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Speaker 1: Every discovery, every moment of insight, every aha or eureka

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Speaker 1: with the ideas click together in someone's mind to reveal

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Speaker 1: a deep truth about the universe. All of those begin

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Speaker 1: the same way with a question. In fact, all of

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Speaker 1: science starts with questions. The reason we know things about

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Speaker 1: clouds and beetles and black holes is because someone out

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Speaker 1: there had a question that kept them up at night,

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Speaker 1: so they were willing to stay up late looking at

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Speaker 1: the stars or counting beetles until they figured it out.

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Speaker 1: Science is just people asking questions they couldn't let go.

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Speaker 1: But it's not just professional scientists who ask questions and

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Speaker 1: move us forward. It's everyone. It's you, and we think

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Speaker 1: your questions also deserve answers, or at least replies that

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Speaker 1: make sense and help you grapple with what we do

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Speaker 1: and don't know about the topic. So if you have

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Speaker 1: a question about science or whatever, please write to us

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Speaker 1: to questions at Daniel and Kelly dot org. We'd love

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Speaker 1: to hear from you, and sometimes we'll answer those questions

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Speaker 1: right here on the pod. And so on today's episode,

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Speaker 1: we're going to be answering questions submitted by listeners and

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Speaker 1: more than that, and I'll admit to being a little

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Speaker 1: bit nervous about this part. We're going to go back

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Speaker 1: to those listeners with our answers and follow up to

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Speaker 1: see if our explanations scratch their itch or not. Today

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Speaker 1: Daniel and Kelly are getting graded by the listeners. So

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Speaker 1: today on Daniel and Kelly's Extraordinary Universe, we'll be answering

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Speaker 1: questions from listeners, Volume one.

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Speaker 2: Hello, I'm Kelly Wienersmith, and I am so excited that

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Speaker 2: we're having our first listener Questions episode today.

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Speaker 1: Hi, I'm Daniel. I'm a particle physicist, and I love

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Speaker 1: answering questions from the internet about physics, about philosophy, even

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Speaker 1: about dating.

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Speaker 2: Really, you've answered questions on the show about dating.

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Speaker 1: People send me all sorts of questions, you know. They

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Speaker 1: send me their treatise on the nature of the Universe,

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Speaker 1: They send me questions about career advice, how to get

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Speaker 1: into physics, and yes, sometimes people ask me questions about

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Speaker 1: their dating life, and hey, I don't claim any particular

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Speaker 1: expertise there, but I'll share my thoughts.

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Speaker 2: Sure. Yeah, no, I'll share my thoughts on anything. So

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Speaker 2: I was actually going to ask you, what is the

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Speaker 2: weirdest or most surprising, like no negative connotation needed, but

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Speaker 2: weirdest or most surprising question you've ever been asked related

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Speaker 2: to your career as a physicist.

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Speaker 1: Oh wow, that is such a good question. Now mentally,

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Speaker 1: cycling through the thousands of questions I've gotten over the years,

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Speaker 1: I think one of the most challenging questions to answer

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Speaker 1: are ones about people's personal experiences. People writing sometimes about

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Speaker 1: like their UFO experiences or their paranormal experiences, and they

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Speaker 1: want my physics knowledge and like, what else could have

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Speaker 1: explained it? And that's a delicate line to walk, because

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Speaker 1: you don't want to suggest that what they experienced is

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Speaker 1: not what they think they experienced, but you also want

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Speaker 1: to help them disentangle it and think about what else

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Speaker 1: might have explained it. That's maybe like the most oddball

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Speaker 1: and challenging kind of question to answer. I also sometimes

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Speaker 1: get really touching stories, like a woman who went through

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Speaker 1: her father's old belongings. He was, of course, a retired engineer,

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Speaker 1: and she found in there a treatise on the nature

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Speaker 1: of the universe, and she sent it to me and

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Speaker 1: she's like, look, I don't know if this is anything,

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Speaker 1: but if it is something, I feel terrible not sharing

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Speaker 1: it with the world. Can you tell me if this

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Speaker 1: is worthwhile or not?

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Speaker 2: Aw, that's so cute. I know, was it worthwhile or

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Speaker 2: was it fun to read? But maybe not earth changing?

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Speaker 1: There was nothing really earth chattering in there, but I

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Speaker 1: think she was happy to know that at least somebody

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Speaker 1: had looked at it.

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Speaker 2: What's so cool that you were able to provide that?

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Speaker 1: And how about you? Do you get weird questions from

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Speaker 1: the internet about parasites? People send you pictures of bits

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Speaker 1: of their body and be like, Kelly, what is this?

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Speaker 1: Do I need to go to the er?

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Speaker 2: I do get photos of feces from time to time,

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Speaker 2: and it's worth noting that I cannot identify parasitic infections

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Speaker 2: from a picture of a bell movement their microscopic and

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Speaker 2: I can't. Also, I'm not a medical professional.

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Speaker 1: So everybody out there who was about to email Kelly

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Speaker 1: a picture of their poop not worth your time.

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Speaker 2: Please don't. I think the hardest question for me to answer, though,

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Speaker 2: was I was doing an interview for our book soon ish,

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Speaker 2: and I think the person doing the interview hadn't really

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Speaker 2: read the book, and so his question was, so, tell

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Speaker 2: me about the robots? The robots, and there was like

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Speaker 2: a different robot in every single chapter, and so I

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Speaker 2: didn't have any idea what he was talking about. This

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Speaker 2: is when I learned the trick that when you do

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Speaker 2: an interview, if someone asks you a question that you

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Speaker 2: don't really know what they're trying to get at, you

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Speaker 2: just decide what is the most interesting thing I feel

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Speaker 2: like talking about right now? And so I just picked

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Speaker 2: like my favorite robot and went off on that tangent.

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Speaker 2: It was, that's a learning experience.

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Speaker 1: Sounds like you're ready to run for higher office.

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Speaker 3: Now.

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Speaker 1: I'm going to dodge your question to talk about the

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Speaker 1: thing I want to talk about instead.

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Speaker 2: I don't think i'd make a good politician, all right.

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Speaker 1: Well, you know I would vote for you to represent Virginia,

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Speaker 1: but not California. I don't think you can really appreciate

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Speaker 1: everything that California has to offer.

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Speaker 2: I lived in California for a while. Is it that

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Speaker 2: you don't like Virginia and that's why you would vote

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Speaker 2: for me for Virginia. You want to harm Virginia in somewhere?

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Speaker 1: Well, no, no, no, Virginia is for lovers. It's fantastic.

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Speaker 1: I just don't feel like you appreciate California. I mean,

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Speaker 1: you did leave, right, and so clearly you don't understand

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Speaker 1: that it's objectively the best place in the world to live.

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Speaker 2: You know, I have not regretted leaving, sorry to say so.

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Speaker 2: I guess you're right. I shouldn't be representing California. And

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Speaker 2: maybe I'm going to regret that a decade from now

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Speaker 2: when I run for governor of California, if I've moved back.

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Speaker 2: But for now, I think we're just going to go

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Speaker 2: with no politics for Kelly.

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Speaker 1: That sounds good because I'm gonna have to hold off

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Speaker 1: on endorsing you until I hear you change your opinion California.

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Speaker 1: All right, But let's not talk about Kelly's your future

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Speaker 1: plans to take over the world slash Solar system slash universe.

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Speaker 1: Let's get to questions from listeners, because today on Daniel

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Speaker 1: and Kelly's Extraordinary Universe, we are answering questions from you.

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Speaker 1: We think your questions are important. We want you to

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Speaker 1: understand the universe. We want you to get that satisfying

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Speaker 1: moment where everything clicks in your mind, and so we

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Speaker 1: encourage you to write to us with your questions to

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Speaker 1: questions at Danielankelly dot org. We will write back to you.

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Speaker 1: You'll hear what we do and don't know about whatever

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Speaker 1: it is you're interested in.

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Speaker 2: We can't we do hear from you.

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Speaker 1: Our first question today is from a really fun guy

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Speaker 1: named Barima who lives in Germany. He has a question

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Speaker 1: about gravity. Here is Barima's question.

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Speaker 3: Hello, my name is Brima, living in Germany from England.

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Speaker 3: I'm a big fan of the podcast and I love

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Speaker 3: what you guys are about, Sir. Gravity becomes so strong

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Speaker 3: that it tarts space time, and I was thinking dark

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Speaker 3: energy basically does the same, but in reverse because it's

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Speaker 3: expanding the universe. Both of these phenomena bend or expand

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Speaker 3: fabric of space time. So my question is could dark

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Speaker 3: energy be anti gravity? Thank you for your time and

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Speaker 3: I hope you guys have a great day.

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Speaker 2: Thank you so much for the question, Barima. Well, you know, Daniel,

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Speaker 2: that sounds like a question.

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Speaker 4: For you.

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Speaker 1: Gravity, space time and dark energy. Ooh, this is my

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Speaker 1: jam for sure.

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Speaker 2: We've recently recorded episodes on what is time and what

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Speaker 2: is space which might provide some important context. But how

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Speaker 2: do we answer this question more directly?

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Speaker 1: This is a great question because it gives us an

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Speaker 1: opportunity to connect a lot of ideas. You hear a

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Speaker 1: lot about space time as a fabric, black holes, having

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Speaker 1: extreme gravity, dark energy pulling space apart. How does it

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Speaker 1: all work? How do you think about that altogether? My

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Speaker 1: interpretation of Brima's question is that he's thinking about black

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Speaker 1: holes and he's heard that black holes tear space time,

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Speaker 1: so he's thinking about that as like pulling space itself apart.

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Speaker 1: And he's also heard that the universe is expanding in

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Speaker 1: an accelerating way, which feels like it's ripping space apart,

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Speaker 1: and so he's wondering, like, are those the same thing

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Speaker 1: or are they the opposite? Because black holes attract and

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Speaker 1: dark energy is pulling space apart, how does it all work?

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Speaker 1: And is dark energy actually the opposite form of gravity?

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Speaker 1: So we're going to give Burrimo a way to think

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Speaker 1: about dark energy in terms of gravity in general relativity

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Speaker 1: and link all these ideas together. But we should probably

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Speaker 1: start with black holes and space time and think about

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Speaker 1: what it means to tear space time.

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Speaker 2: Apart, and does this have anything to do We had

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Speaker 2: a conversation about a map and how you can like

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Speaker 2: make the cities closer or farther apart. Is that the

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Speaker 2: right way to start thinking about this problem, or now

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Speaker 2: that we're talking about black holes, we're in a totally

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Speaker 2: different universe.

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Speaker 1: No, that's exactly the right way to start thinking about this.

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Speaker 1: Let's get a mental picture of what space is or

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Speaker 1: space time is, and what it means to tear space

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Speaker 1: time or what happens when gravity gets really really strong.

