An Honest Dad Ranking (Out Of All 2 Billion)

The statistical reality of "The World's #1 Dad Mug" is nothing but a well meaning lie. In this episode of The Rest Is Science, Michael brings another treasured artifact into the studio: a mug gifted by his daughter. Rather than claiming the top spot, the mug features a specific, mathematically defensible ranking of his fatherly abilities. If he's not the very best...surely he's in the top percentile? Find out on Field Notes. ------------------- For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit ⁠⁠https://cancerresearchuk.org/restisscience⁠⁠ Cancer Research UK is a registered charity in England and Wales (1089464), Scotland (SC041666), the Isle of Man (1103) and Jersey (247). A company limited by guarantee. Registered company in England and Wales (4325234) and the Isle of Man (5713F). Registered address: 2 Redman Place, London, E20 1JQ. ------------------- Find The Rest Is Science all over the internet by ⁠⁠clicking here.⁠⁠ ------------------- Video Producer: Adam Thornton + Oli Oakley + Jack MeekAnimator: Sam BensonVideo & Social: Bex TyrrellAssistant Producer: Lucy LipscombeProducer: Simona RataSenior Producer: Lauren Armstrong-CarterHead Of Digital: Samuel OakleyExec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Hannah Fry?

  Welcome to The Rest is Science. I'm Hannah Fry.

• 0:03Michael Stevens?

  And I am Michael Stevens.

• 0:04Hannah Fry?

  And this is an episode of Field Notes, our weekly detour into objects and stories that we've gathered from across the globe, and sometimes just from the shelves in our homes. But this week, your objects, Michael.

• 0:17Michael Stevens?

  It's my object, and yes, it's from across the globe. This morning, I am in Rotten Rua. This is a little inside joke. It's actually Rotorua, a town in New Zealand in the North Island, in the Bay of Plenty region. It's geothermally very active here.

• 0:34Hannah Fry?

  Hold on, I want to get the joke. How do you spell it?

• 0:37Michael Stevens?

  R-O-T-O-R-U-A.

• 0:41Hannah Fry?

  Rotten Rua.

• 0:42Michael Stevens?

  My aunt-in-law calls it Rotten Rua because it smells rotten. It is a very geothermally active area. It's like Yellowstone in America. As soon as you drive in, you smell all this sulfur. Let me make this very brief. We drove into here from Auckland. So where did we stop along the way? You guessed it, Hobbiton. And it was beautiful. There was a rainbow in the sky as we stood outside of Bilbo's door. It was incredible. It was so exciting. My daughter fell asleep as we finished the drive to Rotorua. And the smell came into the car as we approached. And she wakes up and goes, who farted?

• 1:24Michael Stevens?

  And I said, no, no one farted.

• 1:26Hannah Fry?

  The earth farted.

• 1:27Michael Stevens?

  The earth farted. And by the way, this is where we're going to stay for another nine days. So enjoy.

• 1:34Hannah Fry?

  Yeah, thank goodness you'll adapt to it quickly.

• 1:36Michael Stevens?

  You adapt to it very quickly. Like, it took about half an hour before we were like, wait, did we leave? No, but I mean, and it doesn't cling to your clothes, apparently.

• 1:52Michael Stevens?

  This episode is brought to you by Cancer Research UK.

• 1:55Hannah Fry?

  Scientists have found that cancer risks usually increase with age and size, but some species defy the odds.

• 2:02Michael Stevens?

  For example, deep-sea Greenland sharks. They can grow over six meters long, weigh more than a small car. And yet live for up to 400 years.

• 2:13Hannah Fry?

  Now, understanding how Greenland sharks cellular repair and immune systems seem to have managed to keep them cancer-free for centuries, that could open up exciting research pathways.

• 2:24Michael Stevens?

  Essentially, over millions of years, evolution has been running the world's most successful cancer prevention trial. And sometimes breakthroughs can be found in unusual places.

• 2:34Hannah Fry?

  So by exploring the unexpected, Cancer Research UK scientists are uncovering new ways to tackle over 200 types of cancer. Their work has helped to double survival in the UK over the last 50 years and continues to save and improve lives around the world.

• 2:50Michael Stevens?

  For more information about Cancer Research UK, their research and breakthroughs and how you can support them, visit cancerresearchuk.org/the rest is science.

• 3:02Speaker 02

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• 4:52Speaker 03

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• 5:07Michael Stevens?

  Anyway, speaking of my daughter, the object I want to show you today is the mug that I'm drinking out of. Did you see my short about this mug?

• 5:15Hannah Fry?

  I did, and I loved it. Tell us the story, though.

• 5:18Michael Stevens?

  I'll tell you the story, and then I'm going to reveal a bit of the story I did not tell on YouTube, okay? This is the uncensored full story.

• 5:25Hannah Fry?

