cc  >> You're trying to tell me  this is Professor Sprott frozen  in this block of ice?  >> Oh, yeah.  >> And you're going to  get him out of this?  >> Oh, yeah.  >> And you know  what you're doing?  >> Oh, sure, I got tons  of directions right here.  >> And you're fairly experienced  at doing this?  >> Oh, sure, I invented  this thing.  >> You have lots of credentials  to prove it?  >> Oh, sure.  Actually, we're almost there.  All I got to do is give it a  good smack.  >> That always takes care of it.  >> All right, so this'll be it.  >> This is it, huh?  >> Safety first. 

 (loud pops)  >> Whoa!  >> Oh, no!  >> What did you do?  >> That was my --  It just exploded.  I'm never gonna get another one.  >> Now what are we going to do?  >> Oh, man, we've got to think.  We definitely, uh, got to  thaw him out real slowly,  'cause otherwise all  his internal organs  are just going to frazzle,  and then he's gonna die.  >> No, that's not any good.  >> Uh, okay, um, oh!  I've got an electric blanket  in the back.  We'll plug it in, throw it  over him, turn it on real low.  A couple hours, no problem.  >> Whoa, wait!  A couple hours?  We don't have a couple of hours.  These people want to see  a show now!  Right?  >> Yeah!  >> All right. 

 I've got somebody else  who can help us.  ET-2, step aboard!  >> Yes, sir.  >> It seems that  Professor Sprott is frozen  in this block of ice here.  Do you have anything  that might help us out?  I have just the thing.  >> Great.  >> A high intensity laser.  >> Ha-ha! Lasers!  >> You can't use that!  >> No, it's fine,  I've got goggles.  >> You're just gonna blow a hole  right in the middle of him.  And you know what?  A frozen Sprott is much better  than a gutless Sprott.  >> Well, you know, he's not  doing much good to us this way. 

 So we're going to try the laser.  All right, ET-2,  go ahead and fire.  You know, folks, in order to  fire the laser, we're going to  need a countdown for this one,  though.  So do it on a three.  >> Three, two, one,  fire!  (electronic sounds)  >> Ah-ha! It worked!  Ladies and gentlemen,  get prepared to irrigate your  mind with the man who will open  the floodgates of information,  present a steady stream of  distilled but undiluted amazing  feats of physics, quench your  thirst for imagination  and drench your imagination.  May I present to you  Professor Clint Sprott!  (applause)  >> Welcome to  the Wonders of Physics.  Now you all know I didn't really  come in on a block of ice,  right?  But I do want to talk to you  today about ice, and more  generally, about water, because  water is a form of ice.  It's ice in the form of a solid.  And I have a little bit of ice  right here, a block of ice.  I'm going to do something a  little unusual with it. 

 I have here a very thin wire,  like you might find on a piano.  And I'm going to drape this over  the block of ice, like so.  And I'm going to hang a very  heavy weight on the bottom.  It's very heavy.  And you may know that when you  put pressure on ice, it causes  it to melt.  That's what happens when you  make a snowball.  You take snow, and you compress  it really hard, some of the snow  melts and then when you release  the pressure, it re-freezes, and  you have a nice snowball that  you can throw.  Well, that's what's happening  here.  The weight is going to pull on  that wire, and it's slowly going  to melt the ice.  And maybe before for the end of  the lecture, it will melt its  way all the way through. 

 And the interesting thing is,  it's going to, I hope, re-freeze  above where it went through.  Now, that of course, is water in  the form of a solid.  Water, normally, is the form of  a liquid.  And here I have a little beaker  with some ordinary water in it.  Do you think I could pull this  cloth out from under the beaker  without spilling it?  You think I could?  Well, let's try.  (laughter)  That's not how you do it, is it?  What am I doing wrong?  What?  Tug it?  Fast?  (audience  yelling out suggestions)  Okay!  (musical flourish)  (applause)  Well, that's right.  You've probably often seen  people do that.  But you may not know that's  because of a principle of  physics called the principle of  inertia.  Inertia is the property of an  object that tends to make it  remain at rest.  So, the water was initially  at rest. 

 When I went to pull out the  cloth, it tended to remain at  rest.  I can illustrate another  property of inertia using water.  Here I have a bucket filled with  water.  Do you think I can turn this  bucket upside down over my head  without spilling the water?  >> Yeah!  >> You think?  (laughter)  That's not how you do it, is it?  How do you do it?  Spin it?  Fast or slow?  >> Fast.  >> Fast.  You're sure, now?  Well, I hope you're right.  (musical flourish)  (applause)  That's right.  That's because of the principle  of inertia, also.  When something is moving, it  tends to continue moving in a  straight line with a constant  speed.  And the water, if I hadn't been  pulling on the handle of the  bucket, would've gone flying off  on a tangent. 

 But because I was pulling on the  handle, I was able to make it go  around in a circle.  So, the inertia of the water is  what kept it from spilling out.  There's another use for water.  Did you know you could use water  as a propellant for a rocket?  Well, I have here a little toy  rocket.  And it's got about that much  water in it.  And up here is air.  What I'm going to do is increase  the air pressure by just pumping  more air into it.  And then I'm going to release it  and the air is going to come out  the back of the rocket and take  some of the water along with it.  Let's see what happens.  (musical flourish)  (applause)  It went all the way across the  room. 

 That's because of a principle of  physics called action and  reaction.  The water going that way was the  action.  That made the rocket go that  way.  That was the reaction.  That's a very important  principle of physics, because  that's how rockets work.  Now, this principle of action  and reaction is one that's  familiar to all of you.  Do you some of you have at home  something that looks like this,  that you maybe use out on your  lawn on a hot day in the summer?  It's a lawn sprinkler.  And if those of you in the front  row will duck, I'll turn on the  water.  And it goes around.  Except there's no water coming  out, because I have it  connected, not to water, but to  compressed air. 

