Rachel Feltman: Hey listeners, it’s Rachel. Today’s episode is something a little different. We’re sharing an episode of Vox’s podcast Unexplainable. In it, I chat with host Noam Hassenfeld about the latest issue of Scientific American, which is all about scientific questions that once seemed impossible to answer—and even some mysteries that we still don’t know how to solve. It’s a really fun conversation, and I’m super excited to share it! We’ll be back with a new episode of Science Quickly on Friday, and you’ll see part two of this collaboration with Vox in our feed later this month. Without further ado, here’s Unexplainable.
Noam Hassenfeld: Rachel Feltman
Feltman: Hi.
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Hassenfeld: Welcome to the show.
Feltman: Thank you.
Hassenfeld: So you host Scientific American’s podcast, Science Quickly,
Feltman: Yeah.
Hassenfeld: And I wanted to talk to you because Scientific American has a special issue called Impossible Questions. It’s out in print. It’s out online as of yesterday. And when I found out about it, it was like someone had put the bat signal up in the sky. Like someone somewhere is talking about what we don’t know! So I wanted to talk to you, but before we get into it, for anyone who isn’t familiar with Scientific American, can you just set the stage a little bit?
Feltman: Yeah uh, so Scientific American is the oldest continuously published magazine in the United States.
Hassenfeld: Okay.
Feltman: Yeah, yeah. We’re old, but we’ve, we’ve got a lot of life left in us. Yeah, the magazine was founded in 1845, we have a lot of people say, you know, like, “My grandfather had a subscription to Scientific American, and then my dad did, and now I do, and we love it.”
Hassenfeld: Yeah, one of the last people I interviewed for the show, Hank Green, I was asking him how he got into science in the first place, and the first thing he said was, “When I was a kid, my parents got me a subscription to Scientific American.”
Feltman: Yeah, we, we love to hear that.
Hassenfeld: Yeah so we’re planning to do two episodes on this Scientific American issue. We’re doing one today and one on Monday. And I wanted to kick it off with something we haven’t really done much on our show, because we talk about unanswered questions all the time on our show, but we don’t always zoom out and talk about why they’re all unanswered. And the Impossible Questions issue inspired me to make a sort of, um, I don’t know, taxonomy of unanswered questions. It’s definitely not exhaustive. I’m sure some questions aren’t gonna fit in perfectly here, but I came up with four big categories that helped me wrap my head around why questions are unanswered. So I figured I could run them by you.
Feltman: Yeah.
Hassenfeld: Does that sound good?
Feltman: That sounds great.
[SCORING]
Hassenfeld: Okay. So the first kind of bucket I came up with, is really the clearest, which are the questions that we’re trying to answer but just need more research. Like, the research is hard, and we’re doing it, and we’re not there yet. So we still kind of fundamentally don’t know exactly why things smell a certain way. And you know, I think about a question we talk about a lot, which is, like, do aliens exist? And, and it– like, we’re working on it. Like, we’re looking, and we just need more time.
Feltman: Yeah, you know, I love that bucket because I think a lot of people sort of assume all of the questions that scientists would bother working on are in that bucket, which of course is not the case. But, one that comes to mind is how acetaminophen works.
Hassenfeld: Yeah.
Feltman: So, uh, Tylenol is a big one, but then in a, in a very different category of a very common drug, like most, if not all antidepressants, there is this thing where there are drugs that we know work well enough we use them quite often. They provide immense benefit to many people. But we don’t actually know definitively what the mechanism is by which they are working, which is pretty mind-blowing and does seem like a question that surely must be answerable, if we just get more information.
[SCORING OUT]
Hassenfeld: Intuitively, you might think, okay, unanswered questions are unanswered because they’re so big or they’re so far away. And even things that we’re so physically close to, are still hard to answer. Like, it’s not just is there an alien out there or is there, you know, a mysterious planet in the furthest reaches of our solar system? It’s like, what’s up with our nose?
