5 Applications of Dimensional Analysis

The concept of dimensional analysis was introduced by French mathematician Joseph Fourier in 1822. It is a useful method in physics and engineering to identify the relationships between various physical quantities by analyzing their base quantities.

There are seven base or fundamental quantities of primary importance in physics. The rest of all the physical quantities are derived, that is, written in terms of the following base quantities:

1. Mass (M)
2. Length (L)
3. Time (T)
4. Temperature (K)
5. Electric current (A)
6. Amount of substance (Mol)
7. Luminous intensity (Cd)

Others are derived quantities, for example: Speed is distance upon time, where distance is a type of length. So, the dimension of speed in terms of base quantities is [L][T]^-1

1. Find dimension of unknown quantity

Example: To increase the temperature of a substance by ΔT, heat required is given by Q=mSΔT where m is mass and S is specific heat capacity of the substance. We can find the dimension of S by doing simple algebra.

S=Q/mΔT

S=[M L² T^-2]/[M][K]

S=[L² T^-2 K^-1]

Since heat (Q) is a type of energy we have used the dimension of energy [M L² T^-2]. Knowing the dimensional dependence is useful while performing experiment in laboratory.

2. Find unit of physical quantity

Example: The dimension of force is [M L T^-2]. Therefore, the unit of force in the standard MKS system is kg.m.s^-2 corresponding to the base quantities used. Likewise, the unit of force in the French CGS system is g.cm.s^-2

3. To check correctness of formula

In an equation, the left hand side should match the dimensions on the right hand side. That's because, you can't have apples on one side and oranges on the other. This is useful in multiple choice questions as it helps in eliminating the wrong options.

Example: Is force F=mv²/r correct? where m is mass, v is velocity and r is radius. To find out, we start by writing the dimensions on both sides.

[M L T^-2] = [M][LT^-1]²/[L]

[M L T^-2] = [M][L²T^-2][L^-1]

∴ [M L T^-2] = [M][L][T^-2]

The formula is correct. In fact, it is the centripetal force if you might recall, which acts upon a body directed towards a fixed center, thus keeping it in orbit.

4. To roughly derive formula

Example: Suppose that the time period of a simple pendulum is dependent on mass of the bob, length of the string and gravitational acceleration due to earth.

Let's assume that the time period is proportional to some powers of mass, length and gravity: t∝m^al^bg^c

To find the formula of time period, we must obtain values for a, b and c. We start by writing the dimensions on both sides.

[M]⁰[L]⁰[T] = (constant)[M]^a[L]^b[LT^-2]^c

The dimension of constant is 1. So,

[M]⁰[L]⁰[T] = [M]^a[L]^b[LT^-2]^c

Comparing the exponents on both sides, we get:

a=0, b+c=0 and -2c=1

On solving we obtain values of a=0, b=1/2 and c=-1/2. Now, putting back in the original equation t∝m^al^bg^c  gives:

t ∝ m⁰l^1/2g^-1/2

t=(constant) l^1/2g^-1/2

Thus, time period of a simple pendulum is independent of mass of the bob. This is because, physically speaking, mass is both the cause of swinging motion and the resistance to swinging motion, so it cancels out.

5. To express in new base quantities

This type of questions can come up in competitive exams like the JEE-Main. Example: If pressure, velocity and time are taken as base quantities, then what would be the dimension of force?

Let's start by assuming powers

Force = P^av^bt^c

And write dimensions on both sides

[M L T^-2] = [ML^-1T^-2]^a[LT^-1]^b[T]^c

[M L T^-2] = [M]^a[L]^-a+b[T]^-2a-b+c

Comparing powers on both sides

a=1, -a+b=1 ⇒ b=2 and -2a-b+c=-2 ⇒ c=2

∴ Force = Pv²t²

How Antimatter Was Discovered By Carl Anderson

British physicist Paul Dirac showed in 1928 that every particle in the universe should have an antiparticle with the same mass as its twin, but with the opposite electrical charge. Across the pond, an American physicist would detect the first such particle, four years later.

Carl Anderson, inspired by the work of his Caltech classmate, Chung-Yao Chao, set up an experiment to investigate cosmic rays under the supervision of physicist Robert Millikan. In 1932, he won the Nobel Prize in physics at the age of 31, becoming one of the youngest recipients.