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Speaker 1: So let's start with a model of space. What is

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Speaker 1: space space? We don't know what it is fundamentally, but

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Speaker 1: we know that we can measure the distance between two points.

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Speaker 1: You have like a ruler. You can measure how many

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Speaker 1: ticks are between two points, and you can do that

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Speaker 1: between La and Virginia, or you can do that between

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Speaker 1: Canada and Mexico, or between Seattle and Miami or whatever.

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Speaker 1: You can measure distances between points. So we know that

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Speaker 1: we can measure these distances. We don't understand what is

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Speaker 1: the underlying fabric and what is it doing and how

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Speaker 1: does it work, But we can measure these distances, and

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Speaker 1: we notice that if you put a mass in space,

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Speaker 1: like a star or a planet or whatever, those distances

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Speaker 1: get kind of wonky like things get closer together, things

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Speaker 1: get further apart. This is what we mean when we

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Speaker 1: say space is curved. It's not like it's curving in

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Speaker 1: some external dimension with a whole crazy rubber sheet analogy.

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Speaker 1: It just means that it's changing the intrinsic distances between stuff.

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Speaker 1: The curvature of space is not external and some other dimension.

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Speaker 1: It's internal. It's intrinsic. It's just a relative change of distances.

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Speaker 1: And so when we say space is curve, we just

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Speaker 1: mean you're tweaking all of those distances.

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Speaker 2: I think if I were listening to the podcast, this

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Speaker 2: is where I would pause it and just stare at

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Speaker 2: the wall for five minutes and be like, how do

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Speaker 2: I make sense of this? It's all kind of complicated,

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Speaker 2: but yeah, I'm following.

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Speaker 1: Yeah, And you call up this mental picture of a map.

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Speaker 1: So imagine you had a map the United States and

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Speaker 1: you laid it flat on a table and you measure

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Speaker 1: the distances between these cities. Those distances have to follow

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Speaker 1: some rules because the map is flat. If you measure

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Speaker 1: all those distances like from LA to Seattle, and Seattle

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Speaker 1: to New York and New York to Miami and Miami

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Speaker 1: back to LA, that's kind of a square, right, you

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Speaker 1: measure all those distances, and those distances have to follow

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Speaker 1: some rules because the map is flat on the table. Like,

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Speaker 1: from those distances, I can tell you how far it

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Speaker 1: is from LA to New York. It's constrained by those

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Speaker 1: other measurements. But what if I told you I'm just

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Speaker 1: going to go in and make LA and New York

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Speaker 1: closer together, I'm just squeezing them together. Well, then the

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Speaker 1: map can no longer be flat because I have to

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Speaker 1: like bunch up the material between LA and New York.

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Speaker 1: And that's what curving space does. It changes the relative

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Speaker 1: distances between these points, so they no longer add up

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Speaker 1: in the same way they would if they were on

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Speaker 1: flat space. That's what curved space is, just changes those

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Speaker 1: relative distances. And the crazy thing is that you can

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Speaker 1: do that. You can develop a model of space that

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Speaker 1: incorporates all these weird changes of distances. And that's what

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Speaker 1: we call curved space, all right.

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Speaker 2: So it's never tearing. There's never a spot where it

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Speaker 2: like breaks and then there's nothing in between. It just

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Speaker 2: kind of gets like curvy, like a roller coaster.

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Speaker 1: At some point exactly, you can't really tear space time.

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Speaker 1: That's like a dramatic visual people use, but it's not

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Speaker 1: a helpful way to think about it. And remember, we

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Speaker 1: don't know what space is. We have this beautiful mathematical

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Speaker 1: description from Einstein that lets us think about this concept

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Speaker 1: of curvature in terms of these changing relative distances, but

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Speaker 1: that's just our model. It's useful for describing space. Doesn't

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Speaker 1: always tell us what space actually is, but it does

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Speaker 1: predict crazy stuff like if you have a huge amount

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Speaker 1: of mass, the curvature gets really really strong, and you

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Speaker 1: get things like black holes, places where space is so

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Speaker 1: curved that light can no longer escape because not only

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Speaker 1: does it change the relation so distances, it changes like

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Speaker 1: the directions, and inside a black hole, space is now

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Speaker 1: one directional. Every direction inside a black hole is just

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Speaker 1: towards the center. It's not that light can't escape because

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Speaker 1: the force of gravity is so strong. It's because every

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Speaker 1: direction is towards the center. Now there are no other

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Speaker 1: directions inside a black hole. So a black hole is

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Speaker 1: so massive it like rearranges the relationships between points in space.

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Speaker 2: Okay, so the order of the direction there is that

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Speaker 2: the black hole starts pulling on space. It's not that

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Speaker 2: like space gets bent for some other reason, and that

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Speaker 2: causes a black hole.

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Speaker 1: Yeah, that's right. The presence of mass causes the bending

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Speaker 1: of space, and that's what the black hole is. Yeah, exactly. Okay,

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Speaker 1: So that's the way to think about like gravity and

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Speaker 1: black holes and bending of space time. But Burma is

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Speaker 1: asking us to connect that to the expansion of the

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Speaker 1: universe and how the universe we've noticed in the last

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Speaker 1: twenty years or so is not just getting bigger, it's

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Speaker 1: getting bigger faster and faster as time goes on. And

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Speaker 1: this is the mystery we call dark energy. We don't

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Speaker 1: understand the source of that expansion or why it's accelerating.

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Speaker 2: Okay, so we know that it's accelerating, and we're using

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Speaker 2: dark energy as the explanation, and is that the extent

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Speaker 2: of what we know about dark energy is that it

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Speaker 2: is the magical way that this all works out.

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Speaker 1: Essentially, dark energy is shorthand for saying, we see the

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Speaker 1: universe is accelerating its expansion, we don't understand why. Please

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Speaker 1: somebody figure it out, and we don't have a working explanation.

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Speaker 1: We have sort of like a sketch on the back

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Speaker 1: of a napkin idea that might work out, But currently

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Speaker 1: the calculations are not connecting, and they're off by like

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Speaker 1: ten with one hundred zeros. But the sketch of the

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Speaker 1: explanation actually comes from general relativity. General relativity, of course,

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Speaker 1: is Einstein's generalization of Newton's gravity. Newton says, masses attract

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Speaker 1: each other because there's a force. Einstein says, no, Actually

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Speaker 1: it's more complicated. Space time curves and it gives mostly

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Speaker 1: the same behavior. But there's a little bit more to

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Speaker 1: Einstein's general relativity than just mass bend space time. Einstein's

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Speaker 1: relativity also lets other things happen. So, for example, Einstein says, yes,

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Speaker 1: if you have mass in space time, then space curves

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Speaker 1: and things get closer together. But also if you fill

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Speaker 1: the universe with potential energy, not mass energy, but some

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Speaker 1: weird kind of potential energy, then it causes the opposite effect.

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Speaker 1: It causes things to move apart. It's like a negative pressure.

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Speaker 1: This is the fascinating thing is that Newton's gravity is

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Speaker 1: just attractive. You can only pull stuff together. Einstein's gravity

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Speaker 1: is a generalization of that and allows in some weird

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Speaker 1: situations for things to get pushed apart by general relativity.

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Speaker 2: Okay, so we've got gravity and dark energy. Gravity pulls in,

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Speaker 2: dark energy pushes out. How do we determine who wins where?

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Speaker 1: Yes, all right, great question. But first I want to

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Speaker 1: be technical about what we mean by gravity, because when

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Speaker 1: some people hear gravity, they think the pulling together part.

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Speaker 1: Other people hear gravity they think general relativity, which can

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Speaker 1: include dark energy. So in some sense, gravity could be

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Speaker 1: the attractive part and the dark energy part, or some

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Speaker 1: people could just think about gravity as the attractive part.

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Speaker 1: So let's just call gravity the attractive part, and when

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Speaker 1: we're talking about the whole shebang, we'll call it that

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Speaker 1: general relativity. So you're asking about, like when is the

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Speaker 1: attractive part of gravity, things tugging on each other when?

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Speaker 1: And when does dark energy the universe pulling itself apart? When?

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Speaker 1: And that depends on distance. So the attractive part of

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Speaker 1: the parts is like Newton, that gets strong when things

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Speaker 1: are closer together, Like the closer you are to a star,

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Speaker 1: the more it's gravity is going to pull on you,

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Speaker 1: the more space time is bent in a way that's

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Speaker 1: going to move you closer, and as you get further away,

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Speaker 1: that fades. So like we don't feel much gravity from

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Speaker 1: Jupiter because it's kind of far away. We don't feel

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Speaker 1: much gravity from other stars because they're even further away,

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Speaker 1: et cetera, et cetera. So gravity gets weaker with distance.

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Speaker 1: Dark energy has the opposite relationship. Dark energy is like

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Speaker 1: every chunk of space is getting bigger. So if you

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Speaker 1: just have one little chunk of space, it's getting bigger

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Speaker 1: by a tiny amount. But if you have lots of

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Speaker 1: chunks of space huge day distances, then that adds up,

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Speaker 1: and so over big distances, dark energy becomes very very powerful.

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Speaker 1: So like between our galaxy and other galaxies, there's a

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Speaker 1: lot of space. If all that space is expanding by

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Speaker 1: a little bit, all those little bits add up to

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Speaker 1: a huge expansion. So dark energy gets more powerful at

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Speaker 1: greater distances. So, for example, between our cluster of galaxies

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Speaker 1: and the neighboring cluster of galaxies, dark energy is winning.

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Speaker 1: There's not enough gravity to hold those together, and they're

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Speaker 1: getting pulled apart by dark energy. All that space is

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Speaker 1: expanding faster, and gravity can hold stuff together. But in

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Speaker 1: our Solar system, though, there is dark energy here and

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Speaker 1: it is expanding the space between our planet and the Sun.

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Speaker 1: Gravity is more powerful because it's a fairly small distance

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Speaker 1: so gravity wins, so shorter distances, like smaller than a

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Speaker 1: galactic supercluster, gravity wins big distances, bigger than a galactic supercluster,

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Speaker 1: dark energy wins.

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Speaker 2: Okay, so that makes sense to me. And so you

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Speaker 2: said that that dark energy is a form of kinetic.

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Speaker 1: Energy potential energy.

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Speaker 2: Actually, wow, they're the same thing.

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Speaker 1: They're so one hundred percent not the same time.

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Speaker 2: Smart. Okay, it's a form of potential energy. And so

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Speaker 2: does that make dark energy like negative potential energy? Our

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Speaker 2: gravity and dark energy just opposites of one another.

