Could Sound Make You Levitate?

0:00This episode is brought to you by Cancer Research UK. Dinosaurs walked the earth 180 million years ago. But, you know, cancer was part of their story, too. Scientists have found tumors in ancient fossils. Well, that is part of the reason why cancer is a big, big part of our story, right? It's the other side of evolution. It's the most complex disease that we face. There are more than 200 types of cancer in total, each with distinct characteristics, challenges and mysteries. And that complexity demands scale. Cancer Research UK is the world's largest charitable funder of cancer research, with more than 4 ,000 scientists, doctors and nurses working across more than 20 countries in the search for answers, and then sharing their discoveries beyond borders.

0:45And the impact of this collaboration is clear, because over the last 50 years, the charity's pioneering work has helped to double cancer survival in the UK. That is, more people who are living longer, better lives. Fossils can show us the past, but research is shaping the future. And for more information about Cancer Research UK, their research, breakthroughs, and how you can support them, visit cancerresearchuk.org forward slash rest is science.

1:21Would you like to levitate, Michael? I would love to, every day. Wouldn't it be good? Wouldn't it be good? Well, today on Field Notes, I'm going to give you that chance. There's a couple of caveats, small ones. Don't worry about them. We'll come to them in a bit. But I've got a little acoustic levitator with me. Oh, really? Have you ever played with one of these? I have, but one that was so small, it could only levitate like a tiny little bead of styrofoam, polystyrene, for those of you across the Atlantic. And it was so undramatic. That's exactly what I've got. oh no does it also make this noise that's like and you're like oh please okay yeah i've got that and some calculations let me say let me say i've never played with one but i can't i don't believe it's possible especially something as cool to levitate as styrofoam oh so that's what you brought me you brought me a a sonic levitator and some calculations about how many of these things you need to levitate you okay so what a wonderful intro aren't you excited to show this to me now i've never backed myself more michael this is uh i mean i should have managed your expectations a bit better shouldn't i really i should have said yeah i think i think so but i will say that that i've experienced it but i think that you talking about it and explaining it will show me why it is so cool we'll see shall we okay a friend of mine at cambridge university has been toying around with this little acoustic levitator um incidentally actually you know math departments are completely full of people who care a lot about acoustics did you know this yes I bet.

3:11Like jet engines, for example, when they were first created, they were so noisy that for starters, it was like completely unworkable for commercial flight. But secondly, the vibrations were so dramatic that they would break the components inside of the engine. And who did they turn to to make them all quiet? The mathematicians, my friend. Right. There is a guy who, a mathematician who works in the same department as me, who is now working on a car seat that essentially works as noise cancellation for the road around you. Doesn't that sound nice? Oh, wow. Is it safe? I feel like I need to hear some of these noises.

3:53Do you? I think maybe if you're a passenger. Maybe it's not for the driver. Okay, okay. Anyway, there's just a lot of people who are working on acoustics. and one of them has got this little acoustic levitator. So here is the acoustic levitator. It's a little 3D printed box. My friend is Matthew Nethercote, by the way, who let me steal this in order to impress you, Michael, which was... I'll try a lot harder next time. I'm going to put it that way. No, no, no, no. This looks cool. This looks cooler than the one that I've seen. It's like a hand-sized... Like a hand-sized. And it looks like some kind of Star Trek teleporter.

4:34It does, yeah. So you've got two bits, one at the top, one at the bottom. And inside, there's a dome, effectively, that is filled with lots and lots of tiny little speakers that are all pointing towards this kind of central space. Sort of, hmm, how can you describe it? I never watched Star Trek, but isn't there some device in there where you teleport people? You can sort of imagine stepping in here and being teleported. I think that's the best way to describe it. Yeah, right. But those are speakers pointed up and down, focused on some point in the very middle in between them. The idea here then is that sound is a wave, right?

5:13Sound is like you have this membrane on a speaker that vibrates backwards and forwards. And as it does so, it pushes and then pulls the air that surrounds it, creating this wave. Now, if you have all of these speakers that are tuned to exactly the right frequency and pointing in exactly the right way then what should happen is that in some places the the vibrations will sort of add up together and in some places those vibrations will cancel each other out so that you should get some little effectively jail cells in here of air where the air is perfectly still while all the air around it is like vibrating like crazy so is it running now is it producing the the the sound it is which um i can't hear i assume you can't hear but i can't hear it either 100 meters down the road there are several dogs that are now crying because it is so high pitched very high pitched okay so the idea is that sound waves are compressed they're they're waves of of air that's being compressed and rarefied and if you get what like two two compressed waves side to side you can like hold something in the air exactly now can you change the frequency of the sound with this device and change where these levitation points are not this one unfortunately i think i need to write to matthew nethercoat and tell him he needs to make a more impressive device um i'm not down on this i think it's really cool i think it looks really neat i know what you're That sounds fun, but I want to go.

