- 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 moves toward you and then away from you
at a very slow speed of about two meters per second.
That's about walking speed in fact.
So I can be quite confident that
there is a planet there to visit Mr. Weix.
- 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]