cc  >> Since this is our 25th  Anniversary, this gives us a  chance to reflect back on our  past achievements.  So I've prepared a slide show of  our favorite moments of previous  shows and synched it to Brahm's  Lullaby.  I'm sure you're going to enjoy  it.  >> Wait, wait, Peter!  No, stop that!  They don't want to see a slide  show.  They came to have fun.  >> Rachel, what are you doing up  here?  You're supposed to be back stage  working.  >> I knew that you wanted to  celebrate the 25th Anniversary,  so I built something special.  >> An outhouse?  >> It's not an outhouse, it's a  Type 40-TT Tardis, you know,  a time machine.  >> Ah, a time machine.  You know, we could set the time  machine to 1984, to the very  first Wonders of Physics show. 

 >> Exactly.  And we can yoink out the  original Professor Sprott, and  bring him back here to do the  show today.  >> Yeah.  >> So, what do you guys think?  Do you want to use the time  machine, or do you want to see  the slide show?  >> Time machine!  >> All right, time machine.  All right, show me how this  thing works.  >> Sure, all you have to do, is  you turn this knob here and then  you push that button.  >> Okay.  >> You operate it, and we'll do  a countdown.  All right, ready?  Five, four, three, two, one.  (whooshing sound)  >> I'd like to thank you for  coming to the 25th Anniversary  of the Wonders of Physics. 

 We hope you'll all come back  next year for our 26th  Anniversary.  >> Wait a minute!  What do you mean come back?  You know, we must have gone  forward 60 minutes instead of  going backwards.  Rachel?  This is not working.  Get back here.  (laughter)  Well, Rachel built this time  machine off of plans on the  Internet.  We tried to go back to 1984  to bring you back  from the very first show.  But before we start today, you  need a proper introduction,  so quick, behind the curtain  over here.  Right there, and just cover up  real quick.  There you go.  (laughter)  All right, ladies and gentlemen,  may I present to you the King  the Clocks, the Master of the  metronome, the Wizard of the  Watch, and that Traveler in  Time, Professor Clint Sprott!  (applause)  >> Welcome to the Wonders of  Physics. 

 I would like to take you back in  time today to visit some of the  demonstrations that we've had  over the past 25 years in the  Wonders of Physics.  I'd like to begin with some  demonstrations of motion.  A ball, if I drop it, it falls  toward the Earth.  And you know that happens  because of the Earth's gravity.  But what I'd like to do is step  up on the lecture bench with  this ball in one hand.  In the other hand, I have a ball  of cotton.  I'm going to drop the two side  by side.  Who thinks the ball of cotton  will hit the ground first?  Who thinks the ball will hit the  ground first?  Who thinks they will hit the  ground at exactly the same time?  You know, that's fine in  physics, to have different  opinions, but we don't just  vote.  We do the experiment.  So let's try it. 

 You probably noticed that the  ball did hit the ground a little  bit before the cotton, but not  for the reason that you might  suspect.  Not because the ball is heavier  than the cotton, but because of  the air resistance.  The air affected the motion of  the cotton more than it did the  motion of the ball.  I can illustrate that by doing  the same experiment inside this  tube.  Can you see what's in there?  What? Fuzzy, that's right.  It's a ball of cotton and...?  A penny, that's right.  Anything else in here?  >> Air.  >> Air, that's right.  So let's try this experiment  once more, inside this tube.  You can see how slowly the  cotton falls this time. 

 The penny, of course, falls  right away.  The reason we do it in this tube  is so that we can remove the  air.  And for that purpose, we use  this vacuum pump over here.  I'll connect the hose here.  Mr. Weix will turn on the vacuum  pump.  And you will see the pressure  coming down toward zero.  When it gets down to zero, we  will have removed all the air  from the tube.  Well, it would take forever to  get the last little bit of air  out.  Fortunately, we don't need to do  that.  At this point, I can close this  valve. 

 We don't need the vacuum pump  anymore.  We can take this off.  Now we have a tube with what in  it?  A penny, a ball of cotton.  Anything else?  There's a little bit of air in  there.  We call it a partial vacuum.  Now let's see what happens when  I invert it.  You see how much faster  the cotton falls.  To show you there are no tricks,  I can let the air in, and do it  one last time.  That's shows you that in the  absence of air resistance, all  objects fall at the same rate.  It doesn't matter how heavy they  are. 

 It doesn't matter what color  they are.  It doesn't matter what they're  made out of.  None of that matters.  Objects fall at the same rate,  if they're acted upon only by  gravity.  I want to show you another  a demonstration that involves  motion.  Here I have a little can.  I'm just going to roll the can  across the lecture bench to see  if the bench is level.  Well, I thought for sure we  leveled the bench before the  lecture.  Let's try it the other way.  That's a little odd, isn't it?  It looks like magic. 

 But in fact, it's not magic,  it's a principle of physics.  Inside this can is a spring and  a weight.  And when the can rolls, it winds  up the spring.  This is an illustration of the  conservation of energy.  When the can starts, it has  so-called kinetic energy, energy  of motion.  Then as it slows down, that  kinetic energy is converted into  potential energy of the wound up  spring.  And then the spring unwinds,  releasing the potential energy  and causing the can to move  again.  So that's an illustration of one  of the most important principles  in all of physics, the  conservation of energy.  Now, I'll show you another  demonstration.  Do some of you have a yo-yo, you  know those things on the end of  a string?  You've seen those. 

 Well, here is our very large  yo-yo.  I'm not going to use it as a  yo-yo.  I'm going to set it on the  lecture bench, and I'm going to  pull on the string.  I want to ask you a question.  When I pull on the string, do  you think the spool will roll  toward me, or away?  Who thinks toward?  Okay, who thinks away?  Most of you think the spool will  roll away from me when I pull  the string.  Let's try it.  You were wrong, weren't you?  But let's see.  In fact, I can make it move  toward me, or I can make it move  away from me.  Can you see what I'm doing  differently in the two cases?  I'm moving my hand, aren't I?  When I want it to come toward  me, I hold my hand down low,  like this, so there's a small  angle here.  It comes toward me. 

