(upbeat music) - Star date 02.19.2017. Captain Sprott has heard about a planet orbiting the temperate zone around Proxima Centauri which is the nearest star to our solar system and he has come up with this crazy idea about mounting an expedition and seeking out new life and new civilizations and boldly going where no one has gone before. And so here for the 34th year that indefatigable schemer, that intrepid space explorer, the wonder of physics Professor Clint Sprott. (upbeat music) - Welcome to The Wonders of Physics. Now when I was a student one of the things that inspired me to go into physics was when John Kennedy have that speech and he said we choose to go to the moon in this decade and do the other things not because they are easy but because they are hard. Now that was over 50 years ago and I think we need a new challenge. Going to Mars is too easy. I think we should go all the way to that new planet just discovered around our nearest star. - But Captain Sprott we don't have any rockets powerful enough to get us there. - Nonsense, in fact I have our Chief Engineer Mike Randall working on that problem right now. And he's here to give us his report. Lieutenant Zhulu beam him in. - Aye Captain. (computerized beeping) (audience applauds) - Aye, Captain, call me Scotty. You cannot change the laws of physics. Long may your lum reek. You're a wee scunner. My hovercraft's full of eels. - Scotty? Mr. Randall I didn't know you were Scottish. - Actually I'm not I lost a bet with my wife. Thanks, honey. Anyway let's talk about what it will take to get to Proxima Centauri. Space travel is governed by Newton's three laws of motion. Newton's first law says that an object at rest stays at rest and an object in motion stays in motion. Or put in simple terms stuff, or matter as scientists like to call it, stuff wants to keep doing what it's already doing. If something is sitting still, it wants to keep sitting still. If something is moving it wants to move in a perfectly straight line at exactly the same speed forever. 

Or until some outside of it pushes or pulls on it. Now Newton's first law is good news for space travel. That's because space is mostly space. There's really not much for our spacecraft to run into to slow it down. So once we get it up to speed it will pretty much keep going on its own. Now for Newton's second law I'm going to need help from a cadet in the audience. How about you sir? Yep yep, you right there, yes, yes yes yes.  (audience applauds) All right and what is your name? - Tristen. - Tristen here you go. Just stand right here. Okay Tristen, oh that was a great pass. Hey Tristen how did you get the ball to me? - I threw it to you. - Yeah you threw it to me. What did you do to the ball when you threw it to me? - I pushed it. - Yeah you pushed it. Now scientists would call a push or a pull a force. So Tristen you applied a force to that basketball. Now the ball is made out of stuff. Everyone what do scientists call stuff? - (Audience)  Matter. - Matter, matter. The amount of stuff in that ball, the amount of matter in the ball is called its mass. So you applied a force to a mass. You with me? - Yeah. - When you did that, when you pushed on the basketball the ball which hadn't been moving suddenly did what? - It moved. - It moved but it moved in a very special way. Scientists and astronauts have a word for this. Long word starts with A, shout it out. - (Student) Acceleration. - Acceleration, very good. Acceleration means a change in speed or direction. You made the ball speed up so you made it accelerate. Newton's second law puts all three of those together. Force, mass, acceleration all go together. In fact you may even know it as a math equation force equals mass times acceleration. The important thing to remember is that force, mass, and acceleration go together. Okay, Tristen we're going to do this again. We're just going to do it with a different ball. 

Here you go. - Whoa, okay.  (grunting) - Medicine ball. A lot more mass. So Tristen did you push on that ball the same as before? - No. - No, did you push less or did you push more? - I pushed much more. - Pushed much more. And you knew to do that, I didn't tell you to do that. You knew because you understand Newtons second law. You knew that with more mass you had to apply a bigger force to get the ball accelerating fast enough to make it over to me. Excellent job sir. Let's give Tristen a huge round of applause, thank you.  (audience applauds) Now how does Newton's second law fit into space travel? Well Proxima Centauri's still a long way off so we want our spacecraft to accelerate to the highest speed possible. Newton's second law says there's two ways to do this. We could apply a really large force, and we can also reduce the mass of our spacecraft, make it lighter. For example, world famous physicist Stephen Hawking last year along with his fellow scientists and investors announced a really exciting new project called Breakthrough Starshot where they're planning on building miniature robotic spacecraft. And they're going to send them to nearby stars like Proxima Centauri. These nanobots have about the same as this ping pong ball. Now it turns out I have an identical ping pong ball in this tube. Let's see what happens when I apply a really large force to that small mass. So what I'm going to do is I'm going to pump all the air out of this tube. In a minute I'm going to pop the tape on this end. The air's going to come rushing back in. It's going to apply a force of about 25 pounds to that ping pong ball, we'll see what happens to it. Now this is loud folks. You're going to want to cover your ears. I'm going to put my hearing protection on. And in five, four, three, two, one. (loud thumping)   (organ chord plays) Did we lose it? Oh it's over here. Went right through that one. And it's embedded in this one. Anyway that went really fast right? That ping pong ball experienced almost 2000 G's of acceleration. And ended up at a top speed of almost the speed of sound. Just about 760 miles per hour. Now the nanobots I was talking about earlier, they're not going to be powered by air pressure. Once they're in outer space they're going to unfurl giant reflective sails about the size of this portion of the wall. Huge ground based lasers will shine on those sails and accelerate the nanobots up to 20% the speed of light. That's 134 million miles per hour. 

