# Listener Questions #54

An episode of [Daniel and Kelly’s Extraordinary Universe](https://invisiblenetwork.ai/podcast/1436616330), 27 Oct 2026, 47 min.

Audio: https://podtrac.com/pts/redirect.mp3/traffic.omny.fm/d/clips/e73c998e-6e60-432f-8610-ae210140c5b1/f5d5fac6-77be-47e6-9aee-ae32006cd8c3/dca1597e-849c-4ecf-8991-b4f0004f72f7/audio.mp3?utm_source=Podcast&in_playlist=b26cbbeb-86eb-4b97-9b34-ae32006cd8d6

Daniel and Kelly answer listener questions about algal blooms in the Reflecting Pool, the difference between memory and consciousness, and banana slugs. See omnystudio.com/listener for privacy information.

## Transcript

[0:07] Speaker 1: Renovations were meant to make the reflecting pool American flag blue.
[0:12] Speaker 1: So what caused the massive algal bloom with its stomach-churning hue?
[0:17] Speaker 2: Do you have to be aware to have a memory?
[0:19] Speaker 2: Or can you mindlessly recall things that are purely sensory?
[0:24] Speaker 1: I want to learn more about the charismatic banana slug.
[0:27] Speaker 1: And I'll throw Kelly a bone. She can give slug
[0:30] Speaker 1: parasites a plug.
[0:32] Speaker 2: Whatever questions are keeping you up at night. You know
[0:35] Speaker 2: that Daniel and Kelly's answers will make it all right.
[0:38] Speaker 1: Listener questions episode number 54.
[0:41] Speaker 3: 54.
[0:41] Speaker 1: Not a prime.
[0:59] Speaker 2: Hi, I'm Daniel. I'm a particle physicist. I love thinking
[1:02] Speaker 2: about aliens. And I was wrong again about the Nobel Prize.
[1:07] Speaker 1: Hello, I'm Kelly Wintersmith. I study parasites and space, and
[1:10] Speaker 1: I really don't have any predictions when Nobel Prize time
[1:12] Speaker 1: comes along. And usually I don't actually even pay attention
[1:15] Speaker 1: to the announcement. How were you wrong this year? Oh,
[1:18] Speaker 1: was this a project that you could have been involved in?
[1:21] Speaker 4: No.
[1:22] Speaker 2: Oh, yeah. That's right. My record is flawless.
[1:27] Speaker 1: Is that four projects you could have?
[1:28] Speaker 2: That is four now. Oh, no. So the Nobel Prize
[1:31] Speaker 2: was awarded this week to Francis Halzen, an awesome guy
[1:34] Speaker 2: who wrote a great textbook and the guy who conceived
[1:37] Speaker 2: of the amazing idea of using a cubic kilometer of
[1:41] Speaker 2: ice at the South Pole to see neutrinos. This is
[1:45] Speaker 2: the project where they drilled a kilometer down and dropped
[1:48] Speaker 2: cameras in there and then let it refreeze. Now they
[1:50] Speaker 2: have literally an ice cube to see neutrinos. And when
[1:54] Speaker 2: I was a grad student... In the 90s at Berkeley,
[1:56] Speaker 2: there were folks working on this very early on. And
[1:59] Speaker 2: I could have gone in on the ground floor of
[2:02] Speaker 2: this Nobel Prize winning experiment. But I thought, that's crazy.
[2:06] Speaker 2: They'll never get that to work. Which is what I
[2:08] Speaker 2: also said about many other experiments that went on to
[2:11] Speaker 2: win the Nobel Prize. So, you know, when Daniel thinks
[2:14] Speaker 2: your idea is impractical, you're destined for Nobel gold.
[2:17] Speaker 1: You are on the right track. Do not back down.
[2:22] Speaker 1: Double your efforts.
[2:24] Speaker 2: Daniel's won a Nobel Prize in some alternative universe, but
[2:27] Speaker 2: not this one.
[2:28] Speaker 1: Oh, man, maybe four or five alternative universes, but not
[2:32] Speaker 1: this one. But that's okay. You love what you do,
[2:34] Speaker 1: and you don't need a prize to feel good about it.
[2:36] Speaker 2: That's right. Yes, I didn't want the Nobel Prize anyway.
[2:39] Speaker 2: No sour grapes here. Absolutely not.
[2:41] Speaker 1: That's right. Well, that's good.
[2:44] Speaker 2: But we're not talking about Daniel's lack of curiosity in
[2:47] Speaker 2: Nobel Prize-winning experiments. We're talking about the listeners and the
[2:50] Speaker 2: questions they have about the nature of the universe. how
[2:53] Speaker 2: things work, why things work, and we're here to explain
[2:56] Speaker 2: all of it to you.
[2:58] Speaker 1: And first up today, we have a question from Discord,
[3:01] Speaker 1: and I am maintaining my tradition of not getting first
[3:04] Speaker 1: names ahead of time. So we have a question from
[3:07] Speaker 1: Dernal K from our Discord community.
[3:10] Speaker 4: Hi, Daniel and Kelly. This is David from Dallas via
[3:13] Speaker 4: New Zealand, Australia, and England. Yes, I've lived in lots
[3:17] Speaker 4: of places. On Discord, I'm Dernal K, which is Colonel
[3:21] Speaker 4: D switched up to be unique. My question might be
[3:24] Speaker 4: fun if it's not crossing our currently topical line is,
[3:28] Speaker 4: how do we get algal blooms in ponds and how
[3:31] Speaker 4: that impacts the aquatic ecosystems in waterways and ponds?
[3:36] Speaker 2: All right. This is a very topical question. Unusual for us, Kelly.
[3:40] Speaker 5: It is.
[3:40] Speaker 1: However, one, I... Let it sit on my list for
[3:44] Speaker 1: a while so it's not super topical anymore.
[3:46] Speaker 2: Trying to stay irrelevant.
[3:47] Speaker 4: Good.
[3:48] Speaker 1: That's how we roll. But also, after the 2012 renovations
[3:53] Speaker 1: of the reflecting pool, which were, you know, not during
[3:56] Speaker 1: a Trump presidency, there were also algal blooms in the
[3:59] Speaker 1: reflecting pool. So this is a recurring problem.
[4:02] Speaker 2: OK.
[4:02] Speaker 1: And so, you know, that's my attempt at being apolitical.
[4:05] Speaker 1: But let's let's jump into the the science here.
[4:09] Speaker 2: So what is an algal bloom, first of all? Is
[4:11] Speaker 2: it just a bunch of algae in a pool?
[4:13] Speaker 1: It's a bunch of algae or a bunch of cyanobacteria.
[4:16] Speaker 1: So these are both organisms that photosynthesize. They are in
[4:21] Speaker 1: very different places on the tree of life. And actually,
[4:24] Speaker 1: we think that algae and other plants got the ability
[4:27] Speaker 1: to photosynthesize because way deep in the past, one of
[4:32] Speaker 1: them managed to incorporate a cyanobacteria, which is a bacteria
[4:37] Speaker 1: that can do photosynthesis. And that ended up becoming the chloroplast.
[4:40] Speaker 2: Oh, this is like what we talked about recently on
[4:42] Speaker 2: the symbiosis episode.
[4:44] Speaker 1: Yeah, except you and I are like time travelers. Yes,
[4:47] Speaker 1: we've already recorded the symbiosis episode, but I don't think
[4:50] Speaker 1: it will have come out by the time this listener
[4:52] Speaker 1: question episode comes out. So stay tuned.
[4:53] Speaker 2: Preview of the symbiosis episode.
[4:55] Speaker 1: That's right. That's right. Time traveling extraordinaries.
[4:58] Speaker 2: Awesome.
[4:59] Speaker 1: Anyway, both algae and cyanobacteria use photosynthesis. And when you
[5:03] Speaker 1: say there's an algal bloom, even though cyanobacteria are not algae,
[5:07] Speaker 1: people will still... refer to an overgrowth of both cyanobacteria
[5:11] Speaker 1: and algae as algal blooms.
[5:14] Speaker 2: So you're saying common names are not super clear and
[5:17] Speaker 2: descriptive sometimes.
[5:18] Speaker 1: Which is why sometimes it's helpful to use scientific names. Yes,
[5:21] Speaker 1: that's right.
[5:22] Speaker 2: I saw a comic about that from Zach. I was
[5:24] Speaker 2: wondering if that's been part of the conversation over there.
