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Uranium and the Start of the Earth? - How Geochronology Works · PlanetGeo: The Geology Podcast

• 0:01
  SPEAKER_00: Welcome to Planet Geo, the podcast where we talk about our amazing planet, how it works, and why it matters to you.
• 0:13
  SPEAKER_00: What's up, man?
• 0:13
  SPEAKER_01: Are we recording or not?
• 0:14
  SPEAKER_01: We're recording.
• 0:15
  SPEAKER_01: Are we recording?
• 0:16
  SPEAKER_00: We're we're live.
• 0:18
  SPEAKER_01: Well, you uh, listen, we usually clap in.
• 0:22
  SPEAKER_01: Okay, this is my thing.
• 0:23
  SPEAKER_01: I you this is the one thing you give me control over, right?
• 0:27
  SPEAKER_01: You let me not allow anyone.
• 0:28
  SPEAKER_01: You let me do this.
• 0:30
  SPEAKER_01: I start the show, Jesse.
• 0:32
  SPEAKER_00: I've slowly been grabbing back control from Chris.
• 0:37
  SPEAKER_01: Slowly.
• 0:39
  SPEAKER_01: Okay.
• 0:40
  SPEAKER_01: Oh my gosh.
• 0:41
  SPEAKER_01: You just started it on the slide.
• 0:44
  SPEAKER_00: It doesn't like do a little ping that says, hey, we're recording now.
• 0:47
  SPEAKER_00: No, I don't I didn't get to that.
• 0:49
  SPEAKER_00: To the listener, we've got some new recording software that uh that comes with an editing package we're we're experimenting with.
• 0:55
  SPEAKER_01: And it's not a fan.
• 1:01
  SPEAKER_01: That's true.
• 1:02
  SPEAKER_01: Oh man, that's funny.
• 1:04
  SPEAKER_01: Well, anyway, hey, since I get the top of the show, so I'm gonna ask you then, how are you doing?
• 1:10
  SPEAKER_01: The doctor.
• 1:12
  SPEAKER_00: The doctor's in the house.
• 1:13
  SPEAKER_00: The doctor's in the house today for doctor is on and my doctor hat is on, you know, uh for this episode.
• 1:20
  SPEAKER_00: We're doing is it?
• 1:21
  SPEAKER_01: I can't wait, actually.
• 1:22
  SPEAKER_01: I can't wait.
• 1:22
  SPEAKER_00: I'm I'm excited, so I I have a couple questions.
• 1:25
  SPEAKER_00: Okay, one unrelated question.
• 1:26
  SPEAKER_00: I we have been getting um some listener emails about sediments.
• 1:33
  SPEAKER_00: I mean, in the general theme of the fact that if you listen to this podcast long enough, you kind of become aware that Chris and I don't focus on sediments that much or sedimentary rocks.
• 1:43
  SPEAKER_01: What do you yeah, you just put me to sleep?
• 1:45
  SPEAKER_00: What are your just by the word?
• 1:48
  SPEAKER_01: I'm over here snoring right now.
• 1:50
  SPEAKER_00: What what are what are I mean, what are your thoughts about this?
• 1:52
  SPEAKER_00: What are your thoughts about you know getting I mean, these are these are people who are interested in sediments and and roughly so.
• 2:00
  SPEAKER_00: Sediments can potentially maybe once in a while be interesting.
• 2:03
  SPEAKER_00: Okay.
• 2:03
  SPEAKER_00: When you open an email from a listener that says, Hey, I want to hear more about sediments, knee jerk, what's your gut like what's the Chris Boy has like passion in your heart?
• 2:12
  SPEAKER_01: Okay.
• 2:12
  SPEAKER_01: I think I actually have a well, I have I have my answer to this.
• 2:15
  SPEAKER_01: I do have an answer to this.
• 2:17
  SPEAKER_01: Um, look, I fell in love with geology because of hard rock stuff, just bottom line.
• 2:22
  SPEAKER_00: And what do you mean by that?
• 2:23
  SPEAKER_01: I love igneous rocks, I love metamorphic rocks, and I love the processes that explain them.
• 2:29
  SPEAKER_01: But as a teacher, I I have to own up to sedimentary rocks.
• 2:34
  SPEAKER_01: Um it's kind of like an inside joke, actually.
• 2:37
  SPEAKER_01: Like we mean no offense to this whole slight that we give on on sedimentary rocks, because I actually I like them, I love them.
• 2:45
  SPEAKER_01: They're not boring, and and actually the story that they tell is something that I'm I think it's really cool to try to convey this to young students, you know, because uh sedimentary rocks are deposited in very specific niche environments, and they tell that story, and students often have a hard time with that connection.
• 3:07
  SPEAKER_01: Does that make sense what I'm saying?
• 3:08
  SPEAKER_00: Like, I agree, Chris.
• 3:09
  SPEAKER_00: So let me just interject two things here.
• 3:11
  SPEAKER_00: And real quick, I agree with you completely with your point.
• 3:14
  SPEAKER_00: We jest, I think, about sediments.
• 3:16
  SPEAKER_00: Yeah, and and I agree, I agree with you completely.
• 3:18
  SPEAKER_00: Like, my passion is in the igneous and metamorphic, and those are the cool rocks to me.
• 3:23
  SPEAKER_00: I love a garnet amphibolite, right?
• 3:25
  SPEAKER_00: Like, that's just a cool rock in a way that I just don't look at a sandstone and think, oh wow, cool, right?
• 3:31
  SPEAKER_00: So there's that part, but also but sediments are amazing, and we have this Grand Canyon geological audio visual book on our Camp Geo app that is dominated.
• 3:40
  SPEAKER_00: I mean, the story of the Grand Canyon is so amazing, and it's dominated by the sediments.
• 3:44
  SPEAKER_00: And a lot of that audiobook is focused on sediments because the sediments are tell this amazing story in the Grand Canyon, and they're beautiful and they're shocking, and it's you know spectacular to see them, and there's so many first principles.
• 3:56
  SPEAKER_00: The first principles of geology were derived in sediments, and that's a really important thing to not forget.
• 4:02
  SPEAKER_00: So, back to your teaching point, you can't forget that.
• 4:05
  SPEAKER_00: Like we have to remember that the initial understanding of geological time came from watching streams deposit sediment and then looking at rocks and seeing, oh wait, that's the same thing, just a long time period, right?
• 4:19
  SPEAKER_00: So it's a really important thing to remember.
• 4:21
  SPEAKER_01: I am in constant search for looking for really good animations or like video clips showing deposition and depositional environments.
• 4:32
  SPEAKER_01: Um, because they really struggle with this.