 When I want it to go away, I  hold it up like that, and it  makes a large angle.  That suggests that there must be  an angle in between somewhere  where it doesn't roll toward me  and it doesn't roll away from  me.  Let's see if we can find that  angle and see what happens.  Right about there, if I pull, it  just slides across the table  without rolling either  direction.  And of course, this is one of  the principles of physics that  goes back 300 years, to the time  of Isaac Newton, who is a famous  physicist who gave us the laws  of motion.  I want to show you another  example here of something that  moves.  Here I have a chain, a metal  chain.  If it were a little bit larger,  I would be able to put it over  the top of my head and I could  wear it like a necklace.  Well, I don't want to do that,  but I do want to put it on this  wooden spool back here that's  connected to an electric motor.  I'm going to turn on the motor  and let the chain begin to  rotate very rapidly. 

 At first, it slips, but then due  to the friction, it stops  slipping.  Then I'm going to take a stick  and I'm going to nudge the chain  off the wooden spool, and we'll  see what happens.  (audience reacts)  (musical flourish)  (applause)  >> Professor Sprott!  Professor Sprott!  I've got this sonic screwdriver.  I think it will help fix  the time machine.  >> Okay, let's try it.  (electronic beeps)  >> I think it will work now.  You keep that, just in case.  >> Okay.  Professor Sprott, you know,  I really would like to try  the time machine one more time.  >> Okay, let's see if it works. 

 (whooshing sound)  Excuse me, who are you?  >> Newton!  Isaac Newton!  Sir Isaac Newton!  From England.  >> I see that.  Are you injured?  >> Yes.  I was just coming on the street,  and this fell on my head.  (laughter)  Where am I?  >> You're at the University  of Wisconsin, and this is the  Wonders of Physics.  >> Physics?  I know all of physics.  I know all of physics.  What is this?  >> These are some of our  demonstrations.  Would you like to see one of  these demonstrations?  >> Yes, yes, yes.  The apple. 

 Rotten apple!  >> No, that's no apple.  It is a very heavy steel ball.  It weighs about five pounds.  It's suspended from above  by a string.  And down below, there are two  identical strings.  What I'm going to do is pull  down on this string.  And I'm going to pull hard  enough that one of the strings  will break.  Who thinks this string  will break when I pull?  Who thinks this string  will break?  >> I know!  I know everything!  I'm Newton!  This string will break.  >> Well, let's try it.  We don't just argue in physics,  we do the experiment. 

 >> Ah-- Oh...!  (laughter)  >> So, Sir Isaac was wrong  about that.  But you know, in physics, we  don't like to draw a conclusion  based on a single observation.  We always like to repeat  our experiments.  So, let's do it again with a  second string, and see  what happens.  (loud clunk as ball hits floor)  (laughter)  (musical flourish)  >> Brilliant, brilliant!  >> That time,  the upper string broke.  Could you see what I did  differently in the two cases?  In one case,  I gave it a quick jerk.  In the other case,  I pulled very slowly.  It was the inertia of the ball  that made that happen.  >> Inertia!  That's what I've been looking  for, inertia!  And gravity!  I must get back!  I must write a book!  Inertia and gravity!  Inertia and gravity.  A little memento. 

 Plant it and leave a tree.  Inertia.  Inertia and gravity.  Inertia and gravity.  What was your name?  >> I'm Professor Sprott.  >> I will dedicate my book  to you, sir.  Inertia and gravity.  Inertia and grav--  What was your name?  >> Sprott.  Please spell it right.  >> Two "T"s?  Thank you. 

 Inertia and gravity.  Must get back.  Inertia and gravity.  (musical flourish)  (applause)  >> I'm not really sure  about this time machine stuff.  That looked an awful lot like  Professor George Rowlands  from the University of Roark.  He's been with us in the past,  helping out with these shows.  So it may be that someone's  playing a trick on me.  Anyway, where were we?  >> Professor Sprott,  I don't think that the  sonic screwdriver worked.  I'm going to get a repairman.  I'm just going to give him  a call. 

 >> Okay, but please hurry along.  (telephone rings)  >> You called?  >> My goodness!  It's David Willey,  the Mad Scientist from  the Tonight Show with Jay Leno!  (applause)  >> And you're Professor Sprott.  Pleased to meet you.  >> What are you doing here?  >> I'm the repairman.  Yeah, Leno doesn't really pay  that well.  I have to moonlight.  So, what appears to be the  problem?  >> Well, Rachel built this time  machine from your plans off the  Internet.  >> Okay.  >> And we were trying to bring  Professor Sprott from 1984, but  it doesn't seem to be working  very well.  >> Oh, maybe I can fix it  for you, and-- Ooh!  Ooh, you've got some of my  favorite toys here. 

 I do shows like this.  I'll tell you what.  I'll fix your time machine  if you let me play with some  of your toys for a while.  >> Sure.  >> Is that okay with you?  >> Yeah.  >> Is that okay with you folks?  >> Yeah!  (applause)  >> Okay, boy, you've got some  nice stuff here for me.  Oh, balloons, I like these.  These are great.  What I've got here, yeah, liquid  nitrogen.  This stuff looks like water, but  it's not. 

 It's 200 degrees below the  freezing point of water.  This is air.  And look what happens to things  if you get them cold.  They shrink.  I just wanted to show you that  as a quick intro.  If you'd blow on that for me,  it'll blow right back up again.  I use this stuff in my shows a  lot.  I started doing physics shows  after being inspired by this  gentleman here.  And sometimes when I do shows, I  use this liquid nitrogen.  And afterwards, somebody will  come up and say to me, that's  really cool stuff. 

