(gentle mysterious music)
- So, let's talk about invisibility.
Sometimes I teach optics at the university,
and I tell my students invisibility is impossible.
Light cannot wrap around an object
like water wrapping around a boulder
downstream from a boulder.
You do not even know there's a boulder upstream.
Water wraps around the boulder, reforms on the other side,
and the boulder becomes invisible to anyone downstream.
Light cannot do that, I taught my students.
Well, I was wrong.
(light audience laughter)
So was every single physics textbook on the planet Earth.
This year was achieved on a small scale
at optical frequencies
at the University of California at Berkeley,
University of Karlsruhe in Germany,
and also Caltech in Los Angeles.
Three groups have now shown
that visible light on a microscopic scale
can bend in a way consistent with invisibility.
So,
Harry Potter, watch out!
(light audience laughter)
However, there are problems.
We're not gonna have any invisibility cloak any time soon.
It'll take decades to iron out the problems.
For example, if you are inside the invisibility cloak,
it's a cylinder,
you cannot see, if you're inside, you cannot see outside.
You have to drill two holes.
So, from the outside,
you see two eyeballs floating in midair!
(audience laughing)
Like this!
So, this is not a true invisibility cloak
because otherwise you cannot see outside.
However, it's coming more rapidly than you think.
Now also, Stephen Hawking, my colleague,
has said that he doesn't believe in time travel
because where are the tourists from the future visiting him?
Maybe they're invisible.
(audience laughing and applauding)
Anyway, the way it's done
is that we physicists made a mistake.
When we teach optics, we say the light bends in water,
glass, diamonds, oil.
We talk about uniform substances,
but if there're impurities, we forgot about that,
if there're impurities,
each impurity can kick the light beam
to within the wavelength of light,
and that's how you obtain invisibility.
So, with metamaterials with impurities in it,
light can wrap around the object, reform at the other end,
just like water going around a boulder in a stream.
This was once thought to violate
all the known laws of physics, and now we've done it.
And now, let's move on to something
that's at the heart of every Trekkie,
and that is teleportation. (audience clapping)
Is it possible to dissolve,
and then have your atoms reform
on the other side of the room?
This is the device
that makes the quantum teleportation possible.
It is done with laser beams,
but as I mentioned, cesium, beryllium atoms
have now been teleported,
and one day we'll perhaps be able to teleport large objects.
Now, the next question is what about "Star Wars"?
What about some of the fantastic devices in "Star Wars"?
Like, for example, the lightsaber.
I mean, every kid grows up playing with lightsabers.
It turns out that lightsabers really are possible
using plasmas, very hot gas,
like what you find in the center of the sun.
You can actually create a lightsaber
that'll slice right through any piece of steel.
The problem, though, why don't we have ray guns?
Why don't we have lightsabers?
Does anyone know the reason?
We can create a laser beam
that'll punch right through steel.
We can create lightsabers that'll slice like butter
through any material.
So, why don't we have ray guns and lightsabers
in the battlefield?
Does anyone know the answer to that?
(light audience murmuring)
Yeah, it would just keep on goin' right, yeah.
But, why don't we deploy these on the battlefield, then?
Yeah?
Yeah, there's no portable power pack.
That is the reason why we don't have jet packs
like Buck Rogers,
that's the reason why we don't have ray guns,
that's the reason why we don't have lightsabers
on the battlefield.
No portable power pack.
The only device that small
capable of unleashing power on that scale
is a small hydrogen warhead.
(light audience laughter)
And, you don't want that, okay?
So, a portable power pack is the reason why
we don't have ray guns, force fields, jet packs.
The world's most advanced jet pack
only runs for about two to three minutes.
So, if you're in a fire fight,
and it runs after two or three minutes in space,
you're in deep trouble.
(audience laughs) So, that doesn't work.
However,
the Death Star is possible.
When "Star Wars" first came out, the critic says,
"Ha, you're not gonna be able to create an object
which can destroy the Earth.
You cannot create a planet buster."
Wrong.
We can develop planet busters.
It turns out there's no upper limit to the amount of energy
that can be stored in a hydrogen bomb.
How do I know that?
I was once offered a job designing hydrogen warheads.
I turned it down
because I thought that I didn't wanna work
on these little explosions called atomic bombs.
I wanted to work on big explosions
like the Big Bang, okay?
(light audience laughter)
So, let's talk about this.
It is possible that by stacking H-bombs in layers,
you can create hydrogen bombs of unlimited magnitude.
That is, you could literally crack the Earth in half,
and you can have laser beams which store the energy.
Of course, you have practical problems
like the stability of the lasing material,
but it is theoretically possible to build these things.
And, in outer space,
they may occur naturally.
This is a Gamma Ray Burster, a gigantic hypernova
that releases a pencil thin, pencil thin beam of light
through the north pole and the south pole.
If one of these beams of light ever hit the Earth,
it's all over.
(light audience laughter)
That's why we are keeping track of WR 104.
WR 104 has been developing quite a bit of internet chatter.
It is a Gamma Ray Burster in making
aimed directly at the Earth.
(light audience laughter)
You're staring now at the business end
of an object which may have enough energy
to blow the Earth apart.
Well, the good news is it is 8,000 light-years away,
which is a good comfortable distance to be,
but Gamma Ray Bursters can negotiate that distance.
The latest calculation shows that it's slightly misaligned,
so it'll probably graze the Earth, but not hit the Earth.
And, it's 8,000 light-years away
which means that maybe it blew up 8,000 years ago!
And, tomorrow, you're doing your laundry, and you look up,
and you see this huge ball of Gamma Rays comin' at you,
ionizing the atmosphere in the process.
You can kiss your rear end goodbye.
(light audience laughter)
But, the latest calculation shows that it's far away,
and it probably will just miss the Earth,
but its north pole is pointed directly at us,
slightly misaligned by about one degree.
(gentle music) And now, let's talk about...