? In this episode of Tiny Show and Tell Us, we cover a recent dark energy discovery that has us contemplating what the end of the universe might look like, and then we delve into if hydrangeas can actually absorb water through their petals (ahem, sepals).
Transcript of this Episode
Sam Jones: Welcome to episode three of Tiny Show and Tell Us. I'm Sam Jones. I'm the exec producer of Tiny Matters, and I'm here today with my wonderful co-host Deboki Chakravarti.
For those of you listening who are not regular Tiny Matters listeners, first off, so happy that you're here. Second, there's this thing that we do at the end of every regular Tiny Matters episode called The Tiny Show and Tell. Deboki and I each bring a piece of science news or a story that we recently read and we share it with each other. Now we want you to share with us, hence the name of this bonus series Tiny Show and Tell Us.
Deboki Chakravarti: For these bonus episodes, you can send an email to tinymatters@acs.org with your science story, some science news, you can't stop thinking about maybe a science factoid. We're going to read it and then dive a bit deeper. That's tinymatters@acs.org. We'll put that in the episode description as well.
Sam Jones: And before we get into things, a huge thank you to Anne Hylden for doing research for this episode. Anne is a science writer and chemist, and she's working with Tiny Matters for the next few months. All right, Deboki, episode three. Let's do it.
Deboki Chakravarti: Yes, let's do it.
Sam Jones: You went first last time. I will go first this time. It is only fair. Okay, so this is from listener Dakota who wrote in saying, "My favorite recent science story is how the DESI telescope is hinting that dark energy could be variable over time, which could imply a different end and maybe beginning of our universe." This is a cool one. It was difficult for me to wrap my brain around. However, I feel like I actually understand space a little bit better, which is still not great, but I felt really... I don't know if I would say accomplished, but I was amped when I finished reading about this and thinking about this.
Of course, I'm not an astrophysicist. I'm not going to go into crazy detail here, but I think I will get into things in a way that hopefully then makes it easier to understand why this new finding is cool.
Deboki Chakravarti: Yeah, I'm excited.
Sam Jones: Okay, so the Dark Energy Spectroscopic Instrument, or DESI, telescope at Kitt Peak National Laboratory in Arizona has produced the largest 3D map of the universe to date. Conceptually cool. Just like, what? Okay. Oh, you want to map our universe? Great.
The thing that's interesting is that map suggests that dark energy may vary over time. I say suggests because researchers are really stressing that the evidence it's not strong enough at this point to claim a discovery. However, there are now three distinct sets of observations that all point in a direction that is not what scientists have assumed about dark energy for a very long time.
Deboki Chakravarti: Interesting.
Sam Jones: It's cool. It's really cool. Okay, so I think we need to start by talking about dark energy, which I saw described by Space.com writer Robert Lea as a sort of anti-gravity force providing a negative pressure that fills the universe and stretches the very fabric of space-time. I liked that visualization with that.
We know that dark energy exists because of a 1998 discovery that the universe is expanding at an accelerating rate. So, usually when something explodes, the matter that's being pushed outward will eventually lose momentum and slow down, right? Let's think about a watermelon exploding. It's going to have that initial burst and then it slows down and, because of gravity, drops, right? In the case of the Big Bang, we would expect gravity to start pulling matter back together after the initial expansion.
But what scientists discovered in 1998 is that the opposite is happening and that galaxies in the universe are actually moving away from each other faster and faster. They came to that conclusion based on the redshift in the spectra of Type 1a supernovae, which are dying stars, whose distances can be measured accurately due to their constant luminosity. So, by looking at this shift in light spectra, it was a clever way of being able to see that things are actually moving away from each other, is really what that means.
If the universe is expanding, the leading theory for the end of the universe is something called the Big Freeze or Big Chill. This theory is that the universe will continue to expand and cool, eventually reaching a state where particles are so separated that the universe will be too cold to support life. And we talked about this with astrophysicist Moiya McTier in episode 16 of Tiny Matters titled, "If the Milky Way Could Talk, What Would It Tell Us About the Universe and How Would It Feel About Us Humans?" So, if you want to hear a bit about different potential endings of the universe, go check out that episode.
But back to dark energy. One theory is that dark energy is constant for a given amount of space and is therefore this cosmological constant. Einstein was the first to propose that. Today that constant is labeled as the Greek letter Lambda and is used in a model of the Big Bang known as the Lambda CDM model.
With that said, we still don't understand dark energy that well. And so there was this competing theory that instead of dark energy being this constant where you have the universe expanding over time, this competing theory was that dark energy can vary at different times and places. Plus, dark energy also doesn't currently fit into the standard model of particle physics. Yeah, there are way more questions here than there are answers.
