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Dr. Shini Somara joins us on the Talk Show today to talk Crash Course Physics and her background in fluid dynamics and television. Then Jessi from Animal Wonders brings on Sydney, their Brush-tailed Bettong.

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Hosted by: Hank Green
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 Interview with Shini Somara, host of Crash Course Physics (00:00)


Hank: Hello, and welcome to the SciShow Talk Show.  It's that day on SciShow where we talk to interesting people about interesting stuff, and today, we have the new host of CrashCourse: Physics, Dr. Shini Somara.

Shini: Hi.

Hank: I'm so excited to have you here.

Shini: It's so nice to be on these couches.

Hank: Do you like this couch?

Shini: It's very comfortable.

Hank: We got it just for you.  

Shini: No, you didn't.

Hank: It's a lie, we don't even own that couch.  We don't even own any of this.  This is just some place downtown that they let us borrow.  

Shini: That makes me feel really special.  

Hank: Yeah, we borrowed it just for you.  

Shini: Thank you.

Hank: I'm super excited about CrashCourse: Physics.  You're here recording it right now.  Did you just finish a long day of physics?  

Shini: No, I just got off a plane.

Hank: Oh, okay.

Shini: Um, and like, literally less than an hour ago, and yeah, just really excited to talk to you about this.

Hank: How did you get interested in physics, science, engineering stuff?

Shini: So my father is a mechanical engineer, and he came over to London from Sri Lanka to study at South Bank University.  Back then, it was called South Bank Poly.  

Hank: I don't know what either of those things are, let's be honest.

Shini: Oh, really?  Okay.  Alright, I won't go into it, then, because my dad will be like, 'Why are you telling them that?'  So, South Bank University is a great university for engineering, and that's what he studied.   He met my mum at University and they got married and then three years later, had me, and being the eldest, there was a lot of kind of expectation for me to take over the family business.  

Hank: Is there an actual family business?

Shini: Yeah, my dad ran a mechanical electrical consultancy practice for building services, so all the engineering that happens in a building is down to engineers like my dad, and so yeah, I studied mechanical engineering at Brunel University in West London, and then really found fluid dynamics interesting. So fluids are defined as anything that is gaseous or a liquid.

Hank: Right. Anything that--that flows around, yeah.

Shini: Flows, yeah. And I just loved the idea of visualizing the invisible. Because normally, most fluids are invisible. Like, water, air.

Hank: Mhm. Certainly the air. Yeah, even, like, the-the existence of air was something we didn't really know about for quite a while.

Shini: Yeah.

Hank: Of course, we get hit by wind, but not really think of it as a thing that exists in wind, we're, like, slapping into molecules all the time.

Shini: And that's what's so fascinating about fluid dynamics, is the power of things like wind.

Hank: Mhm.

Shini: Or the power of air. I mean, even just coming over from L.A. today, it was like such bumpy flight conditions, and you just feel like you're this little flea, especially in those bombardier planes.

Hank: Yeah. The little ones. Sorry about that.

Shini: Yeah. It's the mountain ranges. I am the most paranoid flier. Because of--

Hank: Well, you do it a lot, though. So you must not be THE most.

Shini: I-I don't know. I feel sorry for the person that sits next to me on a plane.

Hank: Yeah.

Shini: 'Cause I'm kind of like, grabbing onto things, and--before I studied engineering, I was fine in a plane. I was like, "yeah, you know, whatever." And then now I know so much about convection currents and, you know, turbulence models.

Hank: Well, you know all the fluid dynamics. You need to know the structural engineering stuff, so you know how strong those plane wings are. Nothing--nothing's gonna--

Shini: Yeah, that's finite element analysis.

Hank: Okay.

Shini: That's--that's a thing.

Hank: I don't know.

Shini: Yeah. No, I went more into the things that float, than--

Hank: Well, fluid dynamics has always seemed to me some of the most complicated physics out there, because, of course, you know, all of it's made up of these, sort of, basically infinite numbers of discrete particles bumping into each other and bumping into things and what do they do--

Shini: Yeah.

Hank: --and they're moving in certain--I'm just like--

Shini: And almost infinite possibilities of external conditions.

Hank: Right, right.

Shini: So, like, you know, if the temperature changes, that's gonna change the way things flow.

Hank: Pressure changes.

Shini: Yep.

Hank: Yeah. You know, good old gas law.

Shini: Oh, yeah, it's all down to Boyle. Boyle's good old law. Thanks for that.