• 4:35
  SPEAKER_01: To me, when I teach about uh the common sedimentary rocks, you teach about quartz sandstones and limestones and shales and so on.
• 4:43
  SPEAKER_01: Look, if you can pick up that rock and identify it, who cares?
• 4:47
  SPEAKER_01: That doesn't mean a thing if you don't know what that means.
• 4:51
  SPEAKER_01: You know, if you don't know the environment in which that rock formed, which is indicated by the stuff that's in it, who gives a crap if you can identify the rock?
• 5:00
  SPEAKER_00: I agree completely.
• 5:01
  SPEAKER_00: And just think, Chris, how long we spent making those really what ended up being, I think, really nice gifts of transgression and regression sequences for the Grand Canyon audiobook.
• 5:11
  SPEAKER_00: If you go there, you go to our CampGeo app, you can see these gifts.
• 5:14
  SPEAKER_00: They're really nice.
• 5:15
  SPEAKER_00: That's a hard concept.
• 5:16
  SPEAKER_00: Every year I teach this, that is one sticking point concept that students really struggle to understand because you're taking.
• 5:23
  SPEAKER_00: I think if you understand them, like a magma kind of makes sense.
• 5:25
  SPEAKER_00: It's a okay, you have a magma, it erupts in a volcano, you get ash deposited everywhere.
• 5:29
  SPEAKER_00: That's relatively easy to visualize.
• 5:32
  SPEAKER_00: What happens when the land subsides or the ocean rises, and how the sediments transform and you get this cross section or this vertical column of changing rock compositions?
• 5:41
  SPEAKER_00: That's not intuitive.
• 5:43
  SPEAKER_00: And I think that's the value of a geological education, really, is this ability to think in three dimensions in deep time, like four dimensions, really.
• 5:50
  SPEAKER_00: Four dimensional thinking is really unique to geology.
• 5:53
  SPEAKER_01: Yeah, I have two thoughts on this.
• 5:55
  SPEAKER_01: One is throwing back to sedimentary rocks and due diligence from us, right?
• 6:00
  SPEAKER_01: What is one of your all-time favorite rocks?
• 6:04
  SPEAKER_01: And you were on a massive quest with me to find this rock.
• 6:08
  SPEAKER_00: Okay, are you referring to stretch pebble conglomerate or ripple mark sandstone?
• 6:12
  SPEAKER_00: When which one?
• 6:13
  SPEAKER_01: Okay, neither.
• 6:14
  SPEAKER_01: I'm referring actually, those are awesome.
• 6:16
  SPEAKER_01: Oh, absolutely.
• 6:18
  SPEAKER_01: Yes, of course.
• 6:19
  SPEAKER_00: Well, how could I possibly forget that?
• 6:20
  SPEAKER_00: I mean, it's it's it's arguably the most beautiful rock that I've ever seen.
• 6:24
  SPEAKER_00: Uh uh to me, uh, I mean, it might it it might not be objectively to other people, but to me, that's right, pink, oh, so pretty yellow, orange, red, like layer, faulted.
• 6:35
  SPEAKER_00: I mean, stunningly.
• 6:36
  SPEAKER_00: That is a stun.
• 6:37
  SPEAKER_00: I just made some super cool.
• 6:38
  SPEAKER_00: I sent you and Andy a picture of it.
• 6:39
  SPEAKER_00: I cut a big slab, I made a frame to put it in to hang it on the wall.
• 6:44
  SPEAKER_00: It's super cool.
• 6:44
  SPEAKER_00: I mean, that is just an unbelievable rock.
• 6:46
  SPEAKER_00: I love that rock.
• 6:47
  SPEAKER_01: And I've never seen you, Dr.
• 6:50
  SPEAKER_01: Jesse Reman, because this was pre-doctor.
• 6:53
  SPEAKER_01: But I've never seen you as obsessed about finding a rock as you were about finding the other sandstone.
• 6:59
  SPEAKER_00: We had to fight through all the baby rattlesnakes to get there, but we found them.
• 7:03
  SPEAKER_00: So good.
• 7:03
  SPEAKER_01: Yeah, I ended up in Andy's arms.
• 7:06
  SPEAKER_01: I jumped into his arms in the back of your truck.
• 7:09
  SPEAKER_00: Oh, so good.
• 7:10
  SPEAKER_00: Um, so but let's just summarize for the listeners who are looking for sediment stuff, there's gonna be sediment episodes coming your way.
• 7:17
  SPEAKER_00: Never fear.
• 7:18
  SPEAKER_00: Some of them were planned before we got emails about it, some of them we might be thinking and taking advice from listeners on.
• 7:23
  SPEAKER_00: But there's more sediment stuff coming your way because again, sediments are important.
• 7:27
  SPEAKER_00: But you can also go to the Camp Geo app, and there we have we have a whole chapter in the Camp Geo, the free physical geology audio visual book.
• 7:35
  SPEAKER_00: We have a whole chapter on sedimentary rocks there.
• 7:37
  SPEAKER_00: So you can go learn about that, and we also talk about tectonics and and you know, there's a lot more on sediments there if you want to go to our Camp Geo app.
• 7:44
  SPEAKER_00: It's the first link in your show notes.
• 7:46
  SPEAKER_00: But today, Chris, we're not talking about sediments, we're going into the weeds, and I've got my doctor hat on for this one.
• 7:53
  SPEAKER_00: Um, I want to know, I want to know what is the origin of this.
• 7:58
  SPEAKER_00: And I know you teach an astronomy class that you you mentioned over the phone that this was part of the origin, I guess.
• 8:04
  SPEAKER_01: But what yeah, Jesse, I don't know if I've told you this before, but 15 years ago, maybe, I don't know, it was a long time ago.
• 8:11
  SPEAKER_01: Dr.
• 8:11
  SPEAKER_01: Steve Maddox, you've met him, he's professor at Grand Valley's been a guest on our show.
• 8:17
  SPEAKER_01: We did a presentation at the Michigan Earth Science Teachers Association in Lansing.
• 8:22
  SPEAKER_01: We did a presentation on the geologic evidence for an old earth, and I did a deep dive into geochronology.
• 8:32
  SPEAKER_00: Like it was Oh, really?
• 8:33
  SPEAKER_00: You just got super focused on it.
• 8:35
  SPEAKER_00: I did.
• 8:36
  SPEAKER_00: Oh man, that's awesome.
• 8:37
  SPEAKER_01: Oh, I loved it though.
• 8:38
  SPEAKER_01: I was all in.
• 8:39
  SPEAKER_01: I mean, Jesse, I I can't tell you.
• 8:42
  SPEAKER_01: I'm gonna guess I spent a couple hundred hours at least preparing for a 30-minute talk.
• 8:46
  SPEAKER_00: Yeah, so good.