This brings us to the Dark Energy Spectroscopic Instrument, or DESI, telescope at the Kitt Peak National Observatory in Arizona. This thing was specifically designed for super-fast data collection and it has this four meter mirror with 5,000 robotic fibers that automatically swivel toward different celestial targets. Astronomers spent about a year, so May 2021 to June 2022, recording the night's sky. It gave them the most detailed 3D map of the universe to date, and it covered six million galaxies.
Deboki Chakravarti: Oh, my God.
Sam Jones: I know.
Deboki Chakravarti: That's so many galaxies.
Sam Jones: Yeah, and so their goal is to be able to look at many galaxies in different stages of development and then compare what they find with predictions of different cosmological theories.
Really, all this comes down to is what is actually happening to our universe, right? Are we speeding toward the Big Freeze? Are we not? It really brings in these questions of like, do we actually understand what dark energy even is?
One of the scientists who worked up the data saw something looked off. The Lambda CDM, it wasn't actually capturing what they were seeing that was going on in the universe. Yeah, so the DESI data and then other recent supernova maps all seem to hint that dark energy's power is waning, which is like I just expect…
Deboki Chakravarti: Just like a cosmic villain, yeah.
Sam Jones: Yeah, where it's like the dark energy's power is waning.
Yeah, so what does that mean? Could that mean that the universe won't experience the Big Freeze, that it'll end in some other way? If the dark energy constant gets below zero, what that actually means is that space would slowly begin to contract, which to me sounds like way worse. But this is a hypothetical scenario already that astronomers have talked about called the Big Crunch. Which sounds like a tasty candy bar, but also a lot more upsetting if you think about it being the end of the universe.
Right now, what we really need is more data. DESI is now more than halfway to collecting five years worth of observations, which will incorporate 40 million galaxies. Remember they already have data from six million galaxies, I'm sure much more now…
Deboki Chakravarti: Six million already sounded like so many.
Sam Jones: 40 million. Yeah, so in a couple years, I'm just excited to see what they find. Do they find stuff that actually says, "Actually, you know what? We think the Big Freeze is most likely." Yeah, I'm wondering what they'll find and from that, what they'll conclude seems most plausible for both the beginning and the end of our universe.
Deboki Chakravarti: Yeah, wow. We're still so early on in being able to understand what the data is saying even, so it's like the astronomers are also like, "We're not sure." I agree. I also am not sure, but that's for very different reasons. It's because I can barely wrap my mind around the fact that physicists are able to think in these terms.
Sam Jones: That they're able to analyze data from six million galaxies and then try to draw a conclusion. I just feel like that's a lot of numbers I...
Deboki Chakravarti: Totally. Yeah, there's another great book, The End of Everything by Katie Mack, for people who are curious about some of the techniques that you were talking about and also these ideas of how the universe can end and how they relate to the beginning. Because that's the other weird thing is these two questions are so inherently tied together. How the universe ends is inherently tied to questions of how it began, and that dictates everything that's happened in between those two things.
But the thing that I remember when I was reading The End of Everything that really struck me is just how creative physicists are in their ability to go down these rabbit holes, I guess. That's not even the right word, like these trajectories that just feel so wild, but they're just willing to go down and just imagine what is a Big Freeze, what is a Big Crunch? It feels so ungrounded, even though it obviously is grounded in something. It is grounded in actual physical laws. But compared to something like our backgrounds are in biology, where that feels somehow more grounded to me.
Sam Jones: Right. It's more tangible to me. I understand that physics is very real, but to me there's just something that still feels so theoretical. In this sense it is. A lot of this is theoretical. Dark energy is this hypothetical energy, but we have to find a way to talk about it if we want to talk about the end of our universe.
Deboki Chakravarti: Yeah, yeah. It's more an explanation for something we've observed without knowing fully what that explanation is even, which is weird.
It's funny that this is our experience of physics. But I remember a math class for physicists that I took in grad school, and the professor was a physicist who worked in biology, and so he was teaching a really basic model of how genes are regulated. And that was one of the few things in the class that I could understand, and it was really fascinating seeing the physicists in the class have a harder time. There was a different kind of hurdle for them to go into understanding how genes work compared to, for me, understanding how gravity works or how obviously dark energy works. It's really funny to me these kinds of differences.
Sam Jones: Yeah. Yeah, it is. It just shows you need a lot of different people and brains in the world for us to be able to function as a society.
Deboki Chakravarti: Yeah, totally.
Sam Jones: And to draw any conclusions about the future of our universe or human health. I'm grateful to the biologists out there as well as the physicists out there.
Deboki Chakravarti: Right. Yeah, yeah, yeah. I didn't mean to get super meta about science, but I think it's cool. I think it's really neat how different fields have different ways of thinking. They all have their own language, their own grammar.
I mean, that's fun about our jobs in general. We get to dabble in all these little different worlds. But it also means that we end up in worlds like physics where we got to learn about dark energy.
Sam Jones: Yeah, for sure.