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Speaker 1: Yeah, great question. So number one, we don't know where

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Speaker 1: the potential energy comes from. That's the big mystery. Like

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Speaker 1: to have enough potential energy to explain the accelerating expansion

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Speaker 1: we see, you'd need a lot more energy than we

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Speaker 1: can account for. If you add of all the potential

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Speaker 1: energy we know about in the universe from the Higgs

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Speaker 1: field and all the other fields and all that stuff,

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Speaker 1: you get a number. That number we calculate doesn't match

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Speaker 1: the accelerating expansion we see in the universe, and it's

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Speaker 1: not even close. The two numbers are off by ten

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Speaker 1: to the one hundred and twenty. So general relativity has

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Speaker 1: a mechanism to create this negative pressure requires positive potential energy.

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Speaker 1: We can't explain source of that potential energy we don't know,

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Speaker 1: So that's the remaining mystery, Like there is no potential

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Speaker 1: energy we know about that is capable of doing this,

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Speaker 1: which might mean there's some other field out there we

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Speaker 1: don't understand. But it requires positive potential energy to create

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Speaker 1: this negative pressure, this pulling things apart. So to bring

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Speaker 1: this sort of back to Bhima's question, he's asking, like,

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Speaker 1: could dark energy be anti gravity? And the answer is

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Speaker 1: kind of yes, Like dark energy is a component of

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Speaker 1: general relativity that allows for pulling things apart, sort of

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Speaker 1: opposite to the attractive part of gravity. So if you

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Speaker 1: consider gravity to just be the attractive part of general relativity,

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Speaker 1: and then yeah, dark energy is sort of the opposite

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Speaker 1: of that. It's still a component of general relativity, but

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Speaker 1: it has the opposite effect that creates negative pressure.

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Speaker 2: Okay, well, thank you for that great question, Burima.

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Speaker 1: And so now I'm curious whether we answered Bhurima's question,

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Speaker 1: whether we scratched his itch, or whether we totally misunderstood,

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Speaker 1: or whether we just confused him further with our crazy

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Speaker 1: description of LA and my so I reached out to

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Speaker 1: Burima and I sent him our conversation to hear what

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Speaker 1: he had to say. Here's Burma's reaction. Okay, thank you

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Speaker 1: very much Burima for joining us here on the podcast

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Speaker 1: and for sending in such a wonderful and fun question.

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Speaker 1: So tell me what did you think of our answer

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Speaker 1: and did we answer your question? Did we create more

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Speaker 1: questions in your mind? I'm dying to hear your thoughts.

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Speaker 5: Yeah, So thank you for answering the question. It's great

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Speaker 5: to be here. I think you guys pretty much answered

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Speaker 5: the question bang on. It did blow my mind, if

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Speaker 5: I'm being one hundred percent honest, because at first I

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Speaker 5: was like, Okay, where is this going, and then at

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Speaker 5: the end sort of just landed it very nicely. It

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Speaker 5: did raise another question that I have. You mentioned the

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Speaker 5: dark energy sort of being caused by potential energy, and

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Speaker 5: my follow up question was does that have anything to

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Speaker 5: do with then zero point energy?

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Speaker 1: Yeah, so the two things are definitely connected. Zero point

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Speaker 1: energy is a description of basically minimum energy that a

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Speaker 1: quantum field can have. Quantum fields are like oscillating in space.

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Speaker 1: There's zigging and zagging, they're whizzing back and forth. There's

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Speaker 1: energy there of their motion, the changing of their values.

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Speaker 1: That's kinetic energy, and they can also have potential energy

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Speaker 1: if they're in some weird configuration. Zero point energy just

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Speaker 1: says that the total energy, the combination of kinetic and

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Speaker 1: potential and any other kind of energy, can never go

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Speaker 1: to zero because quantum fields can never be totally flat

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Speaker 1: like a classical field. An electrical field can be just zero.

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Speaker 1: You can have like no electric field because you have

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Speaker 1: no electric charges. It can be totally zero. But if

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Speaker 1: it's a quantum field, it's always buzzing and frothing a

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Speaker 1: tiny little bit. There's a minimum energy there. But the

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Speaker 1: potential energy we think is causing dark energy comes from

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Speaker 1: a field we don't know. We don't know what field

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Speaker 1: is out there doing it. There's only one field we

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Speaker 1: know about that has a lot of potential energy. That's

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Speaker 1: the Higgs field. We know that it fills space with

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Speaker 1: this weird potential energy that gives all particles mass. But

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Speaker 1: when we sit down and try to calculate is the

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Speaker 1: potential energy from the Higgs field enough to explain dark

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Speaker 1: energy and the acceleration, we find that it's not like

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Speaker 1: they're different by ten with one hundred zeros. So, yeah,

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Speaker 1: we're not even close to understanding the source of dark energy. Yeah,

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Speaker 1: we're not even close to being close.

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Speaker 5: Yeah, okay, yeah, well thank you, yeah.

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Speaker 1: Yeah, well, thanks very much for sending your question and

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Speaker 1: for doing this follow up. Lots of fun to chat

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Speaker 1: with you.

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Speaker 5: Yeah, thank you very much. It's been a pleasure and

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Speaker 5: I learned something.

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Speaker 1: And that's our entire goal. All Right, Thanks everyone, And

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Speaker 1: if you have a question about the nature of the universe,

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Speaker 1: or if you'd heard something you haven't quite understood, please

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Speaker 1: send it to us. We'd love to answer your question.

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Speaker 2: All right, Well that was our first question. Now we're

435
00:21:43,119 --> 00:21:45,919
Speaker 2: going to move on to a question in Kelly's wheelhouse,

436
00:21:45,960 --> 00:22:05,040
Speaker 2: which we'll get to after the break. All right, we're

437
00:22:05,080 --> 00:22:06,880
Speaker 2: back from the break and we're going to tackle our

438
00:22:06,920 --> 00:22:12,439
Speaker 2: first biology oriented listener question. So Charlie Davidson had this

439
00:22:12,560 --> 00:22:13,400
Speaker 2: question for us.

440
00:22:14,400 --> 00:22:16,760
Speaker 6: Hi, Daniel and Kelly, I've got a question for your

441
00:22:16,800 --> 00:22:21,440
Speaker 6: new podcast about slime mold computation. How is it possible

442
00:22:21,600 --> 00:22:25,200
Speaker 6: for a bunch of single celled organisms to perform programmable

443
00:22:25,280 --> 00:22:29,800
Speaker 6: computational tasks for people? It just seems wild to me,

444
00:22:30,240 --> 00:22:32,680
Speaker 6: so I'd love to hear more about it and find

445
00:22:32,680 --> 00:22:35,560
Speaker 6: out how on Earth that works. Thanks very much, by.

446
00:22:35,480 --> 00:22:39,720
Speaker 2: Bye, oh Man, Charlie. In my family, we call this

447
00:22:39,800 --> 00:22:44,440
Speaker 2: the ten thousand dollars question because that's how much money

448
00:22:44,440 --> 00:22:48,760
Speaker 2: we lost thinking about this problem. So here is the story,

449
00:22:48,800 --> 00:22:52,919
Speaker 2: all right. So slime molds are single celled organisms that

450
00:22:53,240 --> 00:22:56,280
Speaker 2: are thought to be really great at solving mases. This

451
00:22:56,320 --> 00:22:58,800
Speaker 2: has become like a fact that's entered the you know,

452
00:22:58,920 --> 00:23:01,560
Speaker 2: general consciousness. You say something about slime molds and they'll

453
00:23:01,600 --> 00:23:04,280
Speaker 2: be like, oh, they're really great at solving mazes, and

454
00:23:04,320 --> 00:23:07,760
Speaker 2: they've become famous for like solving straight up mazes. They've

455
00:23:07,800 --> 00:23:11,800
Speaker 2: also become famous for being able to recreate transportation systems.

456
00:23:11,840 --> 00:23:14,320
Speaker 2: So if you put a bunch of different cities on

457
00:23:14,440 --> 00:23:17,399
Speaker 2: a map, and you put a piece of oat on

458
00:23:17,520 --> 00:23:20,600
Speaker 2: the different cities, the slime mold will start growing on

459
00:23:20,640 --> 00:23:22,919
Speaker 2: that oat. I believe it's actually eating the bacteria and

460
00:23:22,960 --> 00:23:25,920
Speaker 2: the fungus on that oat, and then it will spread

461
00:23:25,920 --> 00:23:28,719
Speaker 2: out and it will find the other oats, and if

462
00:23:28,760 --> 00:23:31,240
Speaker 2: it's working the way we want it to work, it

463
00:23:31,280 --> 00:23:35,600
Speaker 2: will then contract and only have the shortest paths between

464
00:23:35,640 --> 00:23:39,600
Speaker 2: those things. And so perhaps you've seen videos that like

465
00:23:40,000 --> 00:23:42,119
Speaker 2: where the slime molds have created this map that is

466
00:23:42,160 --> 00:23:44,439
Speaker 2: almost exactly the same as like the map of the

467
00:23:44,440 --> 00:23:47,520
Speaker 2: transportation system matches up almost perfectly with what the slime

468
00:23:47,520 --> 00:23:49,080
Speaker 2: mold did. It's really impressive.

469
00:23:49,280 --> 00:23:51,640
Speaker 1: This is really appealing. I understand why people are into

470
00:23:51,680 --> 00:23:54,880
Speaker 1: this because it suggests like there's another way to do calculations,

471
00:23:54,960 --> 00:23:57,359
Speaker 1: or this is like a biological computer, or maybe even

472
00:23:57,400 --> 00:24:00,320
Speaker 1: some like awareness. Right. I feel like we were so

473
00:24:00,720 --> 00:24:03,240
Speaker 1: hungry to discover we're not alone in the universe that

474
00:24:03,240 --> 00:24:05,520
Speaker 1: we're looking for like aliens here on Earth, even in

475
00:24:05,560 --> 00:24:06,440
Speaker 1: slime molds.

476
00:24:06,960 --> 00:24:08,560
Speaker 2: Yeah right, well, I mean if slime olds can be

477
00:24:08,560 --> 00:24:11,320
Speaker 2: that smart, what else have we missed? Right? That's incredible. Yeah,

478
00:24:11,359 --> 00:24:13,720
Speaker 2: and did you see the dark matter example?

479
00:24:13,960 --> 00:24:16,760
Speaker 1: Mm hmmm I did. Yet they used slime molds to

480
00:24:16,880 --> 00:24:20,840
Speaker 1: understand the filaments of dark matter between galaxies, which was

481
00:24:20,840 --> 00:24:21,400
Speaker 1: pretty cool.

482
00:24:21,520 --> 00:24:24,439
Speaker 2: I think that they used a computational model based on

483
00:24:24,560 --> 00:24:27,119
Speaker 2: the behavior of slime molds. Yeah, since it's like a

484
00:24:27,160 --> 00:24:28,600
Speaker 2: three D things that would be a little bit harder

485
00:24:28,640 --> 00:24:28,840
Speaker 2: to do.

