- In science fiction,
- In science fiction,

one of the most powerful widely thing tools in battle
one of the most powerful widely thing tools in battle

is the force field.
is the force field.

We've all seen them,
We've all seen them,

a transparent paper thin yet impenetrable field
a transparent paper thin yet impenetrable field

that can be shaped and morphed into practically anything.
that can be shaped and morphed into practically anything.

So with all the money that the military spends
So with all the money that the military spends

on making new and advanced weapons,
on making new and advanced weapons,

you think they would invest in something
you think they would invest in something

as powerful as a force field?
as powerful as a force field?

So why don't they exist?
So why don't they exist?

Are they physically possible?
Are they physically possible?

Well, if you're going to make a force field
Well, if you're going to make a force field

you need a force.
you need a force.

Right now, there are four known forces of the universe,
Right now, there are four known forces of the universe,

gravity, the electromagnetic force
gravity, the electromagnetic force

and the strong and weak nuclear forces.
and the strong and weak nuclear forces.

But could any of them be used to make a force field?
But could any of them be used to make a force field?

First let's look at gravity,
First let's look at gravity,

the reliable force that keeps us from flying off the earth
the reliable force that keeps us from flying off the earth

that holds the solar system and the galaxy together.
that holds the solar system and the galaxy together.

Could we somehow mold gravity into a force field?
Could we somehow mold gravity into a force field?

Well, gravity kind of has the exact opposite properties
Well, gravity kind of has the exact opposite properties

of a force field.
of a force field.

A force field needs to repel things,
A force field needs to repel things,

be ridiculously strong so that nothing can penetrate it
be ridiculously strong so that nothing can penetrate it

and be focused into a thin plane.
and be focused into a thin plane.

Gravity is an attractive force
Gravity is an attractive force

and a pretty weak one at that.
and a pretty weak one at that.

The gravity of an entire planet
The gravity of an entire planet

is counteracted every time you pick up a pencil.
is counteracted every time you pick up a pencil.

It also works over large distances
It also works over large distances

and isn't easy to manipulate, especially into a thin plane.
and isn't easy to manipulate, especially into a thin plane.

So there's not much hope
So there's not much hope

of making gravity of force field.
of making gravity of force field.

Next, there's the electromagnetic force.
Next, there's the electromagnetic force.

You know, the one that powers your PlayStation
You know, the one that powers your PlayStation

and lets you watch cat videos.
and lets you watch cat videos.

It's a bit of a better option than gravity but not by far.
It's a bit of a better option than gravity but not by far.

It can be repulsive
It can be repulsive

which is what you would want in a force field.
which is what you would want in a force field.

So it's got that going for it,
So it's got that going for it,

but it's completely useless against any insulating material
but it's completely useless against any insulating material

like rubber or plastic.
like rubber or plastic.

Also like gravity,
Also like gravity,

it can't really be focused into a thin plane.
it can't really be focused into a thin plane.

So sorry, electromagnetic field,
So sorry, electromagnetic field,

you can't be a force field either.
you can't be a force field either.

The last two forces are the strong and weak nuclear forces.
The last two forces are the strong and weak nuclear forces.

The weak force is the force of radioactive decay.
The weak force is the force of radioactive decay.

It heats up the earth's core
It heats up the earth's core

and is responsible for volcanoes, earthquakes
and is responsible for volcanoes, earthquakes

and continental drift.
and continental drift.

The strong force holds the nucleus of atoms together.
The strong force holds the nucleus of atoms together.

It gives energy to the sun and stars
It gives energy to the sun and stars

effectively lighting up the entire universe.
effectively lighting up the entire universe.

So could either of these make a good force field?
So could either of these make a good force field?

Well, the problem is that
Well, the problem is that

both nuclear forces are too short ranged.
both nuclear forces are too short ranged.

They act over only a few nuclei
They act over only a few nuclei

which makes them extremely difficult to manipulate.
which makes them extremely difficult to manipulate.

In fact, the only way scientists have of manipulating them
In fact, the only way scientists have of manipulating them

are too low subatomic particles up in atom smashes
are too low subatomic particles up in atom smashes

or to detonate atomic bombs.
or to detonate atomic bombs.

So unfortunately they won't work as force fields either.
So unfortunately they won't work as force fields either.

