Fundamental Forces

Introduction to the Universe’s Basic Building Blocks

If one thinks about the creation and existence of the big universe, he will come up with two basic concepts: elementary particles and fundamental forces. These two basic tenets present the base on which the universe stands.

From the smallest microorganisms, viruses, grains of sand, dust particles, up to us, our planet, our solar system, vast galaxies, and everything that exists in this universe-all are made of these elementary particles. In return, the fundamental forces operating on those particles maintain the entire universe in stability.

The Four Fundamental Forces

Forces exist everywhere around us in various forms. Examples: when we push an object it is considered to be a force, when we pull an object upwards or lower it, when the Moon revolves around the Earth, when iron is attracted towards a magnet, when houses fall away due to a bomb explosion, and when a car stops because of friction-all these are examples of forces.

If we just begin to make a list of how many types of forces exist in the world, then we will end up with a very long list. However, the astonishing fact is that there are only four types of forces in nature. Whatever long list of forces we create, they all come under those four basic forces.

What Are Fundamental Forces?

You may ask, “What are fundamental forces?” Fundamental forces are those which do not depend on, and cannot be derived from, any other force. Instead, other forces arise based on these-in different forms.

The four fundamental forces in nature are:

1. Strong Nuclear Force
2. Electromagnetic Force
3. Weak Nuclear Force
4. Gravitational Force

Force-Carrying Particles: Gauge Bosons

The forces that we are discussing here have associated particles with the carriage of the force, referred to as force carrier particles. In the Standard Model, these force-carrying particles are classified as “gauge bosons”. The gauge bosons responsible for carrying the fundamental forces are photon, gluon, and W and Z bosons.

The gluon is a type of boson that carries the strong nuclear force. The strong nuclear force is one that holds neutrons and protons tightly in an atomic nucleus, never to break from each other. It is considered the strongest force of nature with an operating distance of approximately 10^-15 meters.

It is also a boson: the carrier of the electromagnetic force. Being one of the fundamental forces, this is the second most powerful in nature and 10^36 times more powerful than gravity.

Other members of the boson family include the W and Z bosons, which carry the weak nuclear force. This force reaches an even shorter range of about 10^-18 meters and is responsible for radio-active decay of the nucleus, such as the emission of beta radiation -. It became known as the weak nuclear force since it is several trillions of times weaker than electromagnetic force.

The graviton would be the particle carrying the gravitational force. Up to date, there is not any conclusive evidence of its existence. However, scientists believe that it does exist because all fundamental forces have an associate particle that mediates it. The search for the graviton is related to quantum gravity and string theory.

1. Strong Nuclear Force

Of all four basic forces in nature, the most powerful is the strong nuclear force, but it acts on an extremely short range. Its influence is confined among the nucleus of the atoms. This force holds quarks together to form neutrons and protons. After cosmic inflation ended in the early universe, a temperature appeared called quark-gluon plasma. A little later, the quarks and gluons combined into the first protons and neutrons.

Quarks and Gluons: Building Blocks of Protons and Neutrons

A proton consists of two up quarks and one down quark. But by nature, quarks do not stay together because they are highly unstable and move with colossal speeds.

For them to stick together, there has to be a force between the quarks-the Gluon Fields Binding Force. Such a force of attraction stabilizes the quarks and allows them to combine into protons and neutrons in the same manner.

It is known that the nucleus containing protons and neutrons lies at an atom’s centre, while the number of electrons orbiting the nucleus is equal to the number of protons in the nucleus. Protons are positively charged.

Since protons are positively charged, a nucleus cannot be made of protons alone. If it were to be so, the protons would have exerted strong repulsive forces on one another and got thrown out of the nucleus.

Therefore, the nucleus also contains neutrons that carry no charge. The strong nuclear force exerts a very strong attraction between the protons and neutrons that keeps the nucleus intact.

Nuclear Fission: Releasing the Energy of the Strong Force

There is tremendous amount of energy stored in the strong nuclear force inside the nucleus because of the strong attraction among the protons and neutrons.

The process by which the energy is released, due to the split of a nucleus, is called a nuclear fission reaction. In this reaction, a free neutron strikes a Uranium-235 nucleus that absorbs the neutron.

Consequently, the nucleus becomes unstable and then splits to form krypton-92 and barium-141 along with three more neutrons and a lot of energy is released.

However, the combined mass of the resulting particles is less than that of the original Uranium nucleus, and this missing mass is released as energy.

From the famous equation by Einstein, E = mc², even a small amount of mass can create a large amount of energy. Suppose 1 gram of mass were completely converted to energy; the amount of energy that would be released is given by:

E = 1 × (300 000)

= 90,000,000,000 J
= 90,000,000 kJ of energy.

From this, it is easy to see how much energy could come from a tiny amount of mass!