486
00:24:29,000 --> 00:24:31,080
Speaker 1: No, I don't think they had like cosmic slime molds

487
00:24:31,119 --> 00:24:33,119
Speaker 1: between actual galaxies. That would be awesome.

488
00:24:33,240 --> 00:24:36,760
Speaker 2: Wow, that would be made me scary but interesting. So

489
00:24:37,080 --> 00:24:39,720
Speaker 2: my husband and I got really excited about these slime molds.

490
00:24:39,760 --> 00:24:42,320
Speaker 2: We're like, you know, this seems like such an easy

491
00:24:43,119 --> 00:24:45,240
Speaker 2: thing that you should be able to recreate at home.

492
00:24:45,800 --> 00:24:48,840
Speaker 2: And so many science experiments are you know that we

493
00:24:48,920 --> 00:24:50,600
Speaker 2: remembered that we did at school when we were kids.

494
00:24:50,640 --> 00:24:53,240
Speaker 2: We're like, not super exciting. They didn't necessarily stay with you.

495
00:24:53,880 --> 00:24:57,360
Speaker 2: So we got really excited about making slime mold mazes

496
00:24:57,800 --> 00:25:00,520
Speaker 2: that you could sell pretty cheaply to class so that

497
00:25:00,600 --> 00:25:02,360
Speaker 2: they could recreate these experiments.

498
00:25:02,640 --> 00:25:06,080
Speaker 1: I'm getting an ironic foreshadowing vibe here that you're setting

499
00:25:06,119 --> 00:25:07,680
Speaker 1: us up for a big disappointment. Is this going to

500
00:25:07,720 --> 00:25:09,480
Speaker 1: be another Kelly throws cold water on things?

501
00:25:09,560 --> 00:25:11,680
Speaker 2: I mean, that's what I do, right, How else could

502
00:25:11,720 --> 00:25:12,040
Speaker 2: this have.

503
00:25:12,040 --> 00:25:14,639
Speaker 1: Gone into your skills? Kelly?

504
00:25:15,000 --> 00:25:16,440
Speaker 2: You know, yeah, I didn't think this was going to

505
00:25:16,520 --> 00:25:18,520
Speaker 2: be my niche, but it is, so here we go,

506
00:25:18,680 --> 00:25:21,720
Speaker 2: all right. So Zach was excited about this first. I

507
00:25:21,760 --> 00:25:23,520
Speaker 2: was busy with something else at the time. So we

508
00:25:23,520 --> 00:25:25,359
Speaker 2: were living in Alabama and he was like in our

509
00:25:25,440 --> 00:25:29,560
Speaker 2: humid garage trying to use legos to build mazes, and

510
00:25:29,560 --> 00:25:32,000
Speaker 2: then he was pouring auger in there, and augur, is

511
00:25:32,040 --> 00:25:33,520
Speaker 2: this thing that like when it's hot it's sort of

512
00:25:33,560 --> 00:25:36,359
Speaker 2: like viscous and fluidy, but when it cools, it cools

513
00:25:36,400 --> 00:25:39,240
Speaker 2: to like kind of smooshy surface that something can grow on.

514
00:25:39,920 --> 00:25:42,000
Speaker 2: So he was trying to like make mazes in our

515
00:25:42,040 --> 00:25:44,159
Speaker 2: garage out of this stuff. And then he went to

516
00:25:44,200 --> 00:25:48,359
Speaker 2: Carolina Biological website and he bought slime mold. Specifically, he

517
00:25:48,400 --> 00:25:51,840
Speaker 2: bought fisarm polycephalus, which is the main like yellow species

518
00:25:51,840 --> 00:25:54,000
Speaker 2: that people usually see when they're thinking of these mazes.

519
00:25:54,200 --> 00:25:57,040
Speaker 1: But tell us briefly, what is a slime mold exactly?

520
00:25:57,160 --> 00:25:59,399
Speaker 1: Is it a mold? Is it slime? Is it totally

521
00:25:59,400 --> 00:25:59,960
Speaker 1: badly named?

522
00:26:00,320 --> 00:26:02,320
Speaker 2: It's not really a slime. It's not really a mold.

523
00:26:02,400 --> 00:26:05,200
Speaker 2: It's its own thing. It has a complicated life cycle.

524
00:26:05,600 --> 00:26:07,800
Speaker 2: But when it's at the part of its life cycle

525
00:26:07,840 --> 00:26:12,480
Speaker 2: where it is solving these mazes, it's a single cell

526
00:26:12,560 --> 00:26:15,520
Speaker 2: with a bunch of nuclei in it. Wow, which is

527
00:26:15,600 --> 00:26:17,840
Speaker 2: kind of amazing. I think we should actually have a

528
00:26:17,920 --> 00:26:21,040
Speaker 2: whole episode on why organisms would ever have multiple nuclei

529
00:26:21,240 --> 00:26:23,879
Speaker 2: in the same cell, Like what problems does that solve?

530
00:26:23,920 --> 00:26:26,480
Speaker 2: Because my brain like more than one nucleus. That just

531
00:26:26,480 --> 00:26:28,520
Speaker 2: doesn't make sense. So he was trying to do it

532
00:26:28,560 --> 00:26:31,320
Speaker 2: that wasn't working, and so then we moved to Virginia

533
00:26:31,440 --> 00:26:33,000
Speaker 2: and he was like, okay, you know what, I'm going

534
00:26:33,040 --> 00:26:36,160
Speaker 2: to like outsource to experts. So he hired an engineer

535
00:26:36,200 --> 00:26:37,720
Speaker 2: and he was like, all right, engineer, I want you

536
00:26:37,760 --> 00:26:40,440
Speaker 2: to make me a really nice maze because the augur

537
00:26:40,560 --> 00:26:42,960
Speaker 2: kept like seeping through my legos. It just wasn't working

538
00:26:43,040 --> 00:26:45,000
Speaker 2: the way I wanted it. To make me a really

539
00:26:45,080 --> 00:26:47,760
Speaker 2: nice maze with a really nice cover. And the engineer

540
00:26:47,840 --> 00:26:50,600
Speaker 2: is like, okay, great, I'll do that, but it's going

541
00:26:50,680 --> 00:26:53,679
Speaker 2: to cost ten thousand dollars to make an injection molded maze.

542
00:26:54,160 --> 00:26:56,679
Speaker 2: And Zach was like, oh, that's a little steep, but

543
00:26:56,880 --> 00:26:59,320
Speaker 2: I really think kids would enjoy this, and we're going

544
00:26:59,400 --> 00:27:02,080
Speaker 2: to do it. So he pays and he does it. Yeah,

545
00:27:02,119 --> 00:27:04,199
Speaker 2: I know, And so he ran it by me and

546
00:27:04,240 --> 00:27:06,520
Speaker 2: I was like, I don't know that that's a great decision,

547
00:27:06,680 --> 00:27:08,199
Speaker 2: but okay, let's try it.

548
00:27:08,280 --> 00:27:10,000
Speaker 1: This is what happens when you have one family with

549
00:27:10,000 --> 00:27:13,400
Speaker 1: two nuclei right yere, different nuclei i making different decisions,

550
00:27:13,440 --> 00:27:15,720
Speaker 1: like you know, this slime mold is spending ten k

551
00:27:15,840 --> 00:27:18,240
Speaker 1: over here, and that nuclei is objecting to it. You know,

552
00:27:18,240 --> 00:27:19,399
Speaker 1: it's like a model of a family.

553
00:27:19,480 --> 00:27:21,920
Speaker 2: That's totally true. I should have known this problem was coming.

554
00:27:22,359 --> 00:27:24,239
Speaker 2: So he gets this maze, and you know, we've had

555
00:27:24,240 --> 00:27:26,280
Speaker 2: a lot of conversations about like, oh, it's so funny

556
00:27:26,320 --> 00:27:29,840
Speaker 2: that Carolina Biological sells slime mold, but they don't sell

557
00:27:29,880 --> 00:27:32,240
Speaker 2: these mazes. I wonder why they don't sell these mazes.

558
00:27:32,560 --> 00:27:34,560
Speaker 2: And so we get the mazes and then Zach's like, okay,

559
00:27:34,600 --> 00:27:36,760
Speaker 2: so now I'm taking this project to the biologist. So

560
00:27:36,840 --> 00:27:38,560
Speaker 2: I got a bunch of augur, I got a bunch

561
00:27:38,600 --> 00:27:41,720
Speaker 2: of slime molds. I'm like using my sterile technique, and

562
00:27:41,760 --> 00:27:43,960
Speaker 2: I'm trying to run these mazes. And it's my job

563
00:27:44,000 --> 00:27:46,399
Speaker 2: to write the protocol and the direction so the classrooms

564
00:27:46,440 --> 00:27:49,000
Speaker 2: can do this. And so I start doing it and

565
00:27:49,040 --> 00:27:53,920
Speaker 2: it's not working. The slimepuwter is not solving the maze

566
00:27:54,000 --> 00:27:54,919
Speaker 2: the way it's supposed to.

567
00:27:55,480 --> 00:27:57,800
Speaker 1: So what is it supposed to do? Exactly, Like you

568
00:27:57,840 --> 00:27:59,480
Speaker 1: put it in the beginning and you put an ode

569
00:27:59,480 --> 00:28:01,359
Speaker 1: at the end. It's supposed to find the shortest path

570
00:28:01,480 --> 00:28:05,160
Speaker 1: through the maze exactly, and how could it possibly do that?

571
00:28:05,240 --> 00:28:08,320
Speaker 1: Like it's supposed to explore every direction and then eventually

572
00:28:08,320 --> 00:28:10,840
Speaker 1: figure out which of the paths is found is the shortest,

573
00:28:11,040 --> 00:28:13,280
Speaker 1: and then slowly coalesce onto that. Is that the best

574
00:28:13,320 --> 00:28:13,960
Speaker 1: case scenario.

575
00:28:14,280 --> 00:28:16,000
Speaker 2: So that's what we thought was supposed to be happening.

576
00:28:16,040 --> 00:28:19,879
Speaker 2: And so I contacted an expert who works in this field,

577
00:28:20,400 --> 00:28:22,400
Speaker 2: and I was like, it's not working for me? Why

578
00:28:22,440 --> 00:28:23,480
Speaker 2: is it not working for me?

579
00:28:23,480 --> 00:28:25,520
Speaker 1: Meaning what were you seeing? Like it just didn't find

580
00:28:25,520 --> 00:28:28,080
Speaker 1: the end or found the wrong path, or it just didn't.

581
00:28:27,800 --> 00:28:30,240
Speaker 2: Go anywhere, or it was not finding the shortest path.