  For people who are listening rather than just watching, at the moment, Mike was holding a mug. It looks like it could hold a decent cup of coffee, I'll tell you that. And it says, number 1,93750,012 dad.

• 5:43Michael Stevens?

  Not number one dad. It's an honest ranking of myself. Now, I would have ranked myself higher. I would have chosen, like, I don't know, maybe top half a million?

• 5:55Hannah Fry?

  How many dads are there?

• 5:56Michael Stevens?

  Very good question. I had to look this up. Apparently, there's an estimated 1.5 to 2 billion dads alive on Earth right now.

• 6:05Hannah Fry?

  So you're not even top 50%?

• 6:07Michael Stevens?

  I'm not even in the top half. So I've always thought number one dad on coffee mugs or barbecue tools is kind of, it's kind of braggy, okay? Like, I am not, I'm not the number one dad. I'll admit that, you know? I aspire to number one. I look forward to growing. I think growing, not just as a dad, but as a person, is a great thing a parent gets to do. Look. I want something also that it would just be funny if the mug ranked me for real or it tried to. Now, I would have put myself in like the top half million or so.

• 6:43Hannah Fry?

  That's pretty braggy.

• 6:44Michael Stevens?

  Is that still braggy? So I looked it up and by looked it up, I mean, I just Google searched it and I looked at like a few links and they all kind of said, ah, there might be one and a half, maybe two billion dads total alive right now on earth. So that's your, that's your kind of bounds here between one and two billion. Where do I fall?

• 7:03Hannah Fry?

  Top million is like half of a thousandth of a percent.

• 7:06Michael Stevens?

  I know. That would be really high when you think about it. So I'm kind of happy that that didn't happen. What happened is I said, well, I got to ask my daughter. Now, she's six years old. And so what I did is I drew a line on a piece of paper and I, because she, she, she understands, you know, on a scale of one to 10, where would you rank something? So I said, here, this is basically what that is. On a scale of the worst dad in the world to the best dad in the world, where would you put me? And she put me in the bottom half. And I didn't know what to do. I'm like, well, this is what she said. Now this has got

• 7:47Michael Stevens?

  to be how I rank myself on the mug because it's what my daughter said. I can't, I can't ignore that. But I do wish I was higher. Now, what I then did is I measured where her mark on the line was. And I took that, that ratio and I compared it to the two billion dads who are alive today. And that's how I arrived at 1 billion 93 million 750. But then I added 12 to make it look less like a round number, like I had more precision.

• 8:19Hannah Fry?

  This was exactly where my next question was going to be because if you are, if you're at one billion, right? Something similar to that, you're, you're measuring to nine significant figures.

• 8:28Michael Stevens?

  I know.

• 8:29Hannah Fry?

  What kind of laser electron microscope were you using to work out where she put her mark on this line? But now you've clarified it. Still though, you're still measuring to what? Six significant figures?

• 8:42Michael Stevens?

  Well, yeah. So I mean, trying to remember exactly how I did this. I mean, 750, this is just a quarter. So did I really just, was I really that specific? I must have been. Because after I did the math, I had 750,000 and a bunch of zeros. But no, I wasn't counting how many atoms were on either side of her mark. Now, I love this. So, so she and my wife then turned it into a custom mug. And I think it gives me something to aspire to, to be better. My daughter, I asked her, why, do you really think I'm in the bottom half? And she's not really happy with the amount of screen time she gets. She's not happy with the amount of candy she's allowed to have.

• 9:26Hannah Fry?

  I'm not sure if she would be the best person to assess how good a dad you are, though, you know? For those exact reasons, I think that, that her opinion is biased. And actually, I don't, I don't, I don't think you take her word for it. I think what you should do is, um, you should go around to all the people who would be capable of making this assessment. So your wife, um, her school teachers, uh, maybe a pediatrician. You know, all kinds of different experts. And then I think you should wait their responses accordingly. Get a fair, proper metric.

• 9:57Michael Stevens?

  I know, rather than just asking a six-year-old, who really doesn't, I think, know yet all the different ways a dad can be. I should have impaneled a jury that would actually rank me in their experience. And maybe, maybe I'll do that next year. But I think, in some ways, I also kind of think it's fair. Like, I don't think I'm a bad dad. I don't think that I've had a lot of challenges. I'm lucky enough that I haven't had to make a lot of the same sacrifices that other dads have. So I'm happy for them to be ranked above me. Like, what makes you the number one dad? It can't just be that you're fun and like you've never had any kind of struggles.

• 10:42Michael Stevens?

  Like, there are dads who've had a hard time and they've done much more heroic things. And harder things, they've they've made sacrifices that I haven't like I just so again, that's why I don't want to be called the number one dad.

• 10:57Hannah Fry?