And they'll do it in about 10 minutes. Now once they're up to speed it will still take them about 20 years to get to Proxima Centauri. Once they're there they'll start taking pictures and sensor data and they'll radio that data back to Earth. Now radio waves travel at the speed of light but that data will still take another four years to get back here to Earth. Now I've saved the best of Newton's laws for last. Newton's third Law says that for every action there is an equal and opposite reaction. Or put in simple terms, if you push against something it pushes back. Something I didn't tell you at the beginning of the show, I used to be a rocket scientist. I'm not kidding about that. I used to work on the Space Shuttle main engines and other rocket engines so, I know that Newton's Third Law is often referred to as the Law of Rockets, here's why. In a rocket engine you got a lot of gas going this way, that's the action. And the rocket goes this way, that's the reaction. Now I can also tell you as a rocket scientist that this is a leaf blower.  (all laughing) But the idea is still the same. (leaf blower blowing air) (organ music playing) (Captain sickly moaning) (all laughing) Blargh!  (all laughing) Oh, this happens every time. (leaf blower blows)   (children squeal)  I'm sorry. Anyway. Now that we understand how Newton's Third Law works, I have a rocket here with me, you want to see it? - (Audience)  Yeah! - This rocket is powered by ethanol. There's a little bit of ethanol in here. I'm going to shake it up a little bit. Okay, set it up. - Are you sure this is safe? - It's safe for me. - I'm out of here, you're on your own. - We chased off the Klingon. 

Okay, again this is going to be loud. You're going to want to cover your ears. All right, give me a big countdown. And in five, four, three, two, one.  (ethanol explodes)   (water bottle bangs)   (audience applauds) It's safe. - Oh thanks for warming my seat up for me. - You're welcome.  (audience full of excited chatter)  Pretty impressive, all that hot gas went this way and the rocket went that way.  (alarms blare)   (soft electronic noise) - Oh no we've got tribbles in the replicators again. Hey, I bet if I beamed the tribbles over to Mr. Weix's house, if I did that then they'd be no tribble at all. Okay see you later. (audience applauds) - Well he had some very moving ideas. But you know Captain Sprott in space it's very very cold. How are we going to stay warm? - Well heat is the easiest form of energy to generate. There are many ways we can do that. And Dr. I. Kra'Nee will explain. Lieutenant Zhulu beam him in. - Aye, Captain.  (computerized beeping) - Thank you, Captain Sprott. So yes, let's talk a little bit about heat and heat transfer and how we can transfer heat. What I have here is a heating coil. Uses electricity, and is very similar to a coil that you have in your hair dryer at home. Except it's just a little bit bigger. And this coil is going to produce a type of heat called infrared radiation. Now infrared radiation is very similar to visible light, the light that we see. It can be reflected, it can be focused. And by the way do you know what happens to light when it turns bad? It has to go into a prism.  (crickets chirping)   (audience laughs)  All right, we have infrared radiation being produced here, infrared light being produced here. That light is at the focal point of a parabolic mirror. That infrared radiation is going to go into the mirror and be reflected across the room here, the 25 feet or so over to another parabolic mirror over here. And at the focal point of this parabolic mirror I have a match. Now this may take a minute or two. But keep one eye on that match. We're going to use infrared radiation to heat the inside of our spaceship. And it's going to be the main way that we heat the inside of our spaceship. So again watch that while I set up, there it goes. So let's talk about another way of producing heat and moving heat around and that is through the use of gases. So I'm going to light a candle. This is a normal candle here that you might have at home. And I don't know if you've ever thought about how a candle works, it's really quite interesting, really quite simple. We burn the wax and the heat from the wax burning has a tendency to rise. The molecules vibrate faster, they take up bigger spaces. And therefore we say they are less dense. And what do we know about less dense materials? They have a tendency to rise. - (Audience)  Rise. 