Feltman: Totally. Yeah, and not to like climb on my soapbox too much, but, you know, a big category of those unanswered questions are ones that you know, mainstream science has simply not dedicated resources to. So uh, reproductive health and, you know, endometriosis, things that are very present, very close. And we have this big knowledge gap, which thankfully, you know, we are starting to see get resolved. But, yeah, you know, I think there are so many questions like that where it probably isn’t that the question is so insurmountable, but someone does have to put the resources toward trying to answer it, which has not always been the case.
Hassenfeld: Okay, so that is actually a perfect segue into my next bucket.
Feltman: Oh good!
Hassenfeld: In a slightly different way, but the next category I was thinking of, which is easy to miss sometimes, is questions that we really could be answering, but we might not want to, and there might actually be a good reason why we wouldn’t want to. These are sort of moral, ethical “should” questions. Where the best way to answer it would be to test some dangerous substance on people or to withhold something from them, but, you know, one thing that occurs to me in this realm and this is why I, I bring this up after the endometriosis thing is I think a lot about the fact that we know so little about what medications are actually safe for people who are pregnant.
Feltman: Absolutely, yes.
Hassenfeld: And it might be hard to design an experiment for that because it would be very difficult to say, “Hey, you’re pregnant. Take this pill. We don’t know how it’s gonna react.”
Feltman: Yeah, no, this is something that, um, I’ve been thinking about a lot lately because I had my first kid not long ago. And it’s such a problem, but one that, like you said, there isn’t a great solution for, at least in the current paradigm for, like, our best way of studying drugs.
Hassenfeld: Yeah, and drug companies got scared off of testing stuff on people, like people who might just even have a remote possibility of being pregnant.
Feltman: Sure, yeah.
Hassenfeld: And what we’ve ended up with is a world where we actually just don’t know a lot of impacts of medication in general on women?
Feltman: Yeah, no, I definitely think that’s true, and it’s so thorny to even talk about. You know, on the one hand, I think anybody with any kind of moral compass can see that the way that a lot of science was conducted in the 19th and a lot of the 20th century was not good in that respect. That, you know, a lot of unethical decisions were made, but you know, I, I think it’s good that that scared us. But we aren’t great at figuring out the nuance there.
Hassenfeld: And it just, it leads to this place where it’s like we’re somehow okay with the fact that we just don’t know how so many of these drugs work on women.
Feltman: Yeah, exactly.
Hassenfeld: It’s very strange. Um….
Feltman: It is very strange.
Hassenfeld: Okay so the next group of questions I’ve been thinking of is the questions we didn’t know were unanswered because we didn’t even know we could ask them.
Feltman: Yeah.
Hassenfeld: We didn’t have the tech, or we didn’t have the observation, or we didn’t have the right theory to even get to a place where we could ask that question. So, you know, an example I think of is how microscopes let us ask questions about microbes, and then that let us ask questions about the microbiome, and then we get to a place where we can ask questions about the impact of the microbiome on our mental health.
[SCORING]
Hassenfeld: You know, a couple hundred years ago, you couldn’t sit around and be like, “What is the impact of all the little bacteria in our gut on our mental health?” Like, that wouldn’t mean anything.
Feltman: Yeah, you know, one that I, I think, um, works well for this bucket is, uh, the question of what the longest lived animal is.
Hassenfeld: Is this the, the, the Greenland shark?
Feltman: So yeah, for listeners who, who don’t know, in I think it was 2016, researchers looked at proteins from the eye lens of a bunch of Greenland sharks.
[CLIP of CBS NEWS: Almost like a, an organic living carbon footprint in the back of their eye and do an organic version of carbon dating like we would do with some ancient artifact]
Feltman: And they found an average lifespan of 272 years. The largest shark that they looked at was 392 years old, plus or minus another, like, 100 or so years.
Hassenfeld: It’s like a shark that like overlapped with Shakespeare or something
Feltman: Yeah, yeah. And so that’s the longest lived vertebrate.
Hassenfeld: Mm-hmm
Feltman: The oldest invertebrate is a clam, uh, nicknamed Ming because she was born in 1499 during the Ming dynasty.
