1 00:00:08,560 --> 00:00:10,040 Speaker 1: Hey, Daniel, what did it like to look at the 2 00:00:10,039 --> 00:00:13,440 Speaker 1: world through the eyes of a physicist? Oh, it's amazing. 3 00:00:14,120 --> 00:00:17,919 Speaker 1: It's red, there's green, and then there's blue. It's really 4 00:00:17,960 --> 00:00:20,360 Speaker 1: quite beautiful. I mean, like, are you always trying to 5 00:00:20,920 --> 00:00:24,239 Speaker 1: analyze and understand everything? Like it's the world just a 6 00:00:24,440 --> 00:00:29,000 Speaker 1: giant mess of puzzles and interesting phenomenon pretty much. It's 7 00:00:29,040 --> 00:00:31,120 Speaker 1: hard to turn that part of your brain off once 8 00:00:31,160 --> 00:00:32,800 Speaker 1: you've turned it on. I mean, don't you ever want 9 00:00:32,840 --> 00:00:35,479 Speaker 1: to just sit back, relax and just live in the 10 00:00:35,520 --> 00:00:38,960 Speaker 1: moment and experience things? Yeah? Every time I do that, 11 00:00:39,040 --> 00:00:41,240 Speaker 1: I think, how does that work? Living in a moment? 12 00:00:41,240 --> 00:01:01,040 Speaker 1: What do you relaxation? Anyway? I am handmade cartoonists and 13 00:01:01,080 --> 00:01:04,600 Speaker 1: the creator of PhD comics. Hi, I'm Daniel Whitson. I'm 14 00:01:04,640 --> 00:01:08,360 Speaker 1: a particle physicist and I'm incapable of fully relaxing. You 15 00:01:08,400 --> 00:01:10,600 Speaker 1: think that's a personal trade or is that just comes 16 00:01:10,640 --> 00:01:12,720 Speaker 1: with the job of being a physicist? Yeah? I can't 17 00:01:12,720 --> 00:01:14,760 Speaker 1: tell about the cause and effect there? Am I that 18 00:01:14,800 --> 00:01:17,400 Speaker 1: way because I became a physicist? Or did I become 19 00:01:17,440 --> 00:01:21,480 Speaker 1: a physicist because I am that way? Causation versus correlation? 20 00:01:21,680 --> 00:01:24,400 Speaker 1: That's right? But you know, sometimes you can do both. 21 00:01:24,440 --> 00:01:27,240 Speaker 1: Sometimes you can enjoy looking at the world and unraveling 22 00:01:27,280 --> 00:01:30,440 Speaker 1: its mysteries. You know. Uh, some people do puzzles for fun, 23 00:01:30,520 --> 00:01:33,240 Speaker 1: and for me, the universe is my puzzle. Well, hopefully 24 00:01:33,240 --> 00:01:35,800 Speaker 1: that's why people are listening in to this Welcome to 25 00:01:35,800 --> 00:01:39,560 Speaker 1: our podcast Daniel and Jorge Explain the Universe, a production 26 00:01:39,680 --> 00:01:42,000 Speaker 1: of My Heart Radio, in which we look at the 27 00:01:42,040 --> 00:01:43,920 Speaker 1: universe like a big puzzle and we try to take 28 00:01:43,920 --> 00:01:46,440 Speaker 1: it apart for you and hopefully entertain you along the 29 00:01:46,440 --> 00:01:48,840 Speaker 1: way with our terrible dad jokes and attain you and 30 00:01:48,920 --> 00:01:53,040 Speaker 1: also maybe ruin your vacations or your relaxation times, or 31 00:01:53,200 --> 00:01:56,400 Speaker 1: enhance your relaxation by showing you a whole other dimension 32 00:01:56,800 --> 00:02:00,000 Speaker 1: behind the simple plane of reality that everybody else experiences. 33 00:02:00,160 --> 00:02:03,000 Speaker 1: Do you feel like sometimes you are like a neo 34 00:02:03,120 --> 00:02:06,360 Speaker 1: in the matrix where you can see the code behind 35 00:02:07,240 --> 00:02:09,840 Speaker 1: everything around you. No, but I can totally do that 36 00:02:09,919 --> 00:02:13,720 Speaker 1: kick move. You can dodge bullets and look like Keanu Reeves. Hey, 37 00:02:13,760 --> 00:02:16,640 Speaker 1: I've never been shot. Okay, I can say that you 38 00:02:16,800 --> 00:02:21,959 Speaker 1: successfully dodge every bullet that's been fired at you, every 39 00:02:21,960 --> 00:02:25,400 Speaker 1: single bullet fired at anybody I successfully dodged. Oh wow, 40 00:02:25,639 --> 00:02:28,000 Speaker 1: that that's a lot of bullets of bullets. Yeah. So 41 00:02:28,040 --> 00:02:31,040 Speaker 1: today on the podcast will be tackling a phenomenon that 42 00:02:31,160 --> 00:02:34,720 Speaker 1: maybe hopefully a lot of people have done or tried 43 00:02:34,760 --> 00:02:38,160 Speaker 1: to do, or look at and think, hey, that's pretty cool. Yeah. 44 00:02:38,160 --> 00:02:39,720 Speaker 1: I think a lot more people have tried to do 45 00:02:39,760 --> 00:02:42,639 Speaker 1: it than successfully done it. Something you might do when 46 00:02:42,680 --> 00:02:45,320 Speaker 1: you're out for a relaxing stroll or maybe out on 47 00:02:45,440 --> 00:02:49,240 Speaker 1: vacation or just killing time or having some thoughts to yourself. 48 00:02:49,440 --> 00:02:51,280 Speaker 1: So to be on the program, we'll be talking about 49 00:02:56,600 --> 00:03:01,840 Speaker 1: physics of skipping stones. That's right. Why is that even possible? 50 00:03:02,000 --> 00:03:04,959 Speaker 1: Why is it that you can bounce a rock on water? 51 00:03:05,160 --> 00:03:06,920 Speaker 1: I mean it seems sort of crazy. If you had 52 00:03:06,960 --> 00:03:09,280 Speaker 1: never seen it, but somebody described it to you, you 53 00:03:09,320 --> 00:03:12,440 Speaker 1: would be pretty skeptical. Yeah, it's pretty cool. Um. And 54 00:03:12,520 --> 00:03:14,400 Speaker 1: this is you know, when you're walking by a lake 55 00:03:14,520 --> 00:03:17,919 Speaker 1: or a pond, or maybe just even like a fountain. Um, 56 00:03:18,240 --> 00:03:20,760 Speaker 1: you might have seen people or tried to do it yourself. 57 00:03:20,800 --> 00:03:22,400 Speaker 1: As you pick up a little stone, you throw it 58 00:03:22,440 --> 00:03:25,880 Speaker 1: and it skips along the surface of the water, sometimes 59 00:03:25,919 --> 00:03:28,720 Speaker 1: a lot. Yeah, what's your personal record? Jorge probably made 60 00:03:28,720 --> 00:03:32,160 Speaker 1: like ten skips and a stone. Maybe Ten's kind of 61 00:03:32,160 --> 00:03:35,080 Speaker 1: hard to count, right, isn't it hard to count? Especially 62 00:03:35,080 --> 00:03:37,600 Speaker 1: at the end there they get faster and faster. My 63 00:03:37,680 --> 00:03:40,520 Speaker 1: son likes to skip stones. I think his record is eight, 64 00:03:40,920 --> 00:03:43,080 Speaker 1: and mind is something more like five or six. Is 65 00:03:43,080 --> 00:03:45,400 Speaker 1: this a profession some people have, Like are their professional 66 00:03:45,640 --> 00:03:49,240 Speaker 1: stone skippers? There certainly are competitions where people fight voraciously 67 00:03:49,320 --> 00:03:51,440 Speaker 1: for the championship. I don't know if they get paid 68 00:03:51,520 --> 00:03:54,280 Speaker 1: for it, but they do pretty well. The current world 69 00:03:54,320 --> 00:03:59,640 Speaker 1: record for most number of skips is eight eight eight skips. 70 00:03:59,640 --> 00:04:02,720 Speaker 1: So you throw a rock at some water, a body 71 00:04:02,720 --> 00:04:06,040 Speaker 1: of water, and it skips eighty eight times. It's unbelievable, Like, 72 00:04:06,280 --> 00:04:08,400 Speaker 1: how do they even? They must have like a camera, 73 00:04:08,480 --> 00:04:11,600 Speaker 1: like the kind of used that really fancy tennis matches. 