582
00:28:30,400 --> 00:28:33,280
Speaker 2: I see something like twenty to thirty percent of the

583
00:28:33,320 --> 00:28:36,000
Speaker 2: time it would end up at the right path, which

584
00:28:36,080 --> 00:28:39,640
Speaker 2: was essentially like random chance. And I contacted a person

585
00:28:39,680 --> 00:28:42,160
Speaker 2: who was doing even simpler experiments in their class. But

586
00:28:42,160 --> 00:28:44,640
Speaker 2: it was like a peatrit dish and then an oat

587
00:28:44,680 --> 00:28:46,320
Speaker 2: in the middle is a starting point and an oat

588
00:28:46,400 --> 00:28:49,160
Speaker 2: on one side, and so it should have been very

589
00:28:49,160 --> 00:28:51,400
Speaker 2: simple to just like it expands and then it was

590
00:28:51,440 --> 00:28:53,440
Speaker 2: supposed to just sort of contract to just be this

591
00:28:53,560 --> 00:28:56,240
Speaker 2: short straight line distance. And they were like, oh, yeah,

592
00:28:56,280 --> 00:28:59,440
Speaker 2: that experiment never worked, but apparently at always, well maybe

593
00:28:59,440 --> 00:29:01,560
Speaker 2: your students are doing something wrong. So I reached out

594
00:29:01,560 --> 00:29:03,680
Speaker 2: to this expert and he's like, well, first of all,

595
00:29:04,200 --> 00:29:06,800
Speaker 2: the way that it solves it is it's following a

596
00:29:06,880 --> 00:29:11,000
Speaker 2: chemical trail, and so the chemical trail needs to be

597
00:29:11,480 --> 00:29:14,480
Speaker 2: incredibly easy to detect. So instead of oatmeal, you could

598
00:29:14,520 --> 00:29:17,640
Speaker 2: try something that's like creates more chemicals and makes a

599
00:29:17,680 --> 00:29:20,560
Speaker 2: more clear path. And I was like, well that's not

600
00:29:21,040 --> 00:29:23,920
Speaker 2: how I had been taught that this works. And I

601
00:29:23,960 --> 00:29:26,280
Speaker 2: was like, okay, well, what percent of the time, if

602
00:29:26,280 --> 00:29:29,200
Speaker 2: I'm doing it right, should I expect it to solve

603
00:29:29,240 --> 00:29:31,040
Speaker 2: the maze? Because, like I'm thinking, the answer should be

604
00:29:31,040 --> 00:29:32,959
Speaker 2: close to one hundred percent. Based on what people are

605
00:29:32,960 --> 00:29:34,040
Speaker 2: saying on Twitter.

606
00:29:34,760 --> 00:29:38,320
Speaker 1: Always are reliable resource. Twitter is basically one big documentary, Right,

607
00:29:38,360 --> 00:29:39,040
Speaker 1: you can rely on it?

608
00:29:39,120 --> 00:29:39,280
Speaker 6: Yeah?

609
00:29:39,360 --> 00:29:41,200
Speaker 2: Right. We spent ten k based on Twitter advice. It

610
00:29:41,240 --> 00:29:41,920
Speaker 2: was a great choice.

611
00:29:42,040 --> 00:29:44,160
Speaker 1: I cig Twitter in my science papers all the time.

612
00:29:44,880 --> 00:29:48,440
Speaker 2: Oh wow, No, of course it's a good thing. You've

613
00:29:48,480 --> 00:29:49,400
Speaker 2: got tenure.

614
00:29:50,800 --> 00:29:53,760
Speaker 1: Anyway, So you're told that these things don't actually solve

615
00:29:53,760 --> 00:29:55,960
Speaker 1: the problem. They just follow a trail, which is very

616
00:29:55,960 --> 00:29:58,200
Speaker 1: different from like considering all the past to figure out

617
00:29:58,200 --> 00:30:00,200
Speaker 1: which is shortest and then coalescing on that one. That's

618
00:30:00,240 --> 00:30:02,000
Speaker 1: like they just walked through to the solution.

619
00:30:02,160 --> 00:30:04,200
Speaker 2: Sometimes I'll smell a hot dog, and I'll just walk

620
00:30:04,320 --> 00:30:06,840
Speaker 2: towards the source of the hot dog, and it's like,

621
00:30:06,880 --> 00:30:09,160
Speaker 2: not that different. That's not impressive that I can do that.

622
00:30:09,320 --> 00:30:11,640
Speaker 1: Can you actually resist hot dogs? Like if you walk

623
00:30:11,720 --> 00:30:17,480
Speaker 1: after hot dog, everybody knows you're kryptonite. Now wow, it's

624
00:30:17,520 --> 00:30:17,880
Speaker 1: just like.

625
00:30:18,720 --> 00:30:20,760
Speaker 2: I actually can't. I worked at the zoo once and

626
00:30:20,800 --> 00:30:23,440
Speaker 2: we switched from all beef hot dogs to all meat

627
00:30:23,480 --> 00:30:28,120
Speaker 2: hot dogs. Ooh, and wondering what that downgrade meant put

628
00:30:28,160 --> 00:30:30,080
Speaker 2: me off hot dogs because I started thinking about it

629
00:30:30,120 --> 00:30:32,840
Speaker 2: too hard. But anyway, well, let's not droll on hot dogs.

630
00:30:32,920 --> 00:30:35,880
Speaker 2: So I ask, Okay, if I find the perfect, very

631
00:30:36,160 --> 00:30:39,520
Speaker 2: smelly thing that the slime mold can like queue in on,

632
00:30:39,760 --> 00:30:42,520
Speaker 2: that's gonna work better than my oats, what percent of

633
00:30:42,560 --> 00:30:44,880
Speaker 2: the time should I expect this to work? And they

634
00:30:44,920 --> 00:30:48,160
Speaker 2: said thirty or forty percent. That's not great, no, And

635
00:30:48,200 --> 00:30:50,280
Speaker 2: that's when I realized. I went back through all the

636
00:30:50,280 --> 00:30:53,200
Speaker 2: papers and I was like, oh my gosh, it says

637
00:30:53,440 --> 00:30:56,400
Speaker 2: for the slime molds that solved the maize, but they

638
00:30:56,440 --> 00:30:59,600
Speaker 2: don't include the number of times the maze wasn't solved,

639
00:31:00,200 --> 00:31:02,200
Speaker 2: And so I think a lot of times what's happening

640
00:31:02,280 --> 00:31:05,320
Speaker 2: is like these scenarios are set up, and the one

641
00:31:05,360 --> 00:31:07,200
Speaker 2: time out of one hundred that the slime mold gets

642
00:31:07,200 --> 00:31:10,200
Speaker 2: it close, they're like, WHOA, that's incredible and that's what

643
00:31:10,320 --> 00:31:13,280
Speaker 2: makes the news. And maybe I'm missing something, but it

644
00:31:13,360 --> 00:31:16,680
Speaker 2: seems to me that, like, maybe under absolutely perfect conditions,

645
00:31:16,720 --> 00:31:18,800
Speaker 2: when you replicate things a bunch of times, slime molds

646
00:31:18,800 --> 00:31:20,680
Speaker 2: come up with the right answer. But as far as

647
00:31:20,680 --> 00:31:24,160
Speaker 2: I can tell, mostly they're following a chemical gradient. Probably

648
00:31:24,240 --> 00:31:27,000
Speaker 2: chemical gradients aren't that strong in nature, like as strong

649
00:31:27,040 --> 00:31:29,040
Speaker 2: as you're able to make it in these enclosed mazes.

650
00:31:29,320 --> 00:31:32,400
Speaker 2: So I am personally not super impressed with slime old

651
00:31:32,480 --> 00:31:36,640
Speaker 2: computational abilities. And maybe that's just me being bitter that

652
00:31:36,800 --> 00:31:39,080
Speaker 2: we weren't able to make these kits to give to

653
00:31:39,080 --> 00:31:41,520
Speaker 2: classrooms and we like tanked all this time and money

654
00:31:41,560 --> 00:31:44,520
Speaker 2: on the project. But that is my take on slime

655
00:31:44,520 --> 00:31:46,000
Speaker 2: mold computational ability.

656
00:31:46,120 --> 00:31:47,640
Speaker 1: It sounds to me like somebody's got a room full

657
00:31:47,680 --> 00:31:50,120
Speaker 1: of monkeys and one of them types of Shakespeare, and

658
00:31:50,160 --> 00:31:52,320
Speaker 1: they're like, look, monkeys can tap Shakespeare. Let's make a

659
00:31:52,360 --> 00:31:54,400
Speaker 1: meme about it. I mean, is it better than that,

660
00:31:54,560 --> 00:31:56,640
Speaker 1: is actually a little bit better than random? Or is

661
00:31:56,680 --> 00:31:58,000
Speaker 1: it completely exaggerated.

662
00:31:58,240 --> 00:32:01,240
Speaker 2: I think it is probably a little better than random.

663
00:32:01,320 --> 00:32:03,240
Speaker 2: Some of the problems that they're being asked to solve

664
00:32:03,280 --> 00:32:06,400
Speaker 2: are really complicated. But I do think it's mostly following

665
00:32:06,400 --> 00:32:10,120
Speaker 2: a chemical gradient, which is less interesting than doing computations

666
00:32:10,160 --> 00:32:12,320
Speaker 2: about the shortest way to get to a thing or whatever.

667
00:32:12,680 --> 00:32:14,520
Speaker 2: But I just feel like the whole answer has been

668
00:32:14,760 --> 00:32:17,280
Speaker 2: kind of over sold. And if somebody thinks that I'm

669
00:32:17,320 --> 00:32:19,920
Speaker 2: wrong and I've missed something, I would love to hear that,

670
00:32:19,960 --> 00:32:21,560
Speaker 2: because actually, we just found out that we have to

671
00:32:21,560 --> 00:32:23,040
Speaker 2: make a decision about whether or not we're going to

672
00:32:23,120 --> 00:32:25,000
Speaker 2: throw out that injection mold thing.

673
00:32:25,280 --> 00:32:26,000
Speaker 1: You still have it.

674
00:32:26,400 --> 00:32:28,520
Speaker 2: It's in a warehouse somewhere, and they're like, you can

675
00:32:28,560 --> 00:32:30,240
Speaker 2: either pay two hundred dollars to get rid of it,

676
00:32:30,480 --> 00:32:32,400
Speaker 2: or we can ship it to you on a palette.

677
00:32:32,400 --> 00:32:34,440
Speaker 2: And I'm like, I'm a palette. Where am I going

678
00:32:34,520 --> 00:32:36,480
Speaker 2: to keep this thing? Let us know if you know

679
00:32:36,560 --> 00:32:40,320
Speaker 2: the answer. But like, slime molds are still awesome, those

680
00:32:40,360 --> 00:32:43,080
Speaker 2: paths that they're creating that is a single cell with

681
00:32:43,280 --> 00:32:48,400
Speaker 2: multiple nuclei. There's also slime molds called dog vomit slime mold,

682
00:32:48,840 --> 00:32:52,320
Speaker 2: which you often find in your mulch on moist, warm

683
00:32:52,440 --> 00:32:54,640
Speaker 2: summer days and it does kind of look like dog

684
00:32:54,720 --> 00:32:57,320
Speaker 2: vomit and it's one of my favorite full of go septica.