• 8:48
  SPEAKER_01: I mean in fact, I I got so into it that I had a conversation with Jenny about changing my direction.
• 8:53
  SPEAKER_00: It later.
• 8:54
  SPEAKER_00: You know, go get my PhD.
• 8:55
  SPEAKER_01: Oh, really?
• 8:56
  SPEAKER_00: Wow, okay.
• 8:57
  SPEAKER_01: Yeah, I really thought about dropping it all and going in that direction because I was just I was enthralled.
• 9:06
  SPEAKER_01: I I was in love.
• 9:07
  SPEAKER_01: I am in love with it.
• 9:08
  SPEAKER_01: I I love the topic.
• 9:09
  SPEAKER_00: It is a great topic.
• 9:10
  SPEAKER_00: So how did what what had the conversation with Jenny go about a PhD?
• 9:14
  SPEAKER_01: Oh, Jenny was very supportive of it, actually.
• 9:16
  SPEAKER_01: I was I was actually surprised.
• 9:17
  SPEAKER_01: She encouraged me.
• 9:18
  SPEAKER_01: She's like, uh, you know, Chris, if if that's what you want to do, then make it happen.
• 9:22
  SPEAKER_00: Well, how about this, Chris?
• 9:23
  SPEAKER_00: You get your 30 in here pretty quick and then uh come to Penn State and we can uh we could do a pet we could do a PhD here.
• 9:30
  SPEAKER_00: We're find some interesting cosmochemistry thing to uh to work on.
• 9:33
  SPEAKER_01: You and I would not get anything done.
• 9:36
  SPEAKER_00: It'd be so fun.
• 9:37
  SPEAKER_00: But the rest of my research group would be like, what the hell has happened here?
• 9:41
  SPEAKER_00: I mean, my goodness.
• 9:42
  SPEAKER_01: Hey, who's this grandpa walking around Penn State Halls here?
• 9:45
  SPEAKER_01: Like, what is happening going on?
• 9:47
  SPEAKER_01: You know, is it what is this?
• 9:48
  SPEAKER_00: I'm not no.
• 9:49
  SPEAKER_00: I did have this amazing experience in graduate school.
• 9:51
  SPEAKER_00: So I um I won some departmental teaching award, like TA of the year award or something like that in grad school.
• 9:56
  SPEAKER_00: So you go to the faculty of science, like all the science departments, to their like TA award ceremony or whatever, and like the dean is there and a bunch of department heads, whatever.
• 10:04
  SPEAKER_00: I'm sitting down to dinner.
• 10:05
  SPEAKER_00: I'm sitting next to a guy who's about your age, you know, like ancient.
• 10:10
  SPEAKER_00: No, I'm kidding.
• 10:11
  SPEAKER_00: But but he was I was talking to him, and he he had won the TA Award for the math department.
• 10:16
  SPEAKER_00: And he was a retired high school teacher.
• 10:18
  SPEAKER_00: He was like, you know, I taught in the city of Edmonton for my whole career.
• 10:23
  SPEAKER_00: I taught a bunch of students who went to University of Alberta, got PhDs in math, and then I retired, and I was like, I don't want to just sit around and do nothing.
• 10:31
  SPEAKER_00: Uh, I'm gonna go get my PhD.
• 10:33
  SPEAKER_00: So he found a supervisor, it was getting his PhD, and he was like, Yeah, it's actually kind of funny.
• 10:38
  SPEAKER_00: I'm a grad student along with some of my former students.
• 10:41
  SPEAKER_00: Like, there's some students here who I taught high school math to, and I'm being a TA with them, I'm in grad school with them, and he was like, it was it sounded just like the most amazing, you know, experience.
• 10:51
  SPEAKER_00: And my dad considered kind of doing this too a little bit.
• 10:53
  SPEAKER_00: I mean, it was exploring the PhD kind of thing, right?
• 10:55
  SPEAKER_01: I bet your dad did.
• 10:56
  SPEAKER_01: I know your dad very well, and uh, this is right up his alley.
• 11:00
  SPEAKER_01: I don't mean this to be an insulting comment at all, so tell me if it is, but I kind of view what we're doing with this podcast and Camp Geo to be my PhD.
• 11:11
  SPEAKER_00: I would agree with that completely.
• 11:12
  SPEAKER_00: I mean, this is a well, we're we're getting a degree in entrepreneurial activities and online education and all sorts of stuff and experimenting and learning tons about geology.
• 11:23
  SPEAKER_00: I mean, it's an amazing professional development.
• 11:25
  SPEAKER_01: Um Yeah, the amount that I have learned in the last four years that we've done this is I can't believe what I have forgotten, Jesse, to be honest with you.
• 11:36
  SPEAKER_01: With all that we've done and all of the research and deep dives that we've done and the discussions that we have in the background, nobody knows about those.
• 11:44
  SPEAKER_00: You know, we're it's a you know what it's we're fighting, breaking up, uh, you know, we're it's a yeah, I mean, but it is a it's a it's I would put it in the lots of work, but fun work and valuable work.
• 11:55
  SPEAKER_00: There's some quote, you know, I think it's um one of the Roosevelts, Teddy Roosevelt maybe.
• 12:00
  SPEAKER_00: Something along the lines of a good life is if you work hard at work worth doing.
• 12:04
  SPEAKER_00: I put this podcast in Camp 2, that is definitely in the category for me of like I love learning about this stuff.
• 12:09
  SPEAKER_00: I like figuring out how to explain it.
• 12:11
  SPEAKER_00: We get to talk to amazing people too.
• 12:13
  SPEAKER_00: So I second that about the professional device.
• 12:16
  SPEAKER_01: This scratches that itch.
• 12:18
  SPEAKER_00: Totally, totally.
• 12:19
  SPEAKER_01: For me, this scratches my my desire to get a PhD itch.
• 12:23
  SPEAKER_00: Yeah, absolutely.
• 12:24
  SPEAKER_00: I mean, I think so.
• 12:25
  SPEAKER_00: Maybe let's get to that itch a little bit and talk about it.
• 12:28
  SPEAKER_01: And so the question you had asked me it's been a minute since I first asked the question.
• 12:34
  SPEAKER_01: I set the stage now for you.
• 12:36
  SPEAKER_01: So let me re-ask the question and I want you to have at it.
• 12:40
  SPEAKER_01: One of the coolest factoids in geoscience and geochronology is that the ratio of uranium-238 to uranium-235 is 99.3% to 0.7%.
• 12:53
  SPEAKER_01: And I would like your explanation on this.
• 12:57
  SPEAKER_01: Why is that the ratio?
• 12:58
  SPEAKER_00: The way I always kind of explain this is think about nuclear bombs or nuclear materials or nuclear reactors, let's say, and the term enriched uranium.
