Ep. 316: Observational vs. Experimental Science

Sometimes you can do science by watching patiently, and sometimes you’ve just got to get your hands dirty with an experiment or two. These two methods have their advantages and disadvantages for revealing Nature’s secrets. Let’s talk about how and why scientists choose which path to go down.

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This episode is sponsored by: 8th Light, Swinburne Astronomy Online

Show Notes

  • Government shutdown
  • Sarcastic Rover on Twitter
  • Observational Science PDF from USC
  • Stellar Evolution — University of Michigan
  • Kepler Mission 
  • Rubidium
  • OSIRIS-REx asteroid sample return mission
  • Determining the Age of surfaces on Mars – MSSS
  • LISA mission
  • Transcript

    Transcription services provided by: GMR Transcription

    Female Speaker: This episode of Astronomy Cast is brought to you by Swinburne Astronomy Online, the world’s longest-running online astronomy degree program. Visit astronomy.swin.edu.au for more information.

    Fraser Cain: Astronomy Cast Episode 316: Observational Vs. Experimental Science

    Welcome to Astronomy Cast, our weekly facts-based journey through the cosmos. We help you understand not only what we know but how we know what we know.

    My name is Fraser Cain. I’m the publisher of Universe Today and with me is Dr. Pamela Gay, a professor at Southern Illinois University, Edwardsville, and the director of CosmoQuest.

    Hey, Pamela. How are you doing?

    Pamela Gay: I’m doing well. How are you doing, Fraser?

    Fraser Cain: Doing well. Now, we’re not well. We mentioned this –

    Pamela Gay: No, we’re lying.

    Fraser Cain: We’re lying. We are.

    Pamela Gay: The government shutdown hurts!

    Fraser Cain Yes, it certainly does.

    Pamela Gay: It hurts.

    Fraser Cain: Yeah. For me, all of the pictures, all the resources, all the press releases, all of the reporters; everyone that we try to make access with, they’re all offline. No missions, no scientists, nothing. It is just emptiness.

    So, there’s also other stories going on but – but we’re really sort of having to route around with Universe Today.

    But that’s nothin’ for what – compared to what you’ve got happenin’.

    Pamela Gay: Yeah. I have to admit to being just shy of full-on freak-out mode about what’s going to happen with National Science Foundation deadlines and the backlog of paperwork that’s going to be generated by being down for so long and how we’re going to get our money, moving into the future, and – and I’m gonna stop now.

    Fraser Cain: Okay. But, you know, just to — just to see if I can push you to cry, the National Radio Astronomical Observatory was shut down.

    Pamela Gay: Yes.

    Fraser Cain: NOAA was shut down. Like, it’s just – it is – you know, there is no science happening from the US government at all. So –

    Pamela Gay: Yeah.

    Fraser Cain: So, there you go. That’s where we are right now. Hopefully, next week, we’ll be, like, “Woo hoo! It’s over and now we can back to our work!” and I don’t think that’s going to happen. So, yeah.

    Pamela Gay: If you want to help and you’re in the United States, write your congress critters, senators, representatives. If you’re not in the United States and you have some money to give, donate to your favorite science program because, right now, that’s the only source of funding a lot of us have.

    Fraser Cain: The Sarcastic Rover has got a great suggestion, which you should check out at some point. They’re recommending that people do their own science. So they do some science –

    Pamela Gay: Yes.

    Fraser Cain: Take a picture of it and tweet it at The Sarcastic Rover and that’ll help.

    Pamela Gay: Do science on CosmoQuest.

    Fraser Cain: There ya go.

    Pamela Gay: Our site is still up.

    Fraser Cain: Right.

    Female Speaker: This episode of Astronomy Cast is brought to you by 8th Light, Inc. 8th Light is an agile software development company. They craft beautiful applications that are durable and reliable. 8th Light provides disciplined software leadership on demand and shares its expertise to make your project better.

    For more information, visit them online at www.8thlight.com. Just remember, that’s www.8thlight.com. Drop them a note. 8th Light. Software is their craft.

    Fraser Cain: So, sometimes you do science by watching patiently and sometimes you’ve just gotta get your hands dirty with an experiment or two. These two methods have their advantages and disadvantages for revealing nature’s secrets. Let’s talk about how and why scientists choose which path to go down.