[5:28] Speaker 1: No, but you know, Zach Wienersmith listens to DKEU, and
[5:33] Speaker 1: I've been listening to his podcast, Last Humans in the Loop.
[5:35] Speaker 2: It's good.
[5:36] Speaker 1: I've been enjoying it. I'm glad you're liking it, too.
[5:38] Speaker 2: Yeah, yeah.
[5:39] Speaker 1: OK, so back on track. When do you get massive
[5:43] Speaker 1: growths of these photosynthesizing organisms? And some of the things
[5:48] Speaker 1: that cause a lot of growth in these organisms are, one,
[5:51] Speaker 1: loading of phosphorus. So for a lot of algae in
[5:56] Speaker 1: freshwater systems, the thing that limits their growth is the
[5:59] Speaker 1: availability of phosphorus in the environment.
[6:01] Speaker 2: Phosphorus. Why phosphorus?
[6:03] Speaker 1: Phosphorus. Why phosphorus? So I should know that, but I
[6:08] Speaker 1: also am going to point out that that's clearly biochemistry.
[6:11] Speaker 1: So let's go ahead and throw to Katrina.
[6:16] Speaker 3: Well, phosphorus is important for life in general, but what's
[6:20] Speaker 3: really interesting about phosphorus is that it doesn't go into
[6:23] Speaker 3: the atmosphere. So a lot of the other resources like nitrogen, oxygen,
[6:28] Speaker 3: et cetera, have a gas phase in And so you
[6:32] Speaker 3: can just sip them out of the air. And microbes
[6:34] Speaker 3: are so creative that if you like try to grow
[6:37] Speaker 3: them in water that doesn't have any nitrogen, they're like,
[6:39] Speaker 3: no problem for me.
[6:40] Speaker 2: I'll just fix it out of the atmosphere.
[6:43] Speaker 3: However, for phosphorus, it's a little harder because it has
[6:47] Speaker 3: to come out of a solid form, like out of
[6:49] Speaker 3: the rocks. So as rain occurs and like the sediment
[6:54] Speaker 3: is coming out of the rocks and into the water sources,
[6:57] Speaker 3: the cyanobacteria can grab the phosphorus from there. What's really
[7:02] Speaker 3: cool about them.
[7:03] Speaker 2: Is that they can hold on to the phosphorus.
[7:05] Speaker 3: So if it rains in the spring, it doesn't matter
[7:08] Speaker 3: if it's like August, the cells hold on to the
[7:11] Speaker 3: phosphorus and it doesn't like run out right away. But
[7:15] Speaker 3: if they go long enough without any rain or like
[7:17] Speaker 3: perturbation from the solid sources nearby, they will totally run
[7:21] Speaker 3: out of their phosphorus. And that concludes my statement about
[7:25] Speaker 3: cyanobacteria and phosphorus. I wish I could tell you all
[7:28] Speaker 3: about phages and how you could use them to control
[7:30] Speaker 3: algal blooms. And I also wish I could tell you
[7:33] Speaker 3: about agriculture and how phosphorus is a really important resource
[7:36] Speaker 3: that can be limiting for agriculture.
[7:40] Speaker 1: But humans give algae a leg up because we have
[7:43] Speaker 1: phosphorus in our fertilizer because our plants also need phosphorus
[7:47] Speaker 1: to grow.
[7:48] Speaker 2: Mm-hmm.
[7:49] Speaker 1: And so we apply fertilizer to our yards. We apply
[7:52] Speaker 1: fertilizer with phosphorus to our agricultural crops.
[7:55] Speaker 2: Yeah.
[7:56] Speaker 1: Our animals, like our cows, defecate out piles with phosphorus
[8:01] Speaker 1: in it. And then when it rains, that phosphorus accumulates
[8:05] Speaker 1: in the rain and then ends up in our waterways.
[8:08] Speaker 4: Hmm.
[8:09] Speaker 1: And so this is what causes eutrophication which is essentially
[8:12] Speaker 1: just lots of nutrients in the water which allows the
[8:16] Speaker 1: algae to grow like crazy because it's no longer limited
[8:18] Speaker 1: by phosphorus anymore and so often you'll get an algal
[8:21] Speaker 1: bloom because there's been nutrient loading in that system.
[8:24] Speaker 2: So the way you described it suggests that like humans
[8:27] Speaker 2: and cows are putting more phosphorus into the system than
[8:30] Speaker 2: you find naturally, I guess. And that's because of like
[8:34] Speaker 2: human civilization or whatever.
[8:36] Speaker 1: Yeah.
[8:37] Speaker 2: But like these things are living near humans for a
[8:40] Speaker 2: long time. Why isn't there just always more phosphorus? Like
[8:43] Speaker 2: why aren't we always in algal bloom?
[8:46] Speaker 1: We are in algal blooms a lot more now than
[8:48] Speaker 1: we were before. And some areas like Lake Erie, the
[8:52] Speaker 1: lakes have gone what's called eutrophic, which is to say
[8:55] Speaker 1: they almost always have more algae than would be desirable
[8:58] Speaker 1: growing in them. And so this does happen a lot.
[9:01] Speaker 1: And algal blooms are happening more and more often. And
[9:04] Speaker 1: that's a combination of... More phosphorus runoff, but it's also
[9:07] Speaker 1: a combination of warming temperatures, which increase the water temperature,
[9:11] Speaker 1: which makes it easier for algae to grow. And I
[9:13] Speaker 1: should say that, you know, Lake Erie, there was a
[9:14] Speaker 1: period where we were doing a really good job of
[9:16] Speaker 1: keeping runoff with phosphorus and nitrogen because nitrogen is sometimes
[9:21] Speaker 1: also a limiting factor. And our fertilizers have that, too.
[9:23] Speaker 1: We were doing a good job of keeping that from
[9:25] Speaker 1: getting into the waterways. And Lake Erie was looking nicer.
[9:28] Speaker 1: And then we started doing more fertilizer. I think the
[9:31] Speaker 1: problem in this case was agricultural fertilizer. We started doing
[9:34] Speaker 1: more agricultural stuff. And now Lake Erie is starting to
[9:36] Speaker 1: have algal bloom problems again.
[9:39] Speaker 2: And why is it a problem? Like, is it just
[9:41] Speaker 2: it doesn't look as nice? This is like a human
[9:43] Speaker 2: aesthetic thing? Or is it like, you know, tip off
[9:46] Speaker 2: the balance of the ecosystem and everything collapses and pretty
[9:49] Speaker 2: soon it's just goo on the planet?
[9:51] Speaker 1: Oh, good question. OK, so the answer is multifactorial. So
[9:55] Speaker 1: one of the problems is that, okay, so algae produce
[9:59] Speaker 1: oxygen during the day through the process of photosynthesis, but
[10:02] Speaker 1: at night, they actually suck oxygen out of The environment
[10:07] Speaker 1: when they were doing respiration. So if you have massive
[10:10] Speaker 1: amounts of algae at night, they suck the oxygen out
[10:15] Speaker 1: of the water and a big algal mat on the
[10:18] Speaker 1: surface will block sunlight to the plants growing below. And
[10:21] Speaker 1: so now they're not producing oxygen. And at some point,
[10:25] Speaker 1: often these algal blooms die. end and the algae die
[10:28] Speaker 1: off in large numbers. And when they die off, they
[10:31] Speaker 1: get decomposed by bacteria and those bacteria create low oxygen environments.
[10:36] Speaker 1: And so one of the problems is these algal blooms
[10:38] Speaker 1: are associated with sucking the oxygen out of the water
[10:41] Speaker 1: and you often end up with massive fish kills afterwards.
[10:44] Speaker 2: Oh, yeah.
[10:45] Speaker 1: So really bad for the environment. But also, if the
[10:48] Speaker 1: quote unquote algal bloom is caused by cyanobacteria, cyanobacteria release toxins.
[10:55] Speaker 1: And these toxins can either be really bad for your liver.
[10:58] Speaker 1: Some of them are neurotoxins. There are lots of different
[11:01] Speaker 1: species of cyanobacteria. They produce different kinds of toxins.
[11:04] Speaker 2: Do the toxins turn you blue?
[11:06] Speaker 1: You know, that would be interesting.
[11:09] Speaker 2: I mean, we are on brand for cyanobacteria, right? They
[11:12] Speaker 2: should turn you cyan.