• 13:07
  SPEAKER_00: And think about what that might mean.
• 13:08
  SPEAKER_00: What does enriched uranium mean?
• 13:10
  SPEAKER_00: Now, if I said there's two flavors of uranium, there's 235 and 238, and one of them is more stable than the other, one of them's less stable, one of them's more stable, which one would you want to build a nuclear reactor out of?
• 13:26
  SPEAKER_00: Or which one would you think goes into a bomb?
• 13:28
  SPEAKER_00: The more stable or the less stable one?
• 13:31
  SPEAKER_00: Well, the less stable.
• 13:32
  SPEAKER_00: Okay.
• 13:33
  SPEAKER_00: Yeah, right.
• 13:33
  SPEAKER_00: Intuitive, right?
• 13:34
  SPEAKER_00: That makes sense.
• 13:34
  SPEAKER_00: So now a bit of a stretch.
• 13:36
  SPEAKER_00: I don't know if this is as intuitive, but which one, 238, I know you know the answer, but which one would be more stable?
• 13:44
  SPEAKER_00: The odd one or the even one, do you think would be more stable intuitively?
• 13:48
  SPEAKER_00: U238.
• 13:49
  SPEAKER_00: Because it's an even number.
• 13:51
  SPEAKER_00: I mean, it that's a that's a cheap explanation for a really deep concept, but on average, if you have a an even number of nuclei in an atom, it's more stable than an odd number.
• 14:02
  SPEAKER_00: Not always the case, but usually the case.
• 14:04
  SPEAKER_00: So 235 is less stable.
• 14:06
  SPEAKER_00: So if you think about that, like enriched uranium is uranium that has more 235 in it.
• 14:10
  SPEAKER_00: We've artificially enriched the 235 in that batch of uranium, that means that that batch of uranium is less stable, it's better for nuclear reactions uh to go forward.
• 14:21
  SPEAKER_00: So if I take that understanding of what enriched is and which one's more stable, which one's less stable, and I said, okay, which one do you think we have less of on Earth after four and a half billion years, the more stable one or the less stable one?
• 14:34
  SPEAKER_00: My guess is you'd say the more stable one we have more of after time.
• 14:38
  SPEAKER_00: And that would be accurate, right?
• 14:40
  SPEAKER_00: U235 is less stable, it's better for making bombs and nuclear reactors, and therefore it decays faster.
• 14:47
  SPEAKER_00: It's radioactive and it breaks down, and it breaks down at a faster rate, a faster clip than 238 uranium.
• 14:54
  SPEAKER_00: So that's why after 4.568 billion years, we have a lot more 238 left than 235.
• 15:02
  SPEAKER_00: That's part of the reason why.
• 15:04
  SPEAKER_01: Okay, so Jesse, can I put some numbers on what you're saying?
• 15:07
  SPEAKER_01: And by the way, I think that's a really good I do.
• 15:09
  SPEAKER_01: I think that's a really good way of describing it.
• 15:11
  SPEAKER_01: What you're saying is uranium 238 has a half-life of 4.5 billion years.
• 15:19
  SPEAKER_01: If you take a chunk of uranium 4.5 billion years, half of it will have decayed into daughter isotopes.
• 15:26
  SPEAKER_01: It keeps doing this every 4.5 billion years.
• 15:29
  SPEAKER_01: That's right.
• 15:30
  SPEAKER_01: Uranium 235 has a half-life of, can I just average it and say 700 million years?
• 15:36
  SPEAKER_01: That's good enough, right?
• 15:37
  SPEAKER_01: So yeah, it's a much shorter half-life.
• 15:41
  SPEAKER_01: And so it decays faster.
• 15:43
  SPEAKER_01: Okay, now that's the framework.
• 15:46
  SPEAKER_01: Now, can you just answer the question?
• 15:48
  SPEAKER_01: Like, why is the ratio 99.3 to 0.7?
• 15:52
  SPEAKER_01: Because all right, maybe I need to ask this.
• 15:55
  SPEAKER_01: What, Jesse, was the original ratio then of uranium-238 to uranium-235?
• 16:01
  SPEAKER_01: Because we have to find that in order to know why every rock has this ratio of 99.3 to 0.7.
• 16:09
  SPEAKER_00: So that's partially true.
• 16:12
  SPEAKER_00: We need to know, we either need to know what the original ratio was, or we need to know the half-lives.
• 16:17
  SPEAKER_00: If we know how fast 235 decayed and how fast 238 decayed, we can take our modern ratio, and we're saying ratio, we're using percentages, but the ratio, if you take the amount of 238 and divide it by 235, that ratio is 137.818.
• 16:34
  SPEAKER_00: That's the ratio.
• 16:35
  SPEAKER_00: If you have that ratio, you say I have this many atoms of 235 today, this many atoms of 238 today, and I know how fast both of those isotopes decay, then you can just go back in time.
• 16:45
  SPEAKER_00: The calculation is just go back in time 4.5 billion years, and you can get that original ratio.
• 16:50
  SPEAKER_01: Hold on, though, that's an assumption that the solar system is five billion years old.
• 16:57
  SPEAKER_00: If you wanted to know the ratio at a given time, five billion years, four point five billion years, you would just go back however far that number is that you want to figure out the initial ratio.
• 17:06
  SPEAKER_00: So you either need to know the initial starting composition, or you need to know the radioactive decay, the rates of decay, or you need to know that your material you're measuring is the oldest thing we have around, I guess.
• 17:19
  SPEAKER_00: So there's multiple factors in these.
• 17:21
  SPEAKER_01: Right, but if you or if the solar system is only one billion years old, that ratio is not going to be the same as if it was 4.5 billion years old.
• 17:30
  SPEAKER_01: So there is an assumption built into what you're saying.
• 17:32
  SPEAKER_00: Uh I wouldn't quite phrase it as an assumption, because what people do is they find the oldest parts of meteorites, usually what we call chondrules or CAIs or something, and then they measure the lead isotope composition, because uranium doesn't just poof disappear, it turns into lead.
• 17:48
  SPEAKER_00: Two different isotopes of lead, two different flavors of lead.
• 17:50
  SPEAKER_00: So you can measure the uranium lead in those very, very the earliest condensates, the earliest solids in our solar system, and measure the uranium lead clock in there, and you can figure out how old you can figure out what time is.
• 18:03
  SPEAKER_00: So if we have those materials and we measure the uranium lead clock in there, we can figure out time.
• 18:09
  SPEAKER_00: We can figure out how old the thing is.
• 18:12
  SPEAKER_00: Because again, because we have these two clocks, these clocks work in parallel, basically there's a whole bunch of factors that fall out of the equations that cancel each other out when you think about these equations.