  My fundamental problem with this is that you're essentially you're essentially ranking dads on one scale, right? Which is that, you know, you're you're I mean, you're you're literally creating a ranking of them. And so you've got to weigh up all of these things simultaneously. I think that what we should do is we should have a multi dimensional dad ranking system, you know, because and then I think that you can say I'm the one billion, what was it? Ninety three million?

• 11:21Michael Stevens?

  Seven hundred and fifty thousand and twelfth dad.

• 11:23Hannah Fry?

  According to this particular metric in this particular dimension. I mean, look, let's take a proper data science approach for this. Let's do let's let's let's let's take all of the different variables. Let's do a principal component analysis and then we'll find out who the real best dad is based on everything.

• 11:38Michael Stevens?

  And then we could do it to moms, which this brings me to the secret part that I have not revealed yet. So we'll show on the screen the actual picture that my my daughter drew ranking me on this line. Okay. So as you can see, it's in the bottom half. It's just it's just a pencil line and she made a little tick mark down a little bit low, in my opinion. That's what I showed in my video, but I'm going to send you I'm gonna I'm gonna message you Hannah, the full image. I removed some of what was on that page just to avoid the distraction because a short can only be so long. Okay, so I have just

• 12:17Michael Stevens?

  sent Hannah the unredacted uncensored ranking.

• 12:24Hannah Fry?

  Is one of these for your wife?

• 12:25Michael Stevens?

  It is.

• 12:26Hannah Fry?

  Oh, Lordy. Okay.

• 12:28Michael Stevens?

  Yeah, because of course, after I had my daughter rank me, my my wife couldn't help but be like, okay, but what about me? So she drew a line and said, worst mom, the best mom, where would you put me? And here's the results, listeners and viewers.

• 12:43Hannah Fry?

  Okay, the only thing I can't tell is which one is which, but should I give you my guess? Because one of them has all the hallmarks of being written with a mechanical pencil.

• 12:52Michael Stevens?

  Ah, okay. Yes. And for those of you who are just listening, I'll just I'll explain that we're just looking at the back of, I think it's An envelope and like a ripped up envelope. And it's got two horizontal lines with tick marks on them. One of them has a tick mark that's even closer to zero than the other.

• 13:09Hannah Fry?

  Yeah, one of you, one of you did worse out of this than the other. Okay, I'm gonna guess that your wife did worse.

• 13:14Michael Stevens?

  She did. Yeah, she did.

• 13:17Hannah Fry?

  Oh, that was brutal. I mean, it's barely in the first, it's barely in the, in the bottom quarter. You know, she barely makes it 25% of the way along the line.

• 13:25Michael Stevens?

  Well, to be fair, I think my wife had suggested brushing my daughter's hair that morning. So that knocked her down a lot.

• 13:33Hannah Fry?

  Absolutely fair.

• 13:34Michael Stevens?

  Yeah, no, I felt terrible when she, when my daughter ranked my wife below me. I'm like, oh no, this, this Father's Day gift is turning into the saddest, most competitive thing I never wanted it to be. But it's an important piece of family history now, this, this ranking.

• 13:52Hannah Fry?

  How many mothers are there? Are there a similar number of mothers or are there more mothers than fathers?

• 13:57Michael Stevens?

  That is such a good question and I did not come prepared with an answer.

• 14:01Hannah Fry?

  Hmm.

• 14:01Michael Stevens?

  Well, I mean, let's just do a search. I'll do the exact same, completely unrigorous search. All right, so soundvision.com, statistics about mothers around the world. They say there are 2 billion mothers in the world. And 2 billion is about the same number I get when I look up how many fathers are there. There's a Reddit thread from, um, they did the math. And they put it at, whoa, this, this person calculated 1.06 billion moms. That's half as many as that other figure.

• 14:33Hannah Fry?

  So I was gonna say, actually, if I would guess, I would guess it would be lower, right? Because there is a physical upper limit on the number of children that one woman can have. And so you get people like, you know, Elon Musk, right? Who's got like, unknown number of children or Boris Johnson, unknown number of children with many different mums. So I would guess that the number of mums, whereas I don't think you.

• 15:01Hannah Fry?

  Very often get it the other way around where someone has like 15 children, you know, where one woman has like 15 children.

• 15:09Michael Stevens?

  Right. So the, the, the, the things we're considering are if a mother has multiple children with multiple men.

• 15:18Hannah Fry?

  Mm hmm.

• 15:19Michael Stevens?

  Then those kids all have just one mom, but they've, but there are a lot of dads that have been created in that scenario.

• 15:26Hannah Fry?

  Agree, agree.

• 15:27Michael Stevens?

  The reverse.

• 15:28Hannah Fry?

  Is also true. However, there's less of an upper limit.

• 15:34Michael Stevens?

  Right.

• 15:34Hannah Fry?

  You see what I mean? And so I reckon the average number of kids per dad is higher slightly, possibly, which means that the average number of dads or the number of dads should be lower. It's my guess, you guys.