 But the idea is the same.  When the air comes out these  little nozzles around the  outside, that's the action.  And the reaction is the lawn  sprinkler spinning around like  that.  And of course, if water had come  out, you could water your lawn  that way.  So that would be a very useful  gadget that many of you have at  home.  Here's another demonstration of  the same idea.  I have a flask with a little bit  of water in it.  And it also has some nozzles  here.  The nozzles look very much like  the nozzles on the lawn  sprinkler, except in this case,  there's no way for the water to  come out.  However, if I heat the water, I  could cause it to boil, and I  could make steam in here. 

 Then the steam could come out  the nozzles, and it would be  very much like the air coming  out over here.  In order to that, I have to make  the water boil.  The easiest way to do that is to  light a burner underneath the  water that will slowly bring the  water to a boil.  This will take a little while  for it to begin to boil, so  we'll just watch that and then  we'll come back to it in a few  moments after it's boiling.  >> Hey!  >> Oh, my goodness!  Who are you?  >> Excuse me, I'm just passing  through.  >> Oh, I see.  You seem to have a little bit of  a problem here.  What is your problem?  >> You know, I do have a  problem.  I just can't walk straight.  Every time I try to walk  straight, I veer off to the  right. 

 You know, ever since I moved up  here from Argentina.  >> Well, I've never heard of  that.  >> Down there, you know, I used  to veer off to the left.  >> Hmm.  >> My doctor says I have  coriolisitis.  >> I've never heard of that.  But I have heard of the coriolis  effect.  Is that related?  >> Coriolisitis is a  hypersensitivity to the coriolis  effect.  >> I never knew that could  effect people.  But I was about to show a  demonstration of the coriolis  effect. 

 Would you like to see it?  >> Sure.  >> It's right over here.  And what we have is a stream of  water that comes out.  There's a little pump here that  makes a stream of water come  out.  You can see it on the video  there, the stream of water right  there.  It's on a rotating table.  And you can imagine this being  the earth rotating.  And when I rotate it around, and  you view it from a camera that's  rotating with the water, if it  rotates that way, you see the  water curves to the right.  If I rotate it the other way,  the water curves to the left.  That's due to the coriolis  effect. 

 And it's exactly what happens  when the earth rotates.  If the wind blows across the  earth, in the northern  hemisphere, as the earth  rotates, it causes the wind to  veer to the right.  In the southern hemisphere, it  veers to the left.  That's why hurricanes go around  in the direction they do in the  northern and southern  hemispheres.  >> I knew it!  That's why I've been having  trouble.  That's why I can't make my  toilet flush in the other  direction.  (laughter)  It must be this coriolis effect  you're talking about.  I must just have to move to the  southern hemisphere.  >> You know, actually that's a  common misconception.  The coriolis effect is only  strong enough to affect people  who have fictitious diseases  like mine. 

 Normal everyday things like  toilet and bathtubs, you know,  they're not affected by the  coriolis effect.  That's just how your toilet's  designed.  So your only option really is to  buy a new toilet.  Although I do happen to be a  plumber, and my specialty is the  anti-coriolis commode.  (toilet flushes)  (musical flourish)  (applause)  >> Well, you may have heard that  the bathtub drains one way in  the northern hemisphere and  another way in the southern  hemisphere.  It's not true.  The coriolis effect is very  small, unless you're talking  about something very large like  a hurricane.  But look at our little device  going around here just like the  lawn sprinkler.  It's doing so because steam is  coming out of these nozzles.  This is a device that was  invented over 2,000 years ago by  a Greek scientist named Hero. 

 It was so long ago that they  didn't even have last names.  He was Hero of Alexandria, which  is where he lived.  This is one of many inventions  he came up with.  So it illustrates properties of  water and also the physics of  motion.  In particular, action and  reaction, which of course is a  very important principle of  motion.  Another scientist that lived a  long, long time ago, even before  Hero, in fact, was a man named  Archimedes.  He was one of greatest of all  scientists.  And he lived about 200 BC.  And he thought about properties  of water.  He wondered what would happen if  you had something with water in  it, as we have here. 

 We have an aquarium filled right  up to the top.  In fact, I want to be sure it's  all the way to the top.  One way to do that is to put a  little more water in there, till  it just starts to spill over,  and then we stop.  Archimedes thought about the  following question.  If you lower something into the  water, like this block of wood,  how much water spills over?  Well, let's try it.  You see, indeed, some water  spills over the edge.  Well, Archimedes reasoned that  the amount of water that spilled  over is exactly the same as the  volume of the wood that's  beneath the water, right?  Because that's where the water  was before it spilled over.  But you also notice, that when  something is floating in the  water, it's as if something is  holding it up.  Something is pushing upward on  it.  Because if the water weren't  there, the block would just fall  to the floor. 

 And that, we call a buoyant  force.  Archimedes was clever enough to  realize that that upward force  holding up the block is exactly  equal to the weight of the water  that spilled over.  And this is true, whether it's  something floating or something  that sinks.  So imagine we have something  that's more dense than water,  like this cylinder of aluminum.  Now, if we lower this into the  water, again, some of the water  spills over.  And in fact, the amount of water  that spills over is exactly the  same as the volume of the  aluminum.  In this case, there's also an  upward buoyant force, but it is  not large enough to support the  weight of the cylinder.  So eventually, it would just  fall to the bottom if I let go  of it.  However, the upward force on  this is also just equal to the  weight of the water that spills  over.  That's Archimedes principle. 

 And Archimedes discovered that,  or figured it out in a very odd  way.  Archimedes lived in Sicily.  And the king of the city he  lived in, in Syracuse, was  presented with a crown.  They told the king the crown was  made out of gold.  The king was a little suspicious  that maybe it wasn't really  gold.  That maybe the goldsmith had  kept some of the gold, and made  it out of something else that  just looked like gold.  So he knew Archimedes was a  really smart man.  He was 22 years old at the time,  by the way.  And so, the king gave Archimedes  the job of figuring out whether  that crown was really made of  gold.  Well, Archimedes was able to    weigh the crown, and so forth. 