 And I tell them, no, actually,  it's very, very cold.  It's not just cool!  (laughter)  And they're, no, I don't mean  that, I mean it's really neat.  I want to take some to school  for show and tell.  Where do you buy it, and can I  get some?  I'll say, well, I tell them  where to buy it, and yeah, you  can get some, but to get some,  you've got to have a special  dewar to put it in.  And they say, no, I haven't got  a special dewar.  But how much can they cost?  I'll buy one.  I tell them, well, this little  dewar here, just this little one  is probably $200.  Oh, no, I can't do that.  That's way too expensive.  I'll just go down to where you  get this gas and I'll have them  put some in a Pepsi bottle for  me. 

 And I have to tell them that  only an idiot would put liquid  nitrogen in a Pepsi bottle!  (laughter)  No, it's okay, this is  a Mountain Dew bottle.  (laughter)  Actually, of course, that's not  the silly thing, is it?  What's the really silly thing?  Putting the top on,  especially if you put it on  really hard.  See, 'cause what's gonna happen  is when the liquid in this  bottle tries to turn back into a  gas, the molecules are going to  get to be ten times further  apart.  Now, that's ten times this way,  ten times this way, ten times  this way.  A thousand times the volume.  I put about a cup of liquid  nitrogen in there.  It's going to turn into a  thousand cups of gas.  I don't think a thousand cups of  gas will fit in that Mountain  Dew bottle.  So, we'll come back in a minute  and we'll see why it is you  should never, ever put liquid  nitrogen in a sealed container.  Now, while we wait for that, I  need a young lady to help me  with a demo. 

 Oh, a hand shot up immediately.  Gotta love enthusiasm.  Hi, what's your name?  >> Erin.  >> Hi, Erin, I'm David.  I'm very pleased to meet you.  If you're okay with it, we are  going to have a race.  We're going to see who can empty  a bottle of water the fastest.  This is water, it's just got  food coloring in it.  Which would you like.  You want the green one?  Okay. 

 On the count of three, start  drinking!  One...  (laughter)  Two...  Three...  You're not going to do it,  are you?  >> No.  >> You are a very sensible  young woman for not doing it.  I'll tell you what.  What we'll do is this.  We'll just have a race here.  We'll see who can empty their  bottle the fastest, but just by  emptying them into here, okay?  But I'm going to win.  There's a really good scientific  principle as to why I am going  to win. 

 I'm going to cheat.  (laughter)  Yeah, all you're allowed to do  is take your bottle, turn it  upside down and hold it upside  down very, very still.  Can you do that for me?  You promise?  You can start.  She turns it upside down.  I do mine, but I cheat.  I put a swirl on mine.  Even though she started first,  every time, I finish first.  (musical flourish)  (applause)  These people will give you  a nice big hand.  Thank you very much for helping.  Now, the question is, of course,  why did I know I was going to  win?  I said I cheated, but really  there is a good scientific  principle as to why I won. 

 See, what was happening with  your bottle was that air was  trying to get up into the  bottle.  That's light stuff trying to get  up.  Heavy stuff, water, was trying  to get down out of the bottle.  They got in each other's way.  And they made the water in the  neck of the bottle gurgle.  What I did was I put a spin on  my bottle, and that made the  heavy stuff move toward the  outside.  That let the light stuff move up  the inside.  Now, I see you're wondering why  I've got charcoal lighter fluid  in my hands.  I'm going to put some on this  piece of paper here and set fire  to it.  It turns out that a flame does  very much the same as the air in  your bottle did. 

 See, there's light stuff trying  to get up.  That's the flame.  There's heavy stuff trying to  get down.  That's the cold air.  They're getting in each other's  way.  We don't say a flame gurgles.  We say what?  It flickers.  But you can see, it's not a very  high flame.  But what did we do with my  bottle?  We put a spin on it.  That made the heavy stuff go to  the outside, and the light stuff  was able to get up the inside. 

 Let's see if we can get the  light stuff up the inside.  Sure enough, we can.  We get ourselves a wonderful  little tornado of fire.  Now, wait a minute.  For the knowledgeable--  southern hemisphere.  (laughter)  And of course it works--  (loud pop)  >> Whoo!  (applause)  >> Yeah!  Yes, yes, yes!  That is why you should never put  liquid nitrogen in a sealed  container!  Now, I'm guessing I should  probably put that flame out  before it gets to the smoke  detector.  Notice I didn't try to blow it  out.  I couldn't have done that.  I put a cover on it.  For something to burn, it needs  three things. 

 You need fuel.  You need heat.  What else do you need?  Some people said air.  Some people said oxygen.  You're both right, because of  course, it's the oxygen in the  air that things need to burn.  Oxygen is basically about the  other 20% of the air, after the  80% nitrogen.  There's a few other things, but  not that many.  Now, let me show you something  else where we need air to burn.  A friend of mine worked last  summer for NASA.  He came to my house one day and  said, Dave, I've got this great  demo I want to show you. 

 It's how they demonstrate rocket  engines at Space Camp.  He says, you need a five-gallon  bottle to act as the rocket  engine.  Well, I've got one of those.  You need some ethyl alcohol to  act as the fuel.  I've got that.  You need a source of ignition.  So, the first thing you've got  to do, is you've got to mix the  fuel with the air.  Fuel doesn't burn unless it's  mixed with air.  So, let me pop this over here.  And I'll be the equivalent of  what, not in a rocket, but in  your car,  a carburetor, or  a fuel injection system, right?  Basically, I'm mixing the fuel  with the air. 

 Now, I can't send the rocket  upward, because I'm not sure  where it's going to land.  (laughter)  And sending it sideways isn't  such a great idea either.  So, I'm going to have to try to  get this to go downward.  But we'll still see a rocket  effect, I hope.  Maybe we can just dim the lights  a little and see if this works  as a rocket.  (loud whooshing sound)  Sure enough, it does.  They call that a whoosh bottle!  Now, we had a young lady help me  a little while ago, I think it's  only fair if we have a young man  help me with another demo.  I need a volunteer.  You're going to volunteer?  Come on up here.  What's your name?  Hi, I'm Dave. 