• 18:22
  SPEAKER_00: So we have two clocks that both have go from uranium, two different flavors of uranium, indicated two different flavors of lead.
• 18:28
  SPEAKER_00: That's super powerful for this reason, because they decay at different rates.
• 18:32
  SPEAKER_00: So we calculate time by observing it by making measurements of very old pieces of rocks, basically.
• 18:37
  SPEAKER_01: Because they decay independently of each other.
• 18:39
  SPEAKER_01: Exactly.
• 18:40
  SPEAKER_00: Exactly.
• 18:41
  SPEAKER_00: Okay.
• 18:41
  SPEAKER_00: So all right.
• 18:42
  SPEAKER_00: And Chris, let me just interrupt real quick, because you bring up a really good point, I think, is that there is an assumption.
• 18:48
  SPEAKER_00: The assumption is that we know the decay rate or the decay constant.
• 18:52
  SPEAKER_00: That has been measured.
• 18:53
  SPEAKER_01: Well, that's not really an assumption, then.
• 18:55
  SPEAKER_00: It's not an assumption.
• 18:56
  SPEAKER_00: I mean, people would could classify it as an assumption, but it's a measured quantity.
• 19:00
  SPEAKER_00: Like we know the decay rate, we have uncertainties on that.
• 19:03
  SPEAKER_00: So we kind of know how fast uranium-238 decays, how fast 235 decays, and the uncertainties around that known number.
• 19:10
  SPEAKER_01: So all right.
• 19:11
  SPEAKER_01: I'm just gonna say that that's pretty well established.
• 19:14
  SPEAKER_01: Decay rates are established, and and nobody's gonna argue that no, uranium-238 does not decay at that rate.
• 19:19
  SPEAKER_01: I mean, that's a right, that's a step of science.
• 19:22
  SPEAKER_01: But okay, so let me first ask this question.
• 19:24
  SPEAKER_01: It's a yes or no from you.
• 19:26
  SPEAKER_01: No getting into the weeds on this.
• 19:28
  SPEAKER_01: Okay.
• 19:29
  SPEAKER_01: Every natural rock on earth that has uranium in it, let's say it's got zircon in it, has the ratio of 99.3 to 0.7.
• 19:38
  SPEAKER_01: Correct?
• 19:39
  SPEAKER_01: Yes or no?
• 19:40
  SPEAKER_00: Uh mostly.
• 19:41
  SPEAKER_00: It's 99.3 or 99.301 or something like that.
• 19:45
  SPEAKER_00: It's very close to that.
• 19:46
  SPEAKER_00: Yep.
• 19:46
  SPEAKER_01: Yeah, very, very, very close.
• 19:47
  SPEAKER_01: Okay.
• 19:48
  SPEAKER_01: Now, then that brings me to the next question.
• 19:52
  SPEAKER_01: Why is that the case?
• 19:53
  SPEAKER_01: Because what if I have a rock, the uranium barren rock, a zircon barren rock that has that formed one million years ago, and then I have another rock that formed a hundred million years ago.
• 20:05
  SPEAKER_01: Shouldn't they have a different ratio of U238, U235?
• 20:10
  SPEAKER_00: Uh good question, and the answer is no, they shouldn't.
• 20:12
  SPEAKER_00: Was this a yes or no question as well?
• 20:14
  SPEAKER_01: No, that takes a little bit of explanation.
• 20:17
  SPEAKER_01: Okay, I I I think I know what you're going with this, but I just want to be sure.
• 20:21
  SPEAKER_00: So I think it's best to visualize the earth starting.
• 20:24
  SPEAKER_00: The earth gets secreted with a whole bunch of stuff, you know, meteorites smashing into it.
• 20:28
  SPEAKER_00: All the uranium in Earth had the same ratio at the start.
• 20:31
  SPEAKER_00: It wasn't 99.3 to 0.7, it was something different.
• 20:34
  SPEAKER_00: All the uranium everywhere on Earth.
• 20:36
  SPEAKER_00: So if you have start with this molten ball of magma on Earth and you start to crystallize some basaltic crust, that basaltic crust is going to have more uranium in it than, for instance, the mantle would.
• 20:45
  SPEAKER_00: The liquid mantle.
• 20:47
  SPEAKER_00: But that uranium, when sort of geological processes occur, uranium goes certain places, but the the flavors of uranium go together.
• 20:56
  SPEAKER_00: So it doesn't care which flavor of uranium it selects or it takes in.
• 21:00
  SPEAKER_00: It takes it in.
• 21:01
  SPEAKER_00: So all uranium on Earth at any point in time has the same ratio.
• 21:05
  SPEAKER_00: Whether it's today or 10 or 100 or 4.5 billion.
• 21:08
  SPEAKER_01: Right.
• 21:09
  SPEAKER_01: A zircon crystal, as it's growing, does not differentiate between U238 and U235.
• 21:14
  SPEAKER_01: They're the same size, they're the same mass.
• 21:16
  SPEAKER_01: They fit in the crystal lattice of that mineral.
• 21:20
  SPEAKER_00: Now, m the weedy part of me has to qualify this and say it slightly varies, and we can measure the difference, but it's a very, very small deviation.
• 21:28
  SPEAKER_00: And that that's like stabilized subjeochemistry when you have a heavier atom bonds typically prefer the heavier atom.
• 21:36
  SPEAKER_00: So 238 is slightly preferred in bonds when when a mineral is growing and making bonds, it slightly prefers that relative to 235, but it's not a big difference.
• 21:45
  SPEAKER_00: It's a very small difference.
• 21:46
  SPEAKER_00: So but it does matter every once in a while.
• 21:49
  SPEAKER_00: So yeah.
• 21:50
  SPEAKER_01: Okay.
• 21:51
  SPEAKER_01: So because as time goes on, the ratio of new younger minerals growing that have uranium in it is gonna change.
• 22:00
  SPEAKER_01: And that's why all rocks then are gonna have the same ratio of what did you say 136.1?
• 22:08
  SPEAKER_01: What is that?
• 22:09
  SPEAKER_00: Uh 137.818.
• 22:10
  SPEAKER_00: Because it's kind of what we use for geochronology.
• 22:13
  SPEAKER_00: Yep.
• 22:13
  SPEAKER_01: Yeah.
• 22:14
  SPEAKER_01: All right.
• 22:14
  SPEAKER_01: Perfect.
• 22:15
  SPEAKER_01: So that makes I I hope like I think that makes sense to me.
• 22:20
  SPEAKER_00: So this is okay you know, you can show this with an equation, but this is a really beautiful thing because that uranium, 235 and 238, decays to two flavors of lead, 207 and 206.