 But he didn't know how much  metal there was in the crown.  Then, one day, he was in his  bathtub.  When he stepped into the  bathtub, he realized some water  spilled over.  And he said, well, the amount of  water must be the same as the  volume of the crown.  So, by lowering the crown into  the water, he would therefore be  able to find out how big the  crown was, and thus from its  weight, he would be able to  figure out whether it was really  gold.  Well, the story has it that  Archimedes was so excited when  he had this idea that he jumped  from his bath and ran through  the streets without bothering  to put his clothes  on apparently,  yelling "Eureka! Eureka!"  which is Greek for "I have  found it, I've discovered it."  So, that's how Archimedes  Principle was discovered.  It turns out that the crown was  not, in fact, made of gold.  And somebody probably got in big  trouble for that.  But it does illustrate  properties of water.  Over here, I have another flask  with some water in it. 

 This is liquid water.  Do you know the temperature  water boils at?  Who knows?  212 what?  Degrees Fahrenheit, or--  Oh, my goodness!  Let's stop and talk about this.  How many of you have been  to Yellowstone Park?  You know in Yellowstone Park  they have things called geysers.  Have you seen those?  This is our artificial geyser.  And it works by the same  principle.  I was about to ask  what temperature water boils at.  And someone said 212 degrees  Fahrenheit.  Or in Celsius?  100 degrees Celsius.  Except, you know,  that's not quite right.  That's right only at atmospheric  pressure, only at sea level. 

 If you live in a place  like Denver, water will boil  at a lower temperature.  And conversely, if you put water  under pressure, it boils  at a higher temperature.  That's what's we're doing here.  We have a long column of water.  So, down at the bottom,  the water is under pressure,  just like if you go down in your  swimming pool, you feel  the pressure of the water,  if you're down deep.  And so, the water is being  heated by these burners.  And it heats up to a temperature  higher than it would normally  take to boil water, because of  the pressure.  But eventually, it begins  to boil, and then pressure  is relieved, and it boils  very vigorously.  And it shoots the steam  and some of the water as well  up into the air.  It comes in contact with  the cool air. 

 It converts back into liquid  water and it runs back down in  here, and the heating  begins again.  This is just what happens in  Yellowstone Park.  There are crevasses that run  deep down into the earth.  Rain water runs into the  crevasses.  The rocks deep under the earth  are very hot, hot enough to  cause the water to boil,  and it shoots the water up.  And when it cools, it collects,  and the heating begins again.  This will go off every few  minutes for the next little  while, until eventually,  I turn it off.  But the same principle is  actually in effect over here.  Because in this case,  I have some water in a flask.  And what I would like to do, is  not increase the pressure, as we  did over there, but I would like  to decrease the pressure. 

 Well, I can't take the flask  to Denver very easily.  But we can reduce the pressure  using a vacuum pump.  So, if I turn on the vacuum  pump, you will see from the  gauge here that the pressure  is coming down near zero.  And you'll see the water  boiling.  It boils very vigorously.  Now, normally, when water boils,  you expect it to be very hot,  right?  But I can assure you,  I can touch this and it doesn't  feel hot at all.  And in fact, it feels  quite cold.  That's rather peculiar, that  water boils by getting colder.  You don't normally think that  would happen.  Now if you look, something even  more interesting has happened. 

 If you look carefully, you will  notice that ice has formed.  And indeed, if I put my hand on  it, it feels quite cold, just  like a glass of ice water.  And indeed, that's what it is.  It's a mixture of ice and water,  and very little gas.  In fact, I can let the air back  in, and we're left with a flask  of mostly ice in it.  Now that's amazing.  We were able to boil water, and  then we were able to freeze it  without any source of heat or  refrigeration.  How did we do that?  To boil water,  does require energy.  Normally, when you boil  something-- like that--  you have to apply heat,  as we're doing down below  with the burner.  Or, you put it on a burner on  your stove and provide the heat. 

 But over here, we weren't  heating it.  But the energy had to come from  somewhere.  The only place it could've come  from was the water itself.  Now, when you add energy to  water, it gets hotter.  When you take energy out of  water, it gets colder.  And that's what happened there.  When we boiled it, the heat, the  energy required to make it boil  came out of the water, lowering  the temperature of the water all  the way down to the point where  it froze.  That's pretty amazing when you  think about it.  But it does illustrate water in  all three forms, solid, liquids  and gas.  Now, another example of boiling  water. 

 Have you ever had a pan on your  stove at home, and you got it  really not without anything in  it?  And then you took a few drops of  water, maybe on your finger, and  you sprinkled them on the pan?  Does it boil?  It doesn't, at least not very  much.  What you notice is little  droplets of water that dance  around on the top of the pan.  Have you ever seen that?  Well, I don't have a pan here.  But I do have a hotplate.  It's been turned on, and it's  nice and warm.  I have here a beaker with a  little bit of water in it.  I have an eye dropper, so I can  make little droplets of water.  I'm going to take some of these  droplets and put them on the  hotplate.  You'll be able to see on the  television monitor.  Those little droplets of water  sort of dance around, and  eventually roll off the side of  the hotplate. 

 Now, why aren't they boiling?  Well, in fact, they are boiling.  But they're boiling very slowly.  And what happens is, the droplet  of water begins to boil, and  that forms a layer of steam.  So, some of the steam is between  the water droplet and the  hotplate.  Now, steam is not a very good  conductor of heat.  So, as a consequence, it  insulates the water droplet from  the hotplate, so the water  droplet doesn't boil, at least  not very rapidly.  It does boil very slowly, but it  takes a long time for that water  to boil, even though the  hotplate is quite hot.  Now, next time you see that,  you'll know why that is  happening.  But you'll also know the name  for it, because this is called  the Leidenfrost Effect.  It's named after a man named  Leidenfrost. 

