Archive for the ‘Physics’ Category

Some basics.

There are four fundamental forces in nature that we are aware of till date:
Strong force : which binds protons and neutrons to form nucleus of atoms.
Weak force : which is responsible for radioactive decay of subatomic particles.
Electromagnetic force : related with all electrically charged particles.
Gravitational force : accounts for why apple falls down.

Strong, weak and electromagnetic forces are in the realms of atomic scales, and all these three are explained in terms of Quantum Mechanics(QM). Gravitational field is in the realm of cosmic scale, and it is explained using Einstein’s General Theory of Relativity (RT).

So, essentially there are two theories which explains nature, QM in atomic scale, and RT in cosmic scale. But physicist were wondering with the fact that how there could be two different theories that explains the nature in parts, but not one theory which explains the nature in whole.  String Theory(ST) is an effort to bring together QM and RT into a single frame work. But so far no experimental verifications were done to prove ST, and LHC in CERN, Geneva conducts many experiments, and all physicists are looking forward towards ST to become actual science, but for now it is only a mathematical model. The idea of explaining gravity in terms of QM (called quantum gravity) is also an effort towards this, which is also called a unified model.

There are two versions of Relativity Theory that we usually hear of – Special Theory of Relativity and General Theory of Relativity.
Special Theory of Relativity deals with the fact that no particle can travel faster than light.
General Theory of Relativity deals about the theory of gravitational force in the cosmic scale.

Okay, the basics ends here.

Now, focus only on Quantum Mechanics which explains the first three forces, and the theory in general is called Standard Model.
Take any particle, it will be made of many subatomic smaller particles. Again cut down, and see what these smaller particles are made of. When you keep on looking into these, you reach a stage of a particle which does not have any sub-structure. Such particles are called fundamental or elementary particles.

The elementary particles are categorized into two types : fermions and bosons.
All elementary particles have spins. If a particle have fractional spins (for eg, electron has half positive spin, and half negative spins) then such particles are called fermions, and if particle have integer spins, then they are called bosons.

Fermions account for particles that constitutes matter, eg quarks and leptons. Quarks combine to form hadrons, which give rise to protons and neutrons of atomic nuclei.

Bosons accounts for force carriers, and it constitute gauge bosons and higgs bosons (but higgs boson have zero spin).

Gauge bosons are the force carriers between the elementary particles for the first three mentioned fundamental forces – strong, weak and electromagnetic force.

Higgs bosons are hypothetical elementary particles which acts as that force carrier which accounts for mass to other elementary particles like quarks, leptons etc.

It is not yet known how quarks or leptons possess mass, and what contributes mass for it. So it is theoretically proposed that Higgs boson particle and it associated Higgs field interactions contribute mass to other elementary particles. So, essentially Higgs boson contributes mass to matter.

A simple analogy to understand the Higgs field vs mass could be, let us say a popular Hollywood film star has come to a public place. Initially when he was not noticed by anyone, he will be able to move around as fast as he can, which could be considered as a massless particle, but as soon as public notices him, and everybody runs to him to get his autograph, he gains resistance to his free movement, and he automatically slows down because of the effect of public on him which could be here considered as the mass, and the public created a Higgs field, and each individual public acts as a Higgs Boson.

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