Hank: So, what did you think when we reached out to you about Crash Course Physics?

Shini: I was really, really excited about working in an online space. Like, honestly, 'cause I've done TV for quite a number of years, now, and it's such a different experience being online. Just-d'you know the best thing about it, is the interaction with the audience.

Hank: Mhm.

Shini: You know, it's instantaneous. Like, if people don't like something, or if they do, they tell you. And I love that.

Hank: Yeah.

Shini: 'Cause with TV, you're kind of looking down a camera lens. You don't really get--

Hank: Right, and you make the full season, and then you start airing them and it's like, "well, if they don't like something we can't change it now."

Shini: Yeah.

Hank: You've shot all of them.

Shini: Yeah.

Hank: Yeah.

Shini: It's-it's phenomenal to just experience that. I can't describe it. But, like every-everyone just feels like a friend.

Hank: Yeah. It's fantastic.

Shini: So far.

Hank: Well.

Shini: Until we do something in physics and they're, like, "no! We don't like it!"

Hank: Don't-yeah. Well, you know, there will always be haters on the internet. I'm sure that-I'm sure-did we ever have that conversation?

Shini: I think we did.

Hank: Yeah.

Shini: I think you warned me.

Hank: I try to give people a little bit of a warning.

Shini: Yeah.

Hank: But-just so you're ready. But mostly people are very nice.

Shini: Yeah. I think what we're doing is great.

Hank: Hi nice people.

Shini: Hi people.

Hank: Yeah.

Shini: Be nice to us.

[Both laugh]

Shini: I'm looking forward to providing people with free online education.

Hank: Yeah.

Shini: Like, that's another thing that's really great about this opportunity.

Hank: Mhm.

Shini: Because, I think, personally, you know, my parents come from what is maybe considered third world countries?

Hank: Mhm.

Shini: And through education, they carved out a pretty decent life in London.

Hank: Mhm.

Shini: So if I can help to educate and allow people to reach their full potential in STEM, then I feel-that would make me feel good.

Hank: Yeah.

Shini: For sure.

Hank: Yeah. It's really wonderful to be able to work in this space where, like, we get to be creative and make stuff that we like and also, that seems like it's good for the world.

Shini: I think it's good that you're tackling such diverse subjects as well.

Hank: Yeah. It's really fun. It's really interesting that we have, that we, like, have all these concurrent courses and they all get - You know, lots of people are watching all of them, and you know, they're... That's something that I really want to foster in the world, is people who have, you know, not just deep knowledge, but broad knowledge, and - It seems a little bit like we've been pushing not in that direction, for a while, because deep knowledge is so important for actually getting things done, but broad knowledge is, kind of, what you need to be a human. And, hopefully, Crash Course is helping to make that happen. Now, this is, obviously, a SciShow Talk Show where we talked mostly about Crash Course, but hopefully, you know, people don't mind, and, hopefully you know what Crash Course is, and if you don't, you can go to Do you want to meet an animal?

Shini: I do.

Hank: Okay, let's do that.

 Sydney the brush-tailed bettong(7:06)

Hank: Alright, what have we got?

Jessi: This is Sydney, the brush-tailed bettong, and she's cuddled up right now, because she's nocturnal, and these guys are pretty prey-driven.

Hank: Right.

Jessi: Right. Or...

Hank: Right, opposite of that.

Jessi: Yes.

Hank: Predator.

Jessi: Predator-driven. So, they're prey animals, and they're going to be very instinctually-afraid of things, but look.

Hank: Aw, except for the licking.

Jessi: She's licking me.

Hank: She's not afraid of your hand.

Shini: She looks like a giant squirrel.

Jessi: She kind of looks like a squirrel.

Hank: A little bit of a giant squirrel.

Jessi: Kinda. She's got the ears and the eyes.

Hank: Well, it's the fur - it's all the fur colour.

Jessi: Yeah, that's true too. But she has tiny, little - let's see if we can get her a little bit more positioned here so you can see.

Hank: Oh yeah.

Jessi: This would be her normal stance. She has these huge back legs, and let's see if I can pull this out for you.

Hank: Oh!

Shini: Oh, wow!

Hank: Big ol' rat-tail.

Jessi: Kinda! Except rat-tails are naked, so she is most closely-related to a kangaroo.

Hank: OK.

Shini: Wow.