[11:14] Speaker 1: Well, they're also called blue-green algae sometimes, which is, you know,
[11:17] Speaker 1: not a good name. It's like a physicist named them
[11:19] Speaker 1: or something, you know. But, for example, I grew up
[11:25] Speaker 1: in Toledo, and my parents still live there, and Toledo
[11:28] Speaker 1: has their water from Lake Erie. And a couple years ago,
[11:31] Speaker 1: there was a do-not-drink-the-water warning because there was so much
[11:35] Speaker 1: cyanobacteria growing in Lake Erie, and that toxin... that they make,
[11:39] Speaker 1: microcystin in this case, was in the water and it
[11:41] Speaker 1: would have been like dangerous for your liver to drink
[11:43] Speaker 1: the water. And so a lot of money is spent
[11:46] Speaker 1: every year on filtering water in very particular ways to
[11:49] Speaker 1: remove cyanobacteria and toxins in areas where they're present. So
[11:53] Speaker 1: it's a ecological, financial, and human health problem.
[11:57] Speaker 2: So we're on one hand making it worse by putting
[12:01] Speaker 2: phosphorus everywhere. And on the other hand, struggling against it,
[12:04] Speaker 2: constantly trying to remove it. Exactly.
[12:06] Speaker 1: Yep. And and we're also making it worse by warming
[12:10] Speaker 1: our planets. And those warmer temperatures also result in more
[12:13] Speaker 1: algal growth. Other things that contribute to algal bloom are sunlight.
[12:18] Speaker 1: So you're more likely to get algal growth on a
[12:20] Speaker 1: sunny day than a cloudy day. And calm water tends
[12:24] Speaker 1: to be more conducive to the growth of like algal
[12:27] Speaker 1: mats and clumps of algae. And so let's go through
[12:32] Speaker 1: our list again. We've got phosphorus, warm water, sunlight, and
[12:35] Speaker 1: calm water. The reflecting pool in Washington, D.C. was the
[12:40] Speaker 1: perfect storm.
[12:42] Speaker 2: It's like what you would design if you wanted an
[12:44] Speaker 2: algal bloom.
[12:45] Speaker 1: Yes, that's right. If you wanted an algal bloom, these
[12:47] Speaker 1: are the conditions you would create.
[12:49] Speaker 2: Okay.
[12:50] Speaker 1: So first of all, it was painted so that it
[12:52] Speaker 1: would look American flag blue.
[12:54] Speaker 2: Right.
[12:54] Speaker 1: This was a darker shade than was previously covering the
[12:58] Speaker 1: bottom of the reflecting pool. And darker shades mean the
[13:01] Speaker 1: water was warming up more because that darker paint was,
[13:05] Speaker 1: what is it, absorbed? What is the physics answer for
[13:07] Speaker 1: why darker paint is bad, Daniel?
[13:09] Speaker 2: Right. Well, something is lighter because it's reflecting more of
[13:13] Speaker 2: the light. And it's darker. It's absorbing more of the light.
[13:15] Speaker 2: So it heats up.
[13:16] Speaker 1: There you go.
[13:17] Speaker 2: The way that, like, a black car will heat up
[13:19] Speaker 2: faster than a white car in the sun. Okay.
[13:21] Speaker 4: Yep.
[13:21] Speaker 1: And that water is meant to be still so that
[13:23] Speaker 1: you can see the reflection of the Lincoln Memorial and
[13:27] Speaker 1: the George Washington Monument. So that's calm water. And it's warm.
[13:31] Speaker 1: I think this was, what, June or July when this
[13:33] Speaker 1: was happening? Oh, it was meant for the July 4th celebration. So, yes,
[13:36] Speaker 1: this was happening in, like, June. So it was warming up.
[13:39] Speaker 1: And so what they think happens is that there was
[13:41] Speaker 1: algae that was still in the hoses, the lines that
[13:46] Speaker 1: feed the reflecting pool.
[13:47] Speaker 2: Okay.
[13:48] Speaker 1: And so while they were painting it, the algae was
[13:50] Speaker 1: growing in the lines. And then they turned the water on,
[13:53] Speaker 1: they filled it up, and they essentially injected the algae
[13:57] Speaker 1: into the reflecting pool.
[13:58] Speaker 2: Nice.
[13:58] Speaker 1: The water either comes from the tidal basin, which is
[14:02] Speaker 1: a man-made reservoir outside D.C. that has... Phosphorus from runoff
[14:08] Speaker 1: from the area, or sometimes they get it from the
[14:11] Speaker 1: city water supply. And if you get it from the
[14:14] Speaker 1: city water supply, there's still a chance that there will
[14:16] Speaker 1: be phosphorus in it because we use orthophosphates to line
[14:21] Speaker 1: the inside of metal pipes. So here's what you need
[14:24] Speaker 1: to know. They coat the metal pipes. They change the
[14:27] Speaker 1: pH right at the point where like the pipe and
[14:29] Speaker 1: the water meet. And that's important because if you have
[14:32] Speaker 1: lead pipes, you want to make sure that the water
[14:35] Speaker 1: is not causing the lead to leach out of the pipes.
[14:38] Speaker 1: And so putting orthophosphate in the water source means that
[14:41] Speaker 1: the pipes get a little bit coated. They're less likely
[14:44] Speaker 1: to leach out the lead. But now there's phosphorus in
[14:47] Speaker 1: the water, which promotes the growth of algae. So no
[14:51] Speaker 1: matter where the water came from when they refilled the
[14:53] Speaker 1: reflecting pool, there's a good chance that phosphorus was added
[14:56] Speaker 1: to the reflecting pool as well.
[14:58] Speaker 2: Even though this is orthophosphates, not just phosphates, are these
[15:01] Speaker 2: like that have had their teeth straightened or what's an orthophosphate?
[15:05] Speaker 2: I mean, the scientific name is perfectly clear, right? So
[15:08] Speaker 2: help us out here.
[15:09] Speaker 1: Oh, you're being not nice. So I looked at a
[15:15] Speaker 1: chemistry website to get the word orthophosphate. I'm so sorry.
[15:19] Speaker 1: You're right, you're right. And so it was chemical and
[15:21] Speaker 1: engineering news. And so I should have just said a
[15:24] Speaker 1: form of phosphate. I am retreating into my ignorance. But anyway.
[15:30] Speaker 2: Victory against chemistry.
[15:32] Speaker 1: That's right. That's right. Well, I feel like chemistry won
[15:34] Speaker 1: and I'm running away, but.
[15:38] Speaker 2: No, we have pushed back the chemistry. Go away, chemistry.
[15:41] Speaker 1: Go away, chemistry.
[15:41] Speaker 2: I'm running. So what could they have done to combat
[15:44] Speaker 2: the algal blooms in the reflecting pool, Kelly?
[15:48] Speaker 1: Yeah, what could they have done? So they could have,
[15:51] Speaker 1: I don't know, maybe put treatments in earlier to kill,
[15:55] Speaker 1: try to kill all of the algae. It looks like
[15:57] Speaker 1: after the algae grew, they tried to remove it using
[16:00] Speaker 1: like mechanical means, like vacuuming it out. And then I
[16:03] Speaker 1: think they dumped hydrogen peroxide in there, which I believe
[16:07] Speaker 1: is what messed up the lining at the bottom of
[16:09] Speaker 1: the reflecting pool because it was still in the process
[16:11] Speaker 1: of curing.
[16:12] Speaker 2: But I saw these pictures of them, like, emptying one-gallon
[16:15] Speaker 2: jugs of hydrogen peroxide, which I was like, I don't
[16:18] Speaker 2: know what that's really going to do anyway.
[16:20] Speaker 1: Well, and I think the algal blooms came back after that.
[16:24] Speaker 1: So some solutions that I've seen include keeping the water
[16:28] Speaker 1: more well aerated because more well aerated water supports bacteria
[16:34] Speaker 1: that compete with the algae. So you're less likely to
[16:36] Speaker 1: get an algal bloom.
[16:37] Speaker 2: I heard they were using these machines called nanobubblers, but
[16:40] Speaker 2: I never understood what they are and why the bubbles
[16:43] Speaker 2: are so nano.