• 22:30
  SPEAKER_00: So what this means is that we can we don't even need to look at the uranium.
• 22:35
  SPEAKER_00: We can just measure the lead.
• 22:37
  SPEAKER_00: And the way to think about this is if you have a 10 million.
• 22:39
  SPEAKER_01: No, I'm going to interrupt you here because what you're talking about is the daughter isotope, the end isotope that uranium-238 and uranium-235 decay into, which is stable and decay stops at that point, lead 207 and lead-206.
• 22:53
  SPEAKER_01: So, Jesse, this is the thing, and this leads to the second most common misconception in geochronology, which is that you all, you people, don't account for the initial daughter isotope present.
• 23:08
  SPEAKER_01: You're smiling over there.
• 23:09
  SPEAKER_00: That makes you laugh, doesn't it?
• 23:11
  SPEAKER_00: It makes me laugh.
• 23:11
  SPEAKER_00: We go to great.
• 23:13
  SPEAKER_01: You guys are just freewheeling it.
• 23:14
  SPEAKER_01: You don't know what you're doing.
• 23:16
  SPEAKER_01: You're just you're chucking darts in a bottle.
• 23:19
  SPEAKER_01: And then what you come up with is like there's your result.
• 23:22
  SPEAKER_00: If I if it was possible to disprove uranium-led geochronology, like really, really actually disprove it, I'd be the most famous geologist in the world.
• 23:33
  SPEAKER_00: Right?
• 23:33
  SPEAKER_00: Like if you could actually disprove it and say it doesn't work, and here's why, people make careers and become very famous by coming up with monumental shifts like this.
• 23:45
  SPEAKER_01: Jesse, I want to circle back to what you just said because I think in my four years of working with you on this project, that is the most impactful and and like I'm taking a stand on this issue than you've ever said before.
• 24:03
  SPEAKER_01: That's a powerful statement that you just made there.
• 24:05
  SPEAKER_00: I've I yeah, because I think this is the way, and this is a healthy way that science works, is people propose stuff and then people try and disprove it.
• 24:13
  SPEAKER_00: Like there's a competitive forces here.
• 24:15
  SPEAKER_00: And so if if I could actually come up with a real reason that uranium-led geochronology didn't work, or and I've I've written papers about where it works in some ways and doesn't work in others.
• 24:25
  SPEAKER_00: Not not uranium-led geochronology, but for some very specific use case, uranium-led system gets reset in some little portion of a zircon grain.
• 24:33
  SPEAKER_00: You know, that's interesting scientifically.
• 24:35
  SPEAKER_00: Tells us something about that portion of the grain, uh, but it doesn't tell us anything about the uranium-led system.
• 24:39
  SPEAKER_00: If I could disprove, if it was possible to disprove uranium-led geochronology, you'd be very famous very quickly.
• 24:44
  SPEAKER_00: Um yes.
• 24:46
  SPEAKER_01: Well, that's interesting because the ratio of U238 and 235 is going to be the same, but the daughter isotope is really important because that's what resets the clock.
• 24:56
  SPEAKER_00: That's exactly right.
• 24:57
  SPEAKER_00: So if you start, Chris, your example was like a uh a rock formed a million years ago or a hundred million years ago, I think it was.
• 25:03
  SPEAKER_00: A rock formed a million years ago, we're kind of resetting the clock.
• 25:06
  SPEAKER_00: So let's say there's a zircon crystal that starts growing and it takes in uranium in it 238, 235.
• 25:13
  SPEAKER_00: Then over a million years, those are gonna decay to lead.
• 25:16
  SPEAKER_00: But a million years ago, there wasn't that much 235 around.
• 25:20
  SPEAKER_00: So 207 lead is gonna be very, very limited.
• 25:22
  SPEAKER_00: There's not gonna be that much growth of that.
• 25:25
  SPEAKER_00: 206 will grow in at a sort of a constant rate.
• 25:28
  SPEAKER_00: If you go back a hundred million years ago, or let's do it a billion years ago, if you go back a billion years ago, when that zircon grew, a billion-year-old zircon, it had a lot more 235.
• 25:38
  SPEAKER_00: The ratio of 238 to 235 was much closer.
• 25:41
  SPEAKER_00: There was much more 235 in there.
• 25:43
  SPEAKER_00: So over that billion years, 207 lead has grown in a lot more.
• 25:47
  SPEAKER_00: There's way more 207 lead.
• 25:49
  SPEAKER_01: I need to interject because what you're saying is uranium-235 decays to lead 207.
• 25:54
  SPEAKER_01: So because there was more U235, then you're gonna have over that time period much more lead two oh seven, which is the stable end member of that decay process.
• 26:05
  SPEAKER_01: All right.
• 26:06
  SPEAKER_00: And this is where it becomes important for meteorites because now when we think of it that way, we don't even need to look at the uranium necessarily.
• 26:14
  SPEAKER_00: We can just look at the lead.
• 26:15
  SPEAKER_00: If we see a lot of 207 lead, it means that that mineral formed when there was a bunch of 235 uranium around, which has to be a long time ago.
• 26:26
  SPEAKER_00: It allows us to use just 207 and 206 lead.
• 26:29
  SPEAKER_00: Just that ratio in and of itself is a clock.
• 26:32
  SPEAKER_00: If we know the decay rate of uranium-235 and 238, which we know, if we assume a uranium isotopic composition today, which we assume is 137.818, which is a pretty good assumption.
• 26:43
  SPEAKER_01: But doesn't this beg the question that couldn't there have been lead 207 and lead two oh six in the rock originally?
• 26:51
  SPEAKER_00: It's true, and we can look for that.
• 26:53
  SPEAKER_00: We can look at there's other isotopes of lead, like 204 lead, is not radiogenically produced.
• 26:59
  SPEAKER_00: Uh, and so if there's 204 lead in the system, we can say, oh, there's two oh four lead here.
• 27:04
  SPEAKER_00: There was some initial lead, so we have to subtract off some 207.
• 27:07
  SPEAKER_00: Some of the 207 we're measuring is not due to ingrowth.
• 27:11
  SPEAKER_00: It was there initially, and we can we can calculate how much that would be.
• 27:15
  SPEAKER_01: Very cool.
• 27:15
  SPEAKER_01: And then the other thing.
• 27:18
  SPEAKER_01: Right.
• 27:19
  SPEAKER_01: And this is also testable in the lab.
• 27:22
  SPEAKER_01: One scientist can test the accuracy of another lab because if you use any scientist or any geochronologist can create a concoction that they know what's in it.
• 27:34
  SPEAKER_01: And you can let this decay and then have it tested.