- So the air above the candle has a tendency to rise. Then cold air from the sides and the bottom come in and fuel the flame with oxygen molecules. By the way don't ever trust an atom or a molecule. They make up everything.  (rimshot plays)   (audience groans)  You want another one?  (Audience)  Yeah! Two atoms are talking and one says, "I lost an electron." The other says, "Are you sure?" And the first one says, "Yes, I'm positive."  (rimshot plays)   (audience laughs)  Anyway back to my candle. This system of the rising air and the cool air coming in from the bottom will not work in our spaceship. And it won't work because we have no gravity and we have no density difference. So the hot air won't rise and the cold air won't come in to take its place. And I'll talk more about that in just a moment. So what I'm going to do now is take a glass tube. Just a regular glass tube and it fits right over the candle. And I think this is pretty straight forward. But watch what happens when I put it over there. It'll take a second or two but the candle does what? Slowly goes out, okay. And I think that's pretty obvious. We don't have the oxygen air, the cold oxygen air coming in from the bottom to feed the candle. So one of the things about physics and about science is that any experiment is repeatable. So I'm going to do it again. But this time I'm going to throw a little curve at you. I have a piece of metal here, a T type piece of metal. And I'm going to simply put that right down the middle of my tube. Now I'm going to put the tube over the top, like so and you'll notice what happens. It flickers, it's not as strong a flame, but it stays lit. Now why is that? Well what we have here is we have two different paths for the air to flow. The cold air can come down one side with oxygen and feed the flame and the hot air can go up the other side to exit. And again we have a density difference. Now, how do we know which side is going to be which? Well, it's purely by random here but I'll show you that if I use my smoke wand here one side the smoke will rise and the other side it goes down. In the last show it was just the opposite. Okay, to show that, I said earlier that this process is called convection currents. Convection currents cannot be setup in our spacecraft because there's no density. So how are we going to move air around in our spacecraft to heat the astronauts and keep our equipment warm? Well we're actually going to have to use big blowers and fans and because of that it's going to be very noisy inside of our spacecraft. Now to show that an experiment or a demonstration is repeatable I'll simply pull this out and what should happen? - (audience) It goes out. - It goes out.  (audience applauds) So over here I have a balloon. It's obviously less dense because it has a tendency to rise. What do you think the material in that balloon is? - (Student) Helium. - Could be helium, could be helium in there, yes absolutely. Because helium in most of the toy balloons that we have is helium inside of it. What other material could be in there? - (Student) Air. 

- No, if it's plain air, would it rise? Because it has to be less dense than air. Yeah. - (Student) Hydrogen. - Could be hydrogen. Okay, hydrogen is a very explosive material. Helium is not. So how could we tell the difference between that balloon and whether it has hydrogen or helium in it? - (Student) Light it on fire. - Now there's an idea, light it on fire he says. Heaven forbid, what could go wrong with that?  (all laughing)  Maybe we should ask the designers of the Hindenburg blimp what could go wrong. Oh, what the heck let's do it. So I'm going to take a match here. I'm going to put it on here. (match strikes) (balloon pops)  What do you think? - (Student) Helium. - Helium, I popped the balloon. It's just like popping it with a pin, but no big explosion. So obviously I had helium in there. Now over here on the other hand-- (audience laughing) - (Mr. Weix)  We need a volunteer. 

- Chicken. Over here I have another balloon. Well let's see what's in this one all right.  (match strikes)  You may want to cover your ears on this one. (balloon explodes) (audience applauding) Obviously, I had... - (Student) Hydrogen. - ...hydrogen in there. Now we are going to use hydrogen as the main fuel in our rockets to get outside of the Earth's atmosphere and to get outside of the Earth's gravitational field. For two reasons, number one it's very light and not very dense. And secondly, it's very energetic. It has lots of fuel in it. So you see Mr. Weix, we have nothing to worry about here. We can use infrared radiation to heat the inside of our spacecraft. We can move air around inside our spacecraft. And we can use hydrogen to propel our rockets. So we will have a very successful trip. Thank you.  (audience applauds) - Well I'm starting to warm up to the idea of space travel now. So Captain Sprott how so sure are you that there is a planet out there? - Well I'm glad you asked. There are actually four ways we can detect exoplanets. One way is to try to image them directly. But you know our present telescopes are not nearly powerful enough to make that practical. Another way is to use an affect predicted by Albert Einstein almost 100 years ago. It's called gravitational lensing. Imagine if this light bulb is a distant star. And you're seeing it across outer space. And suppose another star comes between you and that star. Now I don't have a star and I don't have a gravitational lens, but I have an ordinary lens. And the phenomenon is the same. When this star comes between you and the star behind it you see the intensity of the light increase. And if you look carefully you may see that the image of this appears as a ring. And that's called Einstein's ring. And he predicted that long before it was ever observed in space. And several planets have been discovered this way. Very distant planets, but it requires this special circumstance of one star in front