Whether or not two things can truly touch depends more on the definition of touch than it does on the reality: all particles are separated by electromagnetic force.
Can Two Things Ever Touch?
Things never touch because everything is made of atoms. Atoms contain electrons and electrons repel each other. This is basic physics. What we call touching is our brain interpreting the electromagnetic force between atoms created by electron repulsion. Thus, whether or not two things can or cannot touch depends on what we mean by touch. This is explained in detail below. 
- All matter is made of atoms. Atoms contain electrons.
- Electrons are negatively charged and they push away from each other when they get close enough (electron repulsion).
- Our brains perceive the electromagnetic force created by electron repulsion as “touching” (it’s actually more like hovering at 10^-8 meters).
- If two particles actually touched it would create a nuclear reaction.
- The only things in the universe that can actually occupy the same space are bosons (like the photon).
TIP: Smaller quantum particles like quarks also repel, but since electrons are the main entity in this process, we will focus on them here. You can look at our elementary particles page for more information on the smaller particles, or check out the Pauli exclusion principle which shows that identical “fermions” (matter particles) can’t occupy the same space (and thus helps to explain aspects of “the touching issue” in more technical terms).
TIP: The electron is a fermion. All matter is comprised of fermions.
How Do Atoms Work?
Before we can understand why nothing actually “touches,” we have to take a quick look at how atoms work.
In simple terms, atoms are mostly empty space. At the center of that empty space is a tiny nucleus containing almost all the mass of an atom, like a marble in an empty soccer stadium. Surrounding the mass of the nucleus are little packets of negatively charged energy called electrons, which are held in place by electromagnetic force like a magnet.
In general, electrons have negative charges and protons have positive charges; in nature particles with a negative charge always repel each other, and those with opposite charges always attract.
TIP: Electrons aren’t tiny stationary dots in planet-like orbit around the nucleus (like the old model of an electron might suggest). Rather, electrons surrounding an atom exist in a state of probability (quantum superposition), moving at fractions of light speed (about 1% of light speed). This creates an “electron cloud.” Each electron in an atom orbits a nucleus at about 1% of light speed (thus creating a cloud of probable and actual locations). Learn more about how electrons work in atoms.
TIP: The concept of “charge” is central to particle physics. See elementary particles for a deeper understanding of charge.
Particles, in general, are attracted to particles with an opposite charge, and they repel particles with a similar charge. Electrons are naturally attracted to protons but repelled by similarly charged electrons. This fundamental behavior of particles (including electrons) prevents them from ever coming in direct contact with each other.
Instead of coming into direct contact, the electrons and other particles have electromagnetic force fields that interact with each other and cause repulsion and attraction.
ALTERNATIVE VIEW: The video below argues that the point at which attraction and repulsion are balanced should be considered “contact.” On this page, we state whether or not two things can touch (AKA make contact) depends on our definition of touch. The counterargument in the video paired with the argument on this page helps show why this all does somewhat depend on what we mean by the term “touch.”Do Atoms Ever Touch?
Going into detail: Everything in the universe is massless energy particles interacting with each other. There isn’t really anything to touch, even electrons are made of massless energy particles. We know that splitting an atom creates a lot of energy. That is because there is a lot of pure energy bound in “matter” as “mass.” This same intense power in a small space is essentially why nothing ever actually touches. And that is only the tip of the mass-energy iceberg.
How To Define Touch?
We know that we don’t touch things, we simply get 10^-8 meters close. However, we also know that when we dig a little deeper into the way things actually work, energy is both a particle and a wave. Or rather, a particle is an excited state in a wave-like field.
Since particles are fields all we are really saying is that fields can touch, but the excited particle states can’t. Electron fields overlap, but their particles don’t.
Is this field touching actually touching? Should we just redefine “touching” to include forces acting on each other? If we do, then we can argue that there is lots of touching going on (and we could say that when two magnets repel, they are touching)!
Since particles never touch but fields do act on each other, do we simply need to throw out the idea of actual physical touch, and realize that touch is relative to perspective? Or should we focus more on the fact that everything is composed of energy fields at its core? These are good questions.A video questioning if it is simply a matter of needing to redefine the concept of “touch”.
Examples of Electron Repulsion in Real Life
Let’s look at two everyday life examples of electron repulsion in the real world. First, a simple example with no explanation, then a more complex example of electron repulsion.
The “We Already Have Hover-boards” Example
When the atoms in your shoes touch the atoms in the floor they aren’t actually touching. Rather the electrons in your shoe’s atoms are repelling the electrons in the floor’s atoms. The same works for the chair you may be sitting on, or that one-wheeled “hover-board” that is only really hovering on an atomic level.
The takeaway You are currently floating at an extremely small distance (about 10^-8 meters) above the surface that you think you are standing or sitting on.
In real life, two physical systems of particles can never touch because the particles they are made from can never touch. Luckily things don’t need to actually “touch”. In the physical universe, objects quantize to the Planck length and emit fields. If you try to clap your hands, the space between your hands gets infinitesimally smaller, but instead of your hands never moving they just move toward each other in Planck-length frames. Quantum particles can exist in a state of superposition and jump frames. When your hands get close enough, the electrons in your hands repel each other. Electron repulsion is a type of electromagnetic effect.
Your hands have never literally touched, but your clapping action has been completed despite “the infinite” space. That is the way that mathematics works within our physical universe. The Energy between two hands is exchanged resulting in a clap. The energy used to perform the action has shaved a tiny bit off the total mass of the system as mass-energy was used for clapping. A small amount of energy has even escaped as a sound wave.
Why Do We Feel We Can Touch Things?
We feel we can touch things because the electromagnetic force of electrons pushing on each other creates a sensation that tells our brain we are touching something. Literally, the sensation of touch is our brain interpreting the electromagnetic field created by electron repulsion. The sensation we get depends on the type of atoms that form the matter we are touching (i.e. how the molecules and elements are structured).
Why Do Different Things Feel Different When We Touch Them?
Different things feel different because of the way our brain interprets their atomic structure. It works like this:
The different types of atoms that make up the periodic table elements hold different amounts of electrons (based on their proton number). When different atoms with different electrons bind together with other atoms it creates the matter we are familiar with. When we touch different types of matter we feel friction based on the atomic structure of the matter (its mass, density, evenness, etc). The friction we feel becomes an electrical signal in our neurons and that signal is interpreted by our brain as sensation.
All sensations related to touch, including hot, cold, pain, and pleasure are a reaction to the atomic structure of the matter we are “touching”. We can store these sensations as sensory memories helping us to remember not to touch a hot stove, but to jump right into a warm bath.
What if Two Things Actually Touched?
When two particles touch they create nuclear fusion or fission (depending upon what happens when they touch). In other words, two things actually touching would cause a nuclear reaction. This is explained by E=mc2. So the bottom line, forces can be exchanged and fields can overlap, but two things can never touch.
- “Why Physics Says You Can Never Actually Touch Anything:“. Fromquarkstoquasars.com. Retrieved Oct 31, 2015.
- “What does it mean for two objects to touch?“. Physics.stackexchange.com. Retrieved Oct 31, 2015.
- “Pauli exclusion principle“. wikipedia.org. Retrieved Feb, 19. 2016.