Have you ever looked through a microscope?
It's a very different world from ours.
But this is what makes up our world.
Those are cells in your lungs.
Well, that makes you wonder what makes of this world?
What would it look like if you zoomed in
even farther to the individual molecules
that make up these cells?
We didn't know until 2009, when a single molecule was imaged
for the first time at atomic resolution,
and it looks like this.
Those lines, those are bonds you're seeing,
bonds between the atoms.
Obviously, bonds don't look like green smears
anymore than these meerkats look like this in visible light.
But that's the thing.
This image was not made with visible light.
In fact, this molecule is invisible.
It's too small to be resolved with visible light.
All light waves have a wavelength, right.
And at the microscopic level, that light,
like this blue light here, reflects off
of things that are about the same size as that wavelength,
like this cholera.
So that's the issue here.
Despite how small visible light is,
you could fit 350 of these molecules
in one wavelength of blue light.
And we know that atoms are even smaller than these molecules.
And atoms have electrons and protons and neutrons.
And protons have quarks.
How far down can we keep going?
Let's zoom back out for a second.
We couldn't image this molecule with visible light.
But to be honest, we couldn't even resolve these cells
with visible light.
Instead, this image was made with electrons.
It works like this.
Imagine I'm trying to figure out what this frog looks like.
I can throw small things at it, and they'll bounce off
in different directions.
And some pass by, and you get the outline of a frog.
That's how a scanning electron microscope works.
It images things like this pollen.
It operates on the weird quantum mechanical principle
that all particles can act like waves.
And the faster the particle, the smaller the wavelength,
which allows us to see down to smaller scales.
If I tried to image this with visible light
that has a much bigger wavelength,
it just wouldn't work.
Answering the original question, scanning electron microscopes
have seen down to half a nanometer, which is still not
small enough to see an atom.
But in 2013, scientists imaged a single hydrogen atom
for the first time using photo ionization microscopy.
Well, sort of.
What you're seeing here is the electrons' wave
function or the probability of finding it in different parts.
It's kind of like making a picture like this.
This atomic portrait is the smallest picture
we've ever taken at the limit of what we've been
able to see with microscopes.
So that's as far as we can go?
With imaging, yes.
But we can always smash stuff.
Particle colliders are one of the more unusual ways
that scientists probe small scales, smashing particles
together since the 1960s.
Particle colliders use that same quantum mechanical principle,
that fast-moving particles have smaller wavelengths.
And of course, particles smashing together
are generally going pretty fast.
So these particle colliders, weird as they are in concept,
work extremely well.
For one, in 1968, we discovered what
makes up protons and neutrons.
We discovered quarks.
And we discovered that quarks are never alone.
When you try to separate two of them,
you have to put in so much energy
that by the mass energy equivalence,
you'd create two new quarks that bind to the original two.
Yeah, quarks are awesome.
These are the types of experiments going on
at the Large Hadron Collider in Geneva, Switzerland.
That's the giant collaboration going on
between over 100 countries and 10,000 scientists.
It has cost over $13 billion.
That's like eight trips to the moon by some estimates.
The LHC takes tiny particles, like protons,
and smashes them together so hard that they explode.
We measure the pieces and recreate where they came from
to figure out more about the structure of these particles.
This method of smashing particles
together is so effective that, in 2013, we
discovered a new particle, one that had only been theorized
previously, the Higgs Boson.
It led to the confirmation of many aspects of particle
theory, as well as a Nobel Prize for Peter Higgs.
So let's keep going.
What is a quark made of?
Well, as far as we can tell, they have no size.
That is, they have no structure.
We've peered down into a quark as far as 10
to the minus 19 meters, and we've
seen nothing, no indication of smaller components.
The same is true of electrons and neutrinos.
These are all elementary particles.
And as far as we've been able to measure,
they are as small as it gets.
Is it possible that they have no size?
Perhaps.
Maybe, they are literally point particles with zero dimension.
But this creates issues of infinite forces
as you get closer and closer to the particles.
String theory has proposed a solution to these infinities,
that the particles are made of one
dimensional loops or strings.
That way, some parts of the string are closer
and some are further away as you approach the particle.
And your problem of infinities disappears.
And how small are these theoretical strings?
Around the size of the Planck length,
which is, in theory, the shortest measurable length
in the universe.
It is 10 to the minus 35 meters.
That's 100 quintillion times smaller than a proton.
Of course, this scale is not very useful to us.
If you asked my height, I'd have to tell you
I'm 107 billion septillion Planck
links, or just 172 centimeters.
But we're nowhere near measuring those distances.
The LHC is turning on again in 2015.
And with more and more energy in its particle beams,
we'll be able to see at smaller and smaller scales
than we ever have before.
And perhaps someday, we'll be able to measure the smallest
distance in the universe.