    Now you threw this topic at me. So, I’m going to let you explain your underlying rationale but you actually gave it a little bit more of a controversial topic, which is, “Battle of the Scientists,” right?

    Pamela Gay: Yes, yes. Well, it –

    Fraser Cain: It’s not a battle. Isn’t it a tool kit? Isn’t it like a series of tools that good scientists use, depending on the nature of the question they’re trying to solve?

    Pamela Gay: Well, so – so one of the weird things that you encounter is, what’s considered a large data set varies from science to science. And in some fields, you get thousands of data points. In astronomy, you’re sometimes kind of happy to have one.

    And there’s fields in between. Anthropologists, how often do you get lucky enough to dig up a pristine find? Animal scientists, how often do you get lucky enough to witness this or that usage of tools?

    And, at the end of the day, it’s often a discussion of, “Well, you don’t have statistically significant enough research,” is the argument you hear from the experimentalists; whereas the observationalist’s like, “Yes! Six data points!”

    And it was just one of those things that, it’s interesting to see how we’re trying to figure out how to be as statistically significant with observational scientists as the experimentalists get to be.

    Fraser Cain: Okay. So let’s get into a clarification of terms here. So, when you’re talking about observational science, what is – what does that mean?

    Pamela Gay: Observational scientist is when you are the type of researcher that just sort of hopes that you’re going to generally, purposefully stumble across the type of object or scenario that you wish to study.

    So, as someone who studies variable stars, I will watch them closely, looking for things like phase shifts or the Blazhko effect, which is a change in amplitude in some sorts of RR Lyrae stars. As someone who has collaborated with people who work on colliding galaxy clusters, you go out, you look at a whole bunch of what you believe are galaxy clusters and ya hope some of ’em are in the process of colliding.

    Anthropologists dig. It’s a matter of you make your own fate by going out and turning over rocks until what you want to study is found under the rock you flip over.

    Fraser Cain: Economists deal with this a bit, too –

    Pamela Gay: Yes.

    Fraser Cain: Because, in many cases, there are experiments – natural experiments – that are kind of morally dubious to perform, right? Like splitting up two children and having one raised in one family and another raised in another family. That’s not a good thing to do. But what they look for, I guess, is these situations where this has happened.

    Pamela Gay: Yeah.

    Fraser Cain: Whether, you know, two twins are put up for adoption and then you can go and seek these situations and then you can observe the results and not feel like you’re a bad person.

    Pamela Gay: Yeah, I don’t think that’s necessarily the economist but, yeah, economy – economists have lots of other dubious scenarios to deal with. Let’s not try tanking the US economy to see how quickly it recovers.

    Fraser Cain: Right, exactly –

    Pamela Gay: But if it accidentally happens –

    Fraser Cain: Right. But look for a – look for an economy that did tank and try to figure out why it happened.

    Pamela Gay: Yes.

    Fraser Cain: So, you know. But, no – but like, you know, even like earning-power or education levels or things like that. So there’s all these situations where you’re looking for something that you’re observing.

    Okay. So that’s – that’s an observational scientist.

    Pamela Gay: Yes.

    Fraser Cain: What is an experimental scientist?

    Pamela Gay: An experimental scientist is someone who gets to deal with controls. Someone who will very carefully set up scenarios where you’re tweaking one or a specific set of variables in known ways to see what happens.

    In some cases, you are – with the Large Hadron Collider – repeatedly causing experiments of varying energies to see – to happen to see what particles are formed in some cases. You are working in the laboratory and exciting gasses to different temperatures to see what spectral lines are emitted.

    But you always have this nice, controlled environment; sometimes less controlled than you’d like but you understand where things are going wrong or you can at least retroactively figure out where things were going wrong and prove it by doing another experiment. And you get to vary the parameters to understand the entirety of the picture. And, it’s nice.

    Fraser Cain: Right. But you – but, of course, the limit is what you can control because it would sure nice to smash galaxy clusters together and sort of see what happens but, obviously, you can’t do that.

    Pamela Gay: And it’s very difficult to explore in a laboratory all the possible ways that a star of a given mass and metalicity can evolve; or, I guess, a series of masses or a series of metalicities can evolve. We just can’t do that.

    So we’re stuck trying to look through the universe to find, well, artificial laboratories that allow us to, through more natural means, find clusters of data points that step through the different parameter space.