6:43I want you to levitate me. Or at least an ant, you know, that would be. Well, yeah, no, I've seen them levitate living frogs in laboratories with very powerful versions of this. And I'm wondering what the applications are beyond the amusement. Well, OK, let's stick on the fun for a second here, because because let's say the average human weighs about, I don't know, what do you reckon, 75 kilograms? That's what I've done with my calculations. um this particular levitator has 72 little transducers right around here uh so if you wanted to raw power lift a human you are going to need 216 million of them which is oh i would say quite a lot um that's a lot but let's say you did it let's say you did it be able to hear the sound or would it still be ultrasonic well here's the thing um you need them to be like super super loud right um in order to uh in order to actually have the sort of strength between them to be able to lift this human uh you can get them up to about 120 decibels but remember you've got 216 million of them um now the slight problem is that any sound above 170 decibels can cause organ and joint damage just because it vibrates you so violently uh that you you start to implode um anything above 240 decibels that would be lethal wow and so at 216 million i think that the reality is we could levitate you uh it's just it would be so loud your head might explode small caveat small caveat it's worth it it's worth it you wanted drama my god i can give you drama so okay this is like a cute little fun toy that you can play with but there is actually a reason behind this stuff so in the 1960s 1970s nasa they they developed these kind of levitators um partly because they wanted to see what it would be like to have a effectively a microgravity environment oh yeah you can imagine if you were like suspending instead of tiny little um balls here you were suspending cells or like other sort of organic matter um it's effectively the same as like being suspended in zero gravity you're not going to feel the force of the earth because it's counteracted by this little cage of air that is wrapped around it.

8:59You can also put liquids in this, which is kind of interesting, but there are some quite interesting medical applications of this stuff. If people have kidney stones in their body, what you can do is with acoustic beams is nudge small fragments of kidney stones. You sort of break them up with ultrasound and then you nudge them into positions in the body where they could sort of be naturally cleared. huh there's also this is the one that i really like you can have a targeted drug delivery with this so you can create a um a sort of micro bubble load it up with a drug you can inject it but then if you want to move it to very specific areas of the body uh and then burst the bubble using ultrasound to release the medication and this is particularly useful if you have something like chemotherapy for instance so some sort of like drug that has like a really bad toxicity and you want to reduce the side effects that it can interact with other parts of your tissue on the way to the bit that it actually wants to um to interact with there's also like this idea that you can use these kind of acoustic levitators i mean essentially what you have here is like a beam of sound that moves stuff yeah and it can move anything made of matter whereas trying to move things around in a body with like magnets or something would require what you're moving to respond to the magnet and they're ultrasonic so they don't bother us yeah just the neighborhood dogs yeah the other thing so so i mean in general moving things around the body you can also use this for pill-sized cameras so you swallow a little camera then you want to move it around the digestive system for instance you can use these kind of acoustic beams to move it all around the body right a little micro cinematographer could make a movie in my body controlling with sound waves and sound waves could be a lot harder to jam than like radio waves in what way go on well i mean like if you want to control something remotely using radio waves there's going to be some limitations on when you can use those and through what mediums but perhaps sound can fill in the gaps.

11:08Because if you think about it, if you happen to be swallowed by a human and we're sitting inside of their stomach and someone was shouting from outside, you would expect to hear it. Like the sound vibration would still get inside. In fact, actually, you know that whole thing about babies when they're in their mother's stomachs, there's certain frequencies which they hear that end up being really soothing. Yeah. And there's things that they see as well, like skin is not completely opaque. The growing, developing baby in the womb isn't in darkness, especially if the mom's topless in bright sunlight it's like kind of like red in the womb to the human eye yeah yeah and they've done studies where they've uh projected like using lasers different shapes onto the womb that the baby could see yeah this is of course a baby that's developed enough to have a retina and the babies react to shapes in fact they're seen to react to and look at and stare longer at shapes that are similar to a human face like it's instinctive wow i'm being serious like um this this pattern right here they don't seem to care very much about okay that's three dots in a triangle shape but they will for like twice as long follow and look at an upside down triangle of dots which is like an like two two eyes and a mouth i mean it's essentially like your your i'm i always think in terms of a british plug whenever i see this experiment it's sort of like hold a british plug in the correct orientation baby don't care turn it upside down baby cares really of course i've only seen it for for babies that have been born yeah well apparently it would work on a prenatal baby what can they hear could they hear this like is this is this frequency that this machine's running at is it something that like teenagers can hear, but not old people.