Jessi: So the brush-tailed bettong, also known as the woylie-- Would you like to try and hold her in your lap?

Hank: Woylie?

Shini: I'll try.

Jessi: Okay, so scooch over here and get your legs straight. We'll get her little blanket.

Shini: Is she going to like that?

Jessi: She might. She might not care.

Hank: Did you - did you say "woylie"?

Jessi: Woylie is what they call 'em in Africa - or, Australia. Here you go. Alright. And she might just want to come right back to me.

Shini: She likes you!

Hank: Oh, right, so the front legs look kind of squirrely, the back legs look like kangaroo legs.

Jessi: Not at all, yes!

Shini: So, is she a baby?

Jessi: She is not a baby, she's about two years old. And they mature at about six months. So, she is fully-grown. What do you think, Sydney? You're doing so good!

Shini: Sydney?

Jessi: Sydney. Shini: From Sydney?

Jessi: So, not from Sydney. More the grasslands of Australia. Not the deserts.

Hank: Right, okay.

Jessi: Don't go down there.

Hank: Oh, look at your big legs! Look at your weird three toes!

Shini: [laughing]

Jessi: Yeah! Kangaroo! Macropod.

Hank: Kangaroos have three toes?

Jessi: Yes, yeah. And she does have a pouch.

Shini: Oh wow!

Jessi: It's down there. So, you can't really see it, actually the pouches that we've learned of in cartoons, it's kind of a misnomer, because they're not, like, this slit where you can just, like, open 'em up and put, like - like a fanny pack- type thing.

Hank: Right, right, you know, you keep your cellphone in there, and your passport.

Jessi: Yeah, yeah. Not so much. Not so much.

Hank: Okay.

Jessi: It's more of, like - and let's see if she'll let me actually feel inside there.

Shini: She just stopped, she was like: "Huh?"

Jessi: She was like: "What are you doing?"

Hank: Yeah, her head was like: "Did you just really?" Did you just really do that?"

Jessi: My finger's in there, did you see that?

Hank: So, it's like an orifice.

Jessi: Kinda, yeah!

Hank: It's just, like, another hole.

Jessi: Hole that's lined with skin.

Hank: Okay.

Shini: And fur?

Jessi: No fur.

Shini: Okay. Jessi: Just skin.

Hank: Just skin.

Shini: And the purpose is...?

Jessi: To hold the baby. And so, the interesting thing is that, these guys will give birth to a joey, and it's teeny-tiny. It climbs up into their pouch.

Hank: Okay.

Jessi: And then it will - And it doesn't have really developed back legs. It'll attach to a nipple in there, and then its jaws will fuse shut. So that it can't fall. So, she's going to be hopping around like crazy. And it's going to be bouncing around in there.

Hank: So, it's just attached to that nipple.

Jessi: It's attached to that nipple.

Hank: Never lets go.

Jessi: Until it grows - develops enough that it can, like, move itself around, and reposition itself, if it needs to. And then its jaws will just develop more, and it'll be good.

Hank: So, it's just a fold of skin? It's not, in any way, inside of the body?

Jessi: No. Hank: There's no mucous membranes, it's all skin in there?

Jessi: It's all skin in there.

Hank: Except for the nipples?

Jessi: Except for the nipples. Yup. So, it'd be, like, if we had, like, an extra flap of skin that came over

Hank: Your nipples.

Jessi: Our nipples. [laughter]

Hank: It's as if that.

Jessi: I mean - And then at the top of it, it's almost like a drawstring.

Hank: Right, okay.

Jessi: At the edge of it. So they have a muscle that can constrict like this.

Hank: A little pouch-sphincter.

Shini: And how long does it stay in there?

Jessi: It takes four months for them to develop in there. So, they're pregnant for about, like, two weeks, and then they give birth, and then four months for it to develop, and then leave the pouch, and be able to hop around on its own.

Jessi: And they're super cute, they're about this big.

Shini: That's amazing. And that's why they're closely related to kangaroos? For that reason?

Hank: Right, marsupials.

Jessi: They're marsupials, yeah. And they're closely related to kangaroos because, on the tree, they split off at the same time as kangaroos. So kangaroos, wallabies, wallaroos, bettongs, they're all very similarly related.

Shini: It's like a whole host of animals that I've just never seen.

Jessi: They're so cool!

Shini: Because they're on the complete other side of the planet to where I'm from.

Hank: And, we weirdly have that one marsupial in the New World, here.

Jessi: Yeah.