So if none of the forces could work as force fields
So if none of the forces could work as force fields

does that mean they are impossible?
does that mean they are impossible?

The laws of physics simply won't allow it?
The laws of physics simply won't allow it?

Well not quite, scientists have another lead.
Well not quite, scientists have another lead.

The fourth state of matter.
The fourth state of matter.

The first three states of matter
The first three states of matter

are gases, liquids and solids
are gases, liquids and solids

and the fourth is something called plasma.
and the fourth is something called plasma.

We're not too familiar with plasma
We're not too familiar with plasma

because it's not very abundant on earth
because it's not very abundant on earth

but it's actually the most common form
but it's actually the most common form

of visible matter in the universe,
of visible matter in the universe,

making up the sun, the stars and interstellar gas.
making up the sun, the stars and interstellar gas.

But what is it?
But what is it?

When you heat up a gas to extremely high temperatures
When you heat up a gas to extremely high temperatures

the electrons are torn away from their mother nucleus
the electrons are torn away from their mother nucleus

because of all the extra energy they get from the heat.
because of all the extra energy they get from the heat.

Because the gas particles have lost electrons
Because the gas particles have lost electrons

they become positively charged
they become positively charged

this new type of gas where the electrons are free
this new type of gas where the electrons are free

and the particles have charged, is called plasma.
and the particles have charged, is called plasma.

Because of all the charged particles,
Because of all the charged particles,

plasma can be influenced by an electromagnetic field
plasma can be influenced by an electromagnetic field

even being shaped into a thin plane
even being shaped into a thin plane

or what's known as a plasma window.
or what's known as a plasma window.

Plasma windows are currently used to weld metal
Plasma windows are currently used to weld metal

using electron beams
using electron beams

as they can separate vacuum from air.
as they can separate vacuum from air.

They may not be force fields in the traditional sense
They may not be force fields in the traditional sense

as they're not made of force,
as they're not made of force,

but they mimic the properties of a force field pretty well.
but they mimic the properties of a force field pretty well.

We've already mentioned that they can be manipulated
We've already mentioned that they can be manipulated

so we could make any shape we wanted with a strong
so we could make any shape we wanted with a strong

and intricate enough electromagnetic fields.
and intricate enough electromagnetic fields.

They can separate air from vacuum
They can separate air from vacuum

which means that in theory
which means that in theory

we could have a spaceship made entirely out of plasma.
we could have a spaceship made entirely out of plasma.

And importantly,
And importantly,

when plasma is heated to extremely high temperatures,
when plasma is heated to extremely high temperatures,

it becomes what's known as impermeable plasma.
it becomes what's known as impermeable plasma.

It becomes very thick and matter has passing through it.
It becomes very thick and matter has passing through it.

An impermeable paper thin, easily manipulated substance?
An impermeable paper thin, easily manipulated substance?

This sounds like a pretty good imitation force field,
This sounds like a pretty good imitation force field,

so why aren't we using them?
so why aren't we using them?

Well, plasma only becomes impermeable
Well, plasma only becomes impermeable

at extremely high temperatures.
at extremely high temperatures.

I'm talking harder than the surface of the sun temperatures.
I'm talking harder than the surface of the sun temperatures.

We have the technology to reach these temperatures
We have the technology to reach these temperatures

just not without using a huge amount of energy.
just not without using a huge amount of energy.

So plasma windows are usually only
So plasma windows are usually only

about three feet high and one foot wide.
about three feet high and one foot wide.

However, as technology improves,
However, as technology improves,

it's not difficult to imagine bigger
it's not difficult to imagine bigger

and stronger plasma windows in the future.
and stronger plasma windows in the future.

But can a plasma window alone
But can a plasma window alone

ever really be enough to withstand
ever really be enough to withstand

cannonballs, bullets and laser beams?
cannonballs, bullets and laser beams?

In science fiction force fields
In science fiction force fields

are practically indestructible.
are practically indestructible.

Could a plasma window ever really be indestructible?
Could a plasma window ever really be indestructible?