• 27:38
  SPEAKER_01: And if the geochronologist that's doing the testing cannot account for that initial daughter isotope that was present, they're going to come up with bad results.
• 27:47
  SPEAKER_01: And that's the thing, Jesse, is that this is reproducible.
• 27:52
  SPEAKER_00: Yeah, and that's a good testable stuff.
• 27:54
  SPEAKER_00: So reproducible is a really important one there, Chris, because this is and this is what happens is so there's a bunch of different ways to think about this.
• 28:00
  SPEAKER_00: Sometimes we use natural samples that we call standards or reference materials, which we know the age really, really well.
• 28:07
  SPEAKER_00: The age of these zircon grains and this granite have been measured at a bunch of different labs with a bunch of different techniques, and they all give the same answer.
• 28:14
  SPEAKER_00: So we assume that's the right answer.
• 28:16
  SPEAKER_00: We assume that answer.
• 28:17
  SPEAKER_00: We know that answer.
• 28:18
  SPEAKER_00: So we measure it in our lab and we we make sure we're getting the right answer when we measure it.
• 28:23
  SPEAKER_00: So we use these to check ourselves.
• 28:25
  SPEAKER_00: Because when we're measuring some sample that we don't know the age of, we bracket it.
• 28:30
  SPEAKER_00: So we will measure six unknowns, and then we'll we'll bracket it with like 12 standards of different ages and different compositions on either side of that measurement.
• 28:39
  SPEAKER_00: So in time, meaning we'll measure 12 standards, 12 samples, 12 standards, and we'll we'll make sure that over the course of a day we're getting the right answer on those standards that we we know the age of.
• 28:51
  SPEAKER_00: So we calibr we calibrate and calibrate and calibrate over and over.
• 28:54
  SPEAKER_00: Because there's nothing more embarrassing.
• 28:56
  SPEAKER_00: For me as somebody who runs a lab, the most embarrassing thing I could do is publish data that is wrong because of something like this, some calibration error.
• 29:05
  SPEAKER_00: That's embarrassing.
• 29:06
  SPEAKER_01: I do a primitive version of what I think what you're talking about with my my geology class, my upper-level geology class.
• 29:13
  SPEAKER_01: I when I did this deep dive getting ready for this presentation with Dr.
• 29:17
  SPEAKER_01: Maddox, I I learned so much.
• 29:19
  SPEAKER_01: I mean, it was just so cool.
• 29:20
  SPEAKER_01: And based upon what I learned, I wrote a lab designed specifically using geochronology, and I invented a scenario where a rock had initial daughter isotope at the time that it formed.
• 29:34
  SPEAKER_01: And so mathematically, I just I walk the students you know down the road, down through this process, right?
• 29:40
  SPEAKER_01: And if they do these they have to account, yeah, and they have to account for that initial initial daughter isotope to tell me how old the rock is.
• 29:50
  SPEAKER_01: So I'm the only one that knows what I initially started with.
• 29:53
  SPEAKER_01: They have to walk it back and then come up to me and say, here's the age of the rock.
• 29:57
  SPEAKER_00: That's a great exercise because it shows you, I mean, it's actually not that complicated, this subtraction.
• 30:02
  SPEAKER_00: I mean, it's complicated when you're thinking about it not knowing it.
• 30:05
  SPEAKER_00: But if you are a student and you're c in Crisple His class and you actually go through the exercises, you realize, oh, this makes sense.
• 30:11
  SPEAKER_00: Like this is a correct calculation.
• 30:13
  SPEAKER_00: The way that this daughter isotope is subtracted is sound.
• 30:17
  SPEAKER_00: It's sound reasoning, it's a sound method.
• 30:20
  SPEAKER_00: But you actually kind of have to walk through those calculations to really understand that, I think.
• 30:25
  SPEAKER_01: That's right.
• 30:25
  SPEAKER_00: Yeah, to see how kind of simple and elegant it is in a way.
• 30:28
  SPEAKER_01: So, Jesse, as we wrap up this episode, I want to finish on one final thought.
• 30:33
  SPEAKER_01: We used to assume that the ratio of U238 to U235 was 137.88.
• 30:41
  SPEAKER_01: That goes back a ways, right?
• 30:43
  SPEAKER_01: Can you talk about that and how that number has gotten adjusted?
• 30:48
  SPEAKER_01: Because it this actually blows me away.
• 30:51
  SPEAKER_01: We're gonna adjust that number, that assumption, just a little bit.
• 30:55
  SPEAKER_01: But the accuracy is absolutely amazing.
• 30:57
  SPEAKER_01: It does matter.
• 30:58
  SPEAKER_01: So, real quick, stay out of the weeds, give us how this number got readjusted.
• 31:04
  SPEAKER_00: Okay, let me restate the number because uh it's hard to think in numbers over audio here.
• 31:08
  SPEAKER_00: So the ratio of 238, the number of atoms of 238, divided by number of atoms of 235.
• 31:13
  SPEAKER_00: And you have said before, Chris, that the percentages are 99.3% to 0.7%.
• 31:19
  SPEAKER_00: So the ratio of those is 137.88.
• 31:22
  SPEAKER_00: What that means is for every atom of 235, we have 137.88 atoms of 238 in uranium.
• 31:29
  SPEAKER_00: That's today.
• 31:30
  SPEAKER_00: Or that's what we assumed it was today.
• 31:33
  SPEAKER_00: So I think the best way to think about this is to think about uh some stupid game.
• 31:38
  SPEAKER_00: I'm gonna give you, Chris, a million checkers, let's say.
• 31:41
  SPEAKER_00: Checkers red and black.
• 31:42
  SPEAKER_00: You have a million of them.
• 31:44
  SPEAKER_00: And I'm gonna say, Chris, measure or tell me how many red ones are there in that million.
• 31:50
  SPEAKER_00: Like, how would you go about doing that if you're Chris Bullheis and I gave you a million of these things?
• 31:55
  SPEAKER_00: What would you do?
• 31:56
  SPEAKER_01: Well, I would count as many of them as I can in a in a reasonable amount of time, and then I'm gonna extrapolate that out.
• 32:04
  SPEAKER_00: Okay, perfect, right?
• 32:05
  SPEAKER_00: You're not gonna sit there and figure out the percentage a week and a half and count a million, right?
• 32:09
  SPEAKER_00: You know, you're not gonna do that, right?
• 32:10
  SPEAKER_00: That's exactly kind of what we do in geochronology.
• 32:13
  SPEAKER_00: We we take a subsample, we're measuring billions and billions of atoms actually in our mass spectrometers, but we're we're doing that exact same, kind of subsampling it.
• 32:22
  SPEAKER_00: But this analogy, I think, will be useful.
• 32:25
  SPEAKER_00: If we had a million checkers, the ratio of 238 to 235, 7,200 of those million would be red.