Hank: The possum.

Jessi: The opossum.

Hank: Well what's - Really?

Jessi: There's a possum, it's a prosimian -

Hank: Wait a second. Are you telling me that there is a possum, and an opossum, and that they're two different things?

Jessi: I am.

Hank: [sighs] Why do we do this to ourselves? So, the opossum, the one that, you know, you see dead on the side of the road in Florida a lot.

Jessi: That's an opossum.

Hank: Is an opossum. And it is a marsupial.

Jessi: Yes.

Hank: And, are there more than one species of opossum in America?

Jessi: No, just the one.

Hank: Just the one. Okay.

Jessi: Just the one.

Shini: How long did it take you to have this relationship?

Jessi: Well, she was actually born at Animal Wonders so, these guys are critically-endangered in the wild, and so, we were part of a conservation breeding program. We had a breeding pair, and they actually had five joeys at Animal Wonders before we sent them on to a larger facility that had more connections than we did, and could get them into bigger facilities to propagate the species better.

Hank: Because they were so good at breeding!

Jessi: They were really good at breeding, and yeah, we didn't have enough places to put the babies. [laughter] So, we sent them and all the babies to facilities that could better propagate their species, but we kept one for education. And so, we've had Sydney since she came out of the pouch.

Shini: So she really knows you.

Jessi: She really knows us.

Shini: I'm envious of your relationship. [laughter] I want to hug her!

Jessi: You can keep petting her. She's doing really good.

Shini: But you're saying she might bite?

Jessi: She's bitten me a couple times already. You guys, I know you haven't noticed. She doesn't bite very hard.

Hank: Oh, bit you a couple times during this talk?

Jessi: Yeah, yeah.

Shini: Oh, really?

Jessi: Yeah.

Shini: Oh, wow.

Jessi: Yeah.

Shini: You hid that well.

Jessi: She was just - A couple of them were, like, little love nibbles, because she's licking me and she's like--

Shini: Love bites!

Jessi: "Oh, I wonder if this tastes good?" And it didn't!

Hank: "Is this food? Is this food?"

Jessi: And then one was when I tried to block her jumping off the - On to the floor. And she was like, "Um, I wanna go down there!" And then she was like, "Okay..." She resigned herself.

Hank: Let us know if you need a band-aid.

Jessi: Oh, she doesn't bite that hard. She doesn't bite that hard, huh? What do you think?

Hank: "Ah, what a weirdo!" [laughter] Sorry...

Jessi: Nice! Nice!

Hank: Sorry!

Shini: It's so many animals mixed into one!

Hank: Yeah! Uh huh.

Jessi: So, I want to see if she'll let me - I want to show off this really cool tail. See how it rolls like that?

Hank: Oh yeah.

Jessi: And, naturally, you can see those bends? Now that, is a prehensile tail. It's a semi-prehensile tail. She can't actually, like, hang from it. She wouldn't be up in the trees anyway. But she uses that tail to help her gather sticks and leaves together, because she has little T. Rex arms. She can't really hold much with her front arms there. And so, she'll gather branches up, and then she'll bounce 'em back to her nest to make a big, cosy nest.

Shini: What does she eat?

Jessi: She eats something really interesting. She's an omnivore. She's going to eat a lot of different things, mostly plant material. Vegetables and stuff. But her biggest part of her diet, in the wild, is a mushroom that grows under the ground, so a fungus. And she digs up - She has a really keen sense of smell, and so she'll find those mushrooms, dig 'em up, eat 'em. Now, the coolest thing that they do, is that they digest 'em in a certain way in their gut, they have special microbes in there, that help break it down, and so, when she poops, there's extra access to the sugars in that feces, so the plants can actually absorb more sugar out of that fertilizer than they can other feces. And it helps the plant grow three times faster and stronger.

Shini: Wow!

Hank: So, you got really good fertilizer coming from your place.

Jessi: Yeah! So, these guys are really cool, which is why it's so sad that they're critically-endangered. It's because they help their ecosystems so much. This tiny, little marsupial.

Hank: That's fascinating. Thank you, Sydney, for joining us! Thank you Jessi! You can see more of Jessi's work at Animal Wonders - You can see Shini, Dr. Shini Somara, on our new Crash Course Physics series. And, you can see me on SciShow, at, as always. Thank you for joining us. Thank you for being here and being interesting. And, if you want to keep getting smarter with us, you can go to and subscribe.

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