• 15:50Michael Stevens?

  You're saying the number of dads should be lower. Yeah. So the mom category is more competitive.

• 15:56Hannah Fry?

  There's more in it. Look, this is my, I'm basing this on no evidence whatsoever, right? Just, just having a story about Boris Johnson and Elon Musk in my mind.

• 16:05Michael Stevens?

  Well, but I mean, this is, this is a part of like critical thinking, you know, let's figure out like, how do we approach this? Not having already consulted the experts. And um, yeah, so I don't know, my, my wife, she, her number might even be like, what if her number was the same? Because even though she was lower, it was out of more moms. Wait, would that work?

• 16:26Hannah Fry?

  Yes, yes, it would.

• 16:27Michael Stevens?

  Yeah.

• 16:28Hannah Fry?

  No, wait, you, you're the other way around. Sorry, it'd be the other way around.

• 16:30Michael Stevens?

  She would need to be higher to have the same rank.

• 16:32Hannah Fry?

  Yeah.

• 16:33Michael Stevens?

  Right. Uh oh.

• 16:34Hannah Fry?

  The thing that this reminds me of is um, there has been like really extensive research into the number of sexual partners that men and women have in heterosexual relationships. Uh, so it's a bit of a heteronormative story, but what's really interesting is that when it comes back, the average number of partners that men have is higher than the average number of partners of females. Okay?

• 17:00Hannah Fry?

  Which sort of doesn't make sense because in the same ways when you have children, you kind of have to have a matching, right? So there were early suggestions, which I think were basically founded in sexism, which said, okay, well, the reason why this still works is because most women have a smaller number of sexual partners than most men, but there are some women who have an extremely large number. And if they're not included in the sample, then that skews the average and that's what's going on. Anyway, turns out that's almost, well, it's almost certainly not the case, certainly not the reason why you see these differences in numbers. The first reason, actually, that you can get this real clue when you look at what the numbers actually are, if you look at a distribution of the

• 17:42Hannah Fry?

  of the numbers of sexual partners and women's has this like very neat distribution, sort of as you would expect. You know, you've got like sort of nice tails on either side of the distribution or on one side anyway, because it's sort of cut off at zero, isn't it? It can't have negative, well, you can have negative encounters, certainly, but not negative.

• 18:04Hannah Fry?

  But when you look at men's, right, you don't see that same pattern. Instead, you see these really big peaks at numbers that are divisible by five.

• 18:18Michael Stevens?

  Ah.

• 18:18Hannah Fry?

  Essentially, and there's two reasons for this, two reasons for this. One is that women are more likely to say, this is like evidence back to this Africa, this is not just sort of hearsay. Although I am doing this from the top of my head, so please correct me in the comments if I've misremembered this. But women are more likely to say, okay, there was this person and then this person and then count upwards, but like thinking of each individual person.

• 18:42Michael Stevens?

  Yeah.

• 18:42Hannah Fry?

  Whereas guys are more likely to estimate and be like, wow, five a year for 10, you know what I mean? For this many years equals this.

• 18:51Michael Stevens?

  Yeah. Oh, fascinating.

• 18:52Hannah Fry?

  And also women are, because of sort of cultural expectations, more likely to estimate downwards, whereas men are more likely to estimate upwards.

• 19:00Michael Stevens?

  Right.

• 19:01Hannah Fry?

  But anyway, I just, when you have, I find those kind of problems very, that's like weirdly mathematically interesting, where it's like, you know, there must be a pairing. There must be a mum and a dad. And yet the statistics for each group individually are not the same. So you get into paradox territory very easily there. I really like it.

• 19:20Michael Stevens?

  I like it too.

• 19:21Hannah Fry?

  I've got the most important question though, about your mug. Does it taste good when you put coffee inside it? Because I think some mugs, coffee tastes better in some mugs than others.

• 19:31Michael Stevens?

  I'll tell you, Coke Zero tastes delicious out of this mug. That's what's in here. I find, I used to drink coffee all the time.

• 19:39Hannah Fry?

  Yeah.

• 19:40Michael Stevens?

  I drank so much because my dad did. He would brew up a whole pot of coffee just before bed. He thought it was really cool that he could like drink coffee in bed and then still go to sleep. I got really into it. Today, I'm just too, I run too hot. Like literally temperature wise, like a hot beverage just makes me too hot. So I drink cold, cold caffeine.

• 20:02Hannah Fry?

  But does it taste good?

• 20:04Michael Stevens?

  It tastes good and there's something about the physicality of a mug. It's just like so sophisticated. It makes me think. It makes me savor. I can just do a little like, you know, I'll do a little slurp, a little ASMR here.

• 20:16Hannah Fry?

  Go on.

• 20:19Michael Stevens?

  Oh, that sounds like coffee, but it's not.