 But anyway, it is a familiar  idea that involves water in the  form of a liquid and a gas.  Now, water can also move from  one place to another, like  flowing through a pipe.  We actually have here a pipe  with water flowing through it.  The water is flowing in this end  of the pipe, and it's flowing  out that end and down into the  drain over there.  You'll notice this is a peculiar  pipe, because it's small here,  and then it's large, and then  it's small, and then it's large  again, and so forth.  So the pipe keeps changing  its size--  It always hiccups at the end.  I'm going to ask you a question.  When the water flows through the  pipe, do you think it flows  fastest when the pipe is big or  when the pipe is small?  Small?  You think the water flows fast  in the small pipe?  You sure?  Well, in fact that's right.  And an analogy is when you're  driving down the highway, and  it's a nice big four lane  highway, and up ahead there's  some construction and it narrows  down to one lane, where do the  cars move slowly?  It's when they're coming up,  before they arrive at the  construction.  Everything slows down and says,  well, there must be some problem  up ahead. 

 Once you get into that one lane,  then you move nice and fast.  And the reason is the same for  water or for cars.  If you have a lot of water  moving through a big pipe, it    can move rather slowly, but once  it gets to the small pipe, to  get that large amount of water  through, it has to move fast.  So, that's exactly right.  We can actually demonstrate that  with this apparatus, because it  has a bunch of little tubes  sticking up vertically above the  different sections of the pipe.  I'm going to put a little red  dye in each of these tubes, just  so you can see how high the  column of water is going.  And you'll notice a peculiar  thing.  That all of these are not going  to the same height.  What that means is, where these  things are high, that means the  water pressure is large.  And where they're low, that  means the water pressure is  small. 

 What this tells you, then, is  that the pressure is high when  the water is moving slowly, but  the pressure is low when the  water is moving fast.  And that may not be quite so  obvious, but the faster  something moves, the less  pressure it exerts on the walls  of the tube that it's moving  through.  This was something that was  discovered or thought through by  a Swiss scientist named Daniel  Bernoulli, in 1738, he explained  that.  And in his honor, this is called  the Bernoulli Effect.  And it's a very important  phenomenon, because this is one  of the principles in action when  an airplane flies.  When the air moves over the top  of the wings, going very fast,  it reduces the pressure there,  and that gives some lift to the  airplane, much like the buoyant  force--  (fire siren blaring)  >> All right, everyone,  just remain calm.  We're going to get through this  safely and efficiently, okay?  We need to evacuate this room.  So, we'll start right here with  you folks in front.  Go ahead, stand on up.  >> Wait a minute!  What are you doing?  >> I'm rescuing these people,  of course, from the unstable  fire house. 

 >> The what?  >> The unstable fire house.  I heard on the radio, they said  there was a fire house  instability here.  >> No, I've never heard of such  a thing.  But I was about to talk about  something called the fire hose  instability.  >> Fire hose instability?  Why didn't they say so?  >> Well, would you like  to see it?  >> Sure.  >> If somebody had a garden  hose, and you connected it up to  water, you turn on the water  really fast without holding onto  it, what does it do?  That's right, it goes all over,  doesn't it?  And that's what I'm going to  show you.  Here I have a garden hose, well,  it's really just a rubber tube--  >> I knew this place wasn't  safe.  >> Don't pay any attention  to that.  We'll clean that up later.  I'm going to turn the water on  in this rubber tube. 

 And you notice the tube moves  back and forth.  That's not really instability  you're seeing there.  In fact, eventually, it's just  oscillating back and forth, sort  of like a mass on the end of a  string swinging back and forth  like a pendulum.  But if I turn up the air  pressure, in this case, a little  bit, you can see a much more  complicated kind of motion.  And that's called the fire hose  instability.  >> Ah-ha!  I know all about these things.  We have to deal with them every  day.  And I know just what to do to  stabilize it.  If you want to keep this fire  hose down, all you've got to do  is hold on real tight.  There we go, try that. 

 >> Okay.  (turns up air pressure)  >> He's right, that did  stabilize the instability.  >> But that's a pretty wimpy  fire hose.  Do you guys want to see the real  thing?  All right!  Ready?  Oh, no!  I think it's broken.  I better go get this fixed,  or I might get--  fired.  (musical flourish)  (applause)  >> It's true, the fire hose  instability, as you could  imagine, if you ever did that  with one of those big fire  hoses, with no one holding onto  it, it would flail around, and  it could be very dangerous.  It could injure someone.  But that's an example of a  special kind of motion that's  called chaotic motion.  It's moving around in a very  complicated way that never  repeats.  I can show you another example  of chaos here that also uses  water. 

 This water has a little blue  coloring in it, just so you can  see it a little better.  This is one of my favorite  demonstrations, because you can  all do it at home.  Maybe you have a faucet or  something in your bathroom or  your kitchen.  Open it so it drips very slowly.  It's going to drip into a little  pie tin down here that has a  microphone next to it, so you  can hear the drip.  (water dripping)  Can you hear it?  Now you notice this is dripping  in a very regular, repeatable  manner, kind of like a clock  ticking.  But I'm going to turn the drip  rate up a little bit.  Listen to what happens.  Now it's not regular at all.  It's very irregular. 

 Let me turn it down again.  It's regular again.  That's another example of  chaotic motion.  If you do this  at home, I would encourage you  to do the following.  Explore the transition, where it  stops being periodic and becomes  chaotic.  What you should observe is  something called a period  doubling bifurcation.  A big, long word, but what it  means is you should hear  something that sounds like  drip-drip, drip-drip, drip-drip,  drip-drip.  It should repeat every second  drip.  Instead of every drip being just  like the one before it, it's  like the one two before it.  Then if you turn it up a little  more, and it takes a lot of  patience, and it's very hard to  do this, but you can try, you  will hear it repeat every fourth  drip. 