74 00:04:11,720 --> 00:04:14,040 Speaker 1: How far is that like when you throw it? Yeah, 75 00:04:14,040 --> 00:04:16,920 Speaker 1: it's actually interesting. In the US they have stone skipping 76 00:04:16,960 --> 00:04:20,560 Speaker 1: competitions and there they count the number of skips, whereas 77 00:04:20,600 --> 00:04:24,400 Speaker 1: if you go to sort of international world championships stone skipping, 78 00:04:24,520 --> 00:04:26,320 Speaker 1: they don't care about the number of skips. They care 79 00:04:26,320 --> 00:04:30,320 Speaker 1: about the distance and the furthest stone anybody's ever thrown 80 00:04:30,400 --> 00:04:35,280 Speaker 1: via skipping is a hundred and twenty one. It's longer 81 00:04:35,279 --> 00:04:39,280 Speaker 1: than a soccer field. It's like a seventh of a kilometer. Yeah, 82 00:04:39,360 --> 00:04:43,360 Speaker 1: it's huge, It's unbelievable. Um. So somebody has really figured 83 00:04:43,360 --> 00:04:45,040 Speaker 1: out how to do this thing. And you know, when 84 00:04:45,080 --> 00:04:47,120 Speaker 1: you're out there and you're skipping stones, you sort of 85 00:04:47,320 --> 00:04:49,159 Speaker 1: get a feeling for You're like, Okay, I need this 86 00:04:49,240 --> 00:04:51,360 Speaker 1: kind of stone. I gotta swing it this kind of way. 87 00:04:51,360 --> 00:04:53,160 Speaker 1: It's sort of like throwing a frisbee a little bit. 88 00:04:53,480 --> 00:04:55,839 Speaker 1: You sort of feel it out with your mind. This 89 00:04:55,880 --> 00:04:57,640 Speaker 1: is when it gets it in your wrist? Is it 90 00:04:57,720 --> 00:05:02,560 Speaker 1: in your you know, our movement? Yeah? About the water, yeah, 91 00:05:02,560 --> 00:05:05,520 Speaker 1: and about the perfect stone. And most people just sort 92 00:05:05,520 --> 00:05:08,680 Speaker 1: of figured out intuitively, right, they try this, they try that, 93 00:05:09,120 --> 00:05:10,880 Speaker 1: and eventually sort of get the hang of it and 94 00:05:10,880 --> 00:05:14,000 Speaker 1: they perfect it right, And that that's how most people 95 00:05:14,640 --> 00:05:17,000 Speaker 1: approach the world. Right. You learn how to walk, not 96 00:05:17,120 --> 00:05:19,520 Speaker 1: by like thinking about the physics of walking. You learn 97 00:05:19,560 --> 00:05:21,119 Speaker 1: how to ride a bike just by sort of trying 98 00:05:21,160 --> 00:05:24,040 Speaker 1: it out. Your rain gets trained to sort of learn 99 00:05:24,080 --> 00:05:28,000 Speaker 1: the physics intuitively. You don't like write down equations. Um, 100 00:05:28,040 --> 00:05:30,800 Speaker 1: but it is possible also to take this really fun 101 00:05:30,880 --> 00:05:33,240 Speaker 1: vacation activity and sort of ruin it by you know, 102 00:05:33,320 --> 00:05:36,920 Speaker 1: turning into an equation. No, it doesn't make you want 103 00:05:36,960 --> 00:05:40,640 Speaker 1: to appreciate it more, you know, wants you to understand 104 00:05:40,680 --> 00:05:43,520 Speaker 1: the physics behind it. Depends on what the answer is. Right. 105 00:05:43,520 --> 00:05:45,600 Speaker 1: If the answer is something oh hum, then you know, 106 00:05:45,880 --> 00:05:47,800 Speaker 1: maybe you've ruined the magic. But if the answer is 107 00:05:47,960 --> 00:05:51,520 Speaker 1: there's some crazy surprising physics in there, then yeah, then 108 00:05:51,600 --> 00:05:54,440 Speaker 1: you know, doing the physics has revealed something fascinating about 109 00:05:54,480 --> 00:05:57,480 Speaker 1: the universe. So we're in for some crazy surprising physics. 110 00:05:57,600 --> 00:06:00,719 Speaker 1: Turns out that the way most people think skipping stones 111 00:06:00,800 --> 00:06:03,280 Speaker 1: works is not the way it actually works. Well, I 112 00:06:03,320 --> 00:06:06,240 Speaker 1: think I've got the trick of it, but maybe we'll see. 113 00:06:06,520 --> 00:06:09,800 Speaker 1: We'll see what I'm doing corresponds to the physics of it. 114 00:06:09,839 --> 00:06:11,200 Speaker 1: All right, I'll give you a physics grade at the 115 00:06:11,240 --> 00:06:13,080 Speaker 1: end of it. All right, Well, it is kind of complicated, 116 00:06:13,279 --> 00:06:16,599 Speaker 1: and we were wondering how many people out there knew 117 00:06:16,880 --> 00:06:19,440 Speaker 1: what it takes, or how it works, or what's actually 118 00:06:19,440 --> 00:06:22,000 Speaker 1: happening when you skip a stone. So I walked around 119 00:06:22,040 --> 00:06:25,080 Speaker 1: the streets of Aspen, Colorado, a beautiful town in the 120 00:06:25,120 --> 00:06:28,559 Speaker 1: mountains with lots of stones and lots of little lakes 121 00:06:28,560 --> 00:06:31,080 Speaker 1: and ponds, so people could have plenty of chance to 122 00:06:31,080 --> 00:06:34,240 Speaker 1: practice their skipping and I asked, folks, do you know 123 00:06:34,680 --> 00:06:37,440 Speaker 1: why it's possible to skip a stone? Then most people respond, oh, 124 00:06:37,440 --> 00:06:41,160 Speaker 1: I don't skip stones. I just they're a gold bulls 125 00:06:43,200 --> 00:06:50,520 Speaker 1: skip stones, I get stoned. That's a different physics episode 126 00:06:50,560 --> 00:06:52,800 Speaker 1: probably somewhere and asking you can buy like a nine 127 00:06:53,279 --> 00:06:56,000 Speaker 1: dollar gold plated perfect skipping stone. So you went out 128 00:06:56,000 --> 00:06:58,000 Speaker 1: there and you ask people in the street if they 129 00:06:58,080 --> 00:07:01,719 Speaker 1: knew why is it possible to skip stones on a lake? 130 00:07:02,040 --> 00:07:04,120 Speaker 1: To think about it for a second and then listen 131 00:07:04,160 --> 00:07:07,279 Speaker 1: to what people had to say. Curface resistance tension should 132 00:07:07,320 --> 00:07:13,160 Speaker 1: be more friction gravity because it's hydroplinion, it's like tight tension. 133 00:07:13,360 --> 00:07:15,920 Speaker 1: Or if you' but if you put a rock on 134 00:07:15,960 --> 00:07:20,880 Speaker 1: the water, the supertension velocity as a flat surface, so 135 00:07:20,880 --> 00:07:22,520 Speaker 1: it's going to spin across the thought if it had 136 00:07:22,560 --> 00:07:26,000 Speaker 1: jagged edges, it was catching it pulled into the water, 137 00:07:26,240 --> 00:07:31,280 Speaker 1: gravity gravity would pull it down. Yeah, okay, I don't know. 138 00:07:31,440 --> 00:07:33,400 Speaker 1: All right, A lot of great answers here, a lot 139 00:07:33,440 --> 00:07:38,200 Speaker 1: of your favorite answers, right, gravity gravity, Yes, always works. 140 00:07:38,800 --> 00:07:44,600 Speaker 1: You can also say the Big Bang or physics, physics, 141 00:07:45,160 --> 00:07:47,680 Speaker 1: and that's usually how things work. Usually physics is the 142 00:07:47,720 --> 00:07:50,840 Speaker 1: way everything works. So yeah, that's a solid answer. I know, 143 00:07:50,920 --> 00:07:54,200 Speaker 1: we've got lots of people saying things like surface tension, right, 144 00:07:54,880 --> 00:07:58,080 Speaker 1: or hydroplaning or just jeez, I have no idea. Some 145 00:07:58,120 --> 00:08:00,560 Speaker 1: people had really never thought about it before. Or That's 146 00:08:00,560 --> 00:08:02,880 Speaker 1: one of my favorite moments is when I spark in 147 00:08:02,920 --> 00:08:05,400 Speaker 1: their minds this moment of curiosity, because then they always 148 00:08:05,440 --> 00:08:06,960 Speaker 1: turn around they ask me. They're like, well, what tell 149 00:08:07,000 --> 00:08:08,680 Speaker 1: me the answer? And now now you asked me, I 150 00:08:08,720 --> 00:08:11,880 Speaker 1: have to know. Yeah, a lot of answers like surface tensions, 151 00:08:12,120 --> 00:08:15,800 Speaker 1: the speed, the shape of the rock, what's what's going on? Yeah, 152 00:08:15,840 --> 00:08:17,720 Speaker 1: so based just on those answers, you might guess that 153 00:08:17,760 --> 00:08:20,120 Speaker 1: the answer is pretty complicated. There might be a lot 154 00:08:20,160 --> 00:08:23,720 Speaker 1: of things going on, right, some physics magic, some physics 155 00:08:24,080 --> 00:08:26,920 Speaker 1: not magic. And it turns out it is pretty complicated. 156 00:08:27,080 --> 00:08:30,120 Speaker 1: We should do magical physics. That can I say magical 157 00:08:30,120 --> 00:08:34,560 Speaker 1: physics physics ruining magic for hundreds of years, magic adjacent physics. 158 00:08:35,640 --> 00:08:37,760 Speaker 1: That's right. Well, the most popular answer that you heard 159 00:08:37,800 --> 00:08:40,839 Speaker 1: there is surface tension. And that makes some sense, right, 160 00:08:41,120 --> 00:08:44,439 Speaker 1: is it the surface tension? Turns out it's not surface tension. Right. 