• 20:22Hannah Fry?

  Well, I think you should get your daughter to, to update her line every year. And I suspect that as she gets older and sees that you put that number on a mug in honor of her drawing, I strongly suspect that your, your number will increase.

• 20:37Michael Stevens?

  I would, I would hope so. I hope, I hope I earn it though. But I will say that of all the, the shorts I've made, she loves the one about this mug the most because it's telling a story about us, you know? And so, yeah, maybe she'll, maybe she'll take it a little bit more seriously next year. I'd love to crack into the top billion at least, like goodness. It is funny though, that being the number one billion, 93 million and so on dad means that from an angle, it almost looks like I have a number one dad mug. And then I can be like, psych, I didn't win the competition. I actually barely placed.

• 21:13Hannah Fry?

  Okay. Should we go for a break? And when we come back, we'll be answering some of your questions.

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• 23:04Michael Stevens?

  Okay, we are back. And first up, we've got a question to Hannah from Catherine and Eli. Here's the question. Hello, I'm writing on behalf of my son Eli, who is 11 years old. He's a budding scientist and sailor in Sydney, Australia. He loves your show, he never misses an episode. Eli's question, what would be the most efficient way to use a fan to power the sail on a sailing boat? Eli's idea, put a huge industrial fan on a second boat, which would motor next to the target boat. Thank you in advance, Catherine.

• 23:40Hannah Fry?

  I absolutely love this. I love this question. This is my favorite bit of the week, by the way, when we get to answer listeners' questions, especially when they're like little ingenious ones like this. Because the thing is, is that the intuitive logic is there, right? You know, like a sail can't distinguish between wind that's created by the sort of geophysics of the earth and wind that's created by a fan. And so if you stick a fan on a boat, it should should sort of make sense that it would move. The kind of traditional, I mean, Eli's not the first person to have had this idea. And the kind of traditional formulation of this is that you just put the fan on the same boat. So you have it on the same deck, just point it at the sail. And when people had like worked this through, they had come to the conclusion that it wouldn't

• 24:23Hannah Fry?

  work at all because of Newton's laws of motion. So every action has an equal and opposite reaction. So it would be like sort of trying to move by kind of pushing your hands together, you know, it sort of it doesn't it doesn't really work, right?

• 24:35Michael Stevens?

  Yeah, right. The fan will blow onto the sail and push the sail forward, which will pull on the boat. But yet, by pushing air forward, the fan gets pushed back and they're even. So the boat's getting pushed forward and back at the same, doesn't go anywhere.

• 24:49Hannah Fry?

  So it doesn't go anywhere. And that is definitely true. If you do small models of this, if you kind of build versions of it to see whether what happens on a car or whatever, instead of necessarily on water, then it's absolutely true, right? Like Newton's laws holds, it's all, you know, no laws of physics are broken and the boat doesn't move. However, Mythbusters, that amazing program with your friend Adam Savage, in fact, they did a version of this where they got this like massive swamp boat, which are Generally driven by fans anyway, and they reversed the fan round and then had it blowing into a sail. And I mean, normally this boat, right, when it doesn't have a sail there, it can go at 20 miles an hour, right?

• 25:34Hannah Fry?

  It can kind of zip along the water. But when they had the sail and the fan, it did move forward. It did, but only by about three miles an hour, so like a really, really small amount.

• 25:47Michael Stevens?

  This is surprising. I I'm surprised, one, because I've never seen this episode.

• 25:52Hannah Fry?

  Uh huh.

• 25:52Michael Stevens?

  Which is unusual.

• 25:54Hannah Fry?

  Yeah.

• 25:55Michael Stevens?

  And I expected something weird as soon as you started telling this story. I'm like, oh, it must work in some way. So why? What was the explanation for how they're able to blow themselves forward with a fan that's on board?

• 26:08Hannah Fry?

  Okay, so there there's arguments about this, right? If you if you want to see a couple of scientists get into a fight, ask them about aerodynamics in general, because it's really difficult to prove which forces is the kind of dominant one, one way or the other. You know, ask ask a pilot about the difference between Bernoulli and Newton and and they'll sort of descend into horror. But this is another one of those examples where basically people have got into massive fights about it. No one is perfectly sure, but I think I think that the most convincing argument is that the sail doesn't just absorb the air that's being blown towards it. It ends up reflecting some of that air backwards.

• 26:47Michael Stevens?

  Uh huh.

• 26:48Hannah Fry?

  And so in reflecting that air backwards, then the opposite reaction is that the the sail moves forwards.

• 26:56Michael Stevens?

  I see.

• 26:57Hannah Fry?

  So that there's like an additional effect.

• 27:00Michael Stevens?

  There's a net forward force on the boat. Because the reflected air doesn't then get reflected back and forth and back and forth. Eventually, it just leaves out the back.

• 27:11Hannah Fry?