of another. And so it's not all that practical. Another way one can do, imagine this is a planet orbiting the star. As it comes around between you and the star you can see the intensity of the light decreases. And so by looking at stars and monitoring the intensity of the starlight. If every now and then you see it dip, decrease, and very periodically, you can infer that there must be a planet in orbit around it. Now some of you over there didn't see that. And that's because you're not in the plane of the orbit. And that's a problem detecting exoplanets as well. We can detect some that way, but certainly not all. And there's actually a satellite devoted to finding planets by this very method. And hundreds of them have now been discovered using that process. But that's not the way the planet was discovered that's around Proxima Centauri. It was discovered using the Doppler effect. Have you heard of that? Oh yeah, you stand beside the road and a car goes by sounding its horn. Sounds something like-- (graded whining)  When it's coming towards you it has a high pitch. When it's going away from you it has a low pitch. Now I can illustrate that with something here that makes a sound. It's a little whistle and when it moves toward you the pitch of the sound goes up. When it moves away from you it goes down. Now you probably couldn't here that very well so let me make it go a little faster.  (oscillating whistling)  Can you hear the pitch go up and down and up and down? But a curious thing it sounds perfectly normal to me. Why would that be? That's right it's not moving toward me or away from me. And you know the police use this to find out how fast your car is traveling. Not with sound, but with radar waves. Now of course planets don't make sounds and neither do stars and even if they did we couldn't hear it across the vacuum of outer space. But stars do emit light and light has particular wavelengths associated with it. And by looking at the shift in those wavelengths we can infer that the star is moving back and forth. How how would that tell you there's a planet? Well if there's a massive planet orbiting a star the star actually moves back and forth as the planet orbits. And that causes the star light to shift in frequency ever so slightly. In the case of Proxima Centauri every 11 days the star mov - Well Captain Sprott, maybe that would work. But how do you plan on building a propulsion system for such a long journey into space? - Well we could use electric propulsion. In fact Lieutenant Seltzman has been working on that. Lieutenant Zhulu beam him in in. - Aye, Captain.  (computerized beeping) (audience laughing) - Gas captain. We call it plasma but it is merely ionized gas. To understand how to build an electric propulsion system we'll first need to understand electrostatic repulsion. We can demonstrate such an affect with this device here called a Van de Graaff generator. In this Van de Graaff generator charge is moved from the blue box at the bottom up onto this sphere by means of putting it on a rotating belt. Let's see what happens if we put a tribble on top.  (tribble squeaks)  Oh, it's fur's standing up. Doesn't seem to like that at all. Now maybe we'll need somebody who can stay still. We'll need a volunteer from the audience. Let's have you. Step right up here on to this plastic stool. And place your right hand on top of this dome. 

Now as you may know like charges repel. So this Van de Graaff generator is putting charge onto your body. That charge is going onto the strands of your hair. Now if you'll shake your head a little bit. Well you see at the top some of your hair is staying on end. The charges on the strands of your hair are repelling from one another. This repulsion causes your hair to stand on end. The demonstration of electrostatic forces at work. Thank you for your assistance.  (organ chord plays)   (audience applauding) Now let's see how we can use these electrostatic forces to create motion. If we connect this Van de Graaff generator to an electrostatic motor we can make things move by electrostatic repulsion itself. The Van de Graaff generator is connected to this aluminum foil coated soda bottle on the left. This soda bottle on the right is connected to the ground while the soda bottle in the center which has aluminum foil segments on it is free to spin. Now we're going to start spraying charge out of fine needle also connected to the Van de Graaff generator onto these aluminum foil segments and see what happens. The charge placed on the bottle in the center is repelled from the bottle on the left towards the bottle on the right thus causing he electrostatic motor to spin solely from electrostatic forces.  (organ chord plays)   (audience applauds) But now let's see how we can use this to generate a propulsion affect with this electrostatic pinwheel. This electrostatic pinwheel has two rockets on each end. At the back of each rocket there's a very fine needle which concentrates the electric field generated by the high voltage from the Van de Graaff generator. This ionizes the surrounding gas. Now as you might know like charges repel. So this ionized gas will be pushed away from the back of the rocket. And with every forces equal and opposite reaction this blowing of the ionized gas out the back of the rocket will 'cause the rockets to move forward. Let's see what happens. The pinwheel begins to spin. A demonstration of propulsion using ionized gas.  (organ chord plays)  But how will we use it to actually propel a spacecraft? Well, we'll need to use a state of matter called plasma. Now plasma is a very high temperature ionized gas. If you took an ordinary gas such as air and continued to add energy to it it would become hotter and hotter. Eventually it would have so much energy that the electrons would be free to move from the atoms. At this point the gas would become ionized. We can create a plasma by adding energy with an electric arc, such as in this Jacob's ladder here. In this Jacob's ladder a transformer at the bottom places a high voltage between these two rods. This breaks down the air between them into a plasma. Now because the plasma is so hot it's less dense then the surrounding air and thus begins to rise upward up the Jacob's ladder until it breaks and it reforms at the bottom. Why, that's so high voltage, if you were to touch it, it would not your Spock's off.  (all laughing) - Aw, you Vulcans are so naive. I think you meant to say it could knock your socks off. - That may be true but in this case it would be one and the same.  (crickets chirping) But there are other ways to generate a plasma. For example we can use radio waves. We can demonstrate this by placing a fluorescent light bulb into a microwave oven. Normally a fluorescent light bulb is plugged into a light socket. In that case the voltage from the light socket drives an electric current through a low-pressure gas in the tube causing it to light up. Much in the same way the Jacob's ladder caused a plasma discharge. But a radio wave also has an electric field in it. In we place this fluorescent bulb into the microwave oven the electric field in the radio wave will excite the gas into a plasma causing the fluorescent light bulb to light up without being plugged in. (organ chord plays)   (audience applauds) Now the thing about plasmas and why they're so important for plasma propulsion is that a plasma rocket can be much more efficient than a chemical rocket. In a chemical rocket you would combust a fuel and an oxidizer such as hydrogen and oxygen. That high temperature exhaust would then be expelled out the back of the spacecraft causing thrust. Now the thing is the hotter you can get that gas, the more efficient the rocket engine will become. And a plasma can be taken to much much higher temperatures than chemical rocket engines thus a plasma thruster can be much more efficient than a chemical rocket engine. In fact we have such a plasma thruster right here. Within this vacuum chamber we'll generate a plasma discharge by exciting a gas into a plasma with an electrical arc. Then using electrostatic repulsion we'll blow out this plasma out of the plasma thruster into the vacuum chamber. Let's have the lights off and see what this looks like. Here is the plasma is being expelled from the plasma thruster, this will generate a small but finite amount of force. 

Now this can add up to extremely high amounts of velocity over a long period of time. Such technically is already in use on a satellite in deep space missions. This is a type of propulsion system we'll use on our journey to Proxima Centauri.  (organ chord plays)   (audience applauds) My scientific expertise is needed on the bridge. Live long and prosper.  (audience applauds) (alarms blaring) - Alert alert, alert alert alert. Captain Sprott, Captain Sprott, what happens if we crash through an ion storm? - Relax Mr. Weix, there's nothing to worry about. Lieutenant Norval can help us. Lieutenant Zhulu beam him in. - Aye, Captain. (computerized beeping) - An ion storm you say Captain? That'll be no problem at all. We can just use some magnetic shielding. - Well while you're doing that perhaps you could explain to us how magnetic fields work. - Sure, so here I have a simple magnet. And the first thing I need to know about a magnet is that every one of them is surrounded by magnetic fields. You guys might have seen the pictures of magnets with their North and South poles and the little field lines coming out and wrapping around from North to South. Those magnetic fields are what's interesting about magnets. They're always invisible so we can't readily see them right away, but I've got a little way of showing you how with this apparatus. Before I do that can anyone out there name for me the metals that are typically magnetic? So we'll start right here in the front. - (Student) Iron. - Iron, iron is one of three commonly known magnetic materials. You there? - (Student) Cobalt. - Cobalt's another one. Anyone know the last one? How about you right there in the glasses, yep. - (Student) Tin. - Tin is not really magnetic. I'll take one more guess before I tell you. All the way up in the back there. 

- (Student) Steel. - Steel is usually magnetic because of the iron in it. Nickel is the last common one. So I've got something here called a ferrofluid. Now for those of you that are good with your Latin you might know what one of those three metals is in the ferrofluid. Anyone want to shout it out? Iron, iron's in the ferrofluid. So let's see what happens then when we bring magnet next to ferrofluid. So I mentioned that the magnet's got magnetic field lines. And each one of the spikes that you see on that hedgehog like structure there is a different magnetic field line. The iron in that fluid bubbles up and attaches itself to those field lines. Now I want to show you guys that there's two poles to the magnet so I can turn it around here. The smooth section in the middle is where the field lines run parallel to the surface and then the South pole over here looks just like the North pole pretty indistinguishable. And back around smooth section, magnet. Now one of the interesting things about magnets is that they don't actually do any work when they're just standing there. I could leave this setup as it is and nothing would change until forever basically. Magnets only do work when they change in time or space. So the only time this magnet actually moves some material around is when I'm moving the magnet, it won't do it on its own, something neat about magnetic fields. So let's take a look over here at how we can make time changing or spatially changing magnetic fields do some work. Here I have an aluminum ring. It's usually not very magnetic at all. But we'll do some interesting things here and I'll make it jump. So the aluminum ring is next to this electromagnet. The electromagnet takes electricity and generates a brief powerful