• 32:34
  SPEAKER_00: That's not many, and then 993,000, 993,000 would be 238 uranium.
• 32:41
  SPEAKER_00: That's the ratio 137.88.
• 32:43
  SPEAKER_00: Now, that ratio is what we assumed it would be, or what we kind of assumed, and we assumed it was kind of constant, as I kind of alluded to before, it's not necessarily constant.
• 32:50
  SPEAKER_00: That ratio changes depending on a little bit, depending on what m thing you're measuring.
• 32:55
  SPEAKER_00: But it matters a lot to geochronologists, and so we spent a lot of time, we as geochrinologists spent a lot of time measuring this.
• 33:01
  SPEAKER_00: We now know that the ratio for most dateable minerals like zircon and apatite, the ratio is one hundred-seven point eight one eight.
• 33:09
  SPEAKER_00: Not point eight eight, but eight one eight.
• 33:12
  SPEAKER_00: All right.
• 33:13
  SPEAKER_00: That's a different one.
• 33:16
  SPEAKER_00: It's not a big difference.
• 33:17
  SPEAKER_00: No, in this decimal place, right?
• 33:19
  SPEAKER_00: So instead of seven thousand two hundred atoms being uranium-235, now it's seven thousand two hundred and four atoms being two thirty-five.
• 33:29
  SPEAKER_00: So, Chris, if you did that exercise, if you counted as many checkers as you could and you measured how many red and black, and then you extrapolated to a million, and I said, ah, you're close, but you're off by four, what would you say?
• 33:41
  SPEAKER_01: Uh I'd have some words for you.
• 33:43
  SPEAKER_01: You'd be pretty pleased with yourself.
• 33:44
  SPEAKER_00: You'd be like, Oh, I'm that's I did really well, right?
• 33:47
  SPEAKER_00: Like if I was a view.
• 33:48
  SPEAKER_01: Well, I would think that, but I would also say, Why are you nitpicking?
• 33:51
  SPEAKER_01: Yeah, exactly.
• 33:52
  SPEAKER_00: I did a good job, right?
• 33:54
  SPEAKER_00: You did a good job.
• 33:55
  SPEAKER_00: You got within four out of a million.
• 33:57
  SPEAKER_00: And that to me, I think this is the reason we sort of focus on this exercise is I think it just shows the care at which your chronologists do these types of things.
• 34:07
  SPEAKER_00: I mean, that that's very careful work.
• 34:09
  SPEAKER_00: And it matters if you take that ratio difference, go from 137.88 to 137.818, and you look at the age of meteorites, the oldest solids in our solar system, it changes the age about a million years.
• 34:22
  SPEAKER_00: So we're going from like 4.568 to 4.567 billion years.
• 34:27
  SPEAKER_00: It's a very small difference, but it's one that we care about.
• 34:31
  SPEAKER_00: So people have spent a massive amount of time making these measurements, changing four atoms out of a million.
• 34:38
  SPEAKER_00: Like it's incredible precision.
• 34:40
  SPEAKER_01: That is incredible precision.
• 34:41
  SPEAKER_01: That is amazing and very I'm excited.
• 34:45
  SPEAKER_01: Like that excites me.
• 34:47
  SPEAKER_01: That you, Dr.
• 34:48
  SPEAKER_01: Jesse Ramink, are a very careful person.
• 34:52
  SPEAKER_00: Yeah.
• 34:52
  SPEAKER_00: Well, this is yeah, I mean, this is the the care of which your chronologists conduct their business, because it's worth it, you know, to be to be cle to get it as precise and accurate as possible.
• 35:03
  SPEAKER_00: So I don't know, to me that that shows you that like everybody's very careful.
• 35:08
  SPEAKER_00: People who do this type of work are very, very careful, right?
• 35:11
  SPEAKER_01: Okay.
• 35:12
  SPEAKER_01: Well, Jesse, you did not give me the top of the episode.
• 35:15
  SPEAKER_01: So I'm gonna take the bottom of the episode and I'm gonna say, in summary, then to wrap up this uh what I think is a fascinating discussion that we just had.
• 35:24
  SPEAKER_01: I hope everybody agrees, but we'll see.
• 35:27
  SPEAKER_01: One, carbon dating is not BS.
• 35:30
  SPEAKER_01: It is a tool that is reliable when appropriate.
• 35:34
  SPEAKER_01: And then I think we learned a lot about how we've established the age of our solar system and our planet to a very high degree of accuracy.
• 35:46
  SPEAKER_01: It's it's an amazing story.
• 35:48
  SPEAKER_01: That was really cool.
• 35:49
  SPEAKER_00: And you know, Chris, I think this leads nicely into some other topics around sort of how the elements formed.
• 35:54
  SPEAKER_00: We've gotten some listener questions on on these sort of themes of like really cosmochemistry, this bridge, this this sort of overlap between astronomy and geology and planetary science, which is a really interesting space.
• 36:05
  SPEAKER_00: And uh, you know, we'll have more episodes on these themes coming up uh because it's it's super interesting stuff.
• 36:10
  SPEAKER_01: I I do this all the time in my astronomy class.
• 36:12
  SPEAKER_01: I I bridge this, like you can't separate them.
• 36:15
  SPEAKER_01: They should not be uh they're married.
• 36:18
  SPEAKER_01: Yep, absolutely.
• 36:19
  SPEAKER_00: Yep.
• 36:19
  SPEAKER_00: If you're studying the moon, if you're studying meteorites, if you're studying Earth, like it, you know, it's it's very related.
• 36:24
  SPEAKER_00: And we will have episodes on sediments coming up for those people who are interested in sediments.
• 36:29
  SPEAKER_00: We got we got some in the works coming up, coming your way.
• 36:32
  SPEAKER_01: We did we did an episode on sand, only the song survived.
• 36:35
  SPEAKER_01: It's true.
• 36:35
  SPEAKER_00: That was a great one.
• 36:36
  SPEAKER_00: Love that one.
• 36:37
  SPEAKER_00: Absolutely love that one.
• 36:38
  SPEAKER_00: Hey, with that, that's a wrap.
• 36:39
  SPEAKER_00: If you have questions for us, if you have thoughts, please send us email planetgeocast at gmail.com.
• 36:43
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• 36:45
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• 36:48
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• 36:49
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• 36:54
  SPEAKER_00: We've got a ton of free stuff.
• 36:55
  SPEAKER_00: Basically, the intro to geology course that Chris, you and I teach, that's there for free on the app.
• 37:00
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• 37:02
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• 37:06
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• 37:10
  SPEAKER_00: So do those things and we get it.
• 37:12
  SPEAKER_00: Cheers.