685
00:32:57,760 --> 00:33:00,240
Speaker 2: And so slime molds are fascinating and we had the

686
00:33:00,320 --> 00:33:02,720
Speaker 2: miscategorized for a while. We kind of couldn't figure out

687
00:33:02,720 --> 00:33:06,080
Speaker 2: what they were. But I'm not totally convinced that they

688
00:33:06,160 --> 00:33:08,680
Speaker 2: are amazing problem solvers.

689
00:33:09,240 --> 00:33:13,160
Speaker 1: Sorry, And are they always single cells? I mean we're

690
00:33:13,160 --> 00:33:15,440
Speaker 1: talking about an extended thing, right, It's like this single

691
00:33:15,480 --> 00:33:17,480
Speaker 1: cell can be like a meter across. That kind of

692
00:33:17,480 --> 00:33:18,240
Speaker 1: blows my mind.

693
00:33:18,600 --> 00:33:22,000
Speaker 2: They have different stages in their life cycle. I think

694
00:33:22,000 --> 00:33:25,640
Speaker 2: at other stages they might not be single celled. Not

695
00:33:25,720 --> 00:33:28,880
Speaker 2: an expert on these, but at the stage that everybody's

696
00:33:28,920 --> 00:33:32,680
Speaker 2: seeing for the maze solving stage, they are a single

697
00:33:32,720 --> 00:33:33,760
Speaker 2: solve with a bunch of nuclei.

698
00:33:34,280 --> 00:33:36,720
Speaker 1: And are there other examples of things out there in

699
00:33:36,800 --> 00:33:39,360
Speaker 1: nature that can do something similar and that are also

700
00:33:39,480 --> 00:33:41,719
Speaker 1: over sold or is there anything out there that actually

701
00:33:41,720 --> 00:33:44,360
Speaker 1: can solve this kind of problem in an impressive way

702
00:33:44,960 --> 00:33:46,880
Speaker 1: or is biology all just a dank meme.

703
00:33:49,160 --> 00:33:52,479
Speaker 2: I'm reaching real far back here. I watched this really

704
00:33:52,720 --> 00:33:56,719
Speaker 2: interesting lecture from a woman who studied crows. So this

705
00:33:56,760 --> 00:33:59,400
Speaker 2: isn't like maze solving, but they're super clever. Like if

706
00:33:59,440 --> 00:34:02,160
Speaker 2: there was another crow in the room, they would bury

707
00:34:02,240 --> 00:34:04,600
Speaker 2: their treat and then when the crow turned around, they

708
00:34:04,640 --> 00:34:07,000
Speaker 2: would take the treat out and they'd bury it somewhere else.

709
00:34:07,080 --> 00:34:10,080
Speaker 2: So they knew like that bird was watching me and

710
00:34:10,120 --> 00:34:11,920
Speaker 2: I want to trick it, and that's not watching now,

711
00:34:11,920 --> 00:34:13,360
Speaker 2: So now it's time for me to move where I

712
00:34:13,440 --> 00:34:17,160
Speaker 2: hid my cash. Clever, there are very smart organisms. I

713
00:34:17,200 --> 00:34:19,719
Speaker 2: think this is just an exciting thing that escaped that

714
00:34:19,760 --> 00:34:21,160
Speaker 2: has maybe since been oversold.

715
00:34:22,280 --> 00:34:25,080
Speaker 1: It sounds like the puzzle you really sold was why

716
00:34:25,120 --> 00:34:28,799
Speaker 1: Carolina Biological doesn't carry meses in their catalog.

717
00:34:29,600 --> 00:34:33,200
Speaker 2: Exactly that is the puzzle we solved. And so now

718
00:34:33,239 --> 00:34:37,560
Speaker 2: we need to find out does Charlie Davidson like answers

719
00:34:37,560 --> 00:34:40,480
Speaker 2: that are kind of a bummer? And did I mistakenly

720
00:34:40,520 --> 00:34:42,719
Speaker 2: assume that he wanted to talk about slime wolds but

721
00:34:42,760 --> 00:34:46,040
Speaker 2: he had another single celled organism in mind. Let's hear

722
00:34:46,239 --> 00:34:47,600
Speaker 2: from Charlie and find out.

723
00:34:48,640 --> 00:34:51,319
Speaker 6: Thank you for answering the question, guys, that's exactly what

724
00:34:51,360 --> 00:34:55,479
Speaker 6: I wanted to have answered. The computational bitites of slime

725
00:34:55,520 --> 00:34:58,680
Speaker 6: molds are no longer impressive to me either, but never mind,

726
00:34:58,960 --> 00:35:00,920
Speaker 6: can't win them all. I was hoping it would be

727
00:35:01,640 --> 00:35:04,400
Speaker 6: something far more amazing, but it's the way it is,

728
00:35:04,440 --> 00:35:07,359
Speaker 6: I guess. Thank you so much, sake. I do believe

729
00:35:07,400 --> 00:35:09,279
Speaker 6: we have dog vomit slime mold. In the UK, we

730
00:35:09,320 --> 00:35:12,080
Speaker 6: call it, which is brew If it's the same thing.

731
00:35:12,239 --> 00:35:15,080
Speaker 6: I'm not sure which name I prefer, but either or

732
00:35:15,160 --> 00:35:18,279
Speaker 6: ice codes. Thanks very much, look forward to future podcasts.

733
00:35:19,160 --> 00:35:21,960
Speaker 1: All right, enough about single cell organisms, hot dogs and

734
00:35:22,160 --> 00:35:24,640
Speaker 1: slime molds. When we come back, we're going to tackle

735
00:35:24,680 --> 00:35:45,000
Speaker 1: another question about space and time and black holes. All right,

736
00:35:45,000 --> 00:35:47,800
Speaker 1: we're back, and we are answering questions from the audience.

737
00:35:47,880 --> 00:35:50,759
Speaker 1: Questions from people like you. If there's something about the

738
00:35:50,840 --> 00:35:53,040
Speaker 1: universe it's never clicked in your mind, or if you've

739
00:35:53,160 --> 00:35:55,640
Speaker 1: heard us talk about something that didn't quite make sense

740
00:35:55,680 --> 00:35:58,000
Speaker 1: to you, please write to us. We want to follow up.

741
00:35:58,120 --> 00:36:01,200
Speaker 1: We want those ideas to connect in your head so

742
00:36:01,239 --> 00:36:03,759
Speaker 1: that you feel like you understand as well. We will

743
00:36:03,760 --> 00:36:06,200
Speaker 1: answer any questions you send to us to questions at

744
00:36:06,320 --> 00:36:11,000
Speaker 1: danieland Kelly dot org, even dating questions. Though we don't

745
00:36:11,000 --> 00:36:12,800
Speaker 1: claim any expertise.

746
00:36:12,760 --> 00:36:14,480
Speaker 2: Oh I'm an expert. I did a lot of dating.

747
00:36:14,560 --> 00:36:16,520
Speaker 2: But I don't know if anyone wants my advice.

748
00:36:18,400 --> 00:36:20,439
Speaker 1: Well, if they know Zach, that they can evaluate whether

749
00:36:20,440 --> 00:36:21,880
Speaker 1: they think that went well for you or not.

750
00:36:23,480 --> 00:36:24,680
Speaker 2: Yeah, it's up in the air.

751
00:36:26,880 --> 00:36:30,040
Speaker 1: TBD. All right. In the meantime, here's a question we

752
00:36:30,120 --> 00:36:33,200
Speaker 1: got from Derek in New Hampshire, who's thinking about black

753
00:36:33,200 --> 00:36:35,080
Speaker 1: holes and Hawking radiation.

754
00:36:36,080 --> 00:36:39,640
Speaker 4: I was wondering, can a black hole be so massive

755
00:36:40,000 --> 00:36:44,479
Speaker 4: that not even Hawkins radiation can escape from its gravitational pull?

756
00:36:45,320 --> 00:36:46,640
Speaker 4: Look forward to you and your answer.

757
00:36:47,000 --> 00:36:47,320
Speaker 1: Thanks.

758
00:36:47,760 --> 00:36:50,359
Speaker 2: All right, So this is a great question. We did

759
00:36:50,360 --> 00:36:52,440
Speaker 2: a little bit of an intro into black holes as

760
00:36:52,480 --> 00:36:55,520
Speaker 2: part of the very first question. Maybe the right place

761
00:36:55,560 --> 00:36:58,480
Speaker 2: to start is what is Hawking radiation?

762
00:36:59,000 --> 00:37:03,400
Speaker 1: Yeah? Great, So Derek's basically asking about the glow that

763
00:37:03,440 --> 00:37:06,759
Speaker 1: we think black holes might make. We talked in the

764
00:37:06,840 --> 00:37:10,040
Speaker 1: earlier question about what black holes are. They are regions

765
00:37:10,080 --> 00:37:13,560
Speaker 1: of space time that are so bent, so deformed, that

766
00:37:13,600 --> 00:37:16,480
Speaker 1: space is now only pointing inwards. So you shine a

767
00:37:16,520 --> 00:37:18,960
Speaker 1: flashlight inside a black hole, it's only going to go

768
00:37:19,040 --> 00:37:21,560
Speaker 1: towards the center. There's no path out from behind the

769
00:37:21,600 --> 00:37:23,920
Speaker 1: event horizon. And that's a description of a black hole

770
00:37:24,000 --> 00:37:27,040
Speaker 1: that comes from general relativity it's Einstein's theory that says

771
00:37:27,400 --> 00:37:29,920
Speaker 1: space gets bent and the space tells matter how to

772
00:37:29,960 --> 00:37:32,120
Speaker 1: move and all this kind of stuff. But we know

773
00:37:32,160 --> 00:37:34,360
Speaker 1: that general relativity can't be the final story of the

774
00:37:34,440 --> 00:37:37,880
Speaker 1: universe because it's not compatible with the other story we

775
00:37:37,960 --> 00:37:41,600
Speaker 1: have about the universe, which is quantum mechanics. And in particular,

776
00:37:41,960 --> 00:37:45,480
Speaker 1: Einstein's theory of black holes predicts that they're totally black,

777
00:37:45,840 --> 00:37:48,160
Speaker 1: that if you look at a black hole, there's no glow.

