The experiment that you're about to see is one of the first things that inspired me to want to become a physicist.
I think it perfectly captures some of the awe,
wonder and mystery surrounding trying to figure out what the world is made of.
To try and capture some of that reaction that I had,
I asked my friends who hadn't seen the experiment before and who are not physicists to have a look and
here's what they thought...
Okay. I have no idea what the double slit experiment is or who Dr. Quantum is
but I'm excited to find out.
I feel like this is a Fine Brothers audition.
This'll be interesting, let's give this a go.
Just want to specify that I know nothing about quantum physics.
I did watch a bit of Bill Nye the Science Guy as a kid
so I'm hoping that works a bit in my favor, but I'm still more than 100% sure
this is going to make me question everything. So let's get started.
And here we are, the granddaddy of all quantum weirdness
the infamous double slit experiment.
I mean look at the man, just look at his hairstyle.
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.
Okay, so far pretty simple, pretty easy to keep up with but um something tells me it's gonna get a bit more complicated than that.
Now if we add a second slit, we would expect to see a second band
duplicated to the right.
Yes, I would expect to see a second band.
Okay, once again
still fairly simple, fairly logical.
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.
Okay, so three for three so far. So far everything's fairly logical
that's uh, that's hoping it stays like this.
Okay waves and marvels making the same sort of thing.
But when we add the second slit...
Oh no, I feel like something's going to happen when there's two slits.
...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.
Not gonna lie that's actually pretty cool.
Okay, so that one's a bit more complicated but it still makes sense. Okay. So far we're coping we are keeping track
hopefully that stays the same.
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.
So is this like the difference between waves and particles and all that?
Good so far, now
let's go quantum!
Oh quantum.
Oh, we're going quantum.
I just can't stop laughing at him.
An electron is a tiny tiny bit of matter,
like a tiny marble.
Are electrons matter? The real question is do electrons matter?
Let's fire a stream through one slit.
It's amazing what they could do these days.
Okay
this is when I think, I just have a small feeling that
things are going to get a bit more complicated than the first few experiments.
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!?
Where do these interferences Keep coming from?
Oh God, there's always an interference with this guy isn't there?
Okay. So this is the point of the video where to me this makes no sense. You've lost me at this point.
I'm I'm trying to make sense of this experiment. The only,
the only way I can
wrap my head around it is
if the marbles, the electrons, aren't matter, but
man I'm hoping at the end of this video they tell us how this is possible.
I hope they give us a logical explanation and not leave us in the dark.
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?
Yeah, I don't know how I'd like to know.
So it starts as matter then becomes a wave and interferes with itself?
I feel like I'm watching a cold case of science.
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 decide 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 is seen 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.
What?
Okay, let's just keep going.
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 these possibilities are in superposition with each other.
It goes through both and and neither...
yeah, that makes sense.
The fact that he's laughing in the background of his own video... I wouldn't trust this guy to deal with my quantum theories.
Physicists were completely baffled by this.
I'm baffled by this!
So they decided to peek and see which slit it actually goes through.
Yes. So now I'm hoping they find out how this is possible.
This is the point where I'm hoping they give us a logical explanation.
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 than they could have imagined.
When they observed, the electron went back to behaving like a little marble. It produced a pattern of two bands,
not 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,
How does someone make sense of this? How are you meant to make sense of this?
The electron decided to act
differently
as though it was aware
It was being watched.
It was here that
physicists stepped forever into the strange never-world of quantum events.
Oh I like the conspiracy music.
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 wavefunction
simply
by observing.
That is by far the most mind-bending video I've ever seen by a longshot and the worst part is that there's no answer at the end of this video,
they just give us the dilemma.
I don't even know how this is possible. I'm just at this point, I'm just trying to comprehend what I just watched.
I personally don't know what to think about this because how did that happen? How did it split? How did it like,
how did it go through both slits, but also neither? That's just, first of all that's a mind blow,
but then the second mind blow is that when it was being watched it was like 'Oh pranked I'm gonna do something different'... what?
And that was definitely trippy, that was something that didn't make sense in the physical world.
I don't know, like matter or waves. Well, maybe it's something else like maybe it's not either/or.
I actually thought that was actually pretty good. I feel like
nobody can relate when your hairstyle looks like that.
