I ask you to look both ways. For the road to a knowledge of the stars leads through the atom; and important knowledge of the atom has been reached through the stars.
– Sir Arthur Eddington
Physics is that branch of human knowledge that concerns itself with the understanding of the working of nature from the gargantuan universe to the microcosm of atoms and subatomic particles through a quantitative approach rather than idle ramblings of purely philosophical nature. The juxtaposition of theoretical frameworks, developed over the years, and the experiments performed in order to verify them have helped us tremendously in a well-structured understanding of the “mind of God”, in Prof. Hawking’s wordings.
With the sale of some popular science books at par with a Sidney Sheldon novel or a Robert Ludlum spy thriller, more and more physicist are shunning their reclusive nature; an image usually ascribed to scientists by general public, to whet the appetite of the information hungry reader who wants to know what is happening at the cutting edge of science and especially physics. After all, it’s the taxpayer’s money that goes into the research and scientists are accountable for every iota of money spent in searching the answers to the ultimate questions concerning life. Many among us who have grown up either reading ‘A brief history of time’ or have at least heard about it would know what the above statement implies. One of the branches of physics that has caught the public fancy and has become a sort of public relations office of physics community over the years is particle physics. With ten Nobel prizes in its kitty and the discovery of the ‘God particle’, it has become an exploding field of knowledge gorging on research funding world over, like a hungry insatiable beast.
What is particle physics? The gentle reader must be introduced to the word particle. A particle is to physics what point is to mathematics. An abstract entity created for the sake of simplicity of physical laws and yet a tangible aspect of nature that generates all the physics of motion viz. kinematics and dynamics. A particle is a minuscule object with a well-defined boundary and is localized in space and time. The picture that comes to mind is of a tiny blob of matter suspended in vacuum and since, Einstein showed that matter and energy are equivalent, so we might as well replace it with energy! Of course, it is correct to envisage corpuscles of energy and the physics of quantum mechanics is based on such an assumption and so far has been stringently tested and has become the foundation of theories that are associated with particle physics.
The structure on which the particle physics stands is called the standard model (SM). This model is simple and presents a coherent picture of fundamental particles and forces based upon the mathematical formalism of Relativistic Quantum Field theory (RQFT) or Gauge field theory developed over a couple of decades ranging from 1960s and 1980s and successfully models the underlying physics of all matter (except gravitation) in terms of just three families of Quark-Lepton particles and their force carrying exchange particles (photons, gluons and W-Z bosons) responsible for Electromagnetic, Strong-nuclear and Weak-nuclear forces respectively. The quark pairs of the three generations are called up-down, charm-strange and top-bottom, while the lepton pairs are the electron, muon and tau leptons along with their partner neutrinos. Of these three families, the first family of up and down quarks or the ‘doublet’ in particle physics jargon and the electron-neutrino lepton doublet constitute all stable nuclear and electronic matter. The Standard Model has been well tested over the years by different experiments like Large Electron-Positron collider (LEP), Tevatron, B-factories, etc.
The material world at the subatomic level is like a restless sea in which continual creation and destruction of particles takes place in backdrop of the vacuum or the ground state. The vacuum is now thought of as a frothing sea of quantum fluctuations rather than an emptiness or void. This is where the experimental particle physics comes into picture. The humongous machines built on two continents separated by Atlantic Ocean, Europe (CERN) and America(FermiLab), are probing this cosmic dance of creation and destruction. The only major component that was let unconfirmed by experiment was the existence of the Higgs particle predicted by the SM (standard model) as the residuum of the symmetry breaking mechanism that gives rise to the mass of Quarks and Leptons and W-Z force particles. This has been hunted down at the CERN labs a few years ago under much fanfare.
In order to have the unification of three fundamental forces to work mathematically in Standard Model, it is required that the force-carrying particles should have no mass. The experiments have proved that this is not true, so to solve this conundrum it is suggested that all particles had no mass just after the Big Bang explosion. As the Universe cooled and the temperature fell below a critical value, an invisible force field called the Higgs field was formed together with the associated Higgs boson, the particle. The field prevails throughout the cosmos: particles that interact with it acquire mass. The more strongly they interact, the heavier they become, whereas particles that never interact are left with no mass at all. This idea provided a satisfactory solution and fitted well with established theories and phenomena.