 Pleased to meet you.  You ever play with bubbles, blow  little soap bubbles?  Yeah?  When I was a hippie,  honest, I was once.  We used to play with soap  bubbles a lot.  I got to the stage  where I wanted to blow really  big bubbles.  I figured out how to do it.  I'm going to make a bubble big  enough that we can put you  inside it, okay?  Come on over here.  You step right up on here.  I'll hold it still.  That's it.  Up on top. 

 Turn and face this lovely  audience.  There we are.  Keep your hands in your pockets.  Let's see if we can put him  inside the bubble.  And sure enough, yes we can.  We can put you inside a really  big bubble.  Now, if mom's out in the  audience, don't worry, this is  just soap detergent, dish  detergent.  Grab my hand, because it's going  to be slippery.  Don't slip.  Great. 

 Give this man a hand.  (musical flourish)  (applause)  Thank you!  Oh, I love doing this stuff.  We've got a classic here.  Remember when we poured the  liquid nitrogen on the balloon,  and how it shrunk?  When things get cold they  shrink?  Well, when things get hot,  they expand.  I'm going to expand the air in  this bottle in a minute.  I'm going to do it to do a  classic demo for you.  Getting air pressure to push an  egg into a bottle.  Now, you see this egg doesn't in  any way fit in this bottle right  now.  But if I take a piece of paper.  Let's use this piece of paper. 

 Set it on fire.  If I put this in the bottle,  it'll make the air in the bottle  expand.  And then--  Whoops, get in there.  If I put the egg on top.  (small pop)  Sure enough, it pops right  into the bottle.  Now, as I said, I do demos like  this in my own shows.  And sometimes after shows,  people will come up and talk to  me.  One time, this one lady comes up  to me and she says, David, that  was a good show, thank you.  Thank you very much.  She says, I wanted to ask you  something. 

 Why do you do this?  Is it the big money that they  pay you as a teacher?  We must have some teachers in  the audience, 'cause you're  laughing.  You know that it's not the big  money they pay you that makes me  do this.  This look comes over this lady's  face.  She says to me, it's not the  money, ah, you do it for the  children, aw.  No!  I do it for the toys!  That's what I do it for.  These people here have made me  one of my favorite toys, a bed  of nails.  Bed of nails.  A bed of nails, ladies.  Are they sharp?  Yeah, they're sharp.  It's not the best bed of nails  they make here. 

 This!  This is the best bed of nails!  This is big enough to lie on!  Now, on the subject of lying on  beds of nails, a serious piece  of advice to you.  Never ever,  lie on a bed of nail.  (laughter)  Yeah, think about it  for a minute.  Never ever lie on a bed  of nail.  Always, lots and lots of nails.  In a minute, we'll get a  volunteer, and we're going to  lie on this bed of nails for us.  Now, I want to show you first,  though, before we even do that,  that these nails really are  sharp.  A cabbage here.  Imagine it's some part of my  anatomy.  (laughter)  Well, the head, actually. 

 Let's see if the nails  are sharp.  Oh, yeah.  In fact, probably sharp enough  that, yep, I can even pick that  up.  Now, if I pull quick.  I think you would not want that  happening to your shirt or  blouse if you were inside it,  right?  But we are going to lie a  volunteer on this bed of nails.  We have to take some  precautions.  The demo I'm going to do is to  show you why it is you want the  front of your car to crumple up  if you're in a head-on accident.  Back in the '40s and '50s, they  used to think that if they made  the cars really strong, then  they wouldn't hardly even dent  in an accident, and that would  keep them safe.  And it did, the cars.  It didn't keep the people inside  safe. 

 So these days, what we do is we  build cars so that if you're in  an accident, the front of your  car will crumple up.  And that crumpling up takes all  the energy of the collision, and  it makes the people inside the  car a lot safer.  We're not going to crash cars,  but we are going to crumple  something up.  This concrete block.  I'm going to put a target on top  of this, because in a second,  we're going to get a volunteer  to lie on that bed of nails.  We're going to put this bed of  of nails, nails down on top of  their chest.  We're going to put the concrete  block on top, and then I'm going  to smash it with a sledge  hammer.  (laughter)  Now don't worry, I've done this  before.  And it's hurt me.  The first time I did this demo,  I knew that I needed goggles,  because I knew that if little  bits of concrete came off and  hit me in the eye, it would hurt  a lot. 

 So I put goggles on.  None of the concrete came toward  my eyes, but a piece the size of  a golf ball came and hit me in  the nose.  (laughter)  Oh, that hurt.  So these days, we have more  protection for our volunteer.  Now, I can't get a volunteer  from the audience, because as I  said, this is a little  dangerous.  So we need a volunteer from  somebody up on stage!  >> Peter, I have a job for you.  >> This is what personal  assistants are for.  All right, Peter, let's do this.  But we're going to give him all  the protection he needs.  You've got goggles. 

 You've got goggles.  Good.  I've got these.  Next time I did it, I decided I  needed a face mask.  No pieces of concrete hitting me  in the nose this time.  They didn't.  They hit me in the elbow!  So now we have elbow protectors.  Another time, a piece came off  and took one of my knuckles off.  It was not that bad, but we now  wear gloves.  So with all of that in place, I  decided now is the time to get  this on video. 

 I was feeling so smug, so  confident everything was going  to go fine.  I had a video crew.  They came in, filmed it.  I'm not going to get hurt.  Yes, I did.  So now, we figured it all out.  This man's going to be safe,  because we're going to take all  of the precautions we need to  this time.  So, let's see if we can lie you  down on that bed of nails, huh?  If you do this at home,  do not sit down fast!  (laughter)  I have a pillow for your head.  Otherwise, what I get is little  dots all over mine.  Small children come up and join  them together. 

