The matter of matter: It’s something we can touch and feel. It’s the ground we stand on and the air that we breathe. It’s our office table, the coffee cup, the milk and coffee inside, the cells of your skin your hand. It’s the white and grey matter in our brain, and maybe the unknown dark matter of the Universe — not going there in this post though.
Let’s turn away from the comfortably far away stars and galaxies and the beginnings and ends of Universes where the unknown can make anything feel like possible, and take a closer look at all of this known matter we consist of in our day to day life.
The ordinary matter might be only 5% of the measurable Universe, but never the less it feels like 100% of our everyday life.
The fundamental building blocks
If we zoom in on everything we know as matter, we zoom through molecules in some structure, made of atoms bound together by electromagnetic forces. Inside the atom is a nucleus made of protons and neutrons and an electron cloud of electrons making a fuzz around the tiny center.
Most of the atom is empty space, but the electron needs all this space, so the Atom from DC Comics would not be possible without changing some fundamental rules in the Universe.
The larger the energy level of the electron, the more space it needs but even the electron in the ground zero state has some amount of energy which gives it an orbital average radius about 0.1 nanometers (10^-10 m or 1 Ångstrom). It might not seem as much, but it’s 100.000 times more space than the nucleus.
Imagine you held a pea of 1 cm in diameter in your hand. The size of the electron cloud would then be 100 km in diameter. For me, sitting in Copenhagen, it would mean that the electron cloud around my pea nucleus would be in most of Zealand and the lower part of Sweden. That’s a mother f*cker electron cloud from my pea nucleus.
So, the tiny nucleus is just about 1 femtometer (10^-15 m) in diameter. It contains neutron and protons, but they are made of even tinier quarks. Three quarks in each proton and neutron, as seen in the first image in this section.
Quarks and electrons are part of the most fundamental particles that we know, which means that they are the tiniest part of matter that we have discovered so far.
Will we one day discover that even they are made of even smaller parts? Who knows … but so far, they are the smallest part of matter that we know.
So far so good. We took a chunk of matter, such as our coffee cup and broke it into smaller chunks. Our coffee cup is just quarks and electrons bound by some forces and rules of the Universe.
But wait, there is more.
The force carriers
The force carriers are part of the fundamental particle family. Force carriers are also particles like electrons and quarks, but they carry the four fundamental known forces in the Universe (and hence also in our boring office space).
The strong force is what holds the three quarks together in a proton or neutron. It’s also what glues the protons and neutron to stick together inside the nucleus, even though the protons should be repelling each other because of the same positive charge.
The electromagnetic force will attract opposite electrical charges and repel those that are the same. But the strong force is stronger than the electromagnetic force on those tiny nucleus distances and hence the nucleus is held together.
Below is a nice graphical representation of the known fundamental forces and where you can find them in your coffee cup and also some of their implications.
So for example, the strong force is mediated by the gluon particle. Here’s where our understanding of everyday matter becomes a bit … unsatisfying. Sure, our coffee cup consists of atoms, which consist of electrons and quarks. It’s just bigger matter, that is broken into smaller matter. We get it.
But the same building blocks that we used for matter, are also used for forces that you cannot touch, but probably feel. It kind of makes sense, when we think of Einstein’s famous equation E = mc², where matter and energy can be converted. Matter particles can likewise be converted to force carrier particles, such as photons.
But they are still described as particles. And when we think about particles, we think about miniature matter, like a sphere or a point or some dot of solid matter. Is the energy transferred through a photon thus a tiny photon-ball jumping back and forth between matter particles?
Or are particles, including quarks and electrons, even tiny balls?
What are particles really?
Is he a dot or is he a speck?
When he’s underwater, does he get wet?
Or does the water get him instead?
— They Might Be Giants, “Particle Man”
Consider this image below. It’s a typical example of a representation of particles, and it even gives a graphical representation of the relative masses of the particles, gluons and photons being massless and the top quark with its top mass.
The fuzziness in the particles might try to tell us, that they are not solid spheres, but still a spherical volume of … something. What? If they are fundamental and hence not divisible, then they cannot further consist of anything else.
In the first image above, there was another example, where we zoomed all the way from our human body into the quarks in the protons, as seen in the image here. We see the three quarks as tiny spheres, and they are held together with gluons — here drawn as springs/waves.
So what are particles? Spherical particles? Waves? Other kinds of interactions? The thing is, that we don’t really know what particles are, and therefore we just represent them in a way that makes the most sense in the context.
But it also makes it hard to understand our Universe on the smallest levels, since we cannot make sense of matter and energy being two sides of the same coin, how particles can be converted to energy and to different particles behind the scene, and how fundamental forces should be small balls of “stuff” interacting with other particles as if they were tennis balls being thrown back and forth between them. It just doesn’t make much intuitive sense to view the particles as tiny balls.
Also, the negatively charged electron should be attracted to the positive nucleus. But why doesn’t it then “fall into” the nucleus? Because electrons are not “tiny balls”. They can be described as a wavefunction of the probability of an energy level around the nucleus. And those energy levels can also be measured inside the nucleus itself. The more energy the electron has, the larger the orbit of the energy probability.
In the image shown, the electron cloud is mathematically plotted as the white spot overlapping the nucleus. The nucleus itself is not shown, but it would be in the center.
If particles aren’t tiny balls, then what are they?
The best description of fundamental particles for both matter particles and force carriers are fields.
Quantum particle fields forever
Consider the fabric of spacetime (including your coffee cup) consist of endless fields. There is a field for each fundamental particle that we know and what we think of as particles are just ripples in those fundamental fields. So a photon is an excitation of the electromagnetic field, and an electron is an excitation of an electron field. Likewise, there are six quark fields for each of the six quarks and fields for the weak and strong force.
So how does that help us? Does it make any more sense?
It can explain such things as why particles can convert into energy and then into other particles. Both matter particles and force carriers would be fields that can closely interact. Excitation of a particle field would interfere with other layers of particle fields and hence be able to excite another field, which is what we would see as a new particle created.
For example, the electromagnetic quantum field and the electron field constantly interact with each other. What we see as an electron absorbing a photon and hence get excited to a higher energy level or emit a photon while dropping in energy level, are really transfers of excitation between the electromagnetic and the electron field.
So, what is Matter?
What we take for granted as matter in our everyday life is hard to describe. When we zoom into the smallest sizes possible, the subatomic particles that matter is made of, it consists of both “matter particles” and “force carrier particles”. What we see as matter and energy are two sides of the same coin, as we know from the famous equation E = mc².
The quantum world is a weird one, where particles exist and don’t exist at the same time, can exist several places at once, and can be entangled in “infinite” distances. We don’t understand the world of particles, and we don’t know what they are exactly.
What we see and understand are the consequences and how the world works at macrolevels. We understand the sizes that our brain is optimized to understand, with our senses. And when the math works out, at least we can count on the current particle and quantum field theories, to give us some practical answers and technological breakthroughs.
But we are still left with wonder. We don’t have to look into the exotic dark matter for matter to be fascinatingly secretive: What are we really made of, what is ordinary matter, what are particles, what are the particles field and are they then fundamental or is there an even deeper level?