  Yeah.

• 27:12Michael Stevens?

  Meaning the boat goes forward, not as quickly as it would.

• 27:15Hannah Fry?

  Not as quickly as it would. But I mean, in general, okay, like in general, putting a fan on the same boat as a sail is like, it's not a good idea. Eli's version is way smarter, right, way smarter, which is that he suggests that you put a fan on a boat. And then blow the fan in and then now Newton's not a problem, right? You don't have to worry about equal and opposite reactions because the two things are physically separated from one another. This would totally work, right? Only slight problem about it is that a jet of air actually it sort of falls apart really quickly, you know, it doesn't sort of keep its strength very quickly. It fans out, it sort of drags other air in or still air loses its speed and so on and so on.

• 27:58Hannah Fry?

  And so you would have to have the the fan like absurdly close to the sail that it's blowing. And also it would have to go along with it, right? So your your boat with the fan on it would have to be

• 28:14Hannah Fry?

  propelled along and be like extremely close to the sail that it was following. At which point you've sort of got a boat

• 28:23Hannah Fry?

  that's already moving and you may you may as well just use a rope instead, you know? So, I mean, in terms of the laws of physics, it's perfectly legal. Economically unhinged, I think, is

• 28:35Hannah Fry?

  is the best description of what he's come up with. But ultimately, that's my favorite category of invention. So, fine by me.

• 28:41Michael Stevens?

  It would look amazing, though. If I looked out on a on a lake and I saw a boat being blown by the fan in another boat.

• 28:49Hannah Fry?

  Yeah.

• 28:49Michael Stevens?

  I would I would watch. I would love that. I'd love to see a race like that because, of course, yeah, it becomes like hilarious because the boat with the fan on it is going to have to be using much more energy to to keep up. Because it's it's fan is blowing it backwards, so it's got to work even harder to move forward and keep up with the boat it's pushing.

• 29:09Hannah Fry?

  And all the energy of the actual fan itself. Yeah, I mean, it's it's it's it's mad, but great.

• 29:15Michael Stevens?

  Mad but great. That's that should be one of the catchphrases of this podcast.

• 29:20Hannah Fry?

  Absolutely.

• 29:20Michael Stevens?

  Now, here's a question from Sever or Steve. Steve asks, Michael, in about 600 million years, the total solar eclipse era will be over. The moon will have drifted far enough from Earth that we will only experience annual eclipses. This, of course, leaves us all wondering the same thing. Will the next Manhattan Hinge solar eclipse be total or?

• 29:46Michael Stevens?

  Annual. Okay, so I love this question because I didn't know, but I'm a huge fan of Manhattan Hinge. Manhattan Hinge is a phenomenon that was first described by Neil deGrasse Tyson. It's based on Stonehenge in England, where these stones appear to be aligned with the sun for the solstices, the winter and summer solstice. And on those dates, the sun is like, it's lined up on certain stones, blah, blah, blah. The details don't matter. What matters is that any big monoliths could be assumed by future civilizations to also be aligned with the sun. So now picture, picture you are a future archaeologist. It's the year

• 30:28Michael Stevens?

  5000 and you've uncovered the ruins, these ancient ruins of New York City. And you notice that of course, this was a celestially important religious site because four times a year, the city aligns with the sun. On May 28th and July 13th, the sun sets exactly in between the buildings on either side of a block. And on December 5th and January 8th, the sunrise happens perfectly in between the skyscrapers. So clearly, that's why it was built the way it was.

• 31:02Hannah Fry?

  That's cool. That's cool.

• 31:04Michael Stevens?

  And Neil deGrasse Tyson calls this the Manhattan Solstice, the Manhattan Hinge. What Steve is asking us is, will the next solar eclipse that happens right in between the buildings on your left and right as you look down a New York block, will that be a full total solar eclipse? Because solar eclipses happen a lot.

• 31:27Hannah Fry?

  Mm hmm.

• 31:28Michael Stevens?

  They happen a lot. They just don't happen right where you are on Earth very often, because the Earth is a big place. And he points out correctly that total solar eclipses are not going to be around forever. The moon is drifting away. In fact, the moon is drifting away at a very funny speed. And I calculated a funny way to keep this in mind. If every morning you woke up and you painted a layer of paint on the bottom of your shoe, and then you walked around, the next morning you woke up, painted another layer on top of that layer, you would be leaving Earth just as fast as the moon is leaving Earth.

• 32:06Hannah Fry?

  Feels like a deleted scene from Twits.

• 32:09Michael Stevens?

  Yes, it's, it's, it's not fast, but, but the moon is getting further and further away.

• 32:14Hannah Fry?

  Yeah.

• 32:15Michael Stevens?

  At the moment, the moon is perfectly aligned so that during a solar eclipse, it completely blocks the sun.

• 32:21Hannah Fry?