 It'll sound something like  drip-drip-drip-drip,  drip-drip-drip-drip,  drip-drip-drip-drip,  drip-drip-drip-drip.  Then it will repeat every eighth  drip, every 16, every 32nd, and  so forth, until very soon, it is  never repeating.  It takes an infinite time before  it repeats.  That's what we mean by chaos.  Have you ever been to the  jeweler, where they have  something called an ultrasonic  cleaner?  You put your rings and your  bracelets and things in it.  It's a little bath of water, and  usually some kind of detergent.  But here we just have ordinary  water in an ultrasonic cleaner.  When I turn it on, you'll be  able to see on the television  monitor little waves on the  surface of the water.  That illustrates that  something's happening, but it's  not obvious that anything much  is going on.  However, I have here a bottle  with water in it. 

 And it's a special kind of water  called carbonated water.  You're familiar with this.  You've all drunk things like  this, a carbonated beverage.  And it has carbon dioxide  dissolved in the water.  You probably know that if you  shake it and then take the top  off, it fizzes.  Well, I'm going to take the top  off.  I don't know whether this one is  shaken, but you can see that  some of the carbon dioxide is  coming out of solution.  I want to do it slowly enough  that when I take it off, it  doesn't bubble over.  So, we are reducing the  pressure, and some of the carbon  dioxide that was previously  dissolved in the water is now  coming out of solution.  But there's still some carbon  dioxide in there, and you see  some of it is still coming off. 

 What I want to do now is put a  little nozzle on here, just like  you would find on a shampoo  bottle, or something.  It just lets the water come out  rather slowly.  I'll put it in the ultrasonic  cleaner, and then turn it on.  Let's see what happens.  (musical flourish)  (scattered applause)  That's evidence that sound is a  form of wave.  It's just as if I was shaking  the bottle really vigorously,  except I wasn't shaking it, the  sound waves in the ultrasonic  cleaner was shaking it.  That was causing some of the  carbon dioxide to come out of  solution.  So, that's an illustration of  some uses of water to do things  with sound.  Another thing that involves  water is electricity.  Is water a good electrical  conductor?  You think so?  Who thinks not?  Well, you know, we don't have to  just argue about it, we can  actually test it. 

 Here, I have some ordinary  water, ordinary tap water, right  out of the faucet.  And in order to see whether  that's a good electrical  conductor, I'm going to use  something that's quite familiar.  It's a light bulb, a rather big  one.  It's a 200-watt light bulb.  Usually, when you have a light  bulb, you plug it into the wall,  as this one is, and there's a  switch here.  When you turn on the switch, the  light bulb comes on.  We don't have a switch.  We just have two wires.  I'm going to use the water as  the switch.  I'm going to lower this down  into the water. 

 And if the light bulb comes on,  that means the water is an  electrical conductor.  Let's try it.  Did the light bulb come on?  Well, look carefully.  It comes on, but not very bright  at all, right?  The water is conducting some  electricity, but not very much.  I can make it conduct more  electricity if I take some  ordinary table salt, sodium  chloride for you chemists.  If I put a little bit of that in  the water, just a few sprinkles,  and I'll stir it, now you see  the light bulb getting brighter.  The more salt I put, the  brighter it becomes.  So, saltwater actually is quite  a good electrical conductor.  But ordinary tap water is not a  very good electrical conductor.  It does conduct, but not all  that well. 

 By comparison, I have another  beaker over here with the  tiniest amount of sulfuric acid,  so little that I could in fact  safely drink it, but I'm not  going to do that.  I do want to lower this down  into the sulfuric acid and show  you.  So that makes a very good  electrical conductor indeed.  (electronic sounds)  Excuse me, who are you?  >> My name's George.  I come from a planet that's  about 37 light years away.  >> What brings you to Earth?  >> I heard all about Earth  from Buck Rogers,  the 21st century radio show.  >> He hasn't been on the air  for 75 years.  >> Yeah, it took me a long time  to get here.  But the trip wasn't boring at  all, because I had my iPod.  We've had iPod technology  for millennia. 

 >> I see, what brings you  here to Earth, George?  >> My planet ran out of clean  water to drink, so I came here  looking for some water.  >> Hey, is this safe to drink?  >> Well, you know, that water  looks awfully dirty.  I think that has a physical  problem.  I wouldn't drink that.  >> Oh, yeah, okay.  Here, can I drink this?  >> You know, that has kind of a  funny color to it.  That could have some strange  chemical in it that might not be  safe.  >> Hmm, I see that.  Oh, okay, okay.  This doesn't have any particles  or color. 

 I can drink this, right?  >> Well, you know, that water  does look rather clean, but that  could have a biological problem.  That could have microorganisms  in it that could be very  dangerous to you.  >> Huh, well, then how do I know  that the water is safe to drink?  >> You know, there's no way to  know by just looking at the  water.  You actually have to go into the  laboratory.  You have to test for physical  contaminants, chemical  contaminants, and biological  contaminants.  It's not easy to test water.  >> All right.  I've got to get back to my  planet though, because I've got  to tell them to stop drinking  the water out of the--  (toilet flushing)  coriolis commodes.  (applause)  >> Okay, well, it is true that a  lot of water is not very clean  and pure to drink.  But some water is, and  fortunately, we have good water  that we can drink here. 

 But water does conduct  electricity.  And do you know what water is  made out of?  Who knows?  Yeah?  H2O, and what is "H"?  Hydrogen.  And what is "O"?  Oxygen, that's right.  We can separate water into  hydrogen and oxygen.  And we do it using electricity,  the same kind of electricity we  have over here.  Here we have a little U-shaped  tube.  It has in it some water.  It's colored red, so you can see  it a little bit better.  I'm going to connect it back  here to a source of electricity  so that one side of it is  positive and the other side is  negative.  And you can see some bubbles  rising, in fact, on both sides. 

