How Small Is An Atom? Spoiler: Very Small.

Atoms are ridiculous and unbelievably
small.

A single human hair is about as thick as

500,000 carbon atoms stacked
over each other.

Look at your fist, it contains trillions
and trillions of atoms.

If one atom in it were about as big as a
marble, how big would your fist be?

Well… about the size of Earth.
Hm… still hard to imagine?

Let’s try something different

Look at your little finger.

Imagine that its tip is as big as the
room you’re sitting in right now.

Now fill the room with grains of rice.

One rice corn represents one cell of your fingertip.

Now let’s zoom in on the rice corn.

And now, one cell is as big as the
room you’re in right now.

Let’s fill it with rice again.
This is about the size of a protein.

And now, let us fill all the empty spaces
between the rice corns

with fine grains of sand.

This is roughly how small atoms are.

What is an atom made of?

Let us just pretend that atoms look
like this for a minute

to make it easier to understand.

An atom consists of three
elementary particles:

neutrons, protons and electrons.

Protons and neutrons bind together and
form the atom core,

held together by the strong interaction,

one of the four fundamental forces in
the universe.

They are made from quarks and
held together by gluons.

Nobody knows exactly how small quarks are.

We think they might literally be points,
like in geometry.

Try to imagine them as being
zero-dimensional.

We suspect that quarks and electrons are

the most fundamental components
of matter in the universe.

Electrons orbit the atom core. They
travel at a speed of about 2,200 km/s,

fast enough to get around the Earth in
just over 18 seconds.

Like quarks, we think electrons are
fundamental particles.

99.999999999999%

of an atom’s volume is just empty space…
Except that it isn’t.

What we perceive as emptiness is actually
a space filled by quantum fluctuations,

fields that have potential energy and
build and dissolve spontaneously.

These fluctuations have a fundamental
impact on how charged particles interact.

But that’s a topic for another video.

How much space do the core and
electrons actually fill?

If you were to subtract all the spaces
between the atom cores

from the Empire State Building,
it would be about as big as a rice corn.

All the atoms of humanity would
fit in a teaspoon.

There are extreme objects where states
like this actually exist.

In a neutron star, atom cores are
compacted so densely

that the mass of three Suns fits into an
object only a few kilometers wide.

By the way, what do atoms look like?

Well, kind of like this.

Electrons are like a wave function and a
particle at the same time.

We can calculate where an electron might
be at any given moment in time.

These clouds of probability,
called orbitals,

are where electrons might be
with a certainty of 95%.

The probability of finding an electron
approaches 0

the further we get away from
the atom core,

but it actually never is zero, which
means that, in theory,

the electron of an atom could be on
the other side of the universe.

Okay, wait a second.

These strange thingies make up all
the matter in the universe.

For many dozens of known elements,

you don’t need many dozens of
elementary particles, just three.

Take one proton and one electron,
and you have hydrogen.

Add a proton and a neutron,
you have helium.

Add a few more, you get carbon,
a few more, fluorine,

even more, gold, and so on.

And every atom of an element is the same:

all hydrogen atoms in the universe,
for example, are the same;

the hydrogen in your body is exactly
the same as the hydrogen in the Sun.

Do you feel confused right now?
We certainly do!

Nothing on this scale of the universe
makes any sense in our world,

and we’ve not even begun talking about
quantum mechanics or the particle zoo,

which are even stranger!

Our model of atoms has changed a number
of times since we first conceived it,

and the current one will certainly
not be the last.

So let us support scientists and research

and wait for the next wave of
mindboggling new information

about this strange world that is the
basis for our existence.