Deboki Chakravarti: Well, I'm going to take us to an equally mysterious question, which is about hydrangeas.
This is from listener Heather, and she said, "I just recently started working part-time at a flower shop and learned that hydrangeas are one of the only flowers that drink water through every part of the plant, including the petals. Curious why and how?" This question is a great question, in part because it stumped us. We don't have a good answer, and I think that's fun too because sometimes that's how things go.
So Anne did a lot of work looking for a good answer for this, and we also tried to dive deeper into it. There are plenty of websites where this claim exists about hydrangeas being able to absorb water through their flower petals. We just couldn't find much in the way of sources that really dove into how true it is, how it works. I'm not doubting that it's true. I just don't have a good source diving into what it means and how it works and all of that.
One of the things though that is interesting, that I didn't know, hydrangeas don't actually have petals. They have something instead called sepals. Sepals are a part of the flower that you usually find on the outside of the flower. They're usually green and underneath the petals, so they're a protective thing that you'll see when the flower is in a bud. And so the thing is flowers are apparently made up of... I think it was four parts that I had read, and those parts are really defined more by their position than by their function, which was really interesting. I didn't know that about flowers at all.
And so one of the things that is generally known about hydrangeas is that the color of the sepal can change depending on how you cultivate it, including using pH to change their color. So that is a thing, but again, I don't know about water being able to go through sepals. There are also flowers like orchids that can absorb water through their leaves. But again, I don't know too much about why or how.
This is a very short response, but basically the answer is we're not quite sure. But I would also love to open it up to the listeners if someone has good insight into how this works. If a botanist is able to explain this or someone else, I'd love to hear more because it seems like something that people share a lot. My assumption is that there's got to be some good anecdotal basis for it, but I don't know beyond that.
Sam Jones: Right. Yeah, and it's fascinating because as I was trying to pick away at this a little bit too... Again, like Deboki said, we were finding this everywhere, but we weren't finding any... Definitely no academic papers at least that we came across, or even a page where someone did some sort of experiment to try and show something.
I thought it was fascinating. But there's a lot of stuff that's like when you go to a flower shop, you often notice that the flowers have been spritzed. It just makes them look nicer, doesn't actually do anything. They're not absorbing anything except for hydrangeas, or one was like except for orchids. This is something that obviously is very pervasive, but is that definitely true? And how do we actually know? There are definitely ways that you could test, I would think, with different dyes and things, if the petals are actually taking up water that is on them directly, and it's not just water that starts in the soil and moves up, right?
I also think that a lot of the language plants is so fascinating and confusing because they say petals are modified leaves, right? They're there mostly, I think, to attract pollinators. But is that 100% true? We need a botanist on Tiny Matters. We really haven't done much plant stuff.
Deboki Chakravarti: That's true.
Sam Jones: Maybe this is a sign that we need to really dive into plants. I feel like plants are not getting...
Deboki Chakravarti: They're not getting the love from us.
Sam Jones: Yeah, they're not getting a lot of Tiny Matters love, so maybe we should reconsider.
Deboki Chakravarti: Yeah, for sure. Yeah, I mean, what you were talking about the language, it took me a while as someone who doesn't have a lot of plant knowledge to understand the difference between the sepals and the petals and really get what the difference was, just because I haven't really heard the term. A lot of websites are just saying hydrangeas have sepals instead of petals. To me as a complete novice, it was like, "I don't know what that means." You could tell me something is a sepal, you could tell me something is a petal, and I would just be like, "Great, that sounds cool."
Sam Jones: Yeah, it looks similar to me.
Deboki Chakravarti: Finally finding a source that broke it down a little bit more was really helpful. For me, coming into it from the outside was like, "Oh, okay. That's interesting. I never really realized this about the flower."
Sam Jones: I feel like this is just a microcosm of what happens all the time in science or even in science communication. Where you have something you want to answer and you have ways of going about it, but sometimes it's just like you're not always going to get a 100% definitive peer reviewed answer to a question. And that's okay. But that being said, if someone knows about some research that has been done on this that we just didn't find, please send it to us because we'll totally mention it in a future Tiny Show and Tell Us.
Deboki Chakravarti: Yeah. Or even if it's something that you have directly experienced, tell us about the way that you've seen this. We would totally love to know about it. I'm really curious about what this means overall, too. What it means to be able to absorb through the sepal versus absorbing through just roots or whatever, I am curious about the implications overall.
Sam Jones: Thanks for tuning in to Tiny Show and Tell Us, a bonus episode from Tiny Matters, which is a production of the American Chemical Society. And thank you again to Anne Hylden for her work on this episode.
Deboki Chakravarti: Send us an email to be featured in a future Tiny Show and Tell Us episode tinymatters@acs.org. You can find Sam on social at samjscience, and you can find me at okidokiboki. See you next time.
;void(0);){kind=link}