161 00:08:44,520 --> 00:08:47,720 Speaker 1: That's a tempting answer because you think, oh, the water 162 00:08:47,800 --> 00:08:49,920 Speaker 1: is sort of holding the surface together. There is some 163 00:08:50,040 --> 00:08:53,200 Speaker 1: resistance there and you may have even seen like bugs 164 00:08:53,200 --> 00:08:55,560 Speaker 1: skimming on the surface of water, or you can put 165 00:08:55,600 --> 00:08:57,800 Speaker 1: a paper clip down on water and it can sit 166 00:08:57,920 --> 00:09:00,800 Speaker 1: on the surface tension, right, So the a sense that 167 00:09:00,840 --> 00:09:03,960 Speaker 1: the water is doing something there to hold something up, right, 168 00:09:04,160 --> 00:09:06,120 Speaker 1: But it turns out service tension has nothing to do 169 00:09:06,200 --> 00:09:08,600 Speaker 1: with skipping stones. Maybe step us through a little bit. 170 00:09:08,600 --> 00:09:11,640 Speaker 1: What is surface tension? Yeah, service tension. It happens when 171 00:09:11,679 --> 00:09:15,360 Speaker 1: you have a liquid and that liquid is attracted to itself, right, 172 00:09:15,400 --> 00:09:17,960 Speaker 1: and so it wants to clump together. So for example, 173 00:09:17,960 --> 00:09:20,240 Speaker 1: if you put a drop of water on a table, 174 00:09:20,480 --> 00:09:23,520 Speaker 1: it doesn't just run totally flat, which is what you 175 00:09:23,520 --> 00:09:27,000 Speaker 1: would expect from a smoothly flowing liquid under gravity, right 176 00:09:27,160 --> 00:09:30,520 Speaker 1: gravity anything. It doesn't spread out, you know, out to 177 00:09:30,520 --> 00:09:34,319 Speaker 1: cover the whole table exactly. It stays together one one 178 00:09:34,400 --> 00:09:39,040 Speaker 1: molecule thick covering coding. But it stays as a droplet, right, 179 00:09:39,200 --> 00:09:41,760 Speaker 1: that's right. It stays as a droplet. And the reason 180 00:09:42,200 --> 00:09:44,319 Speaker 1: is that the molecules are attracted to each other. There's 181 00:09:44,360 --> 00:09:47,760 Speaker 1: some small force pulling the molecules to each other. And 182 00:09:47,920 --> 00:09:49,839 Speaker 1: we've talked on another episode of about how water is 183 00:09:49,840 --> 00:09:53,880 Speaker 1: a dielectric, and so it's neutral, right, the positive negative 184 00:09:53,920 --> 00:09:57,080 Speaker 1: charges balanced overall, but the positive negative charges aren't on 185 00:09:57,080 --> 00:09:59,480 Speaker 1: the same side of the water molecule, and so they 186 00:09:59,480 --> 00:10:01,719 Speaker 1: can line a in this way where the positive end 187 00:10:01,720 --> 00:10:04,640 Speaker 1: of one water molecule attracts the minus end of another one. 188 00:10:04,640 --> 00:10:06,480 Speaker 1: They can tug on each other a little bit. So 189 00:10:06,520 --> 00:10:09,040 Speaker 1: they like to stay together. They're like a little scared 190 00:10:09,200 --> 00:10:12,440 Speaker 1: crowd of children or something. They clump together in fear. 191 00:10:13,120 --> 00:10:16,520 Speaker 1: And it's like having a handful of magnets at a distance. 192 00:10:16,520 --> 00:10:19,959 Speaker 1: Maybe they are neutral to each other, but if you 193 00:10:20,000 --> 00:10:22,120 Speaker 1: get them closed, they'll they'll start to clump together. Yeah, 194 00:10:22,160 --> 00:10:24,320 Speaker 1: maybe a handful of magnets was a better analogy than 195 00:10:24,360 --> 00:10:29,960 Speaker 1: a clump of scared children. Probably where are they scared 196 00:10:30,000 --> 00:10:32,199 Speaker 1: because you're coming out them with a clump of of 197 00:10:32,200 --> 00:10:36,000 Speaker 1: of magnets Because I'm holding a rock right now. M Yeah, 198 00:10:36,000 --> 00:10:38,040 Speaker 1: so it clumps together. That's what surface tension is, is 199 00:10:38,080 --> 00:10:41,720 Speaker 1: the water clumping together um and so it um And 200 00:10:41,760 --> 00:10:44,520 Speaker 1: that happens also on the surface, right, not just inside, 201 00:10:44,520 --> 00:10:46,760 Speaker 1: but also on the surface. It's kind of like why 202 00:10:46,840 --> 00:10:49,000 Speaker 1: in space, if you see a blob of water, it 203 00:10:49,040 --> 00:10:51,400 Speaker 1: doesn't just spread out like a gas, it stays as 204 00:10:51,440 --> 00:10:54,559 Speaker 1: a blob of water. Yeah, exactly, because it's attracted to itself. 205 00:10:55,080 --> 00:10:57,600 Speaker 1: So that causes surface tension. Right, that's what surface tension. 206 00:10:57,600 --> 00:10:59,880 Speaker 1: And wait, what is it? What is it called surface tension? 207 00:11:00,080 --> 00:11:02,640 Speaker 1: Like what's happening at the surface. It's called surface tension 208 00:11:02,679 --> 00:11:04,800 Speaker 1: because at the surface, if you poke it, it's it 209 00:11:05,040 --> 00:11:07,440 Speaker 1: sort of holds together, like it creates this sort of 210 00:11:07,640 --> 00:11:11,600 Speaker 1: sheet at the surface that resists being torn apart or penetrated. 211 00:11:11,800 --> 00:11:14,320 Speaker 1: It's the same way that like the wall holds itself together. Right, 212 00:11:14,320 --> 00:11:16,400 Speaker 1: you have bonds between the molecules that are holding the 213 00:11:16,400 --> 00:11:19,520 Speaker 1: wall together. These bonds are much much weaker, which is 214 00:11:19,559 --> 00:11:22,520 Speaker 1: why water in this case is a fluid. Right, it's 215 00:11:22,520 --> 00:11:24,560 Speaker 1: just a It's just a weaker version of those same 216 00:11:24,600 --> 00:11:28,400 Speaker 1: bonds that hold all matter together, right, right, But there's 217 00:11:28,440 --> 00:11:31,600 Speaker 1: something special about the surface, isn't it? Like the isn't 218 00:11:31,600 --> 00:11:34,080 Speaker 1: it or maybe I'm wrong, is that the molecules on 219 00:11:34,120 --> 00:11:36,120 Speaker 1: the surface are sort of holding on a little bit 220 00:11:36,120 --> 00:11:39,920 Speaker 1: tighter to each other than the ones like inside of 221 00:11:39,920 --> 00:11:42,200 Speaker 1: the water could be you tell me you're the engineer. 222 00:11:42,360 --> 00:11:46,040 Speaker 1: They were completely lost. Now. But the key thing when 223 00:11:46,080 --> 00:11:49,680 Speaker 1: it comes to understanding skipping stones. Is you know, could 224 00:11:49,720 --> 00:11:52,400 Speaker 1: you use surface tension to skip a stone, because you can. 225 00:11:52,520 --> 00:11:55,200 Speaker 1: You can use it to float a bug, right, Like 226 00:11:55,400 --> 00:12:00,240 Speaker 1: some bugs stand on water because the water refus uses 227 00:12:00,280 --> 00:12:02,320 Speaker 1: to sort of be broken apart. That's right. Yeah, the 228 00:12:02,320 --> 00:12:06,360 Speaker 1: water holds itself together and creates a surface, right. Um, 229 00:12:06,400 --> 00:12:09,400 Speaker 1: But that only really works for very, very low weight 230 00:12:09,480 --> 00:12:12,319 Speaker 1: objects because the surface tension is not very strong. I mean, 231 00:12:12,320 --> 00:12:14,080 Speaker 1: you touch a drop of water and it clings to 232 00:12:14,120 --> 00:12:16,920 Speaker 1: you instead, right, It's very easy to break surface tension. 233 00:12:17,360 --> 00:12:19,079 Speaker 1: And if you just if it was just surface tension, 234 00:12:19,080 --> 00:12:20,559 Speaker 1: then you could be able to take a rock and 235 00:12:20,600 --> 00:12:23,079 Speaker 1: put it on water and it would float there, right. 236 00:12:23,360 --> 00:12:25,480 Speaker 1: But a rock that you could easily skip, if you 237 00:12:25,520 --> 00:12:27,000 Speaker 1: put it on the surface of the water, it would 238 00:12:27,000 --> 00:12:29,400 Speaker 1: just sink through. Some people might be wondering, is it 239 00:12:29,600 --> 00:12:33,280 Speaker 1: the surface tension that's creating some kind of trampoline on 240 00:12:33,320 --> 00:12:37,680 Speaker 1: the water that's maybe causing the stone to skip exactly. 241 00:12:37,720 --> 00:12:39,440 Speaker 1: It's kind of that was kind of the scenario we're 242 00:12:39,440 --> 00:12:42,120 Speaker 1: trying to debunk. Yeah, that's definitely not happening, because if 243 00:12:42,120 --> 00:12:44,600 Speaker 1: you put a stone on a trampoline, right, it doesn't 244 00:12:44,640 --> 00:12:47,200 Speaker 1: fall through the trampoline, right, So you know, the trampoline 245 00:12:47,280 --> 00:12:50,040 Speaker 1: is strong enough to bounce the stone back up. But 246 00:12:50,080 --> 00:12:52,080 Speaker 1: if you put a stone just lay it sort of 247 00:12:52,120 --> 00:12:54,240 Speaker 1: gently on the surface of the water, you know what's 248 00:12:54,280 --> 00:12:56,360 Speaker 1: gonna happen. It's not gonna sit there. It's gonna sink 249 00:12:56,760 --> 00:12:58,960 Speaker 1: unless your stone weighs the same as a paper clip, right, 250 00:12:58,960 --> 00:13:01,080 Speaker 1: which case you probably can't it. But anyway, but a 251 00:13:01,120 --> 00:13:04,280 Speaker 1: stone that you could skip won't sit gently on the water. 