[16:44] Speaker 1: Yeah, I think they dump in nanobubbles and there's something
[16:49] Speaker 1: about like the surface area of the bubble and the
[16:51] Speaker 1: bubble is impregnated with a certain kind of gas. I
[16:53] Speaker 1: didn't get into that science, but it was meant to
[16:56] Speaker 1: be a way to keep the oxygen supply in the
[16:58] Speaker 1: reflecting pool up for longer. And I think you can
[17:01] Speaker 1: put other things other than oxygen in there, like some
[17:03] Speaker 1: chemicals to try to kill the algae. But I'm not
[17:05] Speaker 1: an expert on that.
[17:07] Speaker 2: It's a shame that the scientific term nanobubbler isn't clear.
[17:10] Speaker 2: You know, it should just make sense on the surface,
[17:12] Speaker 2: you know, but it doesn't somehow.
[17:14] Speaker 1: Are you throwing shade on me? I can't tell anymore.
[17:16] Speaker 2: I can't tell anymore either.
[17:19] Speaker 4: Okay.
[17:19] Speaker 1: All right. So anyway, this is a long standing problem
[17:22] Speaker 1: because if you do have bubblers in there, then your
[17:25] Speaker 1: reflecting pool is not going to be perfectly still. And
[17:27] Speaker 1: that's kind of the whole point. And so, you know,
[17:29] Speaker 1: this thing I think was built in 1922. We've been
[17:32] Speaker 1: sort of set up for algal blooms ever since then.
[17:35] Speaker 1: And they have been a recurring problem. It's just difficult
[17:38] Speaker 1: to solve.
[17:39] Speaker 5: Okay.
[17:40] Speaker 4: Yeah.
[17:40] Speaker 2: Yeah.
[17:41] Speaker 1: Okay, so, Dirt LK. Does that answer your question? Let
[17:46] Speaker 1: me know.
[17:46] Speaker 6: Wow, thanks for the great discussion as always. So the
[17:49] Speaker 6: problem with the reflecting pool in Washington comes down to
[17:52] Speaker 6: bad chemistry. Hopefully there is a fix for that. This
[17:55] Speaker 6: reminded me of an organic chemistry lab where we had
[17:58] Speaker 6: to measure dissolved oxygen from different points around a pond
[18:01] Speaker 6: in the university park at Sydney University. Collecting samples in
[18:06] Speaker 6: bud flasks needed a very specific technique. No one needed
[18:10] Speaker 6: to titrate with the Wigler method. I've been a listener
[18:14] Speaker 6: since your episode with Ty and Daniel on The Expanse.
[18:18] Speaker 6: Thanks to the great podcast that keeps me entertained and
[18:21] Speaker 6: up to date on the latest science.
[18:43] Speaker 1: Next up, we have a question from Rosalyn about memory
[18:46] Speaker 1: and consciousness.
[18:47] Speaker 7: Hi, Danielle and Kelly. I have a question for you
[18:50] Speaker 7: about the relationship between memory and consciousness. From my understanding,
[18:54] Speaker 7: consciousness is a sense of oneself and working memories occur
[19:00] Speaker 7: in order for us to make sense of ourself in
[19:02] Speaker 7: the world around us, to help learn from past mistakes
[19:07] Speaker 7: and to aid in our survival in the future. So
[19:10] Speaker 7: my question is, Wouldn't the ability to create working memories
[19:15] Speaker 7: require on some level a sort of consciousness? Wouldn't something
[19:20] Speaker 7: need to know that it exists in that state and
[19:25] Speaker 7: that in order to continue to exist in that state,
[19:28] Speaker 7: it needs to retain a certain information about the world
[19:32] Speaker 7: and itself in relation to the world so that it
[19:35] Speaker 7: can continue to do so?
[19:37] Speaker 2: Am I like wildly off base here?
[19:39] Speaker 7: I just have a hard time understanding How one would
[19:43] Speaker 7: retain or how anything could retain a memory without having
[19:47] Speaker 7: a sense of self. that would necessitate why that particular
[19:53] Speaker 7: memory is important for the future thank you i appreciate you.
[19:57] Speaker 1: Guys daniel you love talking and thinking about consciousness.
[20:03] Speaker 2: You know, I'm a physicist, which means that I love
[20:06] Speaker 2: talking about stuff I have no training in and trying
[20:09] Speaker 2: to speak about it confidently. Wow.
[20:13] Speaker 1: Actually, one of many things I really appreciate you is
[20:16] Speaker 1: that you do rein that tendency in. I feel like
[20:19] Speaker 1: you are really– You're really good about being like, I'm
[20:21] Speaker 1: not a biologist. I don't know. Unlike Feynman, who's like,
[20:24] Speaker 1: I'm not a biologist. I don't know. But I'm going
[20:26] Speaker 1: to pretend I do.
[20:27] Speaker 3: Right.
[20:27] Speaker 2: And I'm smarter than the biologists.
[20:28] Speaker 1: That's right.
[20:29] Speaker 2: So, yeah, this is about memory and consciousness and also
[20:32] Speaker 2: like a sense of self. So there's a bunch of
[20:34] Speaker 2: topics in here. They're all getting sort of bundled together.
[20:37] Speaker 2: And Rosalind is asking, you know, which of these things
[20:40] Speaker 2: actually require the others? And I'm not a cognitive scientist,
[20:44] Speaker 2: nor a biologist, nor a philosopher, but I'm interested in
[20:47] Speaker 2: all of these things and like thinking about them. So
[20:50] Speaker 2: these are my thoughts, but, you know, that doesn't mean
[20:52] Speaker 2: that they are reasonable thoughts. I think this is what
[20:56] Speaker 2: Rosalyn wrote in here about, and she knows we're not experts.
[20:59] Speaker 2: So let's go.
[21:01] Speaker 1: That's right.
[21:02] Speaker 7: All right.
[21:02] Speaker 1: So I think first I'd like to try to, like,
[21:04] Speaker 1: untangle memory, consciousness, and sense of self. I feel like
[21:08] Speaker 1: those three terms feel like they could be interchangeable.
[21:11] Speaker 2: Yeah, but the question is basically how they differ and
[21:14] Speaker 2: whether one meets the other. So like, what is memory anyway?
[21:17] Speaker 2: There's lots of different kinds of memory, right? Like most broadly,
[21:21] Speaker 2: you could say memory is like a record of the past,
[21:24] Speaker 2: maybe something that affects how you act in the future. But,
[21:28] Speaker 2: you know, there's like working memory that holds information temporarily,
[21:32] Speaker 2: like a way you can remember what somebody said, like
[21:35] Speaker 2: digits of a phone number for a few seconds. You
[21:37] Speaker 2: have this like loop in your brain. There's like episodic memories,
[21:41] Speaker 2: remembering something that happened to you. There's just semantic memory,
[21:45] Speaker 2: like stored knowledge and facts, you know, like things you
[21:48] Speaker 2: know in your head. You know, the way Kelly has
[21:50] Speaker 2: like a huge pile of ridiculous scientific names, just like
[21:53] Speaker 2: filling up her noggin and preventing her from knowing other
[21:56] Speaker 2: useful stuff.
[21:57] Speaker 1: Oh my gosh, you are on a roll today. Look,
[21:59] Speaker 1: sometimes those Latin names have information in them that's helpful.
[22:03] Speaker 2: Yeah, sometimes, sometimes. And then there's like procedural memory, you know,
[22:08] Speaker 2: like how to ride a bicycle or even implicit memory,
[22:11] Speaker 2: things you don't explicitly remember but do change your behavior.
[22:15] Speaker 2: And so there's lots of different kinds of memory. And
[22:18] Speaker 2: not all of them seem to require you to be
[22:20] Speaker 2: like conscious or self-aware because, you know, like the memory
[22:25] Speaker 2: that you have doesn't always require you knowing like why
[22:29] Speaker 2: the information matters, right? Like, you know, evolution can design
[22:34] Speaker 2: a system that responds to history. In that sense, it
[22:38] Speaker 2: has a memory, but you might not be like consciously
[22:42] Speaker 2: aware of it. Like, for example, your immune system remembers
[22:46] Speaker 2: the bits and the pathogens that it's seen, right? It
[22:49] Speaker 2: has like some catalog inside of it. That is like
[22:53] Speaker 2: a memory. It says, oh, we've seen this. We know
[22:54] Speaker 2: how to respond to hear all the antibodies. But you
[22:57] Speaker 2: don't know that. You don't remember that. Like maybe you
[23:00] Speaker 2: remember being sick, but you don't remember the surface of
[23:03] Speaker 2: these things, right? And you're not aware of them. And
[23:06] Speaker 2: so information can be useful and it can be recorded
[23:10] Speaker 2: and it can affect the future without it being like
[23:12] Speaker 2: part of your conscious experience.