  Which is one of the, the strange coincidences of the solar system, that it should be 400 times smaller than the sun, and yet also 400 times closer. I mean, it is a complete fluke that we get total solar eclipses.

• 32:32Michael Stevens?

  We were born at just the right time to see such a phenomenal event as a total solar eclipse. But in 600 million years, sorry, there will be no more total solar eclipses. The moon will be too far to be large enough in angular diameter to completely block the sun. So will there be a total solar eclipse over Manhattan? That is also aligned with Manhattan Hinge before we lose the moon. Well, at least before the moon is too far away to give us a beautiful total, total, total solar eclipse. And the answer, I'm pretty sure is no. The problem is that the, the next solar eclipse in New York City is in 2079.

• 33:17Michael Stevens?

  Not that far from now, but it's going to be on May 1st.

• 33:20Hannah Fry?

  Right. It needs to be on the correct date.

• 33:22Michael Stevens?

  It needs to be on the correct day. So we need a lot of things to align. We need there to be a solar eclipse that is over Manhattan. It also needs to fall on one of these four days. May 28th, July 13th, December 5th, January 8th. It also has to be at sunrise or sunset. And those variables are not going to align in the next 600 million years. They probably will align at some point, but at that point, the eclipse will be annular. Meaning you'll just see this ring of fire. You'll see the sun with the, the moon silhouetted in the middle.

• 33:57Hannah Fry?

  Of, of all of those three things, the sun, the moon, the earth. I strongly suspect that the Manhattan grid will not, will not be around by the time that the next one.

• 34:07Michael Stevens?

  I think you're right.

• 34:08Hannah Fry?

  600 million years is a bit ambitious, ambitious, I think.

• 34:11Michael Stevens?

  Guess what? Here's, talk about ambitious. We have time. The next total solar eclipse over New York City, 2079 on May 1st. It's not too late to start moving all the buildings. Okay, if we lifted them up, laid them down at a different angle, redid all the streets, we would be able to catch that 2079 total solar eclipse and have a total eclipse of the sun right in between the buildings. Wouldn't that be a really cool six minute payoff?

• 34:43Hannah Fry?

  I think it's time we had something that brought us together, you know? I think it's time we had something to work for, something that everybody could get behind, something that was a sensible moonshot that everybody collectively around the world could celebrate. I don't see any problems with this. Get Mandani on the phone, okay?

• 34:58Michael Stevens?

  Okay, all right, I'm on it. Let's do it. Perfect. This is going to bring humanity together.

• 35:04Hannah Fry?

  Okay, one last question. This is from Clayton. Clayton says, "It might just be my fiance and I, but we wondered, why do we get instinctually scared running up dark stairs? And why do you not feel the same running down dark stairs? Might be a silly question, but I can't get rid of the fear even if I try." Well, okay, I don't know if this is a silly question or a silly fear. I think that the thing about fear is that it happens at a level that's sort of beyond your conscious control. And so I think once you've decided that something is to be fearful of, you kind of sort of, it's a little bit out of your hands. One thing I will say about being scared of the dark is completely legitimate and makes a lot of sense. There's a number of different reasons for this. For one thing, you've got

• 35:49Hannah Fry?

  this loss of visual information, so your brain is having to make guesses about what's out there. We've spoken about this before on this podcast, but we are predisposed to absolutely despise uncertainty, right? We really dislike it. It makes us feel extremely uncomfortable. There's like a very ancient part of your brain called the AIC. It's connected to all of your internal organs, right? So it's sort of like the monitoring system for your internal organs. And when it feels a sense of uncertainty, it essentially reacts by like pulling blood from your gut, by quickening your heart rate, and then reports those same physical sensations back to your brain as like something is not right. So when you're like in, when you have that gut feeling, it is your AIC that is responsible for that really horrible feeling of discomfort.

• 36:33Hannah Fry?

  And it's all happening a sort of below the conscious level. The other thing about being scared of the dark, well, so there's all these lovely theories about how it's actually sort of founded in a kind of evolutionary history. So there's this really famous study where they were looking at this data of lion attacks on humans from Tanzania. And there'd been 500 attacks on people over a couple of decades. And basically, the lions deliberately attack when the moon is really faint or below the horizon.

• 37:05Michael Stevens?

  Really?

• 37:06Hannah Fry?

  So when there is as little light as possible. Essentially, the lions have worked out that they can exploit the differences. I mean, worked out is a bit strong, sort of giving them agency that I don't think necessarily is appropriate in this, in this particular context. But, but our eyesight is so weak when it's very dark and their eyesight is so much stronger, they have a massive advantage. I think that this is the idea generally, that when we, we have this sort of biological memory of when we were hunted. That same fear sort of presents itself when we're in the dark. So I think being scared of the dark actually is a completely rational and normal thing. The stairs thing though, stairs thing is interesting. Do you have this experience, dark stairs?