778
00:37:48,360 --> 00:37:51,279
Speaker 1: It's not emitting anything, No light comes off of the

779
00:37:51,320 --> 00:37:54,000
Speaker 1: black hole. But if you do try to account a

780
00:37:54,040 --> 00:37:56,440
Speaker 1: little bit for quantum mechanical effects, and this is what

781
00:37:56,680 --> 00:37:59,600
Speaker 1: Hawking did, it predicts something different. It predicts that black

782
00:37:59,600 --> 00:38:02,839
Speaker 1: holes aren't not actually totally black, that they glow very

783
00:38:02,880 --> 00:38:06,880
Speaker 1: faintly with this radiation he called, of course, Hawking radiation.

784
00:38:07,520 --> 00:38:11,040
Speaker 2: He named it after himself. Isn't someone supposed to do

785
00:38:11,120 --> 00:38:11,680
Speaker 2: that for you?

786
00:38:12,000 --> 00:38:13,719
Speaker 1: He actually worked it out with a student of his.

787
00:38:14,120 --> 00:38:17,880
Speaker 1: But yeah, it's called Hawking radiation and not Hawking Beckenstein radiation.

788
00:38:18,160 --> 00:38:21,000
Speaker 2: The next wasp by discover is gonna be Wienersmith's wasp

789
00:38:21,719 --> 00:38:22,880
Speaker 2: do it of course.

790
00:38:23,320 --> 00:38:26,280
Speaker 1: Okay, this is really a very impressive bit of physics.

791
00:38:26,400 --> 00:38:29,040
Speaker 1: It's like an end run around a bigger problem. The

792
00:38:29,080 --> 00:38:31,879
Speaker 1: biggest problem in modern physics right now is like, how

793
00:38:31,880 --> 00:38:35,080
Speaker 1: do we reconcile quantum mechanics, which tells us that like

794
00:38:35,440 --> 00:38:37,959
Speaker 1: stuff doesn't have a specific location, it can be here

795
00:38:38,200 --> 00:38:41,439
Speaker 1: or it can be there. And general relativity, which tells

796
00:38:41,520 --> 00:38:44,239
Speaker 1: us like space gets bent based on where stuff is,

797
00:38:44,680 --> 00:38:47,480
Speaker 1: and general relativity can't handle if stuff doesn't have a

798
00:38:47,520 --> 00:38:50,440
Speaker 1: specific location, Like if the particles may be here and

799
00:38:50,480 --> 00:38:53,320
Speaker 1: maybe there is, space may be bent here and maybe

800
00:38:53,360 --> 00:38:56,240
Speaker 1: bent there or partially bent here, partially bent there. Nobody

801
00:38:56,239 --> 00:38:58,600
Speaker 1: knows how to bring these two things together, which is

802
00:38:58,600 --> 00:39:00,319
Speaker 1: what you have to do if you want, I want

803
00:39:00,360 --> 00:39:04,000
Speaker 1: a theory of general relativity that's consistent with quantum mechanics.

804
00:39:04,200 --> 00:39:06,680
Speaker 1: Nobody knows how to do that. Big question, lots of

805
00:39:06,680 --> 00:39:09,360
Speaker 1: Nobel prize is waiting. But what Hacking did was like

806
00:39:09,400 --> 00:39:11,520
Speaker 1: an end run around that. He's like, can't figure out

807
00:39:11,520 --> 00:39:13,839
Speaker 1: the big problem, but maybe I can sort of chip

808
00:39:13,880 --> 00:39:16,440
Speaker 1: away at it a little bit. So he found a

809
00:39:16,480 --> 00:39:19,200
Speaker 1: little trick that let him think about what happened to

810
00:39:19,280 --> 00:39:23,319
Speaker 1: quantum fields near an event horizon, and his trick let

811
00:39:23,400 --> 00:39:26,080
Speaker 1: him make this prediction that black hole should glow a

812
00:39:26,120 --> 00:39:26,600
Speaker 1: little bit.

813
00:39:26,680 --> 00:39:28,680
Speaker 2: Can you remind me what an event horizon is?

814
00:39:29,040 --> 00:39:30,799
Speaker 1: Right? Thank you? An event horizon is what we think

815
00:39:30,840 --> 00:39:32,840
Speaker 1: of is like the edge of the black hole. Inside

816
00:39:32,880 --> 00:39:36,360
Speaker 1: the event horizon, everything is trapped forever. Outside the event horizon,

817
00:39:36,600 --> 00:39:39,000
Speaker 1: you're still free. So you can approach a black hole,

818
00:39:39,080 --> 00:39:41,719
Speaker 1: be near the event horizon, and then escape and go

819
00:39:41,760 --> 00:39:43,680
Speaker 1: back to your planet and live a happy life. If

820
00:39:43,680 --> 00:39:46,520
Speaker 1: you cross the event horizon, you're in the black hole forever.

821
00:39:47,000 --> 00:39:49,360
Speaker 1: I think there's also a lot of confusion out there

822
00:39:49,480 --> 00:39:52,120
Speaker 1: about hawking radiation and what it means and how to

823
00:39:52,280 --> 00:39:55,719
Speaker 1: think about it, because I've said that we don't understand

824
00:39:56,080 --> 00:39:59,640
Speaker 1: how particles are affected by really strong gravity, And the

825
00:39:59,680 --> 00:40:03,160
Speaker 1: typical story you hear is that hawking radiation comes from

826
00:40:03,400 --> 00:40:07,960
Speaker 1: particles being created near the event horizon, like particle antiparticle

827
00:40:08,000 --> 00:40:11,000
Speaker 1: pairs popping out of the vacuum and one falls into

828
00:40:11,040 --> 00:40:14,040
Speaker 1: the event horizon and the other doesn't. And so to

829
00:40:14,040 --> 00:40:16,640
Speaker 1: do that calculation, it feels like you'd need to understand

830
00:40:16,920 --> 00:40:20,239
Speaker 1: how gravity works for particles. Well, the thing is, that's

831
00:40:20,320 --> 00:40:24,439
Speaker 1: not how hawking radiation works. That's the well worn pop

832
00:40:24,560 --> 00:40:27,920
Speaker 1: side cartoon version of it, but it doesn't actually make

833
00:40:27,920 --> 00:40:31,279
Speaker 1: any sense. I mean, virtual particles can't be treated like

834
00:40:31,360 --> 00:40:34,319
Speaker 1: real particles. They're not real particles. You shouldn't think of

835
00:40:34,320 --> 00:40:36,960
Speaker 1: the vacuum as like filled with actual particles that can

836
00:40:37,000 --> 00:40:39,319
Speaker 1: fall into black holes. And we don't know how to

837
00:40:39,360 --> 00:40:43,800
Speaker 1: do those calculations for gravity of particles. Instead, what Hawking

838
00:40:43,840 --> 00:40:46,560
Speaker 1: did was take a very different approach. He just said,

839
00:40:46,880 --> 00:40:51,440
Speaker 1: what happens to quantum fields if there's a discontinuity in space,

840
00:40:51,520 --> 00:40:53,960
Speaker 1: if there's an event horizon, how do I solve the

841
00:40:54,000 --> 00:40:58,080
Speaker 1: mathematics of a quantum field near an event horizon? And

842
00:40:58,120 --> 00:40:59,560
Speaker 1: what he found was the only way to make the

843
00:40:59,600 --> 00:41:03,360
Speaker 1: math work for quantum field near an event horizon was

844
00:41:03,360 --> 00:41:06,440
Speaker 1: to have an outgoing wave of radiation, and that's what

845
00:41:06,520 --> 00:41:10,399
Speaker 1: he interpreted as Hawking radiation. He doesn't have a microscopic

846
00:41:10,480 --> 00:41:14,360
Speaker 1: particle picture of Hawking radiation. What's happening to individual particles?

847
00:41:14,360 --> 00:41:16,560
Speaker 1: We don't know how to do that, but we do

848
00:41:16,719 --> 00:41:19,640
Speaker 1: know that quantum mechanics says, if there's an event horizon

849
00:41:19,680 --> 00:41:23,440
Speaker 1: in space, then your quantum fields have to radiate. And

850
00:41:23,480 --> 00:41:25,359
Speaker 1: the really cool thing about this is that you don't

851
00:41:25,400 --> 00:41:28,400
Speaker 1: need a complete solution to quantum gravity to attack it.

852
00:41:28,480 --> 00:41:31,520
Speaker 1: In this way. This is really Hawking's brilliance of finding

853
00:41:31,560 --> 00:41:33,680
Speaker 1: a sort of an end run around having to have

854
00:41:33,760 --> 00:41:36,640
Speaker 1: the whole picture and still getting this one result from

855
00:41:36,680 --> 00:41:40,000
Speaker 1: this mathematical trick. And there's another beautiful angle to this

856
00:41:40,200 --> 00:41:42,560
Speaker 1: to make it a little bit more satisfying. Even though

857
00:41:42,600 --> 00:41:45,399
Speaker 1: you can't think about the individual particles and how they're

858
00:41:45,400 --> 00:41:50,000
Speaker 1: affected by gravity, you can think about hawking radiation like thermodynamically.

859
00:41:50,680 --> 00:41:53,160
Speaker 1: The way Hawking thought about it and his student Bekenstein

860
00:41:53,719 --> 00:41:58,120
Speaker 1: was that black holes eat information, black holes eat entropy. Right,

861
00:41:58,400 --> 00:42:00,959
Speaker 1: all the disorder in the universe into a black hole.

862
00:42:01,160 --> 00:42:04,240
Speaker 1: Is it decreasing? Is it violating the second law of thermodynamics.

863
00:42:04,760 --> 00:42:06,479
Speaker 1: They showed that on one hand, you can think about

864
00:42:06,480 --> 00:42:09,960
Speaker 1: it mathematically quantum fields radiating energy near an event horizon,

865
00:42:10,239 --> 00:42:13,680
Speaker 1: But you can also think about it thermodynamically, meaning that

866
00:42:13,760 --> 00:42:16,880
Speaker 1: black holes, if they have information, if they have entropy,

867
00:42:17,040 --> 00:42:20,560
Speaker 1: they should have temperature. And if they have temperature, then

868
00:42:20,600 --> 00:42:23,880
Speaker 1: they glow like everything else in the universe that has temperature.

869
00:42:24,239 --> 00:42:27,440
Speaker 1: I glow, you glow, the sun glows. Things glow based

870
00:42:27,520 --> 00:42:32,120
Speaker 1: on their temperatures. Hotter things glow with higher frequency, colder

871
00:42:32,120 --> 00:42:36,520
Speaker 1: things glow with lower frequency. More infrared hot things glow

872
00:42:36,560 --> 00:42:38,799
Speaker 1: in like the X ray and the ultraviolet. So it

873
00:42:38,840 --> 00:42:41,839
Speaker 1: turns out you can model black holes as if they

874
00:42:41,880 --> 00:42:45,400
Speaker 1: are black body radiators, things that glow just based on

875
00:42:45,480 --> 00:42:50,600
Speaker 1: their temperature. Of course, they're extraordinarily cold, tiny, tiny temperatures.