 But let's get on with this,  because that bed of nails is not  as comfortable as the Motel 6  bed.  So, bed of nails, concrete  block.  And if I may, a very vital piece  of equipment.  A piece I forgot.  (laughter)  Oh, yeah, we have a video of me  crumpling like a cheap card  table.  (laughter)  All right, three, two, one.  (musical flourish)  Smashed the top right off it.  Look at that beautiful break.  You okay under that, Peter?  Great.  All right, let's get this man  back up again. 

 (musical flourish)  (applause)  This is so much fun.  I love doing this.  What's next?  Let's see, we've got to move the  bed of nails out of the way.  (telephone rings)  Oh, no.  I know that ring.  That's Leno.  He's got a time machine, too.  His doesn't seem to be working  any better than yours.  I've got to go and fix his.  He's my boss, so. 

 >> What about our time machine?  >> Ooh, let's have a look.  You know, I think all you need  is more power.  >> More power?  >> Yeah, you've got a million  volt Tesla coil right there?  >> Yeah.  >> Hook it up to the time  machine.  That'll get it going.  >> All right.  >> But I've got to go, folks.  Thank you very much,  and thank you.  (musical flourish)  (applause)  >> Well, we have used this  million volt Tesla coil in  almost every one of our 201  shows over the years, but I've  never thought of using it to  energize a time machine.  >> Let's see if we can get back  to our first show, and bring you  back. 

 >> All right, let's try.  (whooshing  and electrical buzzing)  >> Hold on a sec, Jake, I've got  to go grab a wrench.  I'll be right back--  (laughter)  >> Excuse me, who are you?  >> I'm Clint Sprott.  >> You're not Clint Sprott.  I'm Clint Sprott.  >> You can't be Clint Sprott.  I'm obviously the handsome devil  Clint Sprott.  (laughter)  >> You are pretty handsome,  but what is this thing?  >> This is a ham radio that I've  been working on in the garage.  And if you're really Clint  Sprott, then maybe you can show  me how to fix it.  >> Hmm, that does look like  something I built about 40 years  ago. 

 You know, I think if you turn  the zener diode around, the  capacitor will charge just fine,  and it will work.  >> Really?  But how would you know?  Ah, never mind.  >> You know, I think it would do  you some good if you were to  stay around for a little while.  You might learn some physics  that would be useful to you  later in life.  >> Well, I'd love to, but I'm  due at Ham Fest in half an hour,  so I best be off.  (musical flourish)  (applause)  >> It is true.  When I was about that age, I  used to build electronics.  I was a ham radio operator.  In fact, that's how I got  interested in physics.  That's a good way for you to get  interested in science, by  building things and trying to  understand how things work. 

 But you know, with ham radios,  we use them to talk to people  around the world.  So let's talk a little bit about  the physics of sound.  One thing you're all familiar  with, probably, is if you go out  on the side of a road, and when  car is going by at a high speed,  honking its horn,  you hear something like--  (imitates loud horn fading)  You've all heard that, right?  It happens not just with cars,  but with trains.  (train whistle blowing)  And that's something called the  Doppler effect.  When the source of sound is  moving toward you, it's a high  pitch.  When it's moving away from you,  it's a low pitch.  I can actually illustrate that  with this little gadget right  here.  This is a whistle on the end of  an arm, that's connected to a  motor.  What I'm going to do is turn it  on and let the motor spin  around.  The whistle will at some times  be coming toward you and at  other times away from you. 

 Can you hear that funny sound?  (oscillating whistle sound)  That's right, that's the Doppler  effect.  When it's coming toward you,  it's a high pitch.  When it's going away from you,  it's a low pitch.  I have another demonstration of  the same thing.  Here's a little Styrofoam ball.  Inside, there's a source of  sound.  I'll turn it on.  (high pitched tone)  You all hear the sound?  Now, what I have to do, of  course, is make it move so it's  coming toward you and away from  you.  So I'll just put it on this  string and spin it around.  (alternating high and low pitch)  Can you all hear the Doppler  effect?  But you notice something rather  curious. 

 I don't hear anything unusual at  all.  Why is that?  I'm right in the middle.  That's right.  It's not moving any closer.  It's not moving any farther.  It's staying the same distance  from me, so I just hear a single  frequency.  You hear the frequency go up and  down and up and down as it goes  around.  >> Professor Sprott!  I hate to interrupt, but I've  got something that will fix that  time machine.  >> That looks like duct tape.  >> This isn't any duct tape!  This dialectric duct tape. 

 This is going to do it,  I promise.  It'll work this time.  Give it a try.  >> Well, I'm a little skeptical.  >> I really do want to try the  time machine one more time.  >> All right, it hasn't worked  yet, but let's try again.  (whooshing  and electrical buzzing)  >> Stupid...  (laughter)  Who are you?  >> Who are we?  Who are you?  >> That's hardly fair.  I asked first.  But I am Nikola Tesla,  inventor, scientist. 

 A little bit confused right now.  Where am I?  More importantly, when am I?  >> We have accidentally  transported you to the year 2008  in our time machine, which is  malfunctioning today.  >> Time travel?  >> Mm-hmm.  >> It's terribly tempting.  If I could learn the science and  technology that has transpired  in the past 100 years, and then  take that knowledge back.  No, this would surely have  negative consequences.  (man coughing)  Look who it is.  Mr. Thomas Edison.  >> Tesla.  Wait a minute!  What's going on?  Where are we?  When are we?  >> Well, we have accidentally  transported you to the year 2008  in our time machine. 

 >> 2008?  Think of all the knowledge.  You must lead me to your nearest  library.  >> Mr. Edison, think about this.  If we were to take this  knowledge back from the future,  it would be done without any  work.  >> No, you think about this.  If we can garner knowledge about  the future's problems, we can go  into the past and solve them for  our present.  >> Or cause more problems.  I think that perhaps we should  just discuss this back in the  safety of our time.  >> I'm not discussing anything  with you.  (laughter)  >> Just, back, here. 