[23:14] Speaker 1: I'm going to regret saying this, but I've always thought
[23:17] Speaker 1: that immune system memory was a bad use of the
[23:20] Speaker 1: word memory, where we should have just come up with
[23:22] Speaker 1: a different word because that seems like something very different
[23:26] Speaker 1: than implicit memory or procedural memory, for example.
[23:29] Speaker 2: Well, I would say it's sort of more like semantic memory.
[23:31] Speaker 2: It's like stored knowledge and facts, you know, the way
[23:34] Speaker 2: like your computer has a memory, right? You put numbers
[23:37] Speaker 2: into the computer, they're still there. We call it memory
[23:39] Speaker 2: for a reason, right? It can recall it. you can
[23:42] Speaker 2: store it and recall it in that same way your
[23:44] Speaker 2: immune system has a memory of the pathogens it's seen,
[23:48] Speaker 2: even if you're not aware of them. I don't think
[23:50] Speaker 2: my computer is aware of the number 17 that I
[23:52] Speaker 2: put in this register over there. So yeah, that's an
[23:55] Speaker 2: example of like semantic memory that doesn't require you to
[23:59] Speaker 2: be aware. So we've been talking about awareness What do
[24:03] Speaker 2: we mean by that? Like, what is consciousness anyway? Man,
[24:06] Speaker 2: that's like, you know, not a subtopic. That's like such
[24:10] Speaker 2: a deep question that we can't answer today. It's even
[24:12] Speaker 2: harder to define what we mean than memory, which is
[24:15] Speaker 2: already tricky and slippery. You know, you could think of
[24:18] Speaker 2: it as like subjective experience. What is it like to
[24:21] Speaker 2: see something or to feel something or to hear something
[24:24] Speaker 2: or smell something? Philosophers use this word qualia. to describe
[24:28] Speaker 2: the experience of seeing red or eating chocolate or something.
[24:33] Speaker 2: And so that's like the basic concept of consciousness. But
[24:38] Speaker 2: then there's also this other side of it, which is
[24:40] Speaker 2: like a sense of self that Rosalind is talking about.
[24:43] Speaker 2: Sort of like a self-consciousness. So consciousness is like, I'm
[24:48] Speaker 2: feeling pain. Self-consciousness is like, I am a thing and
[24:52] Speaker 2: I am the thing experiencing the pain.
[24:55] Speaker 1: Okay.
[24:55] Speaker 2: You're like aware of the existence of yourself, not just
[24:58] Speaker 2: like raw, I'm feeling pain or I'm eating chocolate, but
[25:01] Speaker 2: like I'm a thing that is eating the chocolate. And
[25:04] Speaker 2: beyond that, I think Rosalind is referencing something deeper, which
[25:08] Speaker 2: is like an autobiographical identity. This feeling that like Daniel
[25:12] Speaker 2: is eating chocolate today is the same Daniel that went
[25:15] Speaker 2: for a jog yesterday to balance out that chocolate. You know, like,
[25:19] Speaker 2: I'm the same person who existed yesterday and tomorrow, and
[25:23] Speaker 2: my memories help define who I am, right? So, you know,
[25:26] Speaker 2: there's like actually experiencing things, that's consciousness. There's realizing that
[25:31] Speaker 2: you are a thing experiencing, so it's like turning that
[25:33] Speaker 2: consciousness inwards. And then there's the autobiographical self, which is
[25:37] Speaker 2: like telling a story about how you evolved through time.
[25:41] Speaker 2: So there's lots of different layers there of consciousness that
[25:44] Speaker 2: all have different relationships to the concept of memory.
[25:47] Speaker 5: Yeah.
[25:48] Speaker 1: So then is the question, which of those can exist
[25:51] Speaker 1: without the others?
[25:52] Speaker 2: Yeah, exactly. So like, can you be conscious without memory?
[25:56] Speaker 2: I think certainly you can, right? There are people, for example,
[25:59] Speaker 2: who can form long-term memories, right? But they're still here
[26:03] Speaker 2: in the world. They can eat chocolate. They can perceive.
[26:05] Speaker 2: They can have conversations. They can solve problems. They can
[26:08] Speaker 2: have emotions, right? They can appear conscious in the present
[26:11] Speaker 2: even if tomorrow or in five minutes they don't remember it, right?
[26:15] Speaker 2: So forming lasting memories doesn't appear necessary to be moment-to-moment conscious.
[26:22] Speaker 2: So you can have consciousness, you can have self-consciousness without
[26:25] Speaker 2: like even a sense of autobiographical identity or long-term memories.
[26:29] Speaker 1: Amazing, yeah.
[26:30] Speaker 2: Imagine, for example, like experiencing 10 seconds of the world
[26:34] Speaker 2: normally and then forgetting those 10 seconds. doesn't mean you
[26:38] Speaker 2: weren't aware. And maybe you were even aware of who
[26:40] Speaker 2: you were and your history. The fact that you don't
[26:43] Speaker 2: remember it later doesn't mean that the original experience was unconscious.
[26:48] Speaker 5: Yeah.
[26:48] Speaker 1: Okay.
[26:49] Speaker 2: And maybe you've had this experience where you're like driving somewhere,
[26:52] Speaker 2: but you're a little distracted. And then you get there
[26:55] Speaker 2: and you're like, I don't remember any of those red lights. Boy,
[26:59] Speaker 2: I hope I didn't like run over a bunch of
[27:00] Speaker 2: pedestrians without noticing.
[27:02] Speaker 1: I hate those moments.
[27:03] Speaker 2: Right? Aren't those terrifying?
[27:05] Speaker 1: How did I get here?
[27:06] Speaker 4: Yeah.
[27:07] Speaker 2: Probably your brain was doing it and you might have
[27:10] Speaker 2: even been aware of it in the moment, but you
[27:12] Speaker 2: weren't paying attention to it in a way that would
[27:13] Speaker 2: get recorded so that later you can retrieve it.
[27:16] Speaker 1: Please don't take away our licenses.
[27:18] Speaker 4: I know.
[27:19] Speaker 2: So probably in the moment if somebody said, hey, Kelly,
[27:22] Speaker 2: are you paying attention? You'd be like, yes, of course.
[27:24] Speaker 2: What are you talking about? And you probably did stop
[27:26] Speaker 2: for all those red lights.
[27:27] Speaker 4: Yeah.
[27:27] Speaker 2: But it wasn't interesting enough to be recalled. So you
[27:31] Speaker 2: were aware, you were conscious, you were self-conscious, but you
[27:34] Speaker 2: don't remember it.
[27:35] Speaker 1: Yes. Scary though that is.
[27:37] Speaker 2: Yeah. So let's flip it around. Can memory exist without consciousness? Right.
[27:42] Speaker 2: Like certainly you can learn stuff without consciously remembering every
[27:47] Speaker 2: time you learned it. Like I don't remember when I
[27:49] Speaker 2: learned arithmetic, but I can do it. Right. A lot
[27:53] Speaker 2: of implicit memory influences later choices, even if you don't
[27:56] Speaker 2: recall exactly why you've learned it.
[27:59] Speaker 1: But did you need to be conscious in the moment
[28:02] Speaker 1: to make that memory? Probably not. See, I feel like
[28:07] Speaker 1: I don't ever want to lead a discussion on consciousness
[28:10] Speaker 1: because every question is a, oh, Kelly needs 10 minutes
[28:13] Speaker 1: to think about this. Do I really know what these
[28:17] Speaker 1: terms mean? That's what I always go back to.
[28:19] Speaker 2: I would say that memory by itself is weak evidence
[28:24] Speaker 2: for consciousness. I don't know that you need to have
[28:27] Speaker 2: been conscious in order to remember something. You're not even
[28:31] Speaker 2: always aware of, you know, why you are doing something
[28:35] Speaker 2: or how something has influenced your behavior. And so it's
[28:38] Speaker 2: like somehow there in your memory, it's changed the way
[28:42] Speaker 2: you operate, but you don't remember learning it. And you
[28:47] Speaker 2: might not have even been paying attention to the facts
[28:50] Speaker 2: that have influenced you. But it does feel like our
[28:53] Speaker 2: sense of self, you know, being one person across time,
[28:56] Speaker 2: like Daniel said, is not the same person he was
[28:59] Speaker 2: a year ago. He knows more chemistry and biology now
[29:02] Speaker 2: than he did, but it's still the same person. You know,
[29:05] Speaker 2: I still feel like I am who I am. And
[29:08] Speaker 2: so memory sort of like stitches all those moments together
[29:11] Speaker 2: into this like biological narrative. And so this makes me
[29:15] Speaker 2: think of like Daniel Dennett's theory of consciousness. He wrote
[29:18] Speaker 2: this great book called Consciousness Explained.