252 00:13:04,840 --> 00:13:07,199 Speaker 1: Um So service tension is not enough to provide sort 253 00:13:07,240 --> 00:13:10,040 Speaker 1: of trampoline effect there, even if it's going fast. I 254 00:13:10,040 --> 00:13:13,680 Speaker 1: could maybe imagine somebody thinking you throw a stone so 255 00:13:13,840 --> 00:13:16,280 Speaker 1: fast at a body of water that it actually kind 256 00:13:16,280 --> 00:13:19,560 Speaker 1: of bounces back from the hitting that service tension. It 257 00:13:19,679 --> 00:13:22,400 Speaker 1: does bounce back, but not because of the service tension, right. 258 00:13:22,720 --> 00:13:25,640 Speaker 1: And you can see this because you can skip stones 259 00:13:25,760 --> 00:13:28,840 Speaker 1: or skip objects on things without as much surface tension. 260 00:13:29,160 --> 00:13:32,280 Speaker 1: For example, you can even skip things off like the atmosphere. 261 00:13:32,520 --> 00:13:35,200 Speaker 1: You know, sometimes when spacecraft are trying to re enter 262 00:13:35,240 --> 00:13:37,920 Speaker 1: the atmosphere, there's an angle they have to enter it 263 00:13:38,160 --> 00:13:40,040 Speaker 1: where if they go too steep then they heat up 264 00:13:40,080 --> 00:13:42,520 Speaker 1: too much, but if they go too shallow, then they 265 00:13:42,559 --> 00:13:46,240 Speaker 1: skip off the atmosphere back into space. Oh you can 266 00:13:46,280 --> 00:13:49,240 Speaker 1: skip spaceships. Yeah, you can skip spaceships. I don't think 267 00:13:49,240 --> 00:13:51,120 Speaker 1: it's a good idea. I don't think anybody's ever done 268 00:13:51,120 --> 00:13:53,120 Speaker 1: it on purpose. I think it's a is there a 269 00:13:53,160 --> 00:13:56,360 Speaker 1: world record for that one or a competition? Yeah one, 270 00:13:56,480 --> 00:13:58,480 Speaker 1: And that guy bounced out into space and nobody's ever 271 00:13:58,480 --> 00:14:03,280 Speaker 1: seen him before. They said, they said the diploma, but 272 00:14:04,400 --> 00:14:06,520 Speaker 1: they didn't get it. You can also skip on on 273 00:14:06,640 --> 00:14:08,520 Speaker 1: surfaces that have no tension at all, Like you can 274 00:14:08,559 --> 00:14:11,560 Speaker 1: skip rocks on sand dunes, right, and sand doesn't have 275 00:14:11,600 --> 00:14:14,640 Speaker 1: any attraction to itself. There's no surface tension on sand. Dudes, 276 00:14:14,679 --> 00:14:18,320 Speaker 1: you don't get drops of sand, right, So you see 277 00:14:18,320 --> 00:14:20,880 Speaker 1: the skipping affected area in places with more or less 278 00:14:20,880 --> 00:14:23,480 Speaker 1: surface tension. And the bottom line, though, is the service 279 00:14:23,520 --> 00:14:26,320 Speaker 1: tension is just super weak and it can't contribute at all. 280 00:14:26,440 --> 00:14:29,520 Speaker 1: All right, So it's not surface tension that's helping you 281 00:14:29,800 --> 00:14:32,600 Speaker 1: or helping us skip stone. So there must be other things. 282 00:14:32,960 --> 00:14:35,120 Speaker 1: So let's get into it. But first let's take a 283 00:14:35,200 --> 00:14:51,320 Speaker 1: quick break. All right. We're talking about why is it 284 00:14:51,360 --> 00:14:54,680 Speaker 1: possible to skip stones on a lake, Like what's the 285 00:14:54,720 --> 00:14:57,320 Speaker 1: physics of it? And so we talked about how it's 286 00:14:57,360 --> 00:15:00,640 Speaker 1: not surface tension which is what a lot of people gets. Um, 287 00:15:00,680 --> 00:15:03,680 Speaker 1: And so maybe, uh, it might be something else. So 288 00:15:03,720 --> 00:15:05,880 Speaker 1: I would guess it maybe has something to do with 289 00:15:05,920 --> 00:15:08,600 Speaker 1: the spin that you put into the stone. Is that 290 00:15:08,760 --> 00:15:11,560 Speaker 1: kind of what's happening. It feels like a good answer, right, 291 00:15:11,600 --> 00:15:14,200 Speaker 1: because when you're skipping stones, you notice that if you 292 00:15:14,240 --> 00:15:17,440 Speaker 1: spin them really fast, they skip better. Right. We will 293 00:15:17,480 --> 00:15:19,800 Speaker 1: talk about it in a moment how the stone spinning 294 00:15:20,000 --> 00:15:23,000 Speaker 1: actually does help it skip, but it's not actually necessary. 295 00:15:23,480 --> 00:15:25,360 Speaker 1: I mean the spin what it does is it helps 296 00:15:25,840 --> 00:15:28,200 Speaker 1: make it fly straight, sort of like a frisbee, so 297 00:15:28,240 --> 00:15:29,920 Speaker 1: that it like it hits the water at a good 298 00:15:29,960 --> 00:15:32,640 Speaker 1: angle and in a good direction and all that stuff. 299 00:15:33,000 --> 00:15:35,960 Speaker 1: But it's not actually necessary. You can skip a stone 300 00:15:35,960 --> 00:15:38,080 Speaker 1: without spinning. It's possible. I always thought that it was 301 00:15:38,120 --> 00:15:41,960 Speaker 1: something to do with like conservation of angular momentum. You know, 302 00:15:42,080 --> 00:15:44,120 Speaker 1: like if you spin it, it wants to keep spinning 303 00:15:44,360 --> 00:15:47,360 Speaker 1: and that keeps it kind of level, which then kind 304 00:15:47,360 --> 00:15:50,320 Speaker 1: of makes it graze the surface of the water. Yeah, 305 00:15:50,320 --> 00:15:53,440 Speaker 1: I mean you're getting there. It's not actually necessary for spinning, 306 00:15:53,440 --> 00:15:56,120 Speaker 1: but you're right, it keeps it sort of flat, right, Um, 307 00:15:56,160 --> 00:15:58,720 Speaker 1: just the way a frisbee flies better when it's spinning 308 00:15:58,800 --> 00:16:01,080 Speaker 1: for the same reason as you say, angular momentum. It 309 00:16:01,080 --> 00:16:02,960 Speaker 1: doesn't like to tip over or it takes more of 310 00:16:03,000 --> 00:16:05,720 Speaker 1: a force to tip it over. Um. And it turns 311 00:16:05,760 --> 00:16:07,800 Speaker 1: out that you skip best when you hit the water 312 00:16:07,880 --> 00:16:10,960 Speaker 1: at just the right angle, and so spinning the stone 313 00:16:11,320 --> 00:16:13,360 Speaker 1: does help it hit at that right at that angle 314 00:16:13,400 --> 00:16:16,400 Speaker 1: that the good angle for for skipping. But it's not 315 00:16:16,440 --> 00:16:19,640 Speaker 1: actually necessary. You can skip a stone without spinning it. 316 00:16:19,640 --> 00:16:22,120 Speaker 1: It is possible. While you're blowing my mind here, you 317 00:16:22,160 --> 00:16:25,720 Speaker 1: can skip stones on sand and you can do it 318 00:16:25,800 --> 00:16:29,600 Speaker 1: without spinning. Yeah, yeah, exactly. Skipping turns out to be 319 00:16:29,720 --> 00:16:32,520 Speaker 1: quite the fascinating physics topic. Um. Alright, so then if 320 00:16:32,560 --> 00:16:37,240 Speaker 1: it's not surface tension or spinning, what's, um, what's happening 321 00:16:37,240 --> 00:16:40,040 Speaker 1: when we skip stones? Well, this is actually really interesting. 322 00:16:40,440 --> 00:16:42,880 Speaker 1: And it turns out there's a physicist about twenty years 323 00:16:42,880 --> 00:16:46,120 Speaker 1: ago whose son asked him, Hey, Dad, how is it 324 00:16:46,160 --> 00:16:48,200 Speaker 1: that you can skip stones? What's the physics of it? 325 00:16:48,600 --> 00:16:50,440 Speaker 1: And he was like, oh, I'm sure it's pretty simple, 326 00:16:50,440 --> 00:16:52,400 Speaker 1: And he started digging into it, and turns out it's 327 00:16:52,440 --> 00:16:57,040 Speaker 1: pretty complicated, and he spent months studying this and doing experiments, 328 00:16:57,080 --> 00:16:59,840 Speaker 1: and he finally came up with an equation, an equation 329 00:16:59,880 --> 00:17:03,560 Speaker 1: that predict how many skips you'll get from a stone 330 00:17:03,880 --> 00:17:06,320 Speaker 1: as a function of the angle of the stone, the 331 00:17:06,440 --> 00:17:09,199 Speaker 1: velocity of the stone, and the speed of skipping, the 332 00:17:09,240 --> 00:17:12,479 Speaker 1: weight of the stone, all this stuff, And so he 333 00:17:12,520 --> 00:17:15,080 Speaker 1: was able to isolate sort of what are the important 334 00:17:15,119 --> 00:17:17,800 Speaker 1: factors in getting a stone to skip? So wait, his 335 00:17:17,920 --> 00:17:21,360 Speaker 1: son asked him a question, like hey, Dad, and then 336 00:17:21,480 --> 00:17:24,040 Speaker 1: three years later he's like, here it is. Here's a 337 00:17:24,080 --> 00:17:29,080 Speaker 1: paper full of equations. That's what you wanted, right, I 338 00:17:29,160 --> 00:17:32,040 Speaker 1: just wanted yes or no. After that, the kid probably 339 00:17:32,040 --> 00:17:35,080 Speaker 1: totally forgot about it. He's like, oh, I don't care whatever, Um, 340 00:17:35,119 --> 00:17:37,240 Speaker 1: that's what it's like to have businesses for a parent. 