13:00Like the mosquito noise. Did you have that in the States where they had a device that was designed to stop teenagers from hanging out in public areas? Yeah. And I experienced one at this show I did where I was like, why is there that buzzing noise out here? And all the guys working there were like, oh, you can hear it. I don't know if I could hear it still. This was years ago, but I was really proud that I could still hear this noise. It's supposed to scare away or not scare away it was supposed to annoy juvenile delinquents well this thing is about 20 000 hertz so it's quite possible that young children could hear this i have a young child in my house should i go and ask them well yeah let's do an experiment shall i for real uh yeah and see if they can guess when it's on or off to see if they're getting it okay here's our test subject here's a test subject okay you want you to have a listen and see you tell me when you can hear it can you hear that yes can you hear that no oh can you hear that yeah can you i can't hear that i can't hear any of these wow super kid super kids 19 000 hertz you went up to i stopped at about 12 000 but this acoustic levitator that you've got it's using 20 000 hertz 22 22 22 wow Wow.

14:16Okay. So it's shaking the air 22 ,000 times a second, creating waves of compressed air separated by rarefied air. And these waves collide from the top and bottom. And what's going on? The compressed waves can sync up and create an even more compressed wave. And if a rarefied area and a compressed one meet, they just make normal air. and this somehow creates like a cage of air pressure that can hold very lightweight objects. Exactly. Try and put something in that's much larger and it'll just flop around all over the place and eventually fall. But if you get something that's the right size and not too heavy so that it doesn't sort of overwhelm the force that's being exerted by the surrounding air pressure, then yeah, you can have it successfully levitate.

15:06I mean, I always thought levitation was a bit of a science fiction myth, but it turns out it actually isn't. Well, yeah, I mean, I got stuck on defining levitation because this isn't levitation. It's using force of air pressure to resist gravity. How dare you? It's not touching the ground, Michael. You're being way too strict with your definition. Okay, so then what about, do airplanes levitate? They're not touching the ground. Shush, shush, shush now. Let's go to a break. Okay, let's go to a break.

15:40this episode is brought to you by cancer research uk every second your cells release millions of microscopic signals fragments of dna tiny molecules little molecular whispers and scientists are trying to work out how to read them it's called a liquid biopsy and this is a test that looks for these tiny little traces of cancer through the body's fluids, often long before symptoms of cancer itself actually end up appearing. So today we're asking, can you really detect cancer from clues floating around in blood, urine, spit and tears? Short answer, yes. Longer answer, how? How? Okay. I mean, this is it, right?

16:19Because, okay, cancer doesn't just appear out of nowhere. It leaves these molecular fingerprints in your body, long before symptoms end up showing. These little fragments of DNA, these proteins, other little molecules that end up floating around your body and your bloodstream, for example, as your cells are dividing, as they're growing and as they're dying. Like a sort of internal messaging system and whether you can tap into it. And the challenge is sensitivity because you've got a lot of cells that are not cancer. Yeah. I mean, there's a whole load of stuff floating around your body. Well, Cancer Research UK researchers are building tools sensitive enough to detect these markers.

16:55Yeah, these faint little signals and detect them even earlier. And this is different. This is separate from traditional biopsies, right, which kind of go in. It means surgery. It means needles. It means you take tissue samples from a suspected tumor or the surrounding tissue around the tumor. And that is amazing. But it really only gives you a snapshot of one tiny area of the body at that one moment in time. But a liquid biopsy is less intrusive and it's a liquid that has come in contact and can contain traces from all over the body. Yeah. Yeah. Like one breath, which is collecting up the molecules that have traveled around your entire body, you know, or urine or blood tests.

17:35It's a quiet revolution, right? It is testing the blood and other bodily fluids instead of the tumor without surgery. And the key thing is that because those fragments, because they can come from different parts of the tumor, it means that just a small sample, you can put these clues together and you can get a really full picture of what's going on inside. One thing I think is really cool is that platelets, which like we've all heard about, they're the things that help you heal when you get cut. They block off the blood flow so the healing can begin. Platelets really help with this search because they also suck up these molecular traces in the blood.

18:09Yeah, these things act like little hoovers, right? They're picking up tiny bits of tumor DNA, all those that circulate around the body and concentrating them. And I mean, they can help us unlock overlooked cancer clues. Exactly. And the MRD edge technology is more like an amplifier that can make the really quiet traces loud enough for researchers to find. The whole thing about this liquid biopsies, this isn't just a theory. This is something that's already being trialed in hospitals to monitor how well cancer treatments are already working. Yeah, the aim is precision, knowing exactly when a treatment works, when to switch course and when cancer might return.