[29:21] Speaker 1: What a Ballsy title.
[29:22] Speaker 2: Oh, wow. Yeah, I know. I loved it. And the
[29:26] Speaker 2: idea he attacks in that book is a sort of
[29:29] Speaker 2: intuitive notion of consciousness. I think a lot of people have,
[29:32] Speaker 2: which is that there's like a little dude inside your
[29:35] Speaker 2: brain watching the world like a movie theater. Right. He
[29:38] Speaker 2: calls this the Cartesian thing. like there's some little homunculus
[29:42] Speaker 2: in your brain and it's like you can't really experience
[29:44] Speaker 2: the world except it just gets the senses and it
[29:47] Speaker 2: sits there hearing and seeing and feeling but it's not
[29:51] Speaker 2: really an answer to the question of consciousness it just
[29:53] Speaker 2: sort of kicks it down the road Right. Because if
[29:55] Speaker 2: there's like a little person in your head watching a
[29:57] Speaker 2: movie about all of your senses, then like who's watching
[30:01] Speaker 2: the movie inside that little person's head.
[30:04] Speaker 5: Right.
[30:04] Speaker 3: Yeah.
[30:04] Speaker 1: Where did that do that come from?
[30:06] Speaker 2: Exactly. And so he's got this kind of bonkers theory
[30:09] Speaker 2: of consciousness. It's called the multiple drafts model. And it
[30:13] Speaker 2: says in the brain is constantly trying to make sense
[30:15] Speaker 2: of what happened and stitch it together into a story
[30:18] Speaker 2: about what has just happened to you. And so it's like,
[30:22] Speaker 2: it tries this, it tries that, it tries to weave
[30:24] Speaker 2: it all together into something that's simplified, that it can
[30:28] Speaker 2: tell as a story. But there's no actual moment of
[30:31] Speaker 2: consciousness in Dennett's theory. It is just a memory of
[30:34] Speaker 2: the story of what just happened. There is no like,
[30:37] Speaker 2: I am experiencing this now. It's just like, I'm recalling
[30:41] Speaker 2: what just happened like a bill a second ago. It's
[30:45] Speaker 2: this interesting theory because in his view, what we call
[30:49] Speaker 2: consciousness emerges from this like, distributed activity where you're like
[30:53] Speaker 2: processing this and processing that and then writing down your
[30:57] Speaker 2: like history. And there is no like, I am having
[31:01] Speaker 2: this experience now that's writing histories. You're like going back
[31:03] Speaker 2: and weaving it together. It's like a journalist telling a
[31:07] Speaker 2: story about what happened and forming a consensus among the journalists.
[31:11] Speaker 2: But there is no like, I'm feeling it right now.
[31:15] Speaker 2: And so in relation to Rosalind's question, It tells you
[31:18] Speaker 2: that consciousness itself is nothing but recalling the immediate past,
[31:24] Speaker 2: which is experiencing memory. And so I think Daniel Dennett,
[31:28] Speaker 2: may he rest in peace. would say that memory is
[31:31] Speaker 2: absolutely essential for consciousness because that's what consciousness is. It's
[31:35] Speaker 2: just the recollection of the immediate past. And like, there's
[31:39] Speaker 2: lots of criticisms of Dennett's idea, by far not like
[31:42] Speaker 2: a widely held view. My favorite criticism is that his
[31:46] Speaker 2: book should have been called Consciousness Explained Away instead of
[31:49] Speaker 2: Consciousness Explained. And so, you know, Rosalind, this is really hard.
[31:56] Speaker 2: Nobody knows the answer. These are just my unqualified thoughts.
[32:00] Speaker 2: You know, memory and consciousness are not the same thing.
[32:02] Speaker 2: Some kinds of memory you can have without consciousness or
[32:06] Speaker 2: a sense of self, right? It also seems like you
[32:09] Speaker 2: can be aware without remembering things. But it does seem
[32:12] Speaker 2: like memory is crucial to our experience of being a
[32:16] Speaker 2: continuous person, part of what defines who you are and
[32:20] Speaker 2: your identity. And so I think memory does help define
[32:23] Speaker 2: who we are and how that changes over time. And
[32:26] Speaker 2: so there's definitely a close relationship between these two concepts.
[32:29] Speaker 1: And I think it's important to mention, didn't Daniel Dennett
[32:32] Speaker 1: say something nice about, do aliens speak physics?
[32:35] Speaker 2: That's right. I wrote a whole chapter about whether we're
[32:38] Speaker 2: smart enough to understand what aliens... think and he's talked
[32:41] Speaker 2: about this like the limits of biological intelligence and i
[32:45] Speaker 2: sent him the book and i was like when you
[32:47] Speaker 2: take a look at this especially the parts where i
[32:49] Speaker 2: reference your work and let me know if i got
[32:50] Speaker 2: it right and he wrote me back just three words
[32:52] Speaker 2: he said this is good i'm so relieved you know
[32:57] Speaker 2: that thing where you step outside your field and you
[32:59] Speaker 2: write something and then you send it to experts and
[33:00] Speaker 2: you're like please tell me if i got this wrong
[33:02] Speaker 2: yep and you're terrified you're gonna get like 10 pages
[33:05] Speaker 2: of rant yep yep so The shorter the response, the better. Anyway,
[33:10] Speaker 2: that was a relief.
[33:11] Speaker 1: I once wrote a Nobel Prize winner to ask if
[33:13] Speaker 1: I could interview them about a topic. And they wrote
[33:16] Speaker 1: back and said, you didn't pick the most interesting thing
[33:19] Speaker 1: to talk about. And then didn't respond to my emails anymore.
[33:22] Speaker 2: Oh, no.
[33:23] Speaker 1: I was like, wow. I guess you have a lot
[33:26] Speaker 1: going on. All right. Anyway, so thank you to the
[33:28] Speaker 1: people who actually respond to emails.
[33:30] Speaker 2: That's right. Thank you.
[33:51] Speaker 1: All right, next up, we have a question from Paul
[33:54] Speaker 1: from New Hampshire, who's really into slugs.
[33:57] Speaker 5: Hey, Daniel and Kelly, since you often mention bananas, How
[34:00] Speaker 5: about an episode on banana slugs, plus slugs and snails
[34:03] Speaker 5: in general? Seems like a relevant topic given the UC
[34:07] Speaker 5: Santa Cruz connection. Though not a UC alumnus, I used
[34:10] Speaker 5: to live in Silicon Valley and would often hike in
[34:13] Speaker 5: the coastal forests, so I got to see banana slugs
[34:15] Speaker 5: in the wild. When I describe them, some people look
[34:18] Speaker 5: at me like I've been smoking banana peels, and I'm
[34:21] Speaker 5: sure Kelly can find some interesting slug parasites like rat lungworm.
[34:25] Speaker 2: I'm into slugs too. I'm banana slugs. Yeah. Go UC. Yeah.
[34:29] Speaker 1: Yeah.
[34:30] Speaker 2: Right.
[34:30] Speaker 1: So University of California, Santa Cruz, their mascot are the
[34:34] Speaker 1: banana slugs.
[34:34] Speaker 2: Awesome.
[34:35] Speaker 1: And I will note that I have been working on
[34:37] Speaker 1: answering Paul's very broad question from a number of different angles.
[34:43] Speaker 1: A while ago, we did an episode, and this was
[34:45] Speaker 1: partly in response to a question from Jane about slugs
[34:48] Speaker 1: and snails and whence shells came from and what the
[34:53] Speaker 1: purpose of the shells is and how the shells are made.
[34:55] Speaker 1: And so that was my beginning of the sluggy answers.
[34:59] Speaker 1: And then Paul also mentioned rat lungworm. We did a
[35:02] Speaker 1: whole episode on rat lungworm, which.
[35:05] Speaker 2: Terrifying episode.