341 00:17:37,720 --> 00:17:39,800 Speaker 1: The kid is still waiting by the lake with the stone, 342 00:17:39,800 --> 00:17:44,480 Speaker 1: and Dad, show me how you just gotta finish this equation. 343 00:17:44,640 --> 00:17:48,320 Speaker 1: Did he figure this out from like equations or was 344 00:17:48,359 --> 00:17:51,160 Speaker 1: this all experimental like I'm gonna change try different stone 345 00:17:51,200 --> 00:17:55,160 Speaker 1: sizes and different angles and different velocities, or a little 346 00:17:55,160 --> 00:17:56,640 Speaker 1: bit of book. It was a little bit of both. 347 00:17:56,640 --> 00:17:59,320 Speaker 1: He started out theoretically. He was like, can I understand 348 00:17:59,320 --> 00:18:01,840 Speaker 1: the forces involved and what we do all the time 349 00:18:01,840 --> 00:18:04,280 Speaker 1: in physics, which is critical? Is he simplified the problem. 350 00:18:04,320 --> 00:18:07,280 Speaker 1: He's like, Okay, let me assume the stone is perfectly flat. 351 00:18:07,359 --> 00:18:10,240 Speaker 1: Let me assume assume it's a perfect circle. Let me 352 00:18:10,280 --> 00:18:12,480 Speaker 1: assume it hits the water at this angle or whatever. 353 00:18:13,000 --> 00:18:15,560 Speaker 1: He made some assumptions to simplify the problem, and then 354 00:18:15,600 --> 00:18:18,080 Speaker 1: he was able to write down equations that he thought 355 00:18:18,320 --> 00:18:22,240 Speaker 1: would describe the forces involved and that let him make predictions. 356 00:18:22,240 --> 00:18:24,680 Speaker 1: He's like, okay, if these are the forces involved, right, 357 00:18:24,960 --> 00:18:27,040 Speaker 1: and he knows how the forces change is a function 358 00:18:27,080 --> 00:18:29,640 Speaker 1: of the angle you throw it in the speed, then 359 00:18:29,840 --> 00:18:32,560 Speaker 1: I can make predictions for how many times the stone 360 00:18:32,600 --> 00:18:34,840 Speaker 1: will skip. Then he went out and checked it and 361 00:18:34,880 --> 00:18:37,640 Speaker 1: he actually did some experiments to see if his equations 362 00:18:37,640 --> 00:18:41,720 Speaker 1: were valid. Yeah, exactly. I want to see what that 363 00:18:41,760 --> 00:18:44,199 Speaker 1: peer review process was like. You know, did somebody go 364 00:18:44,280 --> 00:18:46,560 Speaker 1: out there with a bunch of stones and his paper 365 00:18:46,600 --> 00:18:48,960 Speaker 1: and try this thing out? Um, I'm not quite sure, 366 00:18:49,119 --> 00:18:50,680 Speaker 1: but he published the paper. It's a guy from the 367 00:18:50,760 --> 00:18:54,159 Speaker 1: University of Lyon in France. And in his paper he 368 00:18:54,240 --> 00:18:57,720 Speaker 1: suggests that the critical variables are, of course, the flatness 369 00:18:57,760 --> 00:19:01,359 Speaker 1: of the stone, the viscas city of the fluid, right, 370 00:19:01,400 --> 00:19:03,600 Speaker 1: the viscosity of the liquid, which is not the same 371 00:19:03,640 --> 00:19:07,360 Speaker 1: thing as surface tension, the angle of the stone, and 372 00:19:07,440 --> 00:19:11,080 Speaker 1: its speed, So neither none of those things involved surface 373 00:19:11,080 --> 00:19:14,280 Speaker 1: tension or spinning. Yeah, and spinning again helps because it 374 00:19:14,280 --> 00:19:16,680 Speaker 1: helps you get the right angle right, and it's also 375 00:19:16,760 --> 00:19:19,280 Speaker 1: easier to throw throw a rock really fast if you're 376 00:19:19,280 --> 00:19:21,240 Speaker 1: spinning it sort of out the tip of your finger 377 00:19:21,400 --> 00:19:23,600 Speaker 1: as you throw it. So spinning is sort of like 378 00:19:23,640 --> 00:19:26,920 Speaker 1: a supplemental thing. It's not necessary, but it's helpful. I'm 379 00:19:26,920 --> 00:19:29,360 Speaker 1: waiting for the twist in the story where you say, 380 00:19:29,400 --> 00:19:32,679 Speaker 1: and then he became the world record horbholder. So in 381 00:19:32,720 --> 00:19:35,120 Speaker 1: the end, it's not really surface tension. It's much more 382 00:19:35,119 --> 00:19:39,480 Speaker 1: about like the viscosity of the water, right, because you know, 383 00:19:39,480 --> 00:19:41,919 Speaker 1: think about like meaning like the thickness of it, or 384 00:19:41,960 --> 00:19:44,240 Speaker 1: how goopy it is. Yeah, how goopy it is. Right, 385 00:19:44,760 --> 00:19:47,640 Speaker 1: water not only is it attracted to itself, which caused 386 00:19:47,680 --> 00:19:50,399 Speaker 1: the surface tension. It's a fairly fairly small force, but 387 00:19:50,480 --> 00:19:52,919 Speaker 1: it's also kind of viscous, right, It's like, you know, 388 00:19:52,960 --> 00:19:54,960 Speaker 1: there's a bit of goopiness to it, like honey is 389 00:19:55,000 --> 00:19:58,600 Speaker 1: goopier of course in water, right, And this comes from 390 00:19:58,600 --> 00:20:01,360 Speaker 1: how the molecules would rub each other, like the friction 391 00:20:01,680 --> 00:20:04,679 Speaker 1: the molecule to molecule friction, So it's a different physics, right. 392 00:20:05,240 --> 00:20:08,040 Speaker 1: Surface tension is about attraction of the molecules. This is 393 00:20:08,080 --> 00:20:10,720 Speaker 1: about how the molecules flow past each other. If something 394 00:20:10,800 --> 00:20:13,960 Speaker 1: is really viscous, like tar, or like a giant vat 395 00:20:14,000 --> 00:20:16,439 Speaker 1: of honey, like I would imagine if I throw us 396 00:20:16,480 --> 00:20:19,600 Speaker 1: kipping stone on top, which is kind of blurb kind 397 00:20:19,600 --> 00:20:21,760 Speaker 1: of you know, when it's skip or would it. I 398 00:20:21,760 --> 00:20:25,240 Speaker 1: don't know, that's a good question, I think. Um. I mean, obviously, 399 00:20:25,240 --> 00:20:27,520 Speaker 1: if it's really viscous, then it's a flat surface, then 400 00:20:27,560 --> 00:20:31,480 Speaker 1: it will skip, right, So there's probably some point duper 401 00:20:32,240 --> 00:20:36,959 Speaker 1: super duper but not sticky, yeah, exactly. And you know, 402 00:20:37,000 --> 00:20:39,920 Speaker 1: you can come up with examples of liquids that are 403 00:20:39,960 --> 00:20:42,320 Speaker 1: really viscous but don't have a lot of surface tension, 404 00:20:42,920 --> 00:20:45,880 Speaker 1: or the other way around. So there's a complicated relationship 405 00:20:45,920 --> 00:20:48,320 Speaker 1: between surface tension and viscosity. But in the end, what 406 00:20:48,400 --> 00:20:50,960 Speaker 1: you need is viscosity. And the reason is that when 407 00:20:51,000 --> 00:20:53,800 Speaker 1: the stone hits the water, you want the water to 408 00:20:53,840 --> 00:20:55,520 Speaker 1: not be able to sort of flow out of the 409 00:20:55,520 --> 00:20:58,720 Speaker 1: way fast enough, right, like you want the water to 410 00:20:58,760 --> 00:21:01,040 Speaker 1: push back, Yes, exactly, you need the water to push 411 00:21:01,080 --> 00:21:03,680 Speaker 1: back and so like when you jump off a diving 412 00:21:03,760 --> 00:21:06,800 Speaker 1: board and you land totally flat on the water, right, 413 00:21:07,160 --> 00:21:09,080 Speaker 1: If you've done that, you know that water can feel 414 00:21:09,080 --> 00:21:12,600 Speaker 1: like concrete, right, like belly flop, Like a belly flop, yeah, 415 00:21:12,600 --> 00:21:14,879 Speaker 1: a belly flop