• 37:45Michael Stevens?

  Yes, of course. Like as a kid, I remember being terrified when the lights were turned off in my grandparents' basement while I was down there. And I had to run up the stairs. There was this primal fear that something would be following me.

• 38:00Hannah Fry?

  Chasing you up.

• 38:01Michael Stevens?

  Going down into the dark, I just feel like there's something deep about which way you're facing that matters. If the darkness is behind you, you are, one, not able to see what's behind you. But you're also, you've got two vulnerabilities there. You're going up and you're also in the dark. If you're going down.

• 38:22Hannah Fry?

  You can retreat. You know where you've come from.

• 38:25Michael Stevens?

  I don't know if there is like maybe a fear of heights involved there? Or if just the, the act of going up this, running up the stairs also gets your heart rate going, just like fear does. I think there might be a bunch of modalities all mixing together to increase the physiological fear. Symptoms. It wasn't until literally last week that I realized how dark the night is with no moon. This is almost a bit of a religious experience. I've lived in places that had artificial light at night everywhere. You know, maybe not always a lot, but enough that every night sort of felt the same. But I just came from living off the grid on this island. The moon is such an important part of our environment.

• 39:09Michael Stevens?

  Like, of course, every fantasy novel set in medieval period talks about the moon all the time. Because when there's no moon at night, it is too dark. You can't see where you're gonna step next. But when there's a full moon, you can read a book outside at night. It's, it was so beautiful.

• 39:26Hannah Fry?

  Wow, that's amazing. I'm very jealous.

• 39:28Michael Stevens?

  You've got to experience it because it was like nothing I'd ever felt before. And then, of course, every night is different. As the moon waxes and wanes, you feel each night is going to be different. And the moon rises and sets at different times. So there'll be that moment in the night where the sun is down, but the moon isn't up yet and it's just pitch black. Here's another thing I learned about myself. I'm just like not scared of the dark in the same way I used to be as a kid. I was walking through the bush to get back to our house in the middle of the night. Clear night, but no moon at all. And I turned off my flashlight to see if I could scare myself. Because I was all alone on this path in the middle of the bush. And I just sat there, or I stood there in the dark, and I just wasn't scared.

• 40:12Michael Stevens?

  I know I'm kind of bragging at the moment, but I just, I could not, I could not.

• 40:18Hannah Fry?

  The number one billionth dad was okay in the dark, Hugo.

• 40:22Michael Stevens?

  I'm just saying, maybe I should tell my daughter this story. Could be impressive to her. I think it helped to know that I was in New Zealand. There were no venomous, uh, anything. I guess if I'd heard some twig snapping.

• 40:34Hannah Fry?

  That would have been a bit scarier.

• 40:36Michael Stevens?

  That would have been different. I probably would have just thought it was someone's dog, though.

• 40:39Hannah Fry?

  That whole point about how connected the moon was to our history, you know, the whole idea of lunacy, right? That like.

• 40:45Michael Stevens?

  Ah, yeah.

• 40:46Hannah Fry?

  People kind of go crazy at full moon. There's sort of something to it, but not, not in the sense that, you know, our, our mental state alters. But that actually, when it was full moon, you know, people who liked doing things under the cover of darkness had to change their behaviour, you know, you would get more burglaries, you would get sort of more nefarious activity going on.

• 41:08Michael Stevens?

  Yeah, of course, because the full moon is very bright. And again, if you live where people have streetlights and, and external lights on their homes and all this artificial light every night, every night can feel very similar. And yet they are so different that, yes, when it's pitch dark at night, there's a new moon or it's overcast. You can't do anything outside if you don't have your own artificial light. But when there's a full moon and a clear sky, you can read a book, your shadow is dark and crisp. And it looks like you live on Pluto or something. It's like, it's daytime, but the sun's far away.

• 41:41Hannah Fry?

  Amazing.

• 41:41Michael Stevens?

  It's really, it's really amazing.

• 41:44Hannah Fry?

  That's going to be my next holiday attempt is to go somewhere, genuine dark sky place.

• 41:48Michael Stevens?

  Do it.

• 41:49Hannah Fry?

  Yeah, that sounds amazing. All right, okay, I guess that brings us to the end of this episode. Just to wrap up the question here, Clayton, we don't know, but we agree that it's scary. I think that's a, that's sort of the ultimate conclusion that we can come to.

• 42:01Michael Stevens?

  Yeah, yeah, I think it, I think it activates feary responses from your body in like at least three different ways that going down doesn't.

• 42:10Hannah Fry?

  Well, okay, as ever, you can send us in your questions to therestis science at goalhanger.com. And we will be back for another main episode and then another episode of Field Notes next week.

• 42:20Michael Stevens?

  Until next time, stay curious.

• 42:21Hannah Fry?

  Bye bye.

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