[CLIP of DEMYSTIFIED DAILY: Clam shells are deposited in layers like tree rings. So if you count the layers, you can figure out how old the clam is.]
[CLIP of MINUTEMAN773: And they didn’t discover Ming’s age until they returned to the lab and examined its shell under a microscope]
Feltman: It’s not that we never would have asked, you know, how old is the oldest thing? But, it was just like a philosophical question.
Hassenfeld: Yeah, we wouldn’t have had a way to actually get an answer.
Feltman: Yeah, except, you know, maybe like looking at historical records that are like, “Wow, my family’s been watching this one clam for centuries, and it’s cursed with life.” Um, so yeah, I, I like how that one would’ve absolutely like boggled the mind of scientists from 100 years ago, so that’s pretty cool.
[SCORING OUT]
Hassenfeld: Yeah. So, okay, the last bucket might be the biggest bucket, and this is more of the classic big unanswered questions that people might think of when you say, “Oh, what are the, the biggest unanswered questions in science?” The way I’m thinking about this bucket is like there’s some insurmountable barrier, or at least seemingly insurmountable barrier between us and the answer. Like, how did life start? Or, what happened before the Big Bang? Something that seems like we could never get past.
Feltman: Yeah. There are so many questions like this, And there are several, in fact, in, you know, this, uh, print issue of, of Scientific American.
Hassenfeld: These are sometimes the most fun.
Feltman: Yeah, yeah! Well, so what came before the Big Bang is a really fun one, because the word before is no longer accurate actually, because the Big Bang wasn’t just the start of space, it was the start of spacetime, so it was also the start of time. So what does it mean for something to have happened before the Big Bang?
Hassenfeld: At the same time, though, you never know what kind of tech or what kind of theory is gonna come around and give us a way in. Like the microscope with the microbiome.
Feltman: Hmm.
Hassenfeld: And I don’t know… sometimes just kind of wrestling with these questions, I feel like it can take us to some pretty fun places. So I actually want to try that with this Big Bang question.
[SCORING IN]
Hassenfeld: Even though it seems totally impossible, there are some very interesting theories of what could have happened before the Big Bang.
Feltman: Hmm.
Hassenfeld: And we’re gonna get into it after the break.
Feltman:
[MIDROLL]
[BUMPER]
Hassenfeld: Why don’t we just start with who you are and what you do?
Sarah Scoles: My name is Sarah Scoles, and I am a senior contributor at Scientific American.
Hassenfeld: All right, so you wrote this great piece for the Scientific American Impossible Questions series. And it’s all about what happened before the Big Bang.
Scoles: Yeah.
Hassenfeld: How did you even start thinking about this question?
Scoles: Yeah, I mean, if we go all the way back to when I was a kid, I grew up super religious, but I was always an annoying kid who was like, “Well if God created the universe, who created God? And then what came before that?” And then when I went to college and became not religious anymore, it turned out I was still interested in the same questions.
Hassenfeld: The big impossible questions?
Scoles: Exactly, still annoying. And my roommate and I would sit in our room and be like, “Well, if space is expanding, what is it expanding into?
Hassenfeld: Yeah.
Scoles: And if the Big Bang was the beginning, what happened before that? And now I’m a science journalist and I thought, you know, there’s probably some people thinking about this question professionally, and I could just bother them instead of my Sunday school teachers like I used to.
Hassenfeld: Oh my God, this is such a great entrance into this question. I guess how is it even possible that someone could try to answer a question like this? Isn’t it by definition impossible?
Scoles: Yeah, I think, I mean, it depends on how you think about it. The Big Bang is definitely a hard boundary we can’t even, like, see or gather data from the time right after it, let alone see right back to it. And so, if you can’t even see there, you definitely can’t see before there. So I think the way that scientists think about it is maybe there are some imprints left on the universe that we can see that provide some clues for what happened before.
Hassenfeld: Ok, what did the scientists you talked to tell you about this question? Did they have theories for what might have happened before the Big Bang?