exactly. If you fall off a bridge, 416 00:21:14,880 --> 00:21:18,000 Speaker 1: for example, from high enough, you can die landing in water, right, 417 00:21:18,040 --> 00:21:20,520 Speaker 1: because water just can't get out of the way fast enough, 418 00:21:20,840 --> 00:21:22,960 Speaker 1: and so it pushes back on you just sort of 419 00:21:22,960 --> 00:21:25,399 Speaker 1: the way the ground does right when you land on it. 420 00:21:25,400 --> 00:21:27,520 Speaker 1: It doesn't get out of the way fast enough. Yeah, 421 00:21:27,800 --> 00:21:29,960 Speaker 1: Like if you're falling through air, Air is much much 422 00:21:30,080 --> 00:21:32,440 Speaker 1: less viscous than water, and it gets out of the way, right, 423 00:21:32,440 --> 00:21:34,080 Speaker 1: It just moves out of the way. I mean, there's 424 00:21:34,080 --> 00:21:36,080 Speaker 1: still some friction there, which is why you have a 425 00:21:36,160 --> 00:21:38,360 Speaker 1: terminal velocity, but it gets out of the way fast 426 00:21:38,440 --> 00:21:40,400 Speaker 1: enough for you to pass through it, right. But water 427 00:21:40,520 --> 00:21:43,120 Speaker 1: is much much more viscous, so it provides much much 428 00:21:43,160 --> 00:21:45,840 Speaker 1: more drag. And if you hit the water flat, then 429 00:21:45,880 --> 00:21:48,920 Speaker 1: you're gonna get a big force the other direction, um, 430 00:21:48,960 --> 00:21:51,880 Speaker 1: which is gonna make your belly smart or make your 431 00:21:51,960 --> 00:21:54,199 Speaker 1: rock skip. So that's the key, right, is that the 432 00:21:54,200 --> 00:21:57,080 Speaker 1: water pushes back up on the rock. You can't skip 433 00:21:57,160 --> 00:22:01,000 Speaker 1: rocks on clouds or air. You can skip rocks on air, actually, 434 00:22:01,000 --> 00:22:03,520 Speaker 1: I mean you can skip spaceships on air, but it 435 00:22:03,560 --> 00:22:06,359 Speaker 1: takes much much higher speed. Yeah, well this is a 436 00:22:06,520 --> 00:22:21,760 Speaker 1: perfect point to take a break. So it's about the 437 00:22:21,840 --> 00:22:25,320 Speaker 1: viscosity of the liquid. So the more viscous it is, 438 00:22:25,359 --> 00:22:27,639 Speaker 1: the easier it is to bounce it. Yes, you need 439 00:22:27,680 --> 00:22:30,639 Speaker 1: a flat object and a viscous liquid. And that's a 440 00:22:31,119 --> 00:22:34,399 Speaker 1: flat object, because if it's not flat, it's not flat. 441 00:22:34,440 --> 00:22:36,040 Speaker 1: Like I mean, the most extreme thing is you drop, 442 00:22:36,119 --> 00:22:39,360 Speaker 1: like you know, drop something really thin and sharp into 443 00:22:39,400 --> 00:22:41,159 Speaker 1: the water, it's just going to separate the water and 444 00:22:41,160 --> 00:22:43,440 Speaker 1: sink down to the bottom. Right, So you need to 445 00:22:43,480 --> 00:22:46,640 Speaker 1: drop something flat so that it into the water can't 446 00:22:46,680 --> 00:22:49,280 Speaker 1: move out of the way. You need to belly flop, Yes, exactly. 447 00:22:49,840 --> 00:22:52,760 Speaker 1: Skipping stones should be called belly flopping stones, don't. They 448 00:22:52,760 --> 00:22:55,359 Speaker 1: have funny names for this in other countries, like what 449 00:22:55,600 --> 00:22:58,280 Speaker 1: they call in England. Um, in England they call it 450 00:22:58,440 --> 00:23:01,639 Speaker 1: ducks and drakes, which makes absolutely no sense to me, Like, 451 00:23:01,880 --> 00:23:04,480 Speaker 1: are you shooting ducks? Like what's going on? Well, like, 452 00:23:04,520 --> 00:23:06,760 Speaker 1: if you're you're throwing stones at a leg to skip 453 00:23:07,000 --> 00:23:09,560 Speaker 1: to create those ripples and skips. That that's called ducks 454 00:23:09,560 --> 00:23:12,040 Speaker 1: and drakes. Ducks and drake's. Yeah, somebody out there in 455 00:23:12,080 --> 00:23:14,399 Speaker 1: England explain that to us. In France they have a 456 00:23:14,400 --> 00:23:16,520 Speaker 1: clever name for it. They call it rick o'che, which 457 00:23:16,560 --> 00:23:19,320 Speaker 1: you know makes some sense, right, your rock is ricocheting 458 00:23:19,320 --> 00:23:21,000 Speaker 1: off the surface of the water. What are some other 459 00:23:21,040 --> 00:23:22,760 Speaker 1: funny words? Well, these are words that don't even make 460 00:23:22,800 --> 00:23:25,640 Speaker 1: sense to me. Like in Ireland they call it stone scuffing, 461 00:23:25,960 --> 00:23:28,000 Speaker 1: the way you would scuff your shoes and get marks 462 00:23:28,000 --> 00:23:29,520 Speaker 1: on them, or something you got to say with an 463 00:23:29,520 --> 00:23:33,360 Speaker 1: Irish saxon. I can't do an Irish accent, not at all. 464 00:23:34,720 --> 00:23:36,560 Speaker 1: But every language has a word for it. And the 465 00:23:36,600 --> 00:23:40,480 Speaker 1: funniest one is that according to the Oxford English Dictionary, Right, 466 00:23:40,520 --> 00:23:43,560 Speaker 1: so according to the Brits, the way Americans say it 467 00:23:43,680 --> 00:23:45,960 Speaker 1: is they say it's called dapping, and that's not a 468 00:23:45,960 --> 00:23:48,040 Speaker 1: word I've ever heard. So, like, what are the Brits 469 00:23:48,160 --> 00:23:51,240 Speaker 1: doing over there telling us what we call skipping stones 470 00:23:51,440 --> 00:23:54,600 Speaker 1: and they're getting totally wrong. Well, it's all just ducks 471 00:23:54,600 --> 00:23:58,680 Speaker 1: and drakes to them, So they got no credibility over there? 472 00:23:58,800 --> 00:24:00,359 Speaker 1: Is that where the dap comes from? Where am I 473 00:24:00,359 --> 00:24:03,680 Speaker 1: thinking of the dead. I am not culturally relevant enough 474 00:24:03,680 --> 00:24:07,119 Speaker 1: to answer that question. But it's more than just the viscosity, right, 475 00:24:07,160 --> 00:24:09,360 Speaker 1: and more than just having silly name. Okay, so it's 476 00:24:09,400 --> 00:24:12,600 Speaker 1: more than just having um substance to the thing you're 477 00:24:12,600 --> 00:24:15,600 Speaker 1: trying to skip on, which which water does it has 478 00:24:15,720 --> 00:24:18,879 Speaker 1: enough fixed causity to skip stone? That's right? Because you 479 00:24:18,920 --> 00:24:21,200 Speaker 1: know when you jump off a diving board and belly flop, 480 00:24:21,240 --> 00:24:24,120 Speaker 1: you don't skip right, So there's a difference between belly 481 00:24:24,119 --> 00:24:26,560 Speaker 1: flopping and skipping. And then what else is going on here? 482 00:24:26,640 --> 00:24:29,920 Speaker 1: So another key is the angle. Right when you throw 483 00:24:29,960 --> 00:24:32,399 Speaker 1: the stone, you want it the front edge of the 484 00:24:32,400 --> 00:24:35,399 Speaker 1: stone to be higher than the back edge of the stone. 485 00:24:35,480 --> 00:24:37,000 Speaker 1: So you want the stone when it hits the water 486 00:24:37,840 --> 00:24:40,960 Speaker 1: for the trailing edge to hit first, all right, And 487 00:24:41,000 --> 00:24:43,760 Speaker 1: the reason is that you're pushing down on the water 488 00:24:44,080 --> 00:24:47,080 Speaker 1: and if you have that like a like a wheelie, 489 00:24:47,160 --> 00:24:51,320 Speaker 1: like you're you're tilted back. Yes, exactly, exactly, Though I 490 00:24:51,359 --> 00:24:53,480 Speaker 1: do not recommend trying to do this with your motorcycle 491 00:24:53,880 --> 00:24:57,479 Speaker 1: or your mountain biketycle, or do it and send us 492 00:24:57,480 --> 00:24:59,720 Speaker 1: a video. That would be awesome. I think that's called 493 00:25:00,040 --> 00:25:04,920 Speaker 1: geezs and gooses in England. I think you're probably right. 494 00:25:05,600 --> 00:25:08,080 Speaker 1: And um, what happens when you do that is then 495 00:25:08,119 --> 00:25:10,439 Speaker 1: you push down the water at an angle, and the 496 00:25:10,480 --> 00:25:14,080 Speaker 1: water creates kind of a ramp, right because you've you've 497 00:25:14,119 --> 00:25:16,280 Speaker 1: pushed it down to the back end is further down 498 00:25:16,359 --> 00:25:18,120 Speaker 1: than the front end, and so you have a ramp 499 00:25:18,160 --> 00:25:21,440 Speaker 1: that slopes up. Okay, and here's where the speed comes. 