    Fraser Cain: So, now, do scientists end up going down one road or the other? I mean, I said you called it “battle.” So, is it a battle and they hate each other?

    Pamela Gay: I think not as much as people who do experiments and observation tend to mock. And it’s not hate, it’s the mocking that you get, for instance, between college football teams.

    I think we all universally gang up on the theorists because it’s fun. And –

    Fraser Cain: So everybody hates the theorists. Everybody gives the theorist a hard time because they’re doing –

    Pamela Gay: We all give the theorists a hard time.

    Fraser Cain: Right. Because they’re not observing or experimenting, they’re just thinking.

    Pamela Gay: Yes.

    Fraser Cain: Send all email to: pgay@ – No. But –

    Pamela Gay: But – so, when it comes to the experimentalists versus the observationalists, it’s not so much a battle or a hate, but you do occasionally get the odd comments on a refereed paper, where your referee was not the same thing you are.

    So you also run into just general frustrations and gaps in knowledge if you’re one, and you run into frustrations and gaps in knowledge due to lack of funding to do experiments in the other.

    So a lot of observational science is figuring out how to get around your lack of laboratory –

    Fraser Cain: Right. I guess with observational science, you could do – really do it on the cheap because someone was so kind to smash galaxy clusters together for you.

    Pamela Gay: Exactly, exactly.

    Fraser Cain: You just need to observe them.

    Pamela Gay: And experimentalists, well, they have a lot more funding struggles because, well, at the end of the day, whatever it is that you’re doing in your lab takes money to run, probably.

    Fraser Cain: So then, like, what kinds of answers, what kinds of questions, are the two different methodologies really appropriate for?

    Pamela Gay: So, for instance, let’s go back to that stellar evolution problem. How do stars of different masses, different metalicities, evolve?

    This is where we’re really lucky to have globular clusters to look at. The stars in an individual globular cluster were all formed at about the exact same time and out of pretty much the same set of materials. So all of the stars in a given cluster have the same birthday; or, at least, birth millennium. And they all have the same makeup of materials: the same amount of iron, the same amount of titanium and scandium.

    And so, when we look at an individual globular cluster, the one variable that we have to deal with is the mass of the star. So we can see, at a given age, what do all of the red dwarfs look like; what do all of the O-type stars look like?

    And, if we look at a variety of different globular clusters, we can see a variety of different ages. We can also see a variety of different metalicities. So, by looking at all the globular clusters we can, we can start to explore the parameter space of how do stars evolve if they’re metal-rich, if they’re metal-poor – and metal-rich, you need to add in open clusters, a younger type of star formation or star group, rather.

    What do they look like when they’re young? You get that from open clusters. What do they look like when they’re old? You get that from globular clusters. So, stellar clusters, open or globular, allow us to explore the parameter space of stellar evolution.

    With galaxy evolution, by looking at different mass and different age galaxy clusters, we can see what happens in dense environments, where there’s a high probability of collision, of gravitational interaction and things like ram pressure stripping. And we can start to understand, what are the triggers for star formation? What happens when things collide?

    All of these different things, we’re still trying to understand because galaxy clusters are a lot harder to observe but we, at least, have the clusters to look at, to start to put these different pieces together.

    Fraser Cain: I think one of my favorites is things like the – like Type 1 supernovae, right?

    Pamela Gay: Yes.

    Fraser Cain: Where you’ve got just this tremendous event that happens really rarely. It’s such an exotic thing, right? But yet –

    Pamela Gay: Yeah.

    Fraser Cain: But yet, they’re happening out there: Pop, pop, pop, pop out in space. And so you can observe them and get tons of science out of it.

    Pamela Gay: The universe is a pretty big place and so, when you start to look at things that are one supernova in general per hundred years per spiral galaxy, you just look at a hundred galaxies. And it starts to become easier and easier.

    Now, as you start looking at specific types of galax… – specific types of supernovae, it gets harder and harder but there’s still so many thousands of easily observed galaxies and millions and billions of galaxies, in general, that it’s possible to explore this parameter space.

    Fraser Cain: Another great example is the current search for planets with the Kepler – well, unfortunately, Kepler’s not doing it anymore – but the Kepler space telescope, where it’s just looking for those situations where this planet is just passing in front of the star and so, you can make the observation. It’s only a fraction of stars that you can actually do that but for the ones you can, that tells you a ton of information.

