Building Blocks

The theories and discoveries of thousands of physicists since the 1930s have resulted in a remarkable insight into the fundamental structure of matter, which has boils down to the fact that everything in the universe is found to be made from a few basic building blocks called fundamental particles, governed by four fundamental forces.  The Standard Model of particle physics was developed in the early 1970s, and it has successfully explained almost all experimental results and precisely predicted a wide variety of phenomena.  As theories go, the standard model has been very effective, aside from its failure to fit in gravity.  Over time and through many experiments, the Standard Model has become established as a well-tested physics theory and it has given us more insight into the types of matter and forces than perhaps any other theory we have.  Virtually everything we know about the laws of physics falls into one of two piles.  In one, there’s quantum mechanics, from which we’ve developed the ‘Standard Model’, and three of the four interactions that include electromagnetism, and the weak and strong nuclear forces.  In the other pile, there’s Einstein’s theory of General Relativity, which describes the fourth force, gravity, and gives us black holes, the expansion of the universe, and the potential for time travel.

There are two types of fundamental particles, those being matter particles, some of which combine to produce the world about us, and force particles, one of which, the photon, is responsible for electromagnetic radiation.  Matter particles are split into two groups, and among them are quarks and leptons, there are six of these, each with a corresponding partner.  Leptons are divided into three pairs.  Each pair has an elementary particle with a charge and one with no charge, one that is much lighter and extremely difficult to detect.  The heaviest of all the leptons is the Tauon (also known as the Tau Lepton or Tau Particle).  The lightest of these pairs is the electron and electron-neutrino.  The charged electron is responsible for electric currents.  Its uncharged partner, known as the electron-neutrino, is produced copiously in the Sun and these interact so weakly with their surroundings that they pass unhindered through the Earth.  The other two neutrino pairs (called muon and muon neutrino, tau and tau neutrino) appear to be just heavier versions of the electron.  The electron is a truly fundamental particle (it is one of a family of particles known as leptons), but neutrons and protons are made of smaller particles, known as quarks.  Quarks are, as far as we know, truly elementary.

Most of the matter we see around us is made from protons and neutrons, which are composed of quarks.  There are six quarks, but physicists usually talk about them in terms of three pairs, those being the up/down, charm/strange, and top/bottom.  Also, for each of these quarks, there is a corresponding anti-quark.  A quark is any of a number of subatomic particles carrying a fractional electric charge, and they are postulated as the building blocks of the hadrons.  Quarks have not been directly observed, but theoretical predictions based on their existence have been confirmed experimentally.  A quark is a type of elementary particle and a fundamental constituent of matter.  Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei.

Fermions are one of the two fundamental classes of particles, the other being bosons.  The Standard Model includes 12 types of elementary fermions, which are six quarks and six leptons.  A fermion can be an elementary particle, such as the electron, or it can be a composite particle, such as the proton.  Quarks and leptons, as well as most composite particles, like protons and neutrons, are fermions.  Baryons are fermions, while the mesons are bosons.  Gluons mediate the strong interaction, which join quarks and thereby form hadrons, which are either baryons (three quarks) or mesons (one quark and one antiquark).  Protons and neutrons are baryons, joined by gluons to form the atomic nucleus.  Baryons, and Mesons are included in the overall class known as hadrons, the particles which interact by the strong force.  Baryons are made of two up quarks and one down quark (uud), protons are baryons and so are neutrons (udd).  Neutrinos are ghostly things and billions of them stream through every cubic centimeter of space every second.  But because they feel only the two weakest of the four fundamental physical forces, gravity and the aptly named weak nuclear force, rather than electromagnetism and the strong nuclear force, they hardly interact with the rest of creation.

Each of the four fundamental forces in the universe, those being gravity, electromagnetism, and the weak and strong nuclear forces is produced by fundamental particles that act as carriers of the force.  The most familiar of these is the photon, a particle of light, which is the mediator of electromagnetic forces.  This means that, for instance, a magnet attracts a nail because both objects exchange photons.  The graviton is the particle associated with gravity.  The strong force is carried by eight particles known as gluons.  Finally, the weak force is transmitted by three particles, the W+, the W , and the Z.

Particle accelerators look for new stuff by slamming beams of old stuff together.  But a new particle accelerator observation has managed to be important while doing almost precisely the opposite of what we’d expect.  Physicists have found evidence for hard-to-detect stuff by, well, not slamming particles together.  A team of physicists at the ATLAS experiment of the Large Hadron Collider in Geneva Switzerland have found direct evidence that photons, or particles of light, scatter off of each other.  Classical high school physics expressly forbids this from happening, but the quantum mechanics theory governing light particles has since determined it should.  Two light waves should superimpose onto one another into one wave when they come into contact.  But light, in its smallest unit, can also act as a particle.  While studying how electromagnetism works for individual particles, physicists realized that photons could come into contact with one another, exchange information, and then scatter.

Written for Randomness Inked Scribbling the Unspoken Let it Bleed Weekly Prompt Challenge 18, where the prompt today is “Scatter”.

8 thoughts on “Building Blocks

  1. Actually I do enjoy these posts but then again I once had an engineering physics degree, I’m probably in the minority. But like you, who cares about what other people like, we like what we like!

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