*No, the title isn't a joke....*

Apologies for the formality of what's to follow, but I feel a reminder of what "*everything*" is even made of is probably going to be more than helpful here!

So to kick off, let's talk about *subatomic particles**(they sound worse than they are).*

Scientists are in agreement that atoms are the building blocks of our universe, yet even they can be broken down further, into subatomic particles.

An atom is comprised of 3 subatomic particles:

Neutrons

Protons and;

Electrons

The simplest and most abundant atom in the universe is the hydrogen atom, which in fact contains *no neutrons.*

Within a hydrogen atom, 1 electron exists in a* probability cloud *around only a single proton, something which is unique to the hydrogen atom.

Since hydrogen is the most abundant atom, and the same principal generally applies for every other atom anyway, let's talk about how a hydrogen atom is actually structured, as in:

How far away does this electron exist from its neighbouring proton, and;

What kind of sizes are we looking at for these subatomic particles?

See below my attempt of illustrating a hydrogen atom *(ignoring the fact that it's cut off at the bottom)....*

*An important disclaimer that this is most definitely not to scale!*

As you can see, most of the atom is left unlabelled, as it's simply empty space - *a void that's absent of any particles. *

In fact, a hydrogen atom can actually be said to be 99.9999999999996% empty space!

That's incredible to think about - everything that you see around you, including your own body, is 99.99% *emptiness*. A truly mind-blowing concept....

But let's take a look at the numbers, and see how we can come to this percentage for ourselves!

So, there are 3 properties to consider when we come to answering this question of how empty an atom is:

the volume of the proton

the volume of the electron

the volume of the atom as a whole

Recent studies suggest that the radius of a proton is about 0. 84 × 10^-15m.

Using the formula for the volume of a sphere, we can say the following:

V*proton **=* (4/3)*pi*(0.84 x 10^-15)^3

= 2.5*10^-45 cubic meters

And applying the same formula but with the radius of the entire atom instead, which is equal to 0.529*10^-10, we get:

V*atom **=** *(4/3)*pi*(0.529 x 10^-10)^3

= 6.2*10^-31 cubic meters

Now, the next property that I mentioned was the volume of an electron...

The problem with associating volume with an electron is that they're supposed to be fundamental particles, in that they *cannot* *be broken down further. *

Unlike protons and neutrons, which can be broken down into ** quarks**, electrons are labelled under a group known as

**, which means that they're fundamentally unbreakable - they can't be split up into different parts.**

*Leptons*Therefore, physicists call them ** point particles**, making it non-sensical to ascribe a volume to them.

*It's not that it's zero, or infinite, it just doesn't make sense to describe them in that way. *

You can prove that an electron's volume must be zero, and you can also prove that it cannot be zero, concluding that it just doesn't make sense to describe an electron in terms of volume.

While that might be a bit tricky to understand, if you just keep in mind that an electron is supposed to a * point particle,* and cannot be broken down into smaller "

*bits*", I find that it's a lot more intuitive.

If an electron had a volume, and you applied a force to it, then the side that you applied the force to would move before the other side, implying that an electron is made of parts, otherwise you'd be saying that the electron is both moving and not moving at the same time.

There's multiple different directions that you can take on this, but each one of them conclude that either we're mistaken in our understanding that an electron cannot be broken down further, or that electrons can't be given a volume.

When I first heard of this concept, I think the most convincing argument to me was this, and hopefully it can help clarify things for you as well:

If an electron has volume, then it must be spread over 3 dimensions. The very definition of volume is that it's area in 3 dimensions - it has an x-axis, y-axis and z-axis component. However, this would imply that an electron can at least be broken down into 3 different parts! *(one part for the x-axis, one for the y-axis, and one for the z-axis). *

This is an obvious contradiction to our understanding that an electron is unbreakable, therefore physicists say that an electron isn't 3 dimensional, but rather exists in a point of space - an electron is a **point particle. **

Given this* (perhaps unexpected!) *notion, we can finalise the percentage of an atom that is empty by the following calculation:

The volume of the proton divided by the volume of the atom, multiplied by 100 to get the percentage of volume that the proton is covering, and then 100 minus that number to get the rest of the volume, which is the volume of empty space *(seeing as we've just concluded that an electron can't have volume)*

*V**full **=** **(*2.5*10^-45 *)/(*6.2*10^-31 *)*100*

* = 4*10^-15%*

*V**empty **= 100 - (4*10^-15) %*

* = 99.9999999999996%*

*And there you have it.....*

While we may have just proved it mathematically, obviously it is still an absolutely baffling, mind-blowing concept, and can anyone really imagine it in their head?

*Probably not... It turns out that most things in our universe are like that!*

To better demonstrate this level of emptiness, take a look at this comparison! *credit to Steve Gagnon*

*If a hydrogen atom (the most abundant atom in the universe) were the size of the Earth, then the nucleus (in this case the single proton) at the centre would stretch 200 meters across....* Everything else is completely empty.

I think that perfectly illustrates the kind of scale that we're talking about, and makes the concept of everything being 99.99% emptiness much easier to understand... *I think.*

Obviously, we've been using the hydrogen atom as an example in this article, but the same can pretty much be said for every other atom in the universe, such as oxygen, gold, aluminium, sodium etc...* *

The reason why I think that this concept is so valuable to anyone interested in physics/astronomy, is its potential to unlock the reasoning behind extremely dense objects like black holes and neutron stars.

For example, take 1kg of anything really, but for arguments sake, let's say that it's a block of iron.

That block of iron is 99.99% empty space, but image how much something of that typical volume would weigh if it had no empty space?

Just out of curiosity, we can say that if that 1kg block was suddenly restructured in a way such that 100% of the space was occupied by neutrons, the mass of the iron block would go from 1kg, to 1/(*4*10^-15 ).*

*= 2.5*10^14*

*= 2,500,000,000,000,000 kg!!*

**In other words, 250 trillion kg! **

Naturally, you're probably wondering whether this is even realistic or not?

Could an object really be exclusively made from neutrons that are jam packed together to form a body that has no empty space?

*Welcome neutron stars...*

If you've ever wondered how they're so incredibly dense, it's because their protons have combined with their electrons to form a body that's completely comprised of neutrons, with next to zero empty space. Hence, per unit area, they're incredibly massive objects.

If you're interested in learning more about neutron stars, then you can check out this article __here__!

**And what about black holes?**

Well, nobody knows what they're made of, but whatever it is, it's somehow even denser than the structure of degenerate neutrons that make up neutron stars.

*So, everything truly is 99.99% nothing....*

If this was interesting to you, then I'd recommend checking out some of my other articles here at Expansive, as I quite often talk about unusual concepts such as this!