    Pamela Gay: Right. And here’s another one of those, of the probability is so rare, because you figure not all planets – not all stars have planets; a lot of them but not all stars have planets. And, of those that do have planets, in order to observe the transient, you have to have a very precise alignment so that the orbit cuts exactly across the minuscule disk of the star. So, given it could be face-on, edge-on, and all the angles in between, the fact that this works because there are so many stars to observe, it’s really kind of amazing.

    Fraser Cain: Yeah. Okay. So I think we’ve understood – and I think you can apply that to the non-astronomy fields; although, why would you bother? The observational stuff, right?

    Pamela Gay: Right. Look at enough colonies of chimpanzees or gorillas and you’re gonna see the different types of communication, upbringing, and tool usage that are endemic in their different cultures.

    Fraser Cain: But I – you know, but I’m gonna make the… sort of the bold claim that there are very few sciences that are so reliant on observation as astronomy, that, you know, even with the chimpanzees and the gorillas, you could get in there and muck with their little lifestyle –

    Pamela Gay: Yes.

    Fraser Cain: And start performing some experiments. But you – unless you have a way to crash galaxy clusters together, you know. With astronomy, yeah, you can smash impacters into the moon and you’ll dig up some – some material. Now you’ve performed an experiment. But the rest of it is all observation.

    Pamela Gay: Exactly. Exactly and this is where astronomy is one of the fields that we’re most able to get excited over seeing one example of something; seeing six examples of something. Most other fields call that a fluke.

    Animal sciences is one of the few examples of another field where, when the question is natural behaviors, things occurring in the wild, you’re again going back to – and human studies is another form of animal science – you’re going back to being a purely observational field.

    Fraser Cain: Yeah. How many planets have life on them? Right? One.

    Pamela Gay: Yeah.

    Fraser Cain: One – it’s a very small set.

    Okay. So let’s talk about experimentation then. So what does an experimental scientist do?

    Pamela Gay: Well, here you take one thing that you want to study, or one class of things that you want to study, and you find some parameter that you’re interested in understanding and you step through all the different ways to explore that parameter.

    The example that I turn to the most often is spectroscopy, trying to empirically get at what are all of the different energy level that can be observed within atoms and molecules.

    And there was a vast amount of work done down at Los Alamos Lab where, people working in the lab and also doing quantum-mechanic calculations to verify, and then project out, where lines were predicted, they figured out what are all the possible energies of different atoms, of different isotopes of different atoms, and all of this can be used by us astronomers as we’re trying to figure out the compositions of stars.

    Now, the disturbing side of this is – I got to use a lot of these resources coming out of Los Alamos when I was a grad student, doing stellar spectroscopy. And I was kind of amused and not thinking – I found it interesting that we understood carbon so well; that we understood oxygen so well. And then I had it pointed out to me that these are things that life is made of, that organics is made of. And –

    Fraser Cain: Isn’t it also things that can be lit on fire?

    Pamela Gay: Well, more than that, at a certain point, the types of things they’re studying aren’t the results of basic burning. No, they were actually trying to figure out what energies disassociate the electrons from atoms in organic molecules and we are one giant organic.

    Fraser Cain: Right. And so, they, like, “I wonder what happens if we throw a sandwich in the machine.” “What happens if we – ,” you know?

    Pamela Gay: Well – or more to the point of, what would happen to the human body’s atoms and molecules if it was exposed to this super-high energy that happens to be the side effect of a hydrogen bomb?

    And that starts to get depressing. But it’s an experimental science to figure this out by taking atoms that aren’t involved in being in a human being and exciting them to ever higher and higher energies and seeing what happens.

    Fraser Cain: Right. But you can imagine things like: What does the spectroscopic signature of iron look like?

    Pamela Gay: Right.

    Fraser Cain: Or, what does the signature of uranium look like? And these are the things they find in stars so, you know, they had to – like, what do they do to figure out what iron looks like? Do they burn it? How do they –

    Pamela Gay: It’s not so much burning as creating a gas that has this suspended in the gas and waiting to see how you can excite it. Not all atoms are gotten at experimentally but a lot of them, you can build various types of gasses.

    Rubidium gas is one of my favorite ones because, as light passes through it, it slows down to, like, walking speed. And any time you can slow light passing through medium to the rate at which I can get from one side of the lab to the other and, in fact, I can beat the light across the lab –

    Fraser Cain: Yeah. Come on, light!