 Ugh!  So this is your time machine?  Does this look like an outhouse  to anyone else?  (laughter)  (musical flourish)  (applause)  >> David Willey, he has such a  sense of humor.  He made this time machine look  like an outhouse.  But speaking of David Willey,  maybe we should try to get him  back out here to find out why  his idea didn't work.  >> I don't know.  David Willey might be kind of  busy.  But I do know another person I  could call to come and fix this.  So, why don't I give him a call?  (telephone rings)  >> Why, it's Bassam Shakhashiri!  (applause)  >> Hello, Clint.  >> The famous chemist who  inspired this show some 25 years  ago, by his own presentations  in chemistry.  >> I'm very happy to be here on  this very special anniversary  of yours.  >> I didn't know you knew  anything about time machines. 

 >> Well, somehow I'm here.  (laughter)  And you know, it's been 25 years  since you started this program.  And I'm very, very proud of what  you have done, and all that you  do for not only our local  community, but the community of  youngsters and kids of all ages  all over the world.  So, I brought you a token.  This is your silver anniversary,  25 years.  This is a token of appreciation  for you.  >> That's so kind of you.  But this doesn't look silver at  all.  It looks like copper.  >> It is copper. 

 But you know, if you study  science, you know how to change  one element into another.  So, this is made of copper.  And we can change it to silver.  >> How would you do that?  >> I need a source of heat.  Do you have a burner here?  >> Sure, we have a burner right  here.  >> All right, let's go back  there.  I have with me a couple of items  that I'm going to use here.  I have this casserole.  It's empty except for air.  And we're going to put it right  there. 

 I'm going to put my goggles on.  >> I have mine right here.  Absolutely.  >> All right, safety is  paramount.  I'm going to take a powder.  I'm going to put it in there.  We're going to be heating it, as  we're doing now already.  This is a granular powder.  Then I'm going to take a clear  and colorless liquid and put it  in there.  Then, I'm going to wait until  this gets heated up. 

 And actually, we can just drop  this in.  This is copper.  And I'm going to drop it in  there.  Carefully.  We'll let it cook for a while.  >> Okay.  >> So, let's see now what's  happening here.  Do you think it's changed  enough, or wait a little longer?  >> I think that looks pretty  silver to me.  >> I looks silvery?  >> I think so.  >> Let's see if I can  fish it out. 

 >> Oh, yes.  >> So there.  >> Is that ever nice.  >> Let's cool it off here.  (musical flourish)  (applause)  It's somewhat silvery, right?  It's silver enough?  >> I think so.  You were so good at that.  Could you make it into gold?  >> Gold?  >> Yeah, that would be great.  >> You're going to make it  to a 50th anniversary?  >> I sure hope so.  >> Well, let's see if I can try  to change this into gold now.  I can't change the 25 into 50. 

 But I'm just going to use the  heat like so.  I'm going to heat this in the  flame.  Let's see what happens.  Is it changing into a golden  color?  >> It sure looks like gold to  me.  >> And we've got to be careful  how long we heat this.  Then we cool it off.  You can turn the flame off now,  please.  And there it is.  Well, it's not quite golden, but  it's safe to handle.  >> That's pretty amazing. 

 I really appreciate your  bringing that.  I will honor that.  (applause)  >> Congratulations, again.  And many, many happy returns.  >> Thank you.  >> Thank you.  That's yours.  >> Okay, well, where were we?  Tesla, of course, and Edison  were two rivals who lived about  a hundred years ago.  They were very interested in  electricity, among other things.  So I'd like to show you a couple  of demonstrations that involve  electricity. 

 I'm going to start with a gadget  over here.  I'm going to turn it on and ask  whether you've seen this before.  (organ music)  Frankenstein movies, that's  right.  They always have these, don't  they?  It's a device called a Jacob's  Ladder.  And it consists of two metal  rods that are close together at  the bottom, far apart at the  top.  There's about 60,000 volts  that's applied between them.  It causes a spark to form at the  bottom.  The heat of the spark causes it  to rise until the rods get far  apart, the spark goes out and  then it restrikes at the bottom.  You'll never see one of these in  a modern science laboratory.  They're really not good for very  much other than for props in old  science fiction movies. 

 But they do illustrate what very  high voltages can do.  Over here, we have another  gadget called a Marks Generator  that also consists of a very  high voltage.  Here, we have ten devices.  They're capacitors.  They're like storage batteries.  But unlike an ordinary battery  that stores just a few volts,  these capacitors store about  50,000 volts.  Now, what we're going to do is  charge them up.  Then we're going to discharge  them all in a series.  It's like stringing ten  batteries together to make a  much higher voltage.  So ten times 50 is 500,000  volts. 

 So, if Mr. Weix will charge it  up, we'll see what happens.  >> Okay, but I need some help  from the audience.  I need a countdown.  Five, four, three, two, one.  (loud snap)  >> Whoa.  So that shows you what a spark  of 500,000 volts looks like.  A half a million volts.  And of course, that's what a  bolt of lightning is.  The clouds charge up to very  high voltage, and then at some  point, they discharge to the  earth, and you see a very big  spark like that, and that's what  we call lightning.  Another gadget that makes very  large voltages is this thing. 

 This, you would've seen in a  laboratory, maybe a hundred  years ago, or in a lecture  demonstration.  It's a plastic disk that I can  rotate with a knob here.  It's charging these two  capacitors up.  They go to higher and higher  voltage.  And at some point, they  discharge and a spark occurs  between those two balls.  So, unlike the other two devices  that I showed you, that are  plugged into the wall and get  their electricity from the  ordinary power line, this gets  its electricity from a rotating  disk, from the energy that I'm  putting in by turning this  crank.  So, it shows you how you can  produce very large voltages with  a relatively simple apparatus.  >> Professor Sprott?  Are we alone?  Is Tesla here?  >> No, it's just you and me.  >> Oh, good.  I noticed that you lofty men of  science are having some sort of  a fantastical fair of physical  phenomenon. 