Well famous physicist Michio Kaku
Well famous physicist Michio Kaku

thinks that plasma windows on their own
thinks that plasma windows on their own

may not be enough to live up
may not be enough to live up

to the great expectation of force fields in science fiction,
to the great expectation of force fields in science fiction,

but stacking on a couple of layers of other stuff,
but stacking on a couple of layers of other stuff,

might do the trick.
might do the trick.

He imagines that
He imagines that

if we ever did have force field type things,
if we ever did have force field type things,

the top layer would be a supercharged plasma window
the top layer would be a supercharged plasma window

hot enough to vaporize metals.
hot enough to vaporize metals.

The second layer would be a flat web
The second layer would be a flat web

of high energy laser beams
of high energy laser beams

vaporizing anything that made it through the plasma window.
vaporizing anything that made it through the plasma window.

And the third layer would a sheet of carbon nanotubes
And the third layer would a sheet of carbon nanotubes

only one atom thick
only one atom thick

but 100 times stronger than steel.
but 100 times stronger than steel.

At the moment carbon nanotubes
At the moment carbon nanotubes

are only a few millimeters long
are only a few millimeters long

but Kaku expects that this will change
but Kaku expects that this will change

as technology improves over the years
as technology improves over the years

and we'll be able to make shapes of any length we like.
and we'll be able to make shapes of any length we like.

This combination of plasma, lasers and carbon nanotubes
This combination of plasma, lasers and carbon nanotubes

would truly be impenetrable to most forms of matter.
would truly be impenetrable to most forms of matter.

But, yes, there's still a but,
But, yes, there's still a but,

none of these layers would be any use against a laser beam,
none of these layers would be any use against a laser beam,

being transparent and stopping light going through,
being transparent and stopping light going through,

you don't really go hand in hand.
you don't really go hand in hand.

Unless one way this multilayered shield could stop a laser
Unless one way this multilayered shield could stop a laser

is if one of the layers became partially opaque
is if one of the layers became partially opaque

upon sensing sufficient light intensity.
upon sensing sufficient light intensity.

This technology kind of already exists.
This technology kind of already exists.

It's called photo chromatics.
It's called photo chromatics.

You know, there's glasses that look like regular glasses
You know, there's glasses that look like regular glasses

but then when they're exposed to sunlight,
but then when they're exposed to sunlight,

they turn into sunglasses?
they turn into sunglasses?

That happens because there are molecules in the lenses
That happens because there are molecules in the lenses

that can exist in two states.
that can exist in two states.

In one state, the molecule is transparent
In one state, the molecule is transparent

but when exposed to sunlight,
but when exposed to sunlight,

it changes to its opaque state blocking out the sun's rays.
it changes to its opaque state blocking out the sun's rays.

However, at the moment, photo chromatics
However, at the moment, photo chromatics

that can stop a laser beam don't exist.
that can stop a laser beam don't exist.

Right now the technology just isn't there
Right now the technology just isn't there

to do justice to the impressive force fields
to do justice to the impressive force fields

we see in the movies
we see in the movies

but Michio Kaku classifies force fields
but Michio Kaku classifies force fields

as a type one impossibility.
as a type one impossibility.

That is impossible by today's technology,
That is impossible by today's technology,

but achievable he thinks within the next 100 years or so.
but achievable he thinks within the next 100 years or so.

Of course, this is just one theory
Of course, this is just one theory

and it's very difficult to make predictions
and it's very difficult to make predictions

about the future.
about the future.

There are obviously a lot of kinks to work out.
There are obviously a lot of kinks to work out.

For example, if plasma becomes really thick
For example, if plasma becomes really thick

when will it become opaque?
when will it become opaque?

And some of the things mentioned in this video
And some of the things mentioned in this video

may be discovered to be impossible,
may be discovered to be impossible,

but they haven't yet.
but they haven't yet.

So what do you think force fields, possible or impossible?
So what do you think force fields, possible or impossible?

Thanks for watching guys.
Thanks for watching guys.

This video was based on a chapter of the book
This video was based on a chapter of the book

Physics of the Impossible by Michio Kaku
Physics of the Impossible by Michio Kaku

I've linked it in the description below
I've linked it in the description below

along with any other sources that I've used.
along with any other sources that I've used.

If you liked this video,
If you liked this video,

make sure to like this video and subscribe for more physics
make sure to like this video and subscribe for more physics

and sometimes math. Bye
and sometimes math. Bye