 And what we're doing is making  hydrogen and oxygen right from  the water.  We're separating the water into  the hydrogen and oxygen.  The hydrogen and oxygen, of  course, are gases.  So, they are forming up in this  region up here.  You think this is the hydrogen  or the oxygen?  Oxygen?  Hydrogen?  Well, let's think about it.  Water is H2O.  That means H-2, means there are  two atoms of hydrogen for every  one atom of oxygen.  So the one that is making the  most gas here must be the  hydrogen.  And in fact, if you look  carefully, it's making exactly  twice as much as it's making  oxygen.  Of course, I could just be  kidding you, maybe that's not  hydrogen at all. 

 How could we show that it's  really hydrogen?  Light it on fire?  Oh, my goodness!  (laughter)  Well, you're right, hydrogen  does burn.  I have a little candle here.  I'll light the candle.  And we need to now take some of  the hydrogen and put it over the  candle and see if it burns.  How are we going to do that?  Well, I have a little, tiny  beaker here.  And what if I pour some of the  hydrogen in it, and then walk  over and pour it into the flame.  Would that work?  That wouldn't work?  That's right, because hydrogen  is less dense than air.  You can fill a balloon with it  and it goes up to the ceiling,  so I couldn't really carry it  around in a thing like that.  But here's an idea.  What if I turn this upside down  and put the hydrogen in it. 

 Then it would try to rise, it  would have no where to go.  Then maybe I could carry it over  to the flame.  That would be evidence it's  hydrogen for two reasons.  First of all, because it's less  dense than air.  And secondly, if it burns, that  would be pretty strong evidence,  wouldn't it?  So, as we always do, when we  work with chemicals, I put on my  safety glasses.  I'm going to let some of this  gas out into this little beaker,  upside down, trying not to get  any water in it.  So now we claim I have hydrogen  in here.  Let's see.  (small pop)  Did you see that little puff?  The hydrogen actually ignited.  It was a tiny explosion in  there. 

 Over here, I claim we have  oxygen.  How can we test that?  Burn it?  Well, oxygen doesn't burn.  You need oxygen to make a fire.  In fact, that's what burning is,  you combine things with oxygen  and they burn.  So, oxygen makes things burn  better.  So, if we set something on fire,  like this little popsicle stick,  get it burning, and then if we  put it under the oxygen,  the oxygen should make it burn  even better, right?  Here we've got this burning.  And to make it even more  dramatic, I'm going to blow this  out and then let the oxygen  flow onto it.  (musical flourish)  (loud noise)  Oh, goodness!  Look what happened over here!  This piece of wire went all the  way through the ice.  And look at the ice.  It re-froze behind it. 

 And that's just like as I said  with a snowball, where you make  it melt by putting pressure on  it.  And then you relieve the  pressure and it refreezes.  Okay, now there are other ways  to make energy from water.  Did you know that not all water  is H2O?  One of about every 6,000  molecules of water, instead of  hydrogen, there's something  called deuterium.  That's an isotope of hydrogen.  If you had pure deuterium oxide,  you would call it heavy water,  and people can make that.  But there's an interesting thing  you can do with that little bit  of deuterium.  If you start with a gallon of  water, right out of the lake, or  the river, or the faucet in your  kitchen, and you extract all of  the deuterium, it's about an  eighth of a gram of deuterium.  If it were in the form of a  little ice crystal, it would be  like a grain of sand.  If you put it on the tip of your  finger, you can barely see it. 

 And yet, there's as much energy  in that eighth of a gram of  deuterium as there is in 300  gallons of gasoline.  And it came from one gallon of  water.  The only problem is you have to  burn it at a really high  temperature in something called  a nuclear fusion reactor.  You have to burn it at a  temperature of 100 million  degrees.  That's hard to do.  But some day it will be done,  because we know the stars work  on that principle, and they  work.  So some day, we'll be able to  harness that energy, in a few  decades, perhaps in the lives of  many of you.  There's yet another way we can  make energy from water.  In fact, we do it on a large  scale today.  That's called hydro-electric  power. 

 If you dam up a river, and then  you let the water flow over the  dam, and the falling water turns  a turbine that is then connected  to an electric generator, you  can make electricity.  Well, I can't dam up any rivers  in here, but we do have some  water in that tank way up near  the ceiling.  And we can let it flow downhill,  over this water wheel, make the  water wheel go around.  That's connected to an electric  generator, which will light some  lights up here.  Let's turn on the water.  You see the water wheel go  around.  And you will see the electricity  that we're producing.  If I turn off the water, of  course, the water wheel  continues to turn for a little  while, but eventually it stops  turning, and then the light goes  out.  (scraping sound)  >> I've been at this a long  time.  I've never seen any place  that looked so good  for finding neutrinos. 

 I just know there's a neutrino  here somewhere.  Eh? Ah!  Who are you?  >> Excuse me, who are you?  >> It's a giant, pedantic  penguin.  (laughter)  I'm pleased to meet you.  I'm Swingwell Slugwell,  explorer extraordinaire.  >> What are you doing in my  physics show?  >> I'm doing science.  >> Really?  >> You've heard about neutrinos,  right?  >> Oh, yes, absolutely.  >> They're shy as sub-atomic  particles go.  >> That, they are.  >> They never stop to say hello.  If you ran into one,  you wouldn't know  Oh, where,  oh, where are you,  little neu-trin-o?  Well, all the best neutrino  hunters are in Antarctica. 

 Neutrinos are so shy that the  best place to find them is in  Antarctica.  >> I hear that.  >> So somewhere, amidst the vast  frozen wastes, I will find  the legendary neutrino.  Hold these.  >> Okay.  >> And when I find it,  I'll be famous.  And then, I'll be rich!  I know it's here somewhere.  Is it this way?  You know, I can feel a signal.  It's not.  It's over here. 

 You're not a neutrino.  >> Unh-uh.  (laughter)  >> I can just feel it.  Yes, it's a very strong signal.  It's right here!  Yes!  I have found it!  Excuse me, sir, are you  a neutrino?  >> No!  (laughter)  >> Stop being ridiculous.  That little boy is not  the legendary neutrino.  I ought to know.  I am a neutrino hunter.  >> A neutrino hunter? Oh?  >> That's right.  >> Well, how many neutrinos  have you seen?  >> Today, we have seen  about 646 of them. 

