 First of all, I'd like to welcome you to the Institute of Technology Carlo and the 2009 Tindall Lecture. My name is David Delving, I'm from the School of Science and it's a great pleasure to have here with us today Dr. Kevin McGuigan, who is from the Department of Physiology and Medical Physics at the Royal College of Surgeons in Ireland and he's a senior lecturer and researcher at the RCSI as well as director of the RCSI Minimed School and that is a specialized outreach school which helps special medical education programs around the country and provides an opportunity for the public to learn more about the human body. First of all, before I hand over to Dr. McGuigan, I'd like to thank the organisers of this event here in Carlo, Dr. Lorraine Valilly and Dr. Yvonne Cavanaugh and also Anna Rourke who was on the desk there taking your names as you came in. I'd also like to thank Mora on Audiovisuals for the job she's going to do now organising the display of slides. I'd also like to thank the sponsors of this event which are the Institute of Physics in Ireland and the RDS and of course to remember that this lecture series is in commemoration of John Tyndall who as you probably are aware was born famous all-round scientist and physicist and was born in Carlo, in County Carlo and in the early part of the 19th century. So without further ado, I'll hand you over to Dr. McGuigan and the title of this year's Tyndall lecture is The Human Body is the Ultimate Physics Laboratory. Thank you. Hi folks, it's a pleasure to be here in Carlo giving the Tyndall lecture at the home of Tyndall. Can I get the lights down? Just here, thanks very much. So the theme of the talk is basically the human body, there's a lot of physics in it. It gets a bad press, physics is a bit like the Cinderella of the sciences. It has two ugly sisters, biology and chemistry. And you tend to neglect the physics. People think of the human body and they say oh there's a lot of biology going on there, there's a lot of biochemistry. But really there's a whole lot of physics that you would never suspect is taking place. So to set the scene, we'll start here and I would ask the ladies in particular to just look at what's happening here. It's an eye opener. What's this fellow here? So if a chemist was to look at that, they'd say, God isn't it amazing the effect that a little bit of alcohol has on adolescent males? Or if a psychologist was to look at it, they'd say, Isn't it amazing the effect that peer pressure has on adolescent males, the things they can get one another to do to each other? But as a physicist I'm looking at that and saying, Isn't it amazing the way the brain can't take a sideways impact? If you think of us from an evolutionary perspective, we've evolved to go hunter-gathering through the forest, picking up the berries, catching the rabbits. If we lose concentration, we may walk forwards into a tree and we can handle front ways impacts quite well. But you never expect to get hit sideways by a tree. So your body hasn't evolved any defense mechanisms against that. So when that rather unwise person asked his friend to hit him on the side of the head, what he didn't realize was your brain has two hemispheres and the sideways impacts makes the two hemispheres jiggle relative to each other. And it stretches the nerves between them and your brain doesn't like that. So it flips the reset button and just decides to reboot and we know that as being unconscious. So it's a little bit of stupid behavior, but with a nice bit of physics underlying it. And that's the whole theme of the lecture because I got my PhD in a topic called semiconductor physics, nothing to do with medical physics, and then I got the gig lecturing in the College of Surgeons to medical students. These were students who did not want to learn physics. So you have to make the medical physics course relevant, you've got to let them know why they're doing it. So at first I was worried, can I think of any good examples of the various physics principles in the body? But over the ensuing nearly 20 years now, I've found if you choose any area of physics, there's usually a fantastic example available in the body. And that's the underlying theme of today's talk. So we'll start off, how many people in the room are doing physics either for the leaving search or are thinking of doing it if you're in TY? Slim pickings there, okay. All right, so maybe we can change your minds a little. So we're going to start at the place where usually a physics course starts and it's all about mechanics. This is the science of things in motion. And the first thing that we usually deal with is momentum. Physicists get awfully excited about momentum because it's what's called a conserved quantity. We know what's happening. We know that if we've got so much momentum at the start, we'll have so much momentum at the end. And momentum is a very simple concept. It's what you get when you multiply the mass by the velocity. Now, I'm going to give you a situation here. Here we've got the conservation equation, what you have at the start. For some strange reason, the symbol for momentum is P. Who knows why? That's a rhetorical question. And here we have the momentum at the beginning. I want you to think about Granny McGuigan crossing the road. This is her here, mass, her velocity. U stands for initial velocity. And this is something, let's say it's a bus. And Granny McGuigan sees the bus coming and doesn't know where to go. We're going to assume that she's got no velocity. And the bus is going to hit her. This is where the conservation of momentum comes in. We know whatever momentum there was at the start you'll have at the end. What we're going to get is a redistribution of momentum between the bus and the Granny. The bus very kindly will give some of its momentum to Granny McGuigan. Now, it can't give Granny McGuigan any mass. So the only thing it can give is velocity. And that's what we have in most road traffic accidents. What's the lady? Alternatively, did any of you recognize who that was? Brad Pitt. And if you look closely, you'll see Jennifer Aniston is actually driving the taxi. So you can see in those situations you have a redistribution of momentum and unfortunately for the pedestrian it's always in the form of velocity. And that's where you're going to get some of the injuries from. We can go on to another part of mechanics. It's usually an excruciatingly boring part of mechanics, friction. If you've ever been taught friction in a physics lecture, they usually talk about masses on inclined planes and there are normal forces and it sends you to sleep very quickly. But if we think about the human body, everything is in motion. You've got blood moving, you've got gases going in and out of your lungs. There's a whole lot of motion and wherever you have motion, you have friction. I always think of friction as being the mother-in-law of all forces. Whatever you want to do, it wants to do the exact opposite. It wants to slow you down. And the whole body is in motion. There's always friction. The body has to deal with that friction. And there are loads of different ways it can do that. What's that? What is it? It's not snot. What is it? It's saliva. That's very posh of you. That's exactly what it is. It's saliva. Are there any biology students in the class? What's saliva for?