 >> That's right, this is the  Wonders of Physics.  >> Do you mind if I stay and  observe?  >> Oh, that would be such an  honor.  What would you like to see?  >> This is amazing right here.  >> Yes, this is a large  capacitor--  >> The walls are so thin.  (laughter)  How do you do this?  >> Well, I didn't personally do  that.  They're stamped out by the  thousands on a machine.  And we put drinks in them, and  we drink from it.  >> Hmm, amazing.  Wait, but I recognize this over  here.  I invented this. 

 In fact, I think this is a  phonograph that I donated to  your department last week.  >> Actually, that was donated to  our department by Thomas Edison,  but about 90 years ago.  >> Huh.  Do you still use these?  Might I perhaps get royalties?  >> Well, no, except for  Mr. Weix, he occasionally uses  these.  But no, we don't use them  anymore.  In fact, the way we get our  music now is with a device like  this.  >> Amazing.  Is it some sort of tiny music  box?  >> Well, it does make music.  But it doesn't have any moving  parts.  It stores the music in electric  charges. 

 >> Hmm.  >> Where is he?  Edison, what are you doing?  Didn't we agree that we were  going to go back to our own  time?  >> You agreed to that.  I don't recall agreeing to  anything.  >> You're so--  He's so stubborn.  I will get you back there.  If I have to, I will drag you  back.  >> I'd like to see you try.  >> Okay, come on.  >> Wait, wait!  You two are acting like  children.  I think we have to send you both  back to your time. 

 >> Okay.  >> Ha!  >> But before we go, you have to  settle a matter of longstanding  debate between Mr. Tesla and I.  All these wonderful devices,  these electronic devices, surely  you power them off a grid of DC  current?  >> Please explain to these  people you use the much more  reliable and sophisticated  alternating current system.  >> D-C.  >> A-C.  >> D-C.  >> A-C.  >> D-C.  >> A-C.  (musical flourish)  (applause)  >> Well, it's true that Tesla  and Edison didn't like each  other very much. 

 They were rivals, and they  disagreed on a number of things.   This was one case where Tesla  had it right.  Because AC in fact is more  efficient than DC for  transmission of electricity,  especially over long distances.  But you know, I think they were  both much too gentlemanly to  ever have actually had a fight.  So, I'm not sure that was really  Tesla and Edison.  But they were interested, not  only in electricity, but also in  magnetism.  I can show you a few  demonstrations that involve  magnetism.  This apparatus over here that I  was about to show Mr. Edison is  another demonstration of the  same phenomenon.  Here we have a very large  capacitor, like the ones we have  there.  And we're going to charge this  capacitor up to about 5,000  volts. 

 Then we're going to discharge it  into this five-turn ring of  copper tubing.  Then we're going to take one of  these aluminum cans, lower it  down into the coil, and  discharge the capacitor.  Let's see what happens.  You see it charging up, and you  can see on the meter over there  it coming up to about 2,000  volts.  Now 3,000 volts.  When it gets up to 5,000 volts,  I'm going to discharge it,  making a very large magnetic  field surrounding the can.  So, we're about up to 5,000  volts.  Is everyone ready?  Here we go.  (loud pop)  (musical flourish)  And look what it did to the can.  It in fact crushed the can. 

 That's because an electric  current flowed around.  It's an aluminum can, so it's  not magnetic, but that electric  current made it momentarily  magnetic.  And this magnet was repelled by  that magnet that surrounded it,  and it tried to get as far away  as it could, and it crushed the  can.  Now, would you like to see that  again?  >> Yeah.  >> Okay, so this time--  Sir, do you play baseball?  >> Yeah.  >> Here, take that.  This time, we're going to place  the can, not down in the coil,  but on the top of the coil.  Okay?  We're going to charge it up  again to 5,000 volts.  § §  Ready?  Here we go.  (loud pop)  >> Whoo!  (musical flourish)  (applause)  >> Okay, well, that shows you  this principle of magnetic  induction. 

 Now, I've mentioned to you that  when you cool a metal down,  typically it becomes a better  conductor of electricity.  Aluminum becomes about a seven  times better conductor of  electricity when it's at the  temperature of liquid nitrogen.  But there are materials that at  the temperature of liquid  nitrogen become a perfect  conductor.  And if you cause a current to  flow in them, it will flow  forever.  And I have such a material over  here.  It's something called a  superconductor.  It's a fairly small thing, so  you'll have to look at it on the  television monitor.  This little black disk is a  superconducting material.  It's sitting in a little bath of  liquid nitrogen right now.  And what I'm going to do is take  a little tiny magnet and some  tweezers here. 

 I'm going to set this magnet on  top of the superconductor.  Now you'll see--  >> Whoa!  (applause)  >> The magnet.  The little tiny magnet  is magnetically levitated.  Because when it tries to fall  down onto the superconductor, it  induces an electric current in  the superconductor that repels  it.  That current, unlike over here,  never dies away.  It keeps flowing for as long as  we keep the superconductor very  cold.  Okay, so--  >> Professor Sprott, I'd really  like to try this time machine  one more time.  I'd like to get you back  from that first show in 1984.  >> Peter, you're starting  to annoy me a little bit.  But all right, if you absolutely  insist. 

 Let's see if it's going to work.  (whooshing  and electrical buzzing)  >> Okay, we're going to talk  about where we left off  yesterday.  We were talking about radium,  palladium--  >> I'll be right back.  (laughter)  >> This is not--  >> It's good to see you,  but I was in the middle of a  lecture.  Can we have a coffee or  something?  >> Okay, I'll just--  >> But these are not my  students!  What's going on here?  >> Who are you?  >> I'm Marie Curie, of course.  There's only one woman  professor in the entire  university.  But who are you and what are we  doing here?  >> Oh, well, I'm Professor  Sprott.  And we have accidentally  transported you to the year 2008  in our time machine.  >> 2008?!  This is amazing!  Marie, it's just like I was  saying!  You see, time is just like any  other dimension.  You can go backwards. 