[35:06] Speaker 1: I promise we will not talk about rat lungworm in
[35:08] Speaker 1: any detail again. I think the message that I am
[35:12] Speaker 1: getting is that was maybe the least enjoyed. Our guest
[35:15] Speaker 1: was amazing. It was very informative, but it made many
[35:17] Speaker 1: people squirm.
[35:18] Speaker 2: Yeah.
[35:19] Speaker 1: Which I totally get. And so now I am wrapping
[35:21] Speaker 1: up this question by talking about banana slugs. What do
[35:25] Speaker 1: you know about the banana slugs, Daniel?
[35:28] Speaker 2: They're big. They're yellow.
[35:30] Speaker 1: Sometimes yellow.
[35:31] Speaker 2: They're sometimes yellow. Okay. Can you lick them and get
[35:34] Speaker 2: some sort of interesting experience or is that something else?
[35:39] Speaker 1: No, I think no. Let's say no. So I believe
[35:43] Speaker 1: that there is a thing where sometimes people will go
[35:47] Speaker 1: ahead and smooch banana slugs and their lips tingle afterwards.
[35:51] Speaker 2: Oh, yeah, that's what it is.
[35:52] Speaker 1: Banana slugs will eat poison oak. They also eat mushrooms
[35:57] Speaker 1: that are very toxic to us. You should never pick
[36:00] Speaker 1: up a wild banana slug and stick it up to
[36:03] Speaker 1: your mouth because you don't know where that thing has been.
[36:05] Speaker 1: That's true. I don't know what's going on with the
[36:09] Speaker 1: tingliness there. But so, you know, maybe now's a good
[36:12] Speaker 1: time to talk about the like slime that they produce.
[36:14] Speaker 3: Yeah.
[36:15] Speaker 1: So the slime they produce has these amazing like granules
[36:18] Speaker 1: in them that suck up water. And this is part
[36:21] Speaker 1: of how banana slugs manage to stay moist is that
[36:24] Speaker 1: the slime is constantly like sucking up water. So it's
[36:28] Speaker 1: possible that when you put a banana slug on your lips, again,
[36:31] Speaker 1: do not do that. The tingling feeling you're feeling is
[36:34] Speaker 1: the moisture being sucked out of your lips, maybe. But
[36:39] Speaker 1: don't do that.
[36:40] Speaker 2: But that slime, they also— You're making it sound fun, though.
[36:44] Speaker 1: Well, that's not my fault. People make bad choices. I
[36:49] Speaker 1: am absolving myself of any responsibility.
[36:52] Speaker 2: Please sign this waiver before listening to this episode. That's right.
[36:55] Speaker 1: That's right. So this slime, like one, it helps them
[36:58] Speaker 1: move around their environment, like it lubricates the environment. It
[37:00] Speaker 1: helps them stay moist by sucking the moisture out of
[37:03] Speaker 1: the environment to try to keep them moist. But it
[37:05] Speaker 1: also is this great anti-predator technique. So when like a
[37:09] Speaker 1: salamander or a garter snake or a raccoon tries to
[37:13] Speaker 1: eat them, the slime like essentially starts multiplying as the
[37:18] Speaker 1: saliva inside the predator's mouth starts like getting sucked into
[37:22] Speaker 1: the slime to grow the size of the slime.
[37:24] Speaker 3: Wow.
[37:25] Speaker 1: And so there have been like videos of snakes that
[37:27] Speaker 1: are just their mouths are like full of slime and
[37:30] Speaker 1: like they're spitting the slugs out like, no, just forget it.
[37:33] Speaker 1: This was a mistake. I quit. I guess raccoons have
[37:36] Speaker 1: been observed to be very cleverly rolling the slug in
[37:41] Speaker 1: the dirt. And I think what it's doing is rolling
[37:43] Speaker 1: off the slime so that then it can eat it.
[37:45] Speaker 1: You know, I guess it could also just like. squeeze
[37:48] Speaker 1: it out like a paper towel or something. But anyway,
[37:51] Speaker 1: so this slime is kind of an amazing material that
[37:55] Speaker 1: helps them both stick to things and slide along their
[37:58] Speaker 1: environment and protects them from predators. Way to go, banana slugs.
[38:03] Speaker 7: Yeah.
[38:03] Speaker 1: But I think what these slugs are probably most well-known
[38:06] Speaker 1: for is their reproduction. And so if y'all have kids
[38:11] Speaker 1: around and you don't want them to hear about slug reproduction,
[38:13] Speaker 1: this is just a heads up that here it comes.
[38:16] Speaker 3: Uh.
[38:17] Speaker 1: So the slugs are hermaphrodites. They have really big wieners
[38:22] Speaker 1: in a lot of cases. And they have vaginas because
[38:25] Speaker 1: they're hermaphrodites. So they've got both sets of equipment. They
[38:28] Speaker 1: are able to self-fertilize. But what they usually do is
[38:32] Speaker 1: find a mate. When they find a mate, they begin
[38:35] Speaker 1: like fertilizing each other essentially at the same time. Although
[38:38] Speaker 1: sometimes you can observe slugs where just one of them
[38:41] Speaker 1: is using their penis and the other one is not.
[38:44] Speaker 2: All right, I got to ask, because you mentioned it
[38:46] Speaker 2: twice now. Yep. You say the slug has a really
[38:48] Speaker 2: big wiener. In relation to the slug, what does the
[38:51] Speaker 2: slug wiener look like? Like, give me a visual here.
[38:55] Speaker 1: Let's go to Google.
[38:56] Speaker 2: I'm glad this is not in my search history.
[39:02] Speaker 1: Oh my God, this is not the worst of... Okay,
[39:05] Speaker 1: so I would say it's about... Looking at the one
[39:07] Speaker 1: photo that I'm seeing right now, the wiener is about
[39:10] Speaker 1: the size of their head.
[39:11] Speaker 2: Okay, all right.
[39:12] Speaker 1: Yeah, I mean, that's pretty... Impressive.
[39:17] Speaker 2: Kelly is impressed.
[39:18] Speaker 1: Relative to the size of their body. Although these guys
[39:20] Speaker 1: can get really big. So like I was looking at
[39:22] Speaker 1: one of the measurements and like a big banana slug
[39:26] Speaker 1: can get from like my wrist to the crook of
[39:28] Speaker 1: my elbow. So like the length of my forearms. That's
[39:30] Speaker 1: a pretty big slug, right?
[39:33] Speaker 2: That's a huge slug.
[39:34] Speaker 1: Yeah, huge slug.
[39:35] Speaker 2: Okay.
[39:35] Speaker 1: But so what they're known for is they will go
[39:37] Speaker 1: ahead and have sex. And when sex is done, one
[39:40] Speaker 1: will go to pull their wiener out, but it seems
[39:43] Speaker 1: to get stuck. And so in these cases where it
[39:46] Speaker 1: seems to get stuck, it seems like for a while
[39:48] Speaker 1: they attempt to detach. But if detaching doesn't work, then
[39:52] Speaker 1: one of them will chew the wiener off.
[39:55] Speaker 2: Okay. We should have more warnings, Kelly. Why? I'm... Sorry?
[40:02] Speaker 2: All right, go ahead. What happens next?
[40:04] Speaker 1: That's called apophylation.
[40:06] Speaker 2: Uh-huh.
[40:07] Speaker 1: And so there's this big debate about why do they
[40:12] Speaker 1: do that? Is it like, for example, to make sure
[40:15] Speaker 1: that the mate who just lost the penis invests in
[40:19] Speaker 1: protecting the eggs that just got fertilized by the other individual?
[40:23] Speaker 1: I think at the end of the day, we don't
[40:24] Speaker 1: know why this happens. We all just know that it
[40:26] Speaker 1: kind of makes us uncomfortable to hear about, particularly the
[40:29] Speaker 1: male of the species.
[40:31] Speaker 2: I don't know how I feel about the theory that
[40:33] Speaker 2: it brings the family together. Oh, no, no, no.
[40:35] Speaker 1: That's not that's not at all what I'm saying. And so, OK,
[40:38] Speaker 1: so both individuals get their eggs fertilized in this interaction.
[40:42] Speaker 2: Yeah.
[40:42] Speaker 1: And so now they both have eggs that require a
[40:45] Speaker 1: little bit more like energy to finish like growing up
[40:48] Speaker 1: or whatever. If you don't have A penis. You can't
[40:52] Speaker 1: go find another partner and invest in it doesn't make
[40:54] Speaker 1: sense to invest in making more sperm because you don't
[40:56] Speaker 1: have a penis anymore. Yeah. And so you better invest
[41:00] Speaker 1: in making the set of eggs that you're growing like
[41:02] Speaker 1: really great.