    Pamela Gay: – that’s kind of awesome.

    Fraser Cain: Hurry up, light! Come on. Let’s go, slow poke.

    Pamela Gay: Exactly.

    Fraser Cain: So I think one really great example, where the lines are starting to blur, is – we talked about this last week: The Large Hadron Collider. Suddenly, you’ve got an experimentation device that allows you to do things that previously would only be possible with observation.

    Pamela Gay: Well – and more than that, they – some of the energies that they’re hitting with the Large Hadron Collider – there was only one experiment, and we call it “the Big Bang,” and we can’t go back and watch it.

    But some of the other experiments that are really awesome are the neutron bombardment experiments, where they’re replicating the conditions inside of supernovae and working to build ever-heavier atoms and push the periodic table to higher and higher numbers or create new radioactive isotopes that ever-so-quickly cascade down into other more stable things but we get to see all of the different isotopes along the way and measure how long they’re able to last.

    Fraser Cain: So what are some other fields that – or other – what are currently observational-type situations could you see being brought in to the experimentation world? Or maybe vice versa.

    Pamela Gay: Well, I mean, right now, when it comes to asteroid science, a lot of what we do is we take spectra of asteroids; we kind of formulate, based on the reflected light, what the composition of the asteroid is. We are trying to guess with the surface of Mars – and it’s not guess. It’s very careful analysis and scientific reasoning. We’re working to figure out which craters are at the mouths of volcanoes versus craters formed via impacts. This is observation, not going out and measuring and sampling.

    It would be awesome to be able to figure out what is the chemical diversity of asteroids by going out and bringing back samples from a myriad of different asteroids. It would be amazing to go out and be able to determine if all of these small rocks we think came from Vesta actually did by, well, grabbing a sample of Vesta and all of the small rocks and looking to see if they are, truly, chemically the same.

    So, all of these different things where we’re saying, we think the following based on these observations; if we had ground truth sampling; if we could go out and pick up a rock and bring it back. Well, then we could say for certainty.

    Another one of these is the ages of different surfaces. We’ve brought back Ma… – we’ve brought back moon rocks and we’ve begun to tie together: Well, this area of the moon is this age and it has this many craters. And use that to expand out to make assumptions about what are the ages of surfaces on Mars, on Mercury and other rocky bodies.

    But there’s been a lot of estimations and theorization going in to figuring out: Well, do moon and Mars areas that have the same cratering necessarily have the same age? Some people say yes; some people give really good reasons for why no. If we could just go pick out a rock, we’d know for certain which is which.

    Fraser Cain: Or smash asteroids into them. Right? Wouldn’t that help us?

    Pamela Gay: That would kind of create a polluted sample.

    Fraser Cain: Well, you know – part of the moon. Just smash part of the moon with a bunch of asteroids. Just keep smashing them in and, like, looking at the size of the craters that happen and, you know, keep running your experiment.

    And then – and what if we hit it with, like, a Mars – like ram Mars into the Earth. That would help find out if we could make the moon.

    Pamela Gay: That would definitely kill this planet-harming society we’ve created, I guess.

    Fraser Cain: Alright. Alright, I’ll shelve that experiment.

    So I guess for, you know – Let’s say that someone’s listening to the show and they love science and they really want to get into a field in science. How can you sort of self-diagnose your preference for the observational side, the experimental side, and know which paths to go down?

    Pamela Gay: I think, at a certain level, there’s a very definite personality difference.

    If you’re an observational person, there’s a whole lot of hurry up and wait. And so you have to develop that, “Okay, I’m going to take the time to find a thousand objects; hope 500 of them are maybe doing what I want. Study those and then draw conclusions and know that there’s going to be gaps in my understanding because I couldn’t fully explore the parameter space.” That requires patience.

    At the same time, if you’re more of an immediate satisfaction kind of person, there’s that laboratory experience of, “Let me go into my lab and build this thin film and see how it interacts with this color of light,” and chew through a bunch of different types of thin films.

    Fraser Cain: So it really depends on whether or not you feel like you want to be on nature’s schedule –

    Pamela Gay: Right.

    Fraser Cain: Or whether nature is going to be on your schedule.