 You can go forwards.  This is incredible!  >> Yes, amazing, Einstein.  But how does this thing work?  >> Well, not very well,  apparently.  But you famous scientists could  maybe fix it for us.  >> It must warp space time  somehow.  >> I don't know anything about  space time.  I can tell you all about radium.  Einstein, do you know anything  about this?  >> I'm no quantum mechanic!  I'm a theorist.  How can I help?  >> You don't know anything.  You should be in the lab, like  me. 

 So, you didn't really want us  here, and we don't know how to  help you.  >> Okay, maybe we should let you  go back to your time.  >> That's a very good idea.  I have a very important lecture!  >> Well, I wouldn't guarantee  anything at this point.  But if you step inside and pull  that chain, it might work.  (laughter)  (musical flourish)  (applause)  Well, you know, Marie Curie and  Albert Einstein were two very  important physicists who lived  about a hundred years ago.  They made many discoveries that  we use, even today, to  understand the laws of physics.  One of the things that Albert  Einstein especially was very  interested in, is light, and  what happens when things move  very close to the speed of  light.  So let me show you a few  demonstrations that involve  light.  In order to do that, we need a  source of light, and we have  such a thing here. 

 It's a very powerful laser.  And it's making a beam of light  that's going across.  Can you see it on the wall over  there?  I'll shake it back and forth so  you can see it.  It's a little blue-green dot on  the wall over there.  That's being produced by this  laser.  Of course, you can see the light  over there, but you can't see it  here.  There is a way to make it  visible to you.  If I take these erasers that  have some chalk dust in them and  make some chalk dust in the room  here, the light will scatter off  the tiny particles of chalk, and  you'll be able to see the laser  beam.  Now, the important thing to note  about this laser beam is how  very straight it goes.  And you're accustomed to the  idea that light travels in a  very straight line. 

 But you know, that's not always  the case.  It's possible for light to  actually go around a bend.  It's not something you'll  ordinarily encounter.  But here I have a demonstration  of that.  This is a plastic rod.  It's solid.  It's transparent, light can go  through it.  But it goes around about three  loops and then it comes out  right here.  I'm going to put this in the  laser beam, so the laser light  goes in one end of this plastic  rod.  And we will see if we can make  it come out the other end. 

 Can you see the light go around  three times?  And it comes out over here.  This is something called a light  guide, for obvious reasons.  It's guiding the light around  the bend.  >> Professor Sprott, I found a  loose wire on the conductor down  here.  So, I think I've got this thing  fixed.  I'd really like to try it one  more time.  >> You know, I think you're the  loose wire in this lecture!  (laughter)  But this is absolutely the last  time we're going to put up with  this!  (whooshing  and electrical buzzing)  >> Uh, hello.  >> Excuse me, who are you?  >> Hi, I'm Professor Clint  Sprott.  Who are you?  >> I'm Professor Clint Sprott.  You look nothing like me. 

 >> Ah, time travel, of course.  So you're simply a past  counterpart of myself.  >> No, you're a future  counterpart of me, perhaps.  >> Very true.  >> Okay, so you're both  Professor Sprott.  Look, this is truly amazing.  We've gone into the future.  Tell me, old Sprott, will I live  forever?  Do I still have to pay taxes?  Have I survived the nuclear war?  >> Hmmm, in the future, we will  have flying cars, no government.  >> Great.  >> And everybody will live on  the moon. 

 >> Wow! Really?  >> No!  If I told you what was actually  going to happen in the future,  it could alter the future,  perhaps in a negative fashion.  I'd better be off before I cause  even more disturbance to the  space time continuum than  I already have.  (musical flourish)  (applause)  >> Well, I do hope I live to a  ripe old age, but you know, if  50 years from now you see me and  I look like that, tell me to get  a hair cut!  (laughter)  But you know, there are no time  machines.  And there probably never will  be.  And the reason is that the  future is not yet determined.  Any one of you could go out of  here today and you could make a  discovery, or you could invent  something that would completely  change the future.  But one thing we do know is that  whatever discovery you make or  whatever you invent, will obey  the laws of physics.  And that's why we've been doing  these shows for 25 years, so  that you will all know something  about the laws of physics.  We hope when you make your  discovery, or invent your  device, that it will be  something that will make a  better world, not just for you  and me, but for those who come  after us.  And just to convince you this  time machine does absolutely  nothing, I'm going to step  inside it and have Mr. Weix  turn it on. 

 You'll see it really doesn't  work at all.  >> I'll show you!  (whooshing and  electrical buzzing)  >> Voila!  See, I told you, Professor  Sprott, it would work.  Come on out.  Professor Sprott? Come out here.  Professor Sprott?  Oh, no!  We've lost Professor Sprott!  >> I'm sorry I'm late, welcome  to the Wonders of Physics.  >> Oh, no, wait, wait, wait!  What do you mean, "welcome  to the Wonders of Physics"?  You've already done the show.  We're at the end of the show  now.  >> You mean I've done all these  demonstrations?  >> Yes, you've done all these  demonstrations.  We're at the end.  You need to do the end. 

 >> Okay, we'll end the show the  way we've ended every one of the  201 shows we've done over these  25 years, by making for you  a cloud.  And we do that using this  container of 25 liters  of liquid nitrogen.  We force nitrogen gas into it.  That causes the liquid to come  out through these holes in the  top of this pipe.  The liquid is very cold,  so it will cool the air.  The moisture in the air will  condense into tiny droplets of  liquid water.  And that's what we call a cloud.  With that, I thank you all  for coming.  (applause)