18:46So doctors can always be one step ahead. And Cancer Research UK, they come into this by connecting the lab work, doing the data science, the clinical trials that make all of this stuff possible. So it's discovery that's happening, that's in motion, it's innovation beginning to make its way towards everyday care. Of course, the goal here is that you can spot cancer early and then tailor every single decision around the individual person based on what's going on in their body at that moment in time. That's right. Doctors can detect and be aware of the smallest changes so that they can adjust treatment in real time.

19:18Yeah, rather than having long stretches between biopsies, for example. And this shifts medicine from being just reaction to prediction as well. Instead of waiting for symptoms to arrive, you can get one step ahead. And the same science that spots cancers earlier could become part of routine checkups. Yeah, much less invasive, much more predictive. I mean, you can imagine a future where you go and have a blood test and it is as routine as, I don't know, getting your car in for a service. Only this blood test is monitoring everything that's going on in your body and could potentially save your life.

19:50So Cancer Research UK's researchers are bringing the future closer. They're turning detection into protection. And what is remarkable is just how quickly this field is moving. You are getting discovery beginning to shift from the lab into hospitals. And when we learn to read the body's signals, we can get ahead of cancer. We can have the best shot at beating it. For more information about Cancer Research UK, their research, breakthroughs and how you can help them, visit cancerresearchuk.org forward slash rest is science.

20:27all right we're back and we're going to answer some questions from you i want to start with this great question from neil who asked will a person ever swim faster than a shark no next question whoa whoa whoa whoa wait a second this is one of those questions that suffers from the problem of being a bit too broad like what do you mean by a shark yeah like there are sharks that swim really slowly the greenland shark only swims at about one mile per hour that's about 0.34 meters per second that's extremely slow isn't that the one that's also like 400 years old yeah yeah and so i could out swim one of them but i can't outlive them maybe it's a balancing scale and the fastest human speed is like almost two and a half meters per second which how does that convert to miles an hour uh about five and a half miles per hour okay that's pretty good you could definitely outrun a greenland is that with or without fins that's without fins that's just using the flesh your mother gave you what i will say is i can definitely not swim that fast that's uh yeah that's a sort of michael phelps territory no it definitely is like a uh a very unique speed to be traveling at.

21:44I also want to know how motivated the shark is. So I sort of feel like even fast sharks, whatever the fastest shark might be. What do you reckon the fastest shark is? I mean, not a hammerhead. They are aerodynamically useless. I mean, Google says the fastest shark is the short fin mako, which can travel at 31 to 46 miles per hour in the water. Well, well, this is a whole jumble of units we've got going on here, isn't it? That's a whole jumble. how many fathoms per day not per month look the point what i love about the question though is that it's framed by asking will a person ever swim faster than a shark as though human swim speed is something that is changing and it's getting better and better and in some ways it is there's also belies that kind of like that modern sensibility that like things are just going to get better and stronger and records keep getting broken.

22:38And in some ways it is true. Like we do learn more about nutrition and swimming techniques and also swimming technologies like fins and swimsuits. I think there were some swimsuits that were allowed in Beijing at the Olympics that are no longer allowed, but because they were allowed for that one Olympics event, a bunch of records were set. And so we're at the point where the limits of human bodies are now being augmented and we're going beyond it. Because I think that's the thing, actually, particularly about swimming, is that you have to wear a swimsuit, right? You can't do nudie swimming. That would just not be okay.

23:13And so you have to have some kind of, you know, designed object on your body. What do you mean you can't swim naked? I mean, you can if you want to, but maybe not in competition in the Olympics. Right, right. Maybe not two and a half meters per second, Michael. That's what I'm saying. Right. but those particular swimsuits they had a couple of design features so one was that um because what you really want to do is you want to basically have your your butt uh higher in the water like as high in the water as you can so they had like some elements of buoyancy in them they also along the sort of skin of the swimsuit um they had like uh sort of microscopic design which allowed the water to slip over it much easier so that you didn't get this sort of any resistance or drag on the surface.

24:03And then I think also they were basically like Spanx. They were basically like four sizes too small for the human that was wearing them to make them as streamlined as possible, sort of minimize their surface area. Fascinating. Okay. So all of those things, you know, those things are, oh, actually one other thing about swimming, in fact, you know, this idea that humans can swim faster as time goes on. When I was a kid, swimming lessons, they would say that you have a flat palm and that your fingers are stuck together but actually now that i have a phd in fluid dynamics michael i know that that is not true i know that that is that is not the best way to swim because in fact actually if instead of having your hand flat you have it sort of cupped but also if your fingers are slightly further apart what happens is that for starters you're just displacing more water by having your hand curved So basically, if you have your hand in like a natural relaxed position, what happens is you get these little eddies that appear, this turbulence that appears between your fingers that are, you know, if you get it at the right distance, that are impenetrable to water going through.