Scoles: Yeah, so the first theory is called the no boundary proposal, which is based on this idea that if you look at the modern universe and you say, “How did it get like this?” You can rewind back and say like, what initial conditions would I have needed to go from the past to the present? And then you can kind of go backwards and backwards and backwards forever, But, that doesn’t make sense because as far as we know, the Big Bang created time, and so there cannot be a before the Big Bang because there was no time before the Big Bang. So if this isn’t making sense, that’s how it’s supposed to be because th- this, this, uh, this proposal came from the fact that, like, if you do that, it doesn’t make sense. Like, it sounds like gobbledygook. So in the ’80s, Stephen Hawking and another physicist named James Hartle were like, “This doesn’t make sense, so let’s try to think about it without the universe having a beginning.” Let’s let go of time, our concept of time in that way, and let’s think of the universe.
[SCORING]
Scoles: As a four-dimensional space-time sphere…
[SCORING BUMP]
Scoles: So the way that scientists told me to think about it, because, like, that’s not something… Our brains don’t encounter four-dimensional spacetime spheres.
Hassenfeld: Not often?
Scoles: Not often. So they said think of it like the globe. Like, if the universe in space and time is a globe, then the beginning of the universe, the Big Bang, is the, the North Pole. And so asking what happened before the Big Bang is kind of like asking what is north of the North Pole? Like, nothing.
Hassenfeld:That’s almost like a zen koan or something.
Scoles: Yes, exactly.
Hassenfeld: So that’s not an answer to the question. That’s just sort of like rejecting the question?
Scoles: Yeah, sort of. Yeah, it’s a very fancy way of rejecting the question. Yeah.
Hassenfeld: Are there any ideas of what happened before the Big Bang that are not kind of rejecting it, that are actually taking it seriously?
Scoles: Yeah, one that I found interesting is this one, called the Big Bounce.
[SCORING SWITCH]
Hassenfeld: The big bounce?
Scoles: The Big Bounce. Yeah. So as, as far as scientists know, as far as we can see right now, you know, the universe is expanding at an accelerating rate. But in this cyclic universe theory, there’s the idea that at some point it starts contracting
Hassenfeld: And this is not the Big Crunch?
Scoles: This is not the Big Crunch because it doesn’t shrink all the way to nothing, and it’s not, like, a violent contraction. It kind of contracts slowly and not all the way down and then starts expanding again. And so the Big Bang would kind of be that transition.
Hassenfeld: So wait, wait. This is saying that the universe expands and contracts, and the moment it switches from contracting to expanding, it looks like what we think of as the Big Bang.
Scoles: Correct.
Hassenfeld: But there’s just stuff that’s been in there the whole time. There’s stuff that’s been there forever?
Scoles: Yeah. That’s my, that’s my understanding of it. And, uh, the scientist I spoke to about it said, you know, there is some stuff that get from the previous universe that gets carried along into ours.
Hassenfeld: But I guess, like, it’s not a previous universe, it just looks like a previous universe.
Scoles: Yeah. Which, which I guess is also sort of rejecting the question because then you have to ask how did all of this get started? What was before the first big expansion and big bounce? So, it is also not totally answering the question.
Hassenfeld: Does this scientist have, have an answer to that question or…
Scoles: Uh, no, I think that’s asking too much.
Hassenfeld: Okay. I mean, it is… . it’s asking a lot.
[SCORING OUT]
Hassenfeld: But both of these ideas are kind of saying there’s no big fundamental before and after here. Like the first one says there’s just… no before. Like it doesn’t mean anything. And the second one is kind of saying… there’s no real Big Bang. Or it’s not as bangy as we thought. Are there any ideas out there that are like what’s before is super different from what happened after? Like different from what we can see now?
Scoles: Yeah, so there’s this one idea called a sort of mirror universe. The scientist I spoke to said to picture it like two ice cream cones kind of pointy end to pointy end. Our universe, you know, is expanding, making this cone in one direction. Time is going forward. Stuff is made of matter. And then on the other side, in the other ice cream cone, it’s going the other way. The universe is running backwards. Time flows backwards. Stuff is made of antimatter instead of matter, and all of the directions are reversed. So it’s a literal mirror of what is going on here, and the Big Bang is where those two things are touching.