[41:03] Speaker 2: Exactly.
[41:04] Speaker 5: Yeah.
[41:04] Speaker 2: No, that's what I understood completely. But it's like it
[41:07] Speaker 2: makes the parents invest in the kids. Right.
[41:09] Speaker 1: Oh, I thought you said invest in the family. And
[41:11] Speaker 1: I thought you were. I don't know. That's that was a.
[41:14] Speaker 1: More touchy-feely way of saying it than I– I don't
[41:18] Speaker 1: think anybody necessarily buys that. That's just a idea that's
[41:21] Speaker 1: floated out there. But I think at the end of
[41:22] Speaker 1: the day, we throw our hands up in the air
[41:24] Speaker 1: and we're like, why are you guys eating each other's wieners?
[41:26] Speaker 1: We don't know. That's a weird thing to do.
[41:29] Speaker 2: Glad we agree on that. All right.
[41:32] Speaker 1: Yeah, yeah, yeah. So there was this idea for a
[41:34] Speaker 1: long time that you'll go to some populations– And it
[41:38] Speaker 1: will be hard, if not impossible, to find a banana
[41:41] Speaker 1: slug with a wiener. And so the question was like, oh,
[41:45] Speaker 1: my gosh, did this population just like go to town
[41:48] Speaker 1: on the apophyllation situation? And it looks like actually in
[41:52] Speaker 1: some populations, the hermaphrodites are born without penises. And so
[41:58] Speaker 1: they can still fertilize themselves by like, you know, they've
[42:01] Speaker 1: got like an internal tube system where they can mix
[42:03] Speaker 1: the sperm and the eggs on their own. And they
[42:06] Speaker 1: can still accept sperm if they're able to find another
[42:08] Speaker 1: individual that has a penis. And in that way, they
[42:11] Speaker 1: can mate naturally. You know, with someone other than themselves.
[42:14] Speaker 1: But like why you see this diversity amongst populations in
[42:19] Speaker 1: some species of banana slugs where some of them have
[42:21] Speaker 1: penises and some of them don't. That's another open question.
[42:24] Speaker 1: And so there's lots of questions about the sex lives
[42:27] Speaker 1: of banana slugs that keep scientists.
[42:29] Speaker 4: Up at night.
[42:30] Speaker 2: Wow, that's a whole PhD topic right there.
[42:32] Speaker 1: That could be a couple PhD topics. There's some interesting
[42:35] Speaker 1: questions there about, like, sexual selection and... Anyway, that'll... Yeah.
[42:39] Speaker 1: We just need money, you know?
[42:41] Speaker 2: I hope some student doesn't bite off more than they
[42:42] Speaker 2: can chew, you know?
[42:45] Speaker 1: That was too much. Too much.
[42:48] Speaker 2: But.
[42:49] Speaker 1: Paul gave me an opening to talk about parasites. And
[42:52] Speaker 1: we're not going to talk about rat lungworm.
[42:54] Speaker 2: Yeah.
[42:56] Speaker 1: But we're going to talk real quick about biocontrol. So slugs,
[43:01] Speaker 1: if you are a gardener, slugs are like the bane
[43:03] Speaker 1: of your existence. So we bought six ducks to try
[43:07] Speaker 1: to control the slug population in Zach's garden. And it
[43:10] Speaker 1: turns out the ducks were more work than the slugs.
[43:13] Speaker 2: Yeah. Of course. And now you have ducks to take
[43:15] Speaker 2: care of.
[43:16] Speaker 1: Well, you know, they got taken care of by a predator, unfortunately.
[43:20] Speaker 1: But yeah, it was really sad. Betty White, her passing
[43:24] Speaker 1: was the hardest to deal with. But anyway, so OK,
[43:27] Speaker 1: so another option for getting rid of slugs in an
[43:30] Speaker 1: agricultural setting is. is to release nematodes, which are a
[43:34] Speaker 1: kind of like, you know, hard tube-ish shaped parasite. You
[43:38] Speaker 1: release these slug attacking nematodes into your garden. And when
[43:42] Speaker 1: a slug walks over them, the nematodes, which are parasites
[43:45] Speaker 1: in this case, are like, there's a host. And they
[43:47] Speaker 1: go ahead and they attack the slugs and they kill
[43:49] Speaker 1: the slugs. But the problem is these nematodes don't only
[43:54] Speaker 1: go after slugs that are bad for your garden. They
[43:57] Speaker 1: go after like whatever slug they find. And so on
[44:01] Speaker 1: three different continents, there is a product you can buy
[44:04] Speaker 1: called NEMA slug or NEMA slug 2.0. And these are
[44:09] Speaker 1: two different species of nematodes that can kill slugs. And
[44:12] Speaker 1: so there was a paper in BioRxiv in 2026 where
[44:16] Speaker 1: they wanted to know if we bring this into the
[44:18] Speaker 1: United States, because right now you're not allowed to use
[44:20] Speaker 1: it in the United States because we don't know what
[44:22] Speaker 1: it would do to like native slug populations. If we
[44:25] Speaker 1: brought it into the United States and started using it
[44:27] Speaker 1: in the Pacific Northwest where you find banana slugs, would
[44:30] Speaker 1: this kill banana slugs, too? And the answer does seem
[44:33] Speaker 1: to be yes. These nematodes will kill banana slugs. So
[44:36] Speaker 1: now the question is, will banana slugs, which tend to
[44:39] Speaker 1: live in like moist forest environments, which is to say
[44:43] Speaker 1: not really agricultural fields. Like, is there a risk of
[44:47] Speaker 1: these nematodes getting into those environments and killing the banana slugs?
[44:51] Speaker 1: That's something that we need to think about. But there
[44:53] Speaker 1: is some evidence that if we start using this agricultural
[44:56] Speaker 1: pest control method, there could be some implications for these
[45:00] Speaker 1: most charismatic of slugs.
[45:04] Speaker 2: All right. Thank you very much. Let's send that question
[45:07] Speaker 2: back to Paul and let him chew on it.
[45:09] Speaker 1: Or see if he wants to slug me after talking
[45:11] Speaker 1: about apophylations.
[45:14] Speaker 5: Hey, Kelly and Daniel. Thanks for answering my questions about
[45:18] Speaker 5: slugs and banana slugs in particular. I knew something of
[45:21] Speaker 5: the banana slug reproductive cycle, but not all the, uh, details.
[45:26] Speaker 5: I think they are a great example of creatures that
[45:28] Speaker 5: seem strange at first, but when you dig past appearances,
[45:31] Speaker 5: they're even more interesting than expected. We don't have banana
[45:34] Speaker 5: slugs here in New Hampshire, but at least I could
[45:37] Speaker 5: look at the banana slug plushie on my bookcase shelf.
[45:40] Speaker 2: Right next to my Cthulhu idol.
[45:42] Speaker 5: Thanks again.
[45:43] Speaker 2: All right. Thank you very much, everybody who's curious about
[45:46] Speaker 2: the universe and listens to the podcast. If you have
[45:48] Speaker 2: a question you'd like us to tackle, don't be shy.
[45:50] Speaker 2: Send it to us. We would love to hear from you. Thanks, everybody,
[46:00] Speaker 2: for listening. Please go and do us a favor and
[46:02] Speaker 2: rate the show on whatever podcast app you're using. It
[46:05] Speaker 2: really helps people find us.
[46:07] Speaker 1: Daniel and Kelly's Extraordinary Universe is edited by the amazing
[46:11] Speaker 1: Matt Kesselman.
[46:12] Speaker 2: He really is a wizard. You can also find us
[46:15] Speaker 2: online on Blue Sky, Instagram, and X, D & K Universe.
[46:20] Speaker 2: Come engage with us.
[46:22] Speaker 1: You can email us at questions at danielandkelly.org. We really
[46:26] Speaker 1: do want to hear from you.
[46:27] Speaker 2: And you can find our website, www.danielandkelly.org, where you'll also
[46:32] Speaker 2: find an invitation to join our Discord, where everybody comes
[46:36] Speaker 2: and talks about the amazing universe.
[46:38] Speaker 1: And we also have the most amazing moderators. This is
[46:42] Speaker 1: an iHeart podcast. Thanks for joining us.

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