 >> 646?!  Oh, it must be no ordinary  neutrino hunter school  you went to!  >> In fact, one of the top  neutrino hunter trainer programs  is right here in Wisconsin.  >> In Wisconsin?  Well, tell me, how do you find  a neutrino?  >> Well, you have a neutrino  hunter, such as myself,  adventures deep into the frozen  wastelands of Antarctica, and we  dig a mile below the surface of  the Antarctic ice, where we  search for flashes of light, not  with dousing rods, but with  photo sensors, such as these.  And this provides evidence of  the legendary neutrino.  >> I suppose you have to have a  mile-long shovel to dig that  mile-deep hole?  >> It's very much a challenge to  dig that deep.  But we use very hot water, which  is environmentally safe, to dig  that deep below the surface.  >> You dig holes with a mile of  hot water.  I'd like to see the backpack  that you carry your hot water  in.  I think I'll stick to dousing,  thank you very much.  May I have my ski poles?  >> Suit yourself.  >> Thank you. 

 Cancel neutrino alert!  I just know it's got to be here  somewhere.  (musical flourish)  (applause)  >> Well, you know, they do look  for neutrinos under the ice  in Antarctica.  They're very tiny, very elusive  particles, very hard to observe.  I've heard of people using  dousing rods to look for water.  But I've never heard of them  trying to look for neutrinos  with a dousing rod.  It doesn't work for water and it  doesn't work for neutrinos,  either.  I can guarantee you that.  But how would you get to the  south pole?  If you had to get there, you'd  need something like a compass,  wouldn't you?  It turns out, we have a compass  right here.  Here is a compass needle and  it's floating in the water.  Now, you wouldn't normally think  a compass needle would float  because it's made out of iron,  and iron is more dense than  water. 

 Archimedes would've said it  should just sink.  But because water has a special  property called surface tension,  things that are sufficiently  small can in fact float on the  surface of the water, even if  they're more dense than the  water.  That's how you sometimes see  little bugs dancing around on  the surface of the water.  It doesn't work for you, but it  does for things that are  sufficiently small.  And so, you can see it's really  a compass needle.  I have here a magnet.  If I bring this magnet up near  the compass needle, I can make  it move around like that.  So, it's a way to suspend the  compass needle so it is free to  move with very little friction.  And it will eventually swing  around to point to the north, as  it's doing now.  So, there's not a lot of  application of water with  magnetism, but this shows you at  least one way that you could use  water to make a compass. 

 Most compasses aren't made with  water, they're made in other  ways.  But you could do it that way.  I want to move on and talk about  the physics of light.  And one of the things that  relates to water--  (thunder crashing)  >> Professor Sprott!  Professor, I'm glad I found you.  Did you see the rainbow outside?  >> No, I've been in here doing  the physics show all day.  >> I tried to stop her from  interrupting, but she just  insisted on seeing you.  >> There's no time to give a  physics show!  We need you to help us find the  end of the rainbow!  >> I tried explaining to her  that there is no end of the  rainbow, but she just wouldn't  listen.  >> That's because everyone says  there's an end to the rainbow.  You know, with the Leprechauns  and the pots of gold.  >> Maybe I need to explain this. 

 Maybe I have something that can  help.  Let's see.  >> That doesn't look like a  rainbow.  >> No, I don't think that will  work.  Is that a projector I see up  there.  >> Yes, it makes a very bright  light.  >> Let's pretend this projector  is like the sun making a very  bright light.  We have a ball of water here  that's kind of like a raindrop.  Let's see if we can make a  rainbow.  Do you see my rainbow up there?  The rainbow goes below the  curtains there, just like the  rainbow in the sky would go  below the horizon. 

 So we can't see the same thing,  but it's the same shape as the  raindrop.  If I turn the raindrop here, you  can see the rainbow just keeps  going on.  They're the same shape.  >> That's not the most  impressive rainbow I've ever  seen.  Here's a better rainbow.  This is made out of a prism, a  little triangular piece of  glass, with light going through  it.  It separates the lights and all  of the colors of the rainbow.  >> That's much brighter, you're  right.  Are you convinced now?  >> I guess I am.  But I'm going to go back outside  and look at the rainbow again. 

 >> Okay.  (musical flourish)  (applause)  Thank you.  Whoo! Thanks!  If you like the rainbow, and  some of these other physics  demonstrations, you might want  to ask your teacher to invite me  to your school, since I travel  all around the state of  Wisconsin and do physics shows  like this.  You might want to hang onto  this, in case it starts to rain  in here.  >> Okay.  (musical flourish)  (applause)  That was Rachel Lancor.  And indeed, she does travel  around doing a version of this  show in the schools.  And if she hasn't been to your  school, you should ask your  teacher to invite her some time.  I don't think it's going to rain  in here, Peter, maybe you can  take this.  Oh, my goodness!  >> Ah-ha!  That's the pot of gold!  (laughter)  I'll take that. 

 (musical flourish)  (applause)  >> Well, there goes the budget  for our show next year.  Anyway, we're talking about  light and water.  And another thing we can  talk about involves--  We can use this aquarium over  here to demonstrate something  that you've probably all seen  before.  Have you ever taken a stick like  this, which is nice and  straight, and put it down under  the water?  And have you noticed that it  looks like the stick bends?  You've seen that, right?  Let's try it with this aquarium.  You have to look down from  above, or just look on the  television monitor there.  And you see it looks like it  bends, doesn't it?  And why does it do that?  Well, that's because of a  special property of water.  It's called refraction.  Do you know that light travels  only about three-quarters as  fast in water as it does in air?  It travels a little bit slower.  And so, the light coming from  underneath the water took longer  to get here, because it was  traveling more slowly.  That made it look like this was  bent. 