    Pamela Gay: Right. And I have to also point out that, if you want to be the one doing the observations rather than using archival data or survey data, you also probably have to be happy, not just being on nature’s schedule, but being in nature.

    One of my more interesting experiences as an observational astronomer was looking down and seeing a very small frog, climbing out of my Exabyte drive and understanding that might be why my last Exabyte tape didn’t work so well.

    So, going outside and being one with nature is also sometimes part of it – although there’s now remote telescopes and that makes it a little bit different.

    Fraser Cain: Well, I think the classic example is, we did the Venus – we did a show on Venus and talked about the Venus transits. And just the horrible distances that people had to go and the ordeals they went through, just to make this 2-hour, you know, 6-hour observation.

    Pamela Gay: Yes.

    Fraser Cain: And if they missed it, then they missed it. And that’s it. You don’t get another chance.

    Pamela Gay: Well – and we still have things like that going on. There’s people who are trying to look for moons of Pluto by watching for occultations, where an asteroid is observed to pass in front of it. Or they’re trying to measure various shapes of things by watching for Pluto to go in front of a star and measuring the timing of fading of the background star. That’s the route that most normally happens is Pluto passing in front of a star.

    But where you go on the planet dictates what you’re going to see and so you have to go to that place where the occultation is most perfect and it’s not necessarily a wide band of planet.

    Fraser Cain: So, if you could have one observation – if, you know, some – you know, like we could send a spacecraft anywhere; could build a – whatever – a huge telescope. We could launch into space. We could be a light year’s diameter.

    What would you – what observation do you wish you could make?

    Pamela Gay: I don’t know if any of those things would specifically help me with the one I’m most interested in but the thing we haven’t managed to see yet is a black hole merger, either two stellar black holes actively going “zoink” and merging and releasing vast amounts of energy and gravitational waves or, even better, the merger of super-massive black holes inside of colliding galaxies that are in the process of merging. And I think that would be kind of awesome to find a system in the process of merger.

    Fraser Cain: And what would it take to – like, would it be, like, a big gravitational wave detector; a huge telescope?

    Pamela Gay: Well, probably you’d want to have all of those things going on. I mean, imagine the scenario where you’re able to finally get LISA orbiting, the interferometric gravitational wave detector that’s been proposed to put into orbit, and hopefully will have much greater sensitivity than the one on Earth that hasn’t successfully detected anything yet.

    Imagine if you’re able to detect something with LISA or some similar program that gets launched and somehow get lucky enough to image the field and capture the light in maybe even multiple wavelengths. Gamma-ray burst detector nails it, gets the x-ray, gets the optical, all at once. Getting that multi-wavelength data with the gravitational waves and then multiple colors of light; that would be pretty awesome.

    Fraser Cain: Now, what about an experiment? What’s an experiment that you would wish you could run?

    Pamela Gay: Oh, man.

    Fraser Cain: And like, literally, you can crash galaxy clusters together if you want – if you need to.

    Like, anything in variable stars? Is there anything in variable stars, where you had to, like, make these tough observations that it would have been so nice if you could just –

    Pamela Gay: If I could, like, manually control the magnetic field in a star while it’s pulsating and see what happens, that would make me very happy. Just have a knob connected to the stellar dynamo and crank that magnetic field up and down and watch how it affects the various pulsation modes.

    Fraser Cain: Awesome. Well, hopefully, when the shutdown ends, you can put in a grant for that and we’ll get that –

    Pamela Gay: Exactly.

    Fraser Cain: We’ll get that machine going.

    Alright. Well, thank you very much, Pamela.

    Pamela Gay: My pleasure. Thank you.

    Male Speaker: Thanks for listening to Astronomy Cast, a non-profit resource provided by Astrosphere New Media Association, Fraser Cain, and Dr. Pamela Gay. You can find show notes and transcripts for every episode at astronomycast.com. You can email us at info@astronomycast.com. Tweet us @astronomycast. Like us on Facebook or circle us on Google Plus.

    We record our show live on Google Plus every Monday at 12:00 p.m. Pacific, 3:00 p.m. Eastern or 2000 GMT. If you missed the live event, you can always catch up over at cosmoquest.org. If you enjoy Astronomy Cast, why not give us a donation? It helps us pay for bandwidth, transcripts, and show notes. Just click the donate link on the website. All donations are tax deductible for US residents.

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    Duration: 32 minutes

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