Hassenfeld: Or is it flowing…what does it mean for time to flow backwards?
Scoles: I think this is one of those things again where our human brains, because we live in a universe where time does flow forward, and as far as we know it only flows forward for us, it just, like, doesn’t make sense for time to go backwards.
Hassenfeld: But the idea here is that like everything in the mirror universe is flipped?
Scoles: Yes.
Hassenfeld: And then I guess am I wrong in assuming that this still begs the question of what happened before that?
Scoles: Like how did these mirror images of each other get there in the first place?
Hassenfeld: Yeah, who made the ice cream cones?
Scoles: Yeah, so I think once again we come back to the fact that the question is perhaps impossible because these are ways of answering it in a way that just calls the question again at a different point in the universe’s history.
Hassenfeld: Hmm. What are the chances that any of these theories is right?
Scoles: I think even most of the people who have come up with or work on these theories would say the chances are probably not high that any one of them is correct. I think, yeah, one of them actually said that to me. He said something like we’re just trying to throw spaghetti against the wall and see what sticks, and just keep throwing ideas out there for what could make sense based on what we see in the universe today. And in, in some ways there’s not necessarily definitive ways that we could decide whether any of them was the correct explanation because you can’t see before the Big Bang. And so that’s, that’s frustrating to me and my inner child, yeah.
Hassenfeld: So do, do you think it is ever gonna be possible to get to a final answer on what happened before the Big Bang?
Scoles: Yeah, I’m wary of saying never in science because you never know what sorts of tools scientists are going to come up with. But to me, sitting here in my chair in 2026, it doesn’t seem to me like it’s something we could ever find out definitively. I think there’s fundamental barriers to data gathering in the universe, and I also think there’s probably fundamental barriers to how our brains can think about it. Like, maybe before isn’t a concept that the, that the universe abides by or, you know, I think we’re, we’re stuck in our own reality that really has very little to do perhaps with the, the fundamental laws of the, the universe and I don’t know if our puny brains can figure that out. But…
Hassenfeld: Is there something about the fact that this feels unanswerable that is more exciting to you? Like, if you could answer this, would you want to?
Scoles: Yeah, I mean, I think that I think I would like to have the answer. But it is, it is sort of reassuring to me in a weird way that, that there are things that like are probably beyond us and that we get to wonder about and people get to come up with crazy ideas like the universe is a four-dimensional space-time football or whatever.
[SCORING]
Scoles: And, I think It kind of opens up a different version of maybe awe, I guess, like, not necessarily religious awe, but just, you know, cosmic awe. Like, the universe is so strange and we have so little of it figured out. And I do think that’s exciting. There’s so much out there that we haven’t discovered, and then beyond that there’s stuff we probably never will, and I think that’s great. The universe should be able to keep its secrets if it wants to.
[SCORING BUMP]
Hassenfeld: This was the first episode of our 2 part series with Scientific American. If you want to read more about this and other impossible questions, go check out their special issue. You can find it in print or on their site at scientificamerican.com. You should check out their excellent podcast, Science Quickly! And stay tuned for the second episode next week.
This episode was produced by me, Noam Hassenfeld. It was edited by Meradith Hoddinott, who runs the show. Fact checking from Melissa Hirsch, Mixing and sound design by Cristian Ayala, and music from me. Our video editor is Jacob Reynolds. Our animator is Karyim Carreia. Our editorial director is Joanna Solotaroff.
And Byrd Pinkerton slung the guitar strap over her shoulder and headed back into the passageway. She tried to retrace her steps but before she knew it, she was lost. Alone in the darkness.
Special thanks to Clara Moskowitz, and thanks, as always, to Brian Resnick for co-creating the show with me and Byrd.
If you have thoughts about the show, we’d love to hear from you. Please email us at unexplainable@vox.com. Or, if you’d like to support this show, join Vox! Become a member! Just go to vox.com slash members. And if you signed up because of us, let us know.
Unexplainable is part of the Vox Media Podcast Network, and we’ll be back next time with the second episode of our series with Scientific American.