876
00:42:50,960 --> 00:42:52,719
Speaker 1: And the weird thing is that as a black hole

877
00:42:52,760 --> 00:42:56,560
Speaker 1: gets bigger, it gets more massive, it actually gets colder

878
00:42:56,600 --> 00:43:00,120
Speaker 1: and it glows more dimly. So smaller black holes glow

879
00:43:00,200 --> 00:43:03,920
Speaker 1: more brightly and evaporate more quickly, and larger black holes

880
00:43:04,000 --> 00:43:07,359
Speaker 1: glow more dimly because they're colder. So that's another fun

881
00:43:07,400 --> 00:43:10,480
Speaker 1: way that you can think about hawking radiation that helps

882
00:43:10,480 --> 00:43:12,319
Speaker 1: you sort of get a mental picture of it.

883
00:43:12,640 --> 00:43:14,680
Speaker 2: Okay, and then one more follow up question. So when

884
00:43:14,680 --> 00:43:18,520
Speaker 2: we've talked in the past, we've said that quantum mechanics

885
00:43:18,520 --> 00:43:21,920
Speaker 2: and general relativity they don't make the same predictions, But

886
00:43:22,120 --> 00:43:25,839
Speaker 2: usually that doesn't matter because any question that you have

887
00:43:26,120 --> 00:43:29,040
Speaker 2: usually just requires you to think in one of those terms.

888
00:43:29,200 --> 00:43:32,799
Speaker 2: That's right, Why with black holes, is it important to

889
00:43:32,920 --> 00:43:33,919
Speaker 2: understand both of them?

890
00:43:34,160 --> 00:43:38,080
Speaker 1: Yeah, great question. Usually you can ignore general relativity when

891
00:43:38,080 --> 00:43:41,919
Speaker 1: you're doing quantum mechanics because particles have almost no mass

892
00:43:41,960 --> 00:43:44,919
Speaker 1: and so they hardly bend space, their gravity is basically irrelevant.

893
00:43:45,320 --> 00:43:48,040
Speaker 1: Usually you could ignore quantum mechanics when you're doing general

894
00:43:48,040 --> 00:43:50,840
Speaker 1: relativity because you're dealing with big masses like planets, and

895
00:43:50,920 --> 00:43:53,560
Speaker 1: for planets, the quantum mechanical effects a'll average out to zero,

896
00:43:53,920 --> 00:43:56,440
Speaker 1: so usually you could ignore one or the other. When

897
00:43:56,480 --> 00:43:58,800
Speaker 1: you're dealing with black holes, you're dealing with very short

898
00:43:58,800 --> 00:44:01,920
Speaker 1: distances or very very strong gravity. So now you want

899
00:44:01,920 --> 00:44:03,880
Speaker 1: to know the answer to like what happens to a

900
00:44:03,960 --> 00:44:07,319
Speaker 1: particle near the edge of an event horizon. You have

901
00:44:07,400 --> 00:44:10,160
Speaker 1: like very very strong gravity enough to pull on a particle,

902
00:44:10,719 --> 00:44:12,200
Speaker 1: and you want to know what's going to happen to

903
00:44:12,239 --> 00:44:13,640
Speaker 1: my electron? Is going to go this way? Or is

904
00:44:13,680 --> 00:44:15,040
Speaker 1: it going to go that way? Or if it splits

905
00:44:15,040 --> 00:44:17,879
Speaker 1: into other particles, what happens to it. Now you want

906
00:44:17,920 --> 00:44:20,600
Speaker 1: to answer questions about the gravity of particles, you need

907
00:44:20,680 --> 00:44:23,160
Speaker 1: to be able to include the effects of gravity and

908
00:44:23,440 --> 00:44:25,760
Speaker 1: to be able to describe that particle as a quantum

909
00:44:25,800 --> 00:44:29,000
Speaker 1: mechanical object, So you need both. Usually you don't care

910
00:44:29,000 --> 00:44:31,680
Speaker 1: about the gravity on individual electron, but if you want

911
00:44:31,719 --> 00:44:34,000
Speaker 1: to understand things like Hawking radiation, what happens to a

912
00:44:34,000 --> 00:44:36,839
Speaker 1: particle near the event horizon? You need the answers to those.

913
00:44:37,080 --> 00:44:39,839
Speaker 2: Okay, so let's suggest black holes. If we could understand them,

914
00:44:39,920 --> 00:44:42,600
Speaker 2: that might be the way that we merge our understanding

915
00:44:42,600 --> 00:44:43,520
Speaker 2: of those two things.

916
00:44:43,640 --> 00:44:46,320
Speaker 1: Oh. Absolutely, if we could see inside an event horizon,

917
00:44:46,840 --> 00:44:49,680
Speaker 1: we would know the answer to how to unify quantum

918
00:44:49,680 --> 00:44:51,680
Speaker 1: mechanics and gravity, because we would see is there a

919
00:44:51,680 --> 00:44:55,440
Speaker 1: singularity like general relativity predicts and quant mechanics says it's impossible,

920
00:44:55,680 --> 00:44:58,319
Speaker 1: or is there something else weird and fuzzy? But of

921
00:44:58,320 --> 00:45:00,439
Speaker 1: course we can't so we know the answer. It's there,

922
00:45:00,440 --> 00:45:03,960
Speaker 1: but it's frustratingly hiding behind the veil of the black hole.

923
00:45:04,200 --> 00:45:06,680
Speaker 1: The Derek's question was basically, could you make a black

924
00:45:06,719 --> 00:45:11,280
Speaker 1: hole so massive that even its hawking radiation can't escape?

925
00:45:12,000 --> 00:45:14,760
Speaker 1: So here you have a black hole and its emitting radiation.

926
00:45:15,200 --> 00:45:17,160
Speaker 1: Could it suck at that back in? Could the hawking

927
00:45:17,239 --> 00:45:20,040
Speaker 1: radiation get trapped by the black hole? The answer is,

928
00:45:20,120 --> 00:45:23,400
Speaker 1: we don't really know, because what you're asking requires us

929
00:45:23,400 --> 00:45:26,160
Speaker 1: to be able to think about the gravity on particles

930
00:45:26,480 --> 00:45:28,080
Speaker 1: near a black hole, and we just don't know how

931
00:45:28,080 --> 00:45:30,239
Speaker 1: to do that right because we don't know how to

932
00:45:30,239 --> 00:45:32,520
Speaker 1: think about gravity for things where we don't have a

933
00:45:32,560 --> 00:45:35,399
Speaker 1: way to describe their location exactly where they are through

934
00:45:35,440 --> 00:45:38,680
Speaker 1: space and time. General relativity is basically a classical theory.

935
00:45:38,680 --> 00:45:41,640
Speaker 1: It assumes that everything has a location and momentum, and

936
00:45:41,680 --> 00:45:44,120
Speaker 1: that can be well defined and you can do those calculations.

937
00:45:44,120 --> 00:45:47,239
Speaker 1: So short answer is, Derek, we don't know. The best

938
00:45:47,239 --> 00:45:50,839
Speaker 1: answer though is probably not. Hawking's calculations suggest that black

939
00:45:50,880 --> 00:45:54,600
Speaker 1: holes glow outside of the event horizon. Basically, what he

940
00:45:54,640 --> 00:45:57,120
Speaker 1: did in his calculation is figure out what happens to

941
00:45:57,160 --> 00:45:59,920
Speaker 1: a quantum field near an event horizon, and his solution

942
00:46:00,120 --> 00:46:03,320
Speaker 1: suggests there has to be outgoing radiation, and that radiation

943
00:46:03,440 --> 00:46:06,000
Speaker 1: is past the event horizon. So even if the gravity

944
00:46:06,080 --> 00:46:09,120
Speaker 1: is very very strong, it's past the event horizon, which

945
00:46:09,160 --> 00:46:12,880
Speaker 1: means technically it can still escape. That's the definition of

946
00:46:12,920 --> 00:46:16,120
Speaker 1: the event horizon. So if it couldn't escape, it would

947
00:46:16,160 --> 00:46:18,760
Speaker 1: be within the event horizon. But hawking radiation is always

948
00:46:18,800 --> 00:46:22,480
Speaker 1: emitted past the event horizon, so probably it's.

949
00:46:22,320 --> 00:46:25,200
Speaker 2: Free, all right. So Derek, we want to know if

950
00:46:25,239 --> 00:46:29,320
Speaker 2: that explanation was satisfying. So we've reached out to Derek,

951
00:46:29,480 --> 00:46:30,479
Speaker 2: and here's what he said.

952
00:46:31,040 --> 00:46:31,319
Speaker 1: You did.

953
00:46:31,360 --> 00:46:33,440
Speaker 7: You an excellent job at it, answering the question as

954
00:46:33,440 --> 00:46:35,400
Speaker 7: best as you could I ever want to have a

955
00:46:35,440 --> 00:46:38,479
Speaker 7: big fear of missing out? And I can only hope

956
00:46:38,520 --> 00:46:42,440
Speaker 7: that technology will allow us to have the answers for

957
00:46:42,480 --> 00:46:43,440
Speaker 7: these types of questions.

958
00:46:44,080 --> 00:46:44,400
Speaker 1: Thank you.

959
00:46:44,719 --> 00:46:48,000
Speaker 2: Okay, so that's it for today. Thank you so much

960
00:46:48,200 --> 00:46:52,360
Speaker 2: to Barima and Charlie and Derek for sending in their questions.

961
00:46:52,640 --> 00:46:54,799
Speaker 2: We hope to get more questions. Actually, we already have

962
00:46:54,840 --> 00:46:57,560
Speaker 2: a stack ready for our listener questions number two, So

963
00:46:57,600 --> 00:47:00,279
Speaker 2: if you send your questions, be patient. We are going

964
00:47:00,320 --> 00:47:02,520
Speaker 2: to get to all of them, and we really appreciate

965
00:47:02,560 --> 00:47:05,560
Speaker 2: your questions. Can't wait to hear from you. Send us

966
00:47:05,600 --> 00:47:09,000
Speaker 2: emails at questions at Danielankelly dot org.

967
00:47:09,520 --> 00:47:12,560
Speaker 1: Because it's not just our curiosity that drives sigence forward,

968
00:47:12,600 --> 00:47:15,200
Speaker 1: it's yours. It's the reason we're doing it. It's collective

969
00:47:15,239 --> 00:47:18,680
Speaker 1: curiosity of humanity is why we have science. So thanks

970
00:47:18,719 --> 00:47:20,720
Speaker 1: everyone for pushing knowledge forward.

971
00:47:28,400 --> 00:47:32,239
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972
00:47:32,280 --> 00:47:34,720
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973
00:47:34,880 --> 00:47:37,600
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00:47:37,800 --> 00:47:39,480
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975
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979
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980
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981
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