magnetic field. That magnetic field's going to induce a current in this aluminum ring and it's that current that will feel a magnetic force causing the ring to jump. Let's take a look. Three, two, one. So that wasn't all too impressive by itself. But we can engineer this system to make it better. Better in this case means jumps higher. These tribbles getting in everyone's way. So I have here just an iron rod. Now what this iron rod's going to do is it's going to reshape my magnetic fields. So I told you guys that while in the magnetic field the ring will feel a magnetic force when it's got a current in it. The time-changing field makes a current. So currently before the rod we just had the field bubbling up here and the North pole came back down to the South pole. Now with the rod, the magnetic field's going to extend the entire length of it. So we're going to accelerate the ring for longer. Let's see how high we can get it now. Three, two, one. (organ chord plays)   (audience applauds) Now there's one other thing that we can do to change the ring, I said that it's the current in the ring that feels the force. So if we put more current into that ring we can get more height out of it. One way to change the current in it is to lower the resistance of the ring. And we can do that by dropping its temperature with this liquid nitrogen here. Liquid nitrogen is very cold. It's minus 321 degrees. That's 321 degrees below zero Fahrenheit. Now I want to show you guys that liquid nitrogen's really quite cold. So here I have a plastic tube. I can bend it, I can stretch it. It's very flexible. Let's dip it into liquid nitrogen. So the first thing you notice is that the liquid nitrogen spewed out this other end and that's because it was boiling, much like a teapot at home. Which actually I should keep it in there. So all that's just nitrogen gas coming out. So now you know it's only like 10 seconds in there.  (hammer banging)   (organ chord plays)  Shatters like glass, it's pretty darn hard. Can't really bend or break it anymore. So liquid nitrogen is cold quickly froze that. Now, I like to get a little crazy sometimes. What if I told you guys I wanted to pour this liquid nitrogen over my hands? So some of you up front can see this affect on the ground similarly. And those of you in the back might have seen this at home when you're cooking. It's a very similar affect if you take some water and put it onto a hot skillet. In this case my hand is acting like a hot skillet to liquid nitrogen which is relatively much, much colder. It's called the Leidenfrost effect. When you put that water into a hot skillet or the liquid nitrogen on my hand what happens? Well it beads up and it pools off the edge. Why does it do that? Well because the little bit of nitrogen that first touched my hand evaporated into a gas. And that gas carried the rest of it right on over my hand and so whatever I poured on me almost none of it make contact with me and it just fell on the ground. Neat little trick. Oh it would last until about my hand got cold and then it would get frostbite it'd be horrible, absolutely horrible. So let's take a look at the cold ring now. So I want you guys to make a bet with yourselves. Will the cold ring jump higher or less high then the iron tube? Three, two, one. 

A little less high, right? But now here's the fun part. Do you guys want to see what happens when I combine the two effects, the cold ring and the iron tube? (audience laughing)  So then, I don't know what's funny about this. I want you guys to make a bet with yourself now. Do we hit the ceiling? Okay, give me a countdown, we'll start at three. - (All)  Three, two, one.  (metal ring banging)   (audience applauds) - So in all those experiments I never changed the strength of my electromagnet. I just changed how we use it. Pretty neat. But I want I really came up here to tell you about is how we can use these magnetic fields to protect ourselves from ion storms and other space weather, solar flares and what not. So the magnetic field is doing work on the current in that ring. Now, ion storms are discharged particles. Moving charged particles are currents basically. Which means we should be able to use magnetic fields to affect them. Here I have a cathode ray tube, one that might have been found in an old TV like from the 60's or 70's. And here I have a standard bar magnet. Let's take a look at what happens when we put the bar magnet near the cathode ray tube's beam of electrons. You guys can see the magnet bends the electron beam around. And depending on how I orient my magnet I can bend it in different ways. So if we're flying through an ion storm all we have to do is put a magnetic bubble around our spaceship and the particles will zip right around us without interacting with us or our ship, pretty neat trick.  (organ chord plays)   (audience applauds) Now where that was a pulsed electromagnet this one's an electromagnet that when I turn it on it's going to flip it's North and South poles back and forth very fast. So why might this be interesting? Well other than ion storms and solar flares and charged particles in space, there's the big rock and metal objects that float out in space. You guys know what they're called? Asteroids, asteroids and comets. They're mostly made of metal and magnetic fields like we say with the ring can affect metal. So here I have steel rod and it's attached to these coils, these coils just serve to amplify the affect for the demonstration. And what we're going to see here is that when we place the metal into the magnetic field which is changing back and forth rapidly it's going to do something interesting. After about 20 seconds what happens? The metal rods starting to glow. And if I leave this in here for about another 30 seconds I could liquefy it into slag and it would just crack. So you guys can imagine on our star ship if there's an asteroid coming at us if we had a sufficiently powerful power-supplied nuclear reactor or something and strong enough magnets, we could just pulse a magnetic field, liquefy an asteroid coming at our space ship and be perfectly protected.  (organ chord plays)   (audience applauds) Now there's one last interesting thing about magnetism I want to show you guys. And that's the notion of a superconductor. Superconductors are certain materials, typically rare Earth element that... Get this out of here. Exhibit this very interesting property that when they get really cold, like liquid nitrogen temperatures... they become superconducting so they have no resistance which gives them very high electroconductivity properties and it'll try to exclude magnetic fields. So this track is made of just ordinary bar magnets. And when I put the puck there. You guys can see no trickery here it's truly floating. The puck has a magnetic field so strong that it keeps itself up above gravity. Now I'm going to put it a little lower. You guys can see that this is a pretty frictionless track. And you can spin right around. So how might this be useful on our journey? Well if we have a really big ship like we want to go colonize Proxima Centauri and we want to get from one end to other in a ship we could make a little magnetic tube superconductor and zip from one end of our ship to the other while in space. The other thing is this is defying gravity here. We don't know with the gravity's going to be like on Proxima Centauri. So why even bother dealing with it at all? When we land there and we start unloading colonial supplies and scientific equipment we could just lay out some magnetic track and use superconductors to levitate it all, not even being bothered by gravity. Pretty neat trick.  (organ chord plays)   (audience applauds)  So you see Mr. Weix magnets will make our lives easier and protect us on the journey. You got nothing to worry about. - Well he had some very attractive ideas. But Captain Sprott, I'm still not sure that this is all going to work. - Well, we can erect a large sail and can use the pressure of the sunlight to push our ship along. Or maybe we could aim very powerful lasers at it and push it away from the Earth. Or we could build a nuclear reactor and carry it along with us. In fact Lieutenant Ehlerding has been studying this. Lieutenant Zhulu beam her in. 

- (Lieutenant Zhulu)  Aye, Captain.  (computerized beeping) - You know you're exactly right. To get all the way out to Proxima Centauri we're really going to have to plan it out.  (crickets chirping)  Oh but really though, we have so many more power options available to us all using different types of radiation. Now when I say radiation I'm not talking just about the heat radiation that we learned about earlier. I'm talking about light. Radiation's just a fancy word for light. Now the visible light, the stuff that you can actually see makes up a teeny teeny tiny part of the electromagnetic spectrum. But it's an important part 'cause you know it kind of gets dark out there in space, right? Have you guys ever noticed that when you see a star in sky it kind of looks like it twinkles? Yeah, let me show you why. So I have my laser here, not a star but a laser and it's hitting the wall up there. You guys see that? Now when light comes to us from a star in outer space it's has to go through space, there's nothing there. Kind of like how this laser is going through the air to hit the wall. If I spray some smoke can you guys see the beam there? Yeah, so the laser is going all the way up and hitting the wall up there. So it doesn't really have to go through anything. But when light comes to us from outer space it has to go through our atmosphere which is a bunch of hot gasses and things like that. Kind of like the hot gasses that are caused by my burner here if I can get it to light. And my light twinkles.  ("Twinkle Twinkle Little Star")  And then I turn off my atmosphere and it goes back to being a boring dot.  (organ chord plays)   (audience applauds)  So while I've got my laser here I'm going to show you one other cool thing here. So I've got two cups here. And I'm just going to take some ordinary water and pour it into my cups so we got right there. Pour a little bit of water there. Okay and now I'm going to hold this in front of my laser. Now, we all know that lasers are powerful. You shouldn't shine them in your little brother's eye no matter how annoying he is. And, we'll let this here. Okay and I believe that's good enough. All right, so this one didn't go in the laser. So I'm just going to pour the water back. And then the one that went and the laser. How many of you guys knew that was going to happen? Okay well actually let me let you in on a little secret. So when you're doing a scientific experiment you need a control for all your variables. You need to make sure everything's the exact same between all your situations. Well, there was a sponge in one of them so. You didn't see anything at all. Sorry, guys. Actually it kind of is like magic. Do you guys know the difference between magicians and scientists? Magicians don't tell you their secrets and scientists won't shut up about them. Now as a scientist myself I have another contraption that I would like to show you. I actually have a machine here that can change the color of a balloon using the power of light. Right, I know it's really cool. You know you're at your birthday party and your like, "I don't really think "I like blue balloons anymore. "Maybe I want a yellow one," or something like that. Well, that's where my hand dandy contraption will come in and change the color of your balloon. So I have a light here, not a laser. But I do have a nice bright blue laser. Can you guys see that? All right, so I got my color changing blue laser here. So I'm going to put my balloon into the box. And we're going to count down and we're going to change the color. Sound good? All right so, three, two, one.  (organ chord plays)  Look there. We changed the color of our balloon from blue to clear. I know, well. So since I'm a scientist, I'm going to let you in on the secret. I didn't actually change the color of the balloon. I know, so it turns out there was a clear balloon inside of my colored balloon, yeah, so. - (Student) It's really fun. - It's really fun. So since that blue balloon is colored my laser hits that balloon and the blue balloon absorbs a little bit of that energy and it heats up a tiny little spot on the balloon there. When that balloon spot heats up it makes the balloon pop. But since my inside balloon was clear, the laser just goes right through it. It doesn't absorb any of the  energy so it doesn't pop. It's actually a lot easier if we do it in reverse to see what's going on. So here I have a clear balloon on the outside of a colored balloon. So we'll do the same thing again and I'll show you how it works. I put that in there. A little three, two one, and.  (organ chord plays)  So you can see it, yeah. So laser are really powerful. We could use a laser like that to get us out of our solar system. NASA has actually said that if we could build powerful enough lasers and we could build sails that we could hit them with we could get to Mars in three days. So we could use that to get out of the solar system. Come to think of it, do you know how the solar system holds up its pants? With an asteroid belt.  (rimshot plays)   (audience groans)  So we could get out of our solar system using light and things like that but once we get out there we're going to have to keep going. And that's where we're going to turn to my favorite power, nuclear power. Now, nuclear power just harnesses the energy of atoms as they fall apart or undergo fission. I've actually got some radioactive sources here. And have taken entirely too many classes on how to handle these things safely but when we get out there is space we're going to want to protect ourselves. Well that's what we're going to do here. Now I've got three different sources here. I have an alpha source, a beta source, and a gamma source. Now alpha particles are really big. Beta particles are kind of medium sized. And gamma particles are really light. So if something has a lot of mass is going to go faster or slower than something that's smaller? Slower, right we learned that earlier. So these alpha particles, I'm going to show you with my vintage Geiger counter here, you're going to hear this buzzing sound whenever I'm picking up the particles.  (Geiger counter buzzes)  You guys hear that? So it turns out these alpha particles are so big I can stop them with a piece of paper. Watch this you can hear it.  (Geiger counter buzzes)  Cut it right out, right? These beta particles since they're a little bit smaller. Do you think they can go faster or slower than alpha particles? Faster, so what do you think the paper's going to do? Well let's find out okay. So you here the beta.  (Geiger counter buzzes)  Nothing right? We don't need that. Turns out we need this big piece of lead to stop these beta particles so if you listen you go like this.   (Geiger counter buzzes)  Cuts it right out, right? Now gamma particles are even smaller. So what do you think the lead's going to do? Nothing, let's find out. You hear that?  (Geiger counter buzzes)  You're right it doesn't do anything, so if you guys have ideas about how we're going to shield ourselves from these gamma particles come talk to me after class 'cause we're going to need to figure that out. Well anyway, so nuclear reactors use really, really big atoms like uranium or plutonium, things like that. They're so big they're just kind of unstable. Turns out if we give them a neutron which is a teeny tiny particle usually found in the nucleus of an atom these atoms will fall apart. When they fall apart they give off more neutrons which are absorbed by more atoms which it just kind of keeps going and going and going. It's called a nuclear chain reaction. Now I have a chain reactor over here, not a nuclear chain reactor, but a chain reaction. And I'm going to need somebody to help me set it off. In the red and white there, come on down. What's your name? - Arie. - Arie? Let's give him a round of applause all right.  (audience applauds)  Okay Arie, so we have our neutrons at the top of our reactor here. You can step right here and face the audience. We have our neutrons and we have all of our atoms down here. And you're going to put the neutrons into our reactor and set it off. Let me give you this and you're going to pull it when we count down. Let's go, three, two, one, give it a tug.  (balls thumping) Good job Arie, thank you, you can have a seat.  (organ chord plays)  All right, and it just keeps going. It's got so much power. You so see Mr. Weix, we have so many ways to get out there to outer space, don't you think so? - (Mr. Weix)  Yes you have some very illuminating ideas. - I know I do but it's time for me to make like uranium and split.  (audience applauds) - All right Captain Sprott, maybe this is going to work. But how long is all of this going to take? - Well, I was hoping that we would have this space ship built by today but Steve Narf who sets out all our demonstrations was too busy playing with all the apparatus, and didn't get around to making it. But we do owe him a debt of gratitude for all the work he's done.  (audience applauds)  But seriously I think we know enough physics to mount an expedition like this. But there's a lot of technology that needs to be developed to carry humans on such a long voyage. And that may take another 100 years, who knows. Furthermore Proxima Centauri is very far away. And even if we could travel at 20% the speed of light it would take us 20 years to get there. But I'm quite confident that someday this will be done. And maybe one of you will be on that first voyage. And so I'd better get back to making the star ship that will eventually take us there. And I would like to thank you all for coming. (upbeat music)