Discovering the positron was no easy feat but the mechanism he employed to do so was fairly simple and ingenious enough to overcome the limited budget. He found the mysterious particle almost by accident with the help of his own improved version of the cloud chamber.

A cloud chamber is a sealed box with water vapor. When a charged particle goes through it, the vapour is ionized and leaves behind a trail. Thus, the trajectory of the particle can be seen virtually. Carl used a mixture of water and alcohol to get clearer photographs.

Carl included a Lead plate in the middle to slow down the particles and surrounded the chamber with a large electromagnet, which caused the paths of ionizing particles to curve under the influence of magnetic field.

As can be seen in the picture, the radius of curvature of the track above the plate is smaller than that below. Thus, the particle entered from the bottom, hit the Lead plate and came to a halt above it due to loss of energy. This and the direction in which the path curved helped in identifying that the charge was positive.

That it was antielectron and not proton was determined by the observation that the upper track was much longer in length than predicted for proton. A proton would have come to rest in a much shorter distance, since it is heavier. The trajectory observed was that of a particle much much lighter than the proton.

So, that's how the first antimatter was found and Dirac was proven right within a matter of few years. Furthermore, antiproton and antineutron were discovered in 1955 and 1956 respectively. The first antiatom was produced by CERN in 1996.

Why antimatter is important? Because, studies related to antimatter will help in our understanding of the early universe. Also, Positron emission tomography or PET scan is used to detect early signs of cancer. Scientists hope that some day, antimatter may be used for the treatment of cancer. Who knows!?

Science is either physics or stamp collecting?

What is science? In one simple sentence, science is the study of nature. However, different sciences like: astronomy, chemistry, biology, geology, etc. have different approaches to do so. Thus, not all sciences are equal.

The quote 'All science is either physics or stamp collecting' by New Zealand physicist Ernest Rutherford perfectly reflects that inequality. According to him, physics is the king of sciences because it is fundamental to all other fields of study.

But why exactly did Rutherford think in that manner? Despite himself being the recipient of Nobel Prize in chemistry, what made him consider physics the most noble of sciences?

The answer lies in stamp collecting - a hobby in which people collect and classify stamps as objects of interest or value.

Stamps are available in many varieties - big and small, square and round, stamps with famous human faces, stamps with animals and birds, stamps commemorating anniversaries, etc.

 Rutherford's stamp 

Similarly, some branches of science, such as zoology or botany for example, are mostly concerned with collection and classification of species - animals and plants, respectively.

Although this would be dumbing down those sciences but that is more or less the purpose, isn't it? In other words, those sciences are not fundamental sciences and their scope is limited only to Earth.

Physics, according to Rutherford, is the only science that has an elaborate structure consisting of observation, experiment and mathematics. Physics captures our imagination from mysterious atoms to supermassive galaxies. It truly is the universal embodiment of the scientific method.

By this definition, the science which is closest to physics is astronomy. You observe and measure the effects of, say a black hole on its surroundings, with the help of a telescope and basic knowledge of mathematics. In this way, like engineering, astronomy is an application of physics and mathematics.

Chemistry is a unique science because it has the 2nd most direct impact on day to day life after physics. The objects we use, such as plastic, glass, steel, etc. are all obtained by chemical processes.

Our body is a chemical engine and the food we eat are organic molecules. But just like biology, there is a lot of nomenclature and classification rules in chemistry to deal with. Chemistry is also not universally the same, like on different planets, but the laws of physics governing those chemistries are the same.

Likewise, sciences like computer science and psychology are neither fundamental nor universal. They are narrowed specializations and are heavily dependent on logic, mathematics and observation.

All the sciences, however, must ultimately be experimental because that is how they progress. That is how the hypotheses are tested and verified and accepted. So it is worth pointing out that no amount of belief can make something true. Sciences keep evolving with time as new evidence is uncovered.

Finally, it is equally important to mention that the statement "all science is either physics or stamp collecting" had more truth to it back in Rutherford’s time than today.

As you know, for example: With Darwin's theory of evolution, biological sciences have too become observational rather than just being classification sciences.

So, over time, sciences evolve and become more and more physics-like. They are no longer merely observe and classify but start using mathematical models. Still, Rutherford's point is intact, physics will be the king of sciences.

Hawking's black hole theorem confirmed by gravitational waves

A black hole has often been portrayed as the ultimate villain in sci-fi movies due to its mysterious nature. From the death of a large-enough star it emerges with such a strong gravitational field that