So far, we have focused on the grandeur and scale of the heavenly bodies and how they were formed in the Primordial Era of our Universe following the Big Bang. Visible matter i.e. stars, galaxies, planets, nebulae, interstellar dust, comets and asteroids only accounts for 5% of what the universe is actually made of. In cosmic terms we know what the visible matter is, the other 95% accounts for dark matter and dark energy, both still under investigation for their properties.
So far in the series I have used the word “matter” quite frequently. So what is matter? The definition of “matter” as outlined in the Oxford English Dictionary;
“Physical substance in general, as distinct from mind and spirit; (in physics) that which occupies space and possesses rest mass, especially as distinct from energy”.
So what is this physical substance we call matter made of? Matter is made up of 12 elementary particles that have been discovered to date and that includes the elusive Higgs Boson that was discovered at CERN by the Large Hadron Collider in 2012. For nearly all matter in the universe three basic building blocks are needed; an electron, an up quark and a down quark, the up quark is the lightest of all known quarks and the down quark has a much higher mass. These elementary particles have different properties like mass, charge and velocity and this is what differentiates one particle from another. Another property that can differentiate particles is their spin, whether they spin to the left or spin to the right, something we call chirality. So subatomic particles can either be described as right handed or left handed depending on which direction they spin. The Higg Boson, interestingly doesn’t have any spin at all. Or electric charge! The decay of the higgs boson is 0.0000000000000000000001 seconds. Quite a short time, this is why it was so challenging to detect. The marvel of its discovery is that it decays within a sextillionth of a second and it was observed. Think about that. Look at the second hand in your watch, the Higgs Boson will have been born, had its half-life and decayed in one sextillionth of a second you just watched!
An electron cannot be split or broken down any further into other particles; however, the protons and neutrons can. A proton is made of two up quarks and one down quark. A neutron is made of one up quark and two down quarks. Technically speaking, this idea of three quarks in a proton or neutron is a big oversimplification but for now it will do for a loose introduction to the Standard Model of Particle Physics.
Protons, neutrons and electrons are infinitely tiny although through the famous equation E=MC2, they have mass as mass and energy are equal, this is called Einstein’s equivalence principle. Energy contributes to mass and if an object. A stationary car will have more mass as it is storing the potential energy it contains. A moving car will weigh less as it is expending energy whilst moving. As a loose example this does work for visual purposes. I suppose this is a good time to mention that mass and weight are not interchangeable as weight is the measure of gravity on a specified mass.
All the subatomic particles make up atoms, molecules and compounds. This strays into chemistry somewhat but for physics it is relevant for the way these building blocks influence the behaviour of celestial objects. The sun isn’t actually on fire or burning, it is hydrogen atoms fusing into helium via nuclear fusion.
The Higgs Field is a field which permeates the entire universe and which gives particles mass. Electrons and protons etc interact with this field to give the associated particles mass. No, we cannot actually see the Higgs Field itself but given that the elementary particles have mass, this is attributed to the Higgs Field and the associated Higgs Boson particle. Photons are massless; they have no mass whatsoever and are the elementary particles associated with light and electromagnetism. Photons can be viewed as “light particles”, this is again almost insultingly simple but there is an awful lot more to it than that, it is a crutch that can be used with extreme caution. I will discuss light, the speed of light and photons as waves in an upcoming series about Quantum Mechanics and Quantum Field Theory. Nothing can travel through space faster than the speed of light that we know of at present so a photon can travel from one end of the observable universe, to the other without interacting with the Higgs Field at all to make it massless. The speed of light is what we call “invariant”. It is the same for all observers regardless.
I would encourage everyone to have a look into the Standard Model of Particle Physics. It seems extremely brainy and complicated but I promise you it is really easy to read and will give you a good understanding about the nature of reality and the very things that make the Universe the Universe.