Dr Quantum - Double Slit Experiment

Dr Quantum - Double Slit Experiment

And here we are!
The Granddaddy of all Quantum weirdness!

The infamous Double Slit experiment.

To understand this experiment,

we first need to see how particles,
or little balls of matter, act.

If we randomly shoot a small object,
say, a marble, at the screen,

we see a pattern on the back wall,

where they went through the slit, and hit.

Now, if we add a second slit,

we'd expect to see
a second band duplicated to the right.

Now, let´s look at waves.

The waves hit the slit and radiate out,

striking the back wall
with the most intensity

directly in line with the slit.

The line of brightness on the back screen
shows that intensity.

This is similar
to the line the marbles make.

But, when we add the second slit
something different happens.

If the top of one wave meets the bottom
of another wave,

they cancel each other out.

So now, there is an interference pattern
on the back wall.

Places where the two tops meet
are the highest intensity,

the bright lines,

and where they cancel,
there is nothing. So...

When we throw things, that is, matter,
through two slits, we get this.

Two bands of hits.

And with waves, we get
an interference pattern of many bands.

Good, so far. Now, let´s go quantum.

An electron is a tiny tiny bit of matter,
like a tiny marble.

Let´s fire a stream through one slit.

It behaves just like the marble,
a single band.

So, if we shoot these tiny bits
through two slits,

we should get, like the marbles,

two bands.

What? An interference pattern!

We fired electrons,
tiny bits of matter, through,

but we get a pattern like waves,
not like little marbles!

How? How could pieces of matter

create an interference pattern
like a wave?

It doesn´t make sense!

But, physicists are clever.

They thought, maybe those little balls
are bouncing off each other,

and creating that pattern.

So, they decided to shoot electrons
through one at a time.

There is no way they could interfere
with each other.

But, after an hour of this,

the same interference pattern
seemed to emerge.

The conclusion is inescapable:

The single electron leaves as a particle,
becomes a wave of potentials,

goes through both slits,

and interferes with itself,
to hit the wall like a particle.

But mathematically, it´s even stranger:

it goes through both slits
AND it goes through neither.

And it goes through just one,
and it goes through just the other.

All of these possibilities
are in superposition with each other.

But physicists were completely baffled
by this.

So, they decided to peek and see
which slit it actually goes through.

They put a measuring device by one slit
to see which one it went through,

and let it fly.

But the quantum world is
far more mysterious

that they could've imagined.

When they observed,

the electron went back
to behaving like a little marble.

It produced a pattern of two bands,
ot an interference pattern of many.

The very act of measuring or observing
which slit it went through meant

it only went through one, not both.

The electron decided to act differently,

as though it was aware
it was being watched.

And it was here that physicists stepped forever

into the strange netherworld
of quantum events.

What is matter? Marbles or waves?

And waves of what?

And, what does an observer have to do
with any of this?

The observer collapsed the wave functions
simply by observing.