The discovery of Higgs particle or popularly known as ‘God’ particle would give an insight into why particles have certain mass, and help to develop subsequent interaction physics at a deeper level. However, there are indications that SM gives incomplete description of the nature, and a more fundamental theory awaits discovery. Many of these answers are expected to be answered by the Large Hadron Collider Experiment which would be run again in near future and the results will be fruitful once large amount of data have been accumulated and analyzed in various labs across the globe. The earlier results from the ATLAS and CMS experiments at CERN had narrowed the Higgs particle location to a small window between 116 GeV (See glossary below) and 127 GeV. On that fateful day of “4 July” 2012, the discovery of a new particle with a mass between 125 and 127 GeV was announced the enthused media. It was Christened the Higgs boson and dubbed the ‘God’ particle. This appears to be the first elementary scalar field / particle discovered by the powerful colliders.
Whatever new is discovered will have a vital bearing on the continuing quest to discover the even deeper levels of reality behind the beautiful broken symmetries of the Standard Model. Besides the tremendous intellectual and technical achievements we have benefited enormously from spin-off technologies. By spin-offs, we mean devices and techniques developed to do basic research which turn out to have other uses. Some examples are:
- semiconductor industry – more powerful chipsets and memory devices to hold and calculate large amount of data.
- Sterilization – food, medical, sewage
- radiation processing
- non-destructive testing
- cancer therapy
- incineration of nuclear waste
- power generation and storage
- source of synchrotron radiation (biology, condensed matter physics…)
- source of neutrons (biology, condensed matter physics…)
- Crystal Detectors
- medical imaging
- non-destructive testing
- World Wide Web
- Simulation program
- Fault diagnosis
- Control systems
- Stimulation of parallel computing Grid or cloud computing
- Particle physics
- multi-filamentary wires/cables
- nuclear magnetic resonance imaging
- cryogenics, vacuum and electrical engineering and more additions to the list every year.
The scientific achievements are the symbols of our search for truth. The human audacity to engage nature and the urge to know about the wonders hidden in the dark crevices of existence, the unknown realm of knowing and curiosity to fathom what lies beyond any limit has lead the way of the few souls of humanity who work relentlessly to find the answers and satiate the hunger for knowledge of their fellow layperson who engages in a different and at the same time important activity in the web, we call life.
1 eV: it is the amount of energy gained (or lost) by the charge of a single electron moving across an electric potential difference of one volt. By Einstein’s famous mass–energy equivalence relation i.e. E = mc2, energy and mass are actually the same thing physically i.e. m = E/c2. In particle physics, it is common to express mass in units of eV/c2, where c is the speed of light in vacuum . It is common to simply express mass in terms of “eV” as a unit of mass, with c = 1. Then the numbers on the right hand side give the mass related to that amount of energy.
So, if we were to completely annihilate this much kg of matter, we would get and energy equal to 1eV, which is good enough to push an electron across a potential difference of 1 volt. To compare, we know that it takes 13.6 eV, to ionize atomic hydrogen i.e. eject its electron from its orbital. Moreover, 1.6 eV to 3.4 eV is the typical energy of a photon (particle of light) in the visible part of the spectrum.
Giga: is a unit prefix in the metric system denoting a factor of a (short-form) billion (109 or 1000000000). It has the symbol G and GeV means Giga-electron volts i.e. we multiply the energy of 1eV with a factor of 109.
Tera : a prefix in the SI system of units denoting 1012, or 1 000 000 000 000; an example is when you go out and buy your hard drive it comes in terabytes i.e. a trillion bytes. Its symbol is T.
Superconductivity: is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain metals/materials when cooled below a characteristic critical temperature.
Quantum Field theory: is the theoretical framework for constructing quantum mechanical models of subatomic particles in particle physics and quasiparticles in condensed matter physics. A QFT treats particles as excited states of the underlying physical field, so these are called field quanta. In quantum field theory, quantum mechanical interactions between particles are described by interaction terms between the corresponding underlying quantum fields. These interactions are conveniently visualized by Feynman diagrams, that also serve as a formal tool to evaluate various processes.
Standard Model: is a theory concerning the electromagnetic, weak, and strong nuclear interactions, as well as classifying all the subatomic particles known. It was developed throughout the latter half of the 20th century, as a collaborative effort of scientists around the world.
More at http://www.pha.jhu.edu/~dfehling/