 And that's an important effect  that you're all familiar with  called refraction.  There are other things I could  show you that are related to  this.  Have you ever seen water go  around a bend?  Sorry, light go around a bend?  Well, I can actually do that  using a device over here.  This is a very powerful laser.  And you'll see that the laser  beam.  Oops, get the fireman out of the  way here.  The laser beam is going across  the room and is striking that  piece of paper that Mr. Weix  is holding up over there.  This laser is going through a  tank of water here.  It's going through a window on  one side, and it's coming out a  window on the other side.  What I'm going to do is open the  little trap door here, and let  the water stream out. 

 And the laser beam will be  trapped inside the stream of  water, and it will reflect off  of the interface between the  water and the air.  And the light will stay trapped  inside the stream of water.  So let's try that.  And we have a trough down there  to catch the water.  (musical flourish)  (applause)  That's a very important effect.  It's called total internal  reflection.  It's something called a light  guide, because it's guiding the  light.  And you can do the same thing  with fine threads of glass, with  something called fiber optics.  That's a very important  technology some day.  I want to show you something  else you can do with a laser  that may surprise some of you. 

 I have here two Styrofoam cups.  They're empty, nothing in them.  But what I'm going to do is put  just a little bit of water in  the two cups.  First, a little bit of water in  this, about a tablespoonful, and  then the same amount of water in  this one, about that much.  And then, I'm going to take this  one and I'm going to put it in  the laser beam, if I can find  it, right here.  You see the laser beam hitting  it.  And I'll just let the laser  shine on it for a moment.  Then I'm going to take the two  cups.  And this one, of course, is not  in the laser beam.  It still has water in it. 

 This one, on the other hand--  (musical flourish)  No water at all.  Now, how many of you knew  a laser would do that?  A few people, but not very many.  That's good, because a laser  can't do that.  This one had a sponge  in the bottom.  (laughter)  Well, it's a trick.  But there is a point to this.  There's a point to this.  When you do an experiment,  it is important to have a  control.  One was in the laser beam, one  was not.  But it's important when you have  a control, that there is only  one difference, the laser beam. 

 If one had a sponge, and one  didn't, maybe it had nothing to  do with the laser beam.  And that was the case here.  So, it's a lesson of how you do  proper experiments, and how you  really test to be sure that you  don't fool yourself into  thinking that a laser will do  something that in fact it will  not do at all.  Let me show you one other  demonstration here that involves  light.  Here I have a beaker of water  back here.  And up here in front, there's a  candle.  I'm going to light the candle.  Then we'll turn some of the  lights down.  I'm going to rotate this around.  Does it look to you as if that  candle is burning underneath the  water?  Well, in fact, it's not. 

 You can't burn a candle  underneath the water.  But what you're seeing is the  reflection of the candle off of  this plate of glass right here.  You know, you can see your  reflection in a plate of glass.  It doesn't need to be a mirror.  Some of the light is reflected  off of the surface.  And when you look at yourself in  a mirror, it looks like there's  someone behind the mirror that  looks just like you, that's  looking at you.  But there's really not, of    course.  And so, what you think you see  as the candle back here, when in  fact, the candle is there, in  front of the mirror.  And of course, you're seeing the  water through the glass right  here.  This is the kind of thing that  magicians like to often do in  order to trick you into thinking  you're seeing something that in  fact you're not. 

 You've heard the expression,  "smoke and mirrors"?  Well, this is  a kind of a mirror.  The last thing I want to show  you that involves water,  involves a special kind of water  that you're all familiar with.  Snow.  Snow is a form of water, in the  form of a solid.  It's not quite like ice.  It's little tiny crystals that  we call snowflakes.  I want to show you some  photographs of snowflakes that I  found on the web.  These are actual photographs  taken by Professor Kenneth  Libbrecht, who's at the  California Institute of  Technology.  He's very famous for taking  pictures like this.  Have you heard that no two  snowflakes are alike?  Well, you know, nobody knows for  sure, because no one has looked  at all of them. 

 But Professor Libbrecht points  out that probably no two grains  of sand are alike, either, but  nobody ever talks about that.  But it certainly is true that  there are lots and lots of  different shapes that snowflakes  can take.  I wanted to show you a few of  the snowflakes that Professor  Libbrecht has photographed.  You may notice that many of  these snowflakes have a  particular property of having  six sides.  They are so-called hexagons.  And that is one of the forms  that ice crystals prefer to  take.  So, even within the  six-sidedness, though, you see  an enormous variety of shapes  from these snowflakes.  So, the last thing I want to do  for you involves another example  of water.  Traditionally, we always  completed these shows by making  a cloud.  Nothing could be more relevant,  because a cloud is water. 

 Did you know that?  A cloud is very, very tiny  droplets of liquid water.  And how do you make a cloud?  Well, how nature does it, you  cool the air.  And air, normally, has some  water vapor in it, water in the  form of a gas.  And when you cool air with water  vapor in it, some of the water  condenses into tiny droplets of  liquid water.  If the droplets are too big,  they fall as rain.  But if they're very tiny, they  stay suspended in the air in the  form of a cloud.  So how do we cool the air?  Well, we use liquid nitrogen.  Liquid nitrogen is very cold  stuff.  It's at a temperature  of about 321 degrees  below zero Fahrenheit,  or 196 below zero Celsius.  Or a mere 77 degrees above the  absolute coldest anything can  be. 

 And we have a large tank of  liquid nitrogen here.  What we do is force nitrogen gas  into the tank.  That forces some of the liquid  up into this pipe, where the  liquid vaporizes and forms  nitrogen gas.  It's still very cold, however.  The nitrogen gas, and some  liquid as well, fill the room  here, cooling the air, and  making the moisture in the air  condense, the vapor in the air  condense into the tiny droplets  of liquid that we call a cloud.  So, with that,  I will put on my hat,  and I will thank you all  for coming.  § §  (applause)