500 00:25:22,119 --> 00:25:24,680 Speaker 1: You've got to be moving fast. So you push down 501 00:25:24,680 --> 00:25:26,479 Speaker 1: on the water to create a ramp, and then that 502 00:25:26,560 --> 00:25:29,119 Speaker 1: ramp launches you back up into the air at the 503 00:25:29,119 --> 00:25:31,920 Speaker 1: same angle. You're not really bouncing then, it's more like 504 00:25:32,040 --> 00:25:34,720 Speaker 1: you're going into the water and then creating a ramp 505 00:25:34,800 --> 00:25:37,120 Speaker 1: for you to take off of. Yeah, well you're doing 506 00:25:37,160 --> 00:25:39,280 Speaker 1: both at the same time. One of my favorite things 507 00:25:39,359 --> 00:25:42,240 Speaker 1: about sort of projectile motion in physics is how you 508 00:25:42,280 --> 00:25:45,880 Speaker 1: can break things up into two dimensions that are totally independent. Right, 509 00:25:45,960 --> 00:25:48,840 Speaker 1: motion in one dimension is independent from motion in the 510 00:25:48,880 --> 00:25:51,399 Speaker 1: other dimension. Somebody in the question intersection said that the 511 00:25:51,440 --> 00:25:53,360 Speaker 1: reason that you can skip a rocket is because it's 512 00:25:53,680 --> 00:25:56,439 Speaker 1: moving really fast, um, in one direction, and so it 513 00:25:56,440 --> 00:25:59,439 Speaker 1: doesn't fall down, which is totally not true. Right, Like 514 00:25:59,640 --> 00:26:01,840 Speaker 1: you shoot the bullet, you know, it is moving really 515 00:26:01,840 --> 00:26:04,040 Speaker 1: really fast parallel to the surface of the earth. But 516 00:26:04,040 --> 00:26:07,160 Speaker 1: it's also at the same time falling and falling towards 517 00:26:07,160 --> 00:26:09,360 Speaker 1: the surface of the earth is not affected by your 518 00:26:09,400 --> 00:26:12,280 Speaker 1: motion parallel to the surface. And so you've got two 519 00:26:12,320 --> 00:26:16,080 Speaker 1: things going on here. One is you're bouncing perpendicular to 520 00:26:16,080 --> 00:26:19,000 Speaker 1: the surface of the water, right, but you're also moving parallel, 521 00:26:19,680 --> 00:26:22,480 Speaker 1: So you've got the belly flop in the perpendicular direction, 522 00:26:22,600 --> 00:26:25,600 Speaker 1: and you've got this little ramp action in the parallel direction. Well, 523 00:26:25,640 --> 00:26:28,040 Speaker 1: what happens if if you don't hit the water at 524 00:26:28,080 --> 00:26:30,160 Speaker 1: a good angle, like let's say your head, you can 525 00:26:30,920 --> 00:26:34,639 Speaker 1: hit the water kind of leaning forward instead of leaning back, 526 00:26:35,040 --> 00:26:37,400 Speaker 1: then you end up the front edge of your rock 527 00:26:37,440 --> 00:26:39,680 Speaker 1: will dig into the water and it'll slow it down 528 00:26:39,720 --> 00:26:41,879 Speaker 1: and it'll flip, and then you don't don't then you 529 00:26:41,880 --> 00:26:44,920 Speaker 1: don't get any more skips. You don't create this little ramp. Yeah, 530 00:26:45,040 --> 00:26:47,240 Speaker 1: because remember the key to getting a lot of skips 531 00:26:47,640 --> 00:26:50,280 Speaker 1: is doing the same thing over and over again. So 532 00:26:50,320 --> 00:26:52,439 Speaker 1: you want that when you leave the water, you're at 533 00:26:52,440 --> 00:26:55,200 Speaker 1: the same angle as when you hit the water, right, 534 00:26:55,280 --> 00:26:57,199 Speaker 1: so that you can hit the water again at that 535 00:26:57,240 --> 00:27:00,560 Speaker 1: same angle. So anything that flips you over start to spinning, 536 00:27:00,880 --> 00:27:02,639 Speaker 1: you're losing your energy and you're not gonna hit the 537 00:27:02,640 --> 00:27:04,359 Speaker 1: water at the right angle the next skip. Well, I 538 00:27:04,359 --> 00:27:06,560 Speaker 1: would have thought the spin was really important because without 539 00:27:06,600 --> 00:27:09,879 Speaker 1: the spin, wouldn't you lose that angle really quickly with 540 00:27:09,960 --> 00:27:13,080 Speaker 1: all the water slushing around. Yeah, spinning is important, and 541 00:27:13,160 --> 00:27:17,000 Speaker 1: nobody wins the stone Skipping World Championship without a really 542 00:27:17,040 --> 00:27:20,360 Speaker 1: good spin. But it's not technically necessary. But yeah, it's 543 00:27:20,640 --> 00:27:24,040 Speaker 1: really important to maintaining the angle and to maintaining your speed. 544 00:27:24,520 --> 00:27:26,360 Speaker 1: So there's a lot of different things going on when 545 00:27:26,400 --> 00:27:28,720 Speaker 1: just one simple rock hits the water, all right, and 546 00:27:28,760 --> 00:27:31,760 Speaker 1: then um so viscosity angle, and then what's the last 547 00:27:31,920 --> 00:27:35,760 Speaker 1: critical ingredient? Last critical ingredient is speed? Right? If you 548 00:27:36,000 --> 00:27:38,439 Speaker 1: are not moving fast enough, then you sink when you 549 00:27:38,480 --> 00:27:40,720 Speaker 1: hit the water because the ramps are dissolves, right, that 550 00:27:40,880 --> 00:27:43,720 Speaker 1: ramps is not doesn't stick around for very long. You 551 00:27:43,840 --> 00:27:46,720 Speaker 1: hit the water right, and you bounce back because the 552 00:27:46,720 --> 00:27:48,280 Speaker 1: water doesn't have a lot of time to move out 553 00:27:48,320 --> 00:27:51,640 Speaker 1: of the way. But um, you want to get off 554 00:27:51,680 --> 00:27:54,040 Speaker 1: of that ramp as soon as you can, because just 555 00:27:54,200 --> 00:27:56,399 Speaker 1: pass the ramp as a little divid right, and so 556 00:27:56,480 --> 00:27:58,080 Speaker 1: you want to get off of that ramp, and so 557 00:27:58,119 --> 00:28:00,679 Speaker 1: you need enough speed. You need to me moving faster 558 00:28:01,720 --> 00:28:05,760 Speaker 1: than the water is, of course moving faster horizontally or 559 00:28:05,800 --> 00:28:08,639 Speaker 1: does it help to go fast a little bit, you know, 560 00:28:08,760 --> 00:28:11,280 Speaker 1: into the water or do you get that anyways, you 561 00:28:11,320 --> 00:28:14,040 Speaker 1: need both. You need if you if you're not moving 562 00:28:14,040 --> 00:28:17,640 Speaker 1: fast enough perpendicular to the water, then you won't get 563 00:28:17,640 --> 00:28:19,760 Speaker 1: the bounce right. You need to be hitting the water 564 00:28:19,800 --> 00:28:21,720 Speaker 1: with enough speed that the water can't get out of 565 00:28:21,720 --> 00:28:23,880 Speaker 1: the way and pushes back at you. You also need 566 00:28:23,960 --> 00:28:26,440 Speaker 1: horizontal velocity so you can get off that ramp before 567 00:28:26,440 --> 00:28:29,679 Speaker 1: it dissolves. But if you're going to slow then you know, 568 00:28:29,720 --> 00:28:31,560 Speaker 1: you push the water into a ramp, but then you 569 00:28:32,840 --> 00:28:36,160 Speaker 1: you don't take off, You just kind of move exactly. 570 00:28:36,480 --> 00:28:38,480 Speaker 1: That's exactly the sound it makes. Why you must have 571 00:28:38,480 --> 00:28:42,560 Speaker 1: done these experiments. That's what it sounds like in every 572 00:28:42,560 --> 00:28:47,000 Speaker 1: slow motion video clip I've seen on YouTube. But every 573 00:28:47,040 --> 00:28:49,480 Speaker 1: time you bounce, you also do lose energy. It's impossible 574 00:28:49,520 --> 00:28:52,160 Speaker 1: not to because this friction and so you hit the 575 00:28:52,160 --> 00:28:54,440 Speaker 1: water and it slows you down a little bit. So 576 00:28:54,560 --> 00:28:58,840 Speaker 1: every bounce is in the best case scenario, like of 577 00:28:58,880 --> 00:29:01,400 Speaker 1: the neck of the previous ounce, And so that's why 578 00:29:01,400 --> 00:29:04,080 Speaker 1: you know, they get faster and faster. The time between 579 00:29:04,080 --> 00:29:06,880 Speaker 1: bounces it gets smaller and smaller because you're not going 580 00:29:06,920 --> 00:29:09,440 Speaker 1: as fast, you're not going as far up, so it 581 00:29:09,480 --> 00:29:11,600 Speaker 1: doesn't take as much time to come back down. So 582 00:29:11,640 --> 00:29:15,800 Speaker 1: that's pretty good. Like you only lose in each skip 583 00:29:15,920 --> 00:29:18,040 Speaker 1: or is that like a you know, is that is 584 00:29:18,080 --> 00:29:20,080 Speaker 1: that what the pros do? Or is that what happens 585 00:29:20,080 --> 00:29:23,440 Speaker 1: when anyone skip stones? Is that it's always now that's 586 00:29:23,600 --> 00:29:27,600 Speaker 1: the like top level performance, like eighty yeah, And that's 587 00:29:27,640 --> 00:29:30,400 Speaker 1: the key to getting a lot of skips is losing 588 00:29:30,440 --> 00:29:34,280 Speaker 1: the smallest amount of energy every skip, which means hitting 589 00:29:34,400 --> 00:29:37,120 Speaker 1: the water at just the right angle. And it's one 590 00:29:37,160 --> 00:29:40,120 Speaker 1: of these things where it's very sensitive. You're slightly off 591 00:29:40,120 --> 00:29:42,080 Speaker 1: of the optimal angle, you're gonna lose a lot more 592 00:29:42,160 --> 00:29:44,120 Speaker 1: energy in the first skip, and then you're gonna be 593 00:29:44,200 --> 00:29:46,080 Speaker 1: off on the next angle and the next angle, and 594 00:29:46,120 --> 00:29:48,320 Speaker 1: pretty soon you know you're sinking to the bottom of 595 00:29:48,320 --> 00:29:51,520 Speaker 1: the lake. That's pretty impressive. So that's how they get 596 00:29:51,560 --> 00:29:55,600 Speaker 1: to like a hundred yeah, exactly eight skips, which still 597 00:29:55,640 --> 00:29:57,480 Speaker 1: blows my mind. It feels like that would take like 598 00:29:57,520 --> 00:29:59,360 Speaker 1: an hour, you know, Like you throw the rock and 599 00:29:59,400 --> 00:30:02,040 Speaker 1: then you're just like and minutes later, still scount counting 600 00:30:02,080 --> 00:30:04,560 Speaker 1: skips or something. Well, towards the end, it's it's it's 601 00:30:04,560 --> 00:30:08,080 Speaker 1: not like skips skips skip. It's like, yeah, exactly, it's 602 00:30:08,080 --> 00:30:10,320 Speaker 1: like stuttering skips at the end, which is what tells 603 00:30:10,360 --> 00:30:14,720 Speaker 1: me what these really like massively competitive events. They must 604 00:30:14,720 --> 00:30:16,880 Speaker 1: have some sort of camera that's taking pictures to count 605 00:30:16,920 --> 00:30:19,280 Speaker 1: these skips. They can't have like a super spot or 606 00:30:19,440 --> 00:30:21,800 Speaker 1: something just using their eyeballs. You think it's at that 607 00:30:21,920 --> 00:30:25,280 Speaker 1: high tech. You think they have like corporate sponsors and 608 00:30:25,680 --> 00:30:30,000 Speaker 1: pro athletes, probably some Swiss watch companies you know, sponsoring it, etcetera. Yeah, 609 00:30:30,360 --> 00:30:33,040 Speaker 1: but the top guys have groupies and travel around and 610 00:30:33,080 --> 00:30:35,400 Speaker 1: fancy busses and all sorts of stuff. All right, So 611 00:30:35,480 --> 00:30:38,600 Speaker 1: then have you tried this? Since you're learning the secrets here, 612 00:30:38,600 --> 00:30:40,640 Speaker 1: have you tried and does it help? Did it help 613 00:30:40,680 --> 00:30:44,080 Speaker 1: you skip stones better? No? And that's the thing about physics. 614 00:30:44,160 --> 00:30:47,160 Speaker 1: It tells you how the universe works, It gives you inside, 615 00:30:47,360 --> 00:30:50,200 Speaker 1: but it doesn't help you actually navigate the situation. You know. 616 00:30:50,240 --> 00:30:52,680 Speaker 1: For example, we did that whole podcast episode about how 617 00:30:52,680 --> 00:30:54,960 Speaker 1: to ride a bike, right that just made me ride 618 00:30:54,960 --> 00:30:57,880 Speaker 1: bikes any better, especially because we learned that physics doesn't 619 00:30:57,920 --> 00:31:01,840 Speaker 1: know why why bicycles. Allan's right, but you can still 620 00:31:01,960 --> 00:31:05,520 Speaker 1: ride a bike. So there's this disconnect between understanding something 621 00:31:05,560 --> 00:31:07,520 Speaker 1: and being able to do it. Well, you know, it 622 00:31:07,600 --> 00:31:09,560 Speaker 1: did help me. I mean after learning all of this, 623 00:31:09,720 --> 00:31:12,360 Speaker 1: I did try it, and it does help. Like if 624 00:31:12,400 --> 00:31:14,880 Speaker 1: you know that you have to throw it at the 625 00:31:14,920 --> 00:31:17,880 Speaker 1: water kind of at a little bit of an angle 626 00:31:17,960 --> 00:31:20,760 Speaker 1: leaning bag that's a huge hill, like because you know 627 00:31:20,840 --> 00:31:23,280 Speaker 1: before you I would try to like throw it at 628 00:31:23,280 --> 00:31:26,120 Speaker 1: the water so it's perfectly parallel to the water. I 629 00:31:26,160 --> 00:31:28,480 Speaker 1: thought that was the secret, you know, but like once 630 00:31:28,480 --> 00:31:30,000 Speaker 1: you know you have to kind of lean it back 631 00:31:30,040 --> 00:31:32,440 Speaker 1: a little bit. It does help you skip better. All right, 632 00:31:32,440 --> 00:31:36,320 Speaker 1: well you go, I skips, but you know, physics has 633 00:31:36,360 --> 00:31:38,440 Speaker 1: improved your life for her for the first time, it 634 00:31:38,600 --> 00:31:41,720 Speaker 1: ruined my vacation, but it increase my standing in the 635 00:31:41,720 --> 00:31:44,600 Speaker 1: world rankings of It's amazing to me that the universe 636 00:31:44,720 --> 00:31:47,400 Speaker 1: is mathematical, that we can understand it at all, that 637 00:31:47,480 --> 00:31:49,480 Speaker 1: it seemed to follow these rules and we can write 638 00:31:49,480 --> 00:31:52,680 Speaker 1: down on paper manipulate with our minds um. It's amazing 639 00:31:52,720 --> 00:31:54,320 Speaker 1: that that works, and it's a joy to see what 640 00:31:54,360 --> 00:31:56,720 Speaker 1: it happens. You know that we can actually isolate the 641 00:31:56,760 --> 00:31:59,400 Speaker 1: critical elements and understand something. So the next time you 642 00:31:59,440 --> 00:32:01,560 Speaker 1: see something weird, the next time you see something you 643 00:32:01,600 --> 00:32:03,520 Speaker 1: don't understand, you know, think about the physics of it, 644 00:32:03,880 --> 00:32:07,120 Speaker 1: what's making that happen? Um, what's going on inside is 645 00:32:07,120 --> 00:32:10,840 Speaker 1: there's some microscopic explanation that can help you understand why 646 00:32:10,920 --> 00:32:13,640 Speaker 1: those ducks are chasing that funny bird or you know 647 00:32:13,680 --> 00:32:16,000 Speaker 1: why those clouds form in that weird way. And there's 648 00:32:16,040 --> 00:32:18,760 Speaker 1: physics all around us. And if you don't understand, just 649 00:32:18,920 --> 00:32:21,680 Speaker 1: send the question to Daniel and we'll answer it on 650 00:32:21,760 --> 00:32:24,520 Speaker 1: the podcast that's right before after I do a bunch 651 00:32:24,560 --> 00:32:29,560 Speaker 1: of experiments at Jorge's house skipping gold coins on my Hey, 652 00:32:29,560 --> 00:32:31,360 Speaker 1: can I borrow a few of those gold coins please? 653 00:32:31,360 --> 00:32:33,600 Speaker 1: I gotta do some experiments. Whoops, they sank to the 654 00:32:33,600 --> 00:32:37,960 Speaker 1: bottom of the lake. Sorry about that? All right? Well, 655 00:32:38,000 --> 00:32:41,280 Speaker 1: we hope you enjoyed Dad, And as Neo says, whoa, 656 00:32:41,600 --> 00:32:51,920 Speaker 1: thanks for tuning in. See you next time. Before you 657 00:32:52,040 --> 00:32:54,920 Speaker 1: still have a question after listening to all these explanations, 658 00:32:54,960 --> 00:32:57,920 Speaker 1: please drop us a line. We'd love to hear from you. 659 00:32:57,920 --> 00:33:00,719 Speaker 1: You can find us on Facebook, Twitter, and Instagram at 660 00:33:01,080 --> 00:33:04,200 Speaker 1: Daniel and Jorge that's one word, or email us at 661 00:33:04,480 --> 00:33:08,200 Speaker 1: feedback at Daniel and Jorge dot com. Thanks for listening 662 00:33:08,200 --> 00:33:10,920 Speaker 1: and remember that Daniel and Jorge Explain the Universe is 663 00:33:10,960 --> 00:33:14,440 Speaker 1: a production of I Heart Radio. For more podcast from 664 00:33:14,480 --> 00:33:18,240 Speaker 1: my heart Radio, visit the i heart Radio app, Apple Podcasts, 665 00:33:18,360 --> 00:33:26,120 Speaker 1: or wherever you listen to your favorite shows. Yeah.