This is applied in nuclear power stations as well as atomic bombs that were dropped on Hiroshima and Nagasaki during World War II.

Nuclear Fusion: Power Behind the Stars

Nuclear fusion is, on the contrary, a reaction of much smaller nuclei combined into one larger nucleus, normally with an even larger return than that of the fission process.

Nuclear fusion serves as the powerhouse behind the stars, such as the Sun, and also applies in hydrogen bombs.

Scientific efforts continue their attempt to harness fusion energy for peaceful uses because it can offer unlimited energy supplies in the future since water is plentiful.

Electromagnetic Force

Electromagnetic force is the second most powerful force in nature, next to strong nuclear force. Unlike the latter, electromagnetic force reaches out for an infinite distance. What’s more amazing with this force is that it can attract as well as repel, while other fundamental forces only attract.

Everyday Examples of Electromagnetic Force

You must have done those experiments in school when you rubbed a pen on your hair and then you could pick up small pieces of paper with that pen, or after combing your hair you find that the comb attracts bits of paper.

Similarly, magnets also attract or repel each other by their poles. Those were instances of the electromagnetic force acting. Interestingly enough, electricity and magnetism are not independent forces but rather different manifestations of the same thing.

Electricity and Magnetism: Unified by Maxwell’s Theory

in 1873, James Clerk Maxwell showed that electricity and magnetism were united in what is now termed the electromagnetic force.

Electromagnetic Waves and Light

This force acts through a field-the electromagnetic field-that encompasses both electric and magnetic forces. Light, along with all of its wavelengths, is a wave in this field.

Obviously, without light, it would be impossible for us to see and observe the universe; hence, it is crucial for our understanding of the cosmos.

Interactions Between Charged Particles

Electromagnetic force describes interactions not only between static and dynamic charged particles but also between charged particles.

When two charged particles are at rest then only the electric force acts between them, while when these particles are in motion then both electric and magnetic forces come into play.

The attraction and repulsion between magnets is yet another manifestation of the electromagnetic force. In fact the force between two charged particles is far greater compared to the gravitational force acting between them.

Friction and spring forces are some of the common forces that originate from the electromagnetic interactions between charged particles.

The Role of Electromagnetic Force in Atoms

On an atomic level, electrons have negative charge, while the nucleus has positive charge. Electrons revolve around the nucleus due to the electromagnetic force between oppositely charged particles.

At an atomic level, electrons would not revolve around the nucleus without an electromagnetic force, and atoms as such would not exist.

Weak Nuclear Force

The weak nuclear force is the third most powerful, after the strong nuclear force and the electromagnetic force. Like the strong nuclear force, it acts over very short distances. It plays the main role in beta decay.

Role of Weak Nuclear Force in Beta Decay

The weak nuclear force governs beta decay, a process in which a neutron in an atomic nucleus is converted into a proton, while a negatively charged electron and an antineutrino are emitted.

Here’s the reaction:

(n0→p^+ + e- + v-)

This shows that a neutron is changed into a proton, an electron and an anti-neutrino, while charge is conserved. The anti-neutrino is a strange particle, nearly massless. The energy carried away by the anti-neutrino determines the energy of the β particle.

Beta Particles and Their Properties

Since beta particles are electrons, they have a negative charge and, as a result, can be deflected by both electric and magnetic fields.

As they pass through matter, these particles can ionize atoms by collision and can penetrate deeply into materials. However, they can be stopped by a few millimeters of aluminum.

When a nucleus emits a beta particle, one of the neutrons is transformed into a proton; the atomic number increases; the element changes but the nucleon count does not.

Gravitational Force

Gravitational force is the weakest of all the fundamental forces but also travels the largest distance, virtually infinity.

Though the force diminishes with distance, it is never zero. Irrespective of its weakness, gravity has become one of the most prominent forces within the universe, with significant roles in star, planet, and galaxy and other extended structure formations.

It is gravity that pulls together gas clouds into stars, and gravity is responsible for the collapse of a star when it has exhausted its fuel into a black hole or a neutron star.

Even the gigantic galaxies owe their orderly structures to the gravitational pull of supermassive black holes at their centers.

Earth-Moon Interaction Through Gravity

Gravity keeps the Moon in orbit around Earth much as the gravity of the Moon tugs on Earth. While each pulls with gravity on the other, Earth’s mass is larger, and because of that fact, its pull is stronger. This is why the Moon orbits Earth.

Gravity and Everyday Phenomena on Earth

Gravity gives us weight and at the same time does not allow us to be thrown off Earth, which is spinning. It always pulls things toward the center of Earth, and that is why things, when thrown upwards, fall back to the ground. This force is responsible for holding Earth’s atmosphere and the ozone layer intact, thereby protecting us from dangerous external forces such as UV radiation and space debris.