25:10So you effectively increase the size of your hand by having your fingers slightly apart. Basically, you want to like think of your hand as these big scoops going through the water. Right. And those eddy currents are almost like webbing made of water that stops water from going through. that's really cool so maybe maybe science will make people swim faster i know watch out mako shark thanks for the question neil uh you want to take ellie's question yeah go on uh ellie asks if you had to invent a completely useless yet scientifically fascinating machine what would do it and what basic principle of physics or chemistry would it exploit okay i've had this idea for a long time I want to build a clock that uses a titration process to tell time.

25:57So what you've got in my mind, you've got like a beaker with some kind of solution in it, and you're dripping another chemical into it at a regular interval, like one drop per second. And you do this all day. All right. And the more of the above chemical falls into the one below, the more the color changes. So, for example, maybe it's becoming more and more red throughout the day. And then on the clock, there's a gradient from clear to red and you just like turn it until it matches the color of the beaker. And that happens to be the time that it is. So to check the time, you just go, let's look at this.

26:35How red is it? And you move the dial until the reds match and you go, oh, wow, guys, it's afternoon now. I like that so much. I've actually wanted something like a like an hourglass for a really long time that lasts much longer than an hour. Right. I wanted one. You know, there's some things that you want to do every couple of weeks. Every couple of weeks, maybe you want to like water your plants, for example. And what I really wanted is a physical device that you can turn over, leave it and then know when two weeks is up. Unfortunately, if you use sand or something, they end up being so gigantic that they're completely impractical.

27:08It's like the size of a room. I know, I know. Well, there's an hourglass in Japan that goes for an entire year. Is there? How big is it? It's really big and it's supported way up on these giant metal truss. And on New Year's Eve, every year, they turn it over. And it's beautiful. And it's one of my dreams to go and visit it. Oh, that's incredible. But this idea of having a liquid that drops, I like this a lot. Because there's that experiment, the pitch drop experiment. You know about this, I imagine? Yeah, the longest running experiment. Since 1927. So this is... So it's going to be hitting its 100 year anniversary in a couple of years.

27:47That'll be a special moment. Should we work out a way to get the rest of science to go and visit for its 100 year anniversary? Yeah, we should do a special celebratory episode there as we watch it. For those who don't know, the pitch drop is an experiment looking at the viscosity of pitch, a material that is so so not flowy that it pours out of the funnel that it's in like well i mean so slowly that it's been almost 100 years and it's still coming out yeah yeah i think there's only been it's it's it's like tar right it's like the kind of thing that you would use to waterproof your roof like that kind of thing um there's about a one drop every decade or so um i think that there's an online camera i think that there's like a live feed yeah the feed okay Okay, so the experiment uses pitch that is 100 billion times more viscous than water.

28:39Wow, that's incredible. Absolutely incredible. Can I just read you? I want to read. This is so fascinating. Please. In 1927, Professor Parnell heated a sample of pitch and poured it into a glass funnel with a sealed stem. He allowed the pitch to cool and settle for three years. And then in 1930, he cut the funnel's stem. and since then the pitch has slowly dripped out of the funnel it took eight years for the first drop to fall and more than 40 years for another five to follow my gosh harnell though he never got to see it even though he was in the same building for decades and when when he died i think no one had ever you you sort of know that it's happened but you come back in you're like damn it i missed the drop and you got away another 10 years um someone who took over the experiment after um thomas parnell uh was like completely obsessed with it so was waiting like 40 years set up loads of cameras sometimes to sleep near the apparatus when he thought that the pitch was imminent right um in 1977 apparently he left the lab for a few minutes and then the drop fell and then in 1988 the next time uh it fell again but the camera had jammed and then in 2000 he set up a webcam and the webcam crashed right before the drop he is no half his career trying to see a single drop in the jar and uh yeah died without having seen it what a life i feel like you could do a pitch drop experiment timer at home and you would just set a knob to the temperature for the speed that you wanted and you could set it for a fast speed or like remind me in six months Yeah.

30:16Let's invent that. I think that's something that you could do. You could definitely do that. I'd like a two-week pitch drop timer, please. On that note, I'm going to go and water my plants and try and levitate some household items acoustically. Oh, sounds like a fun time. Very good. We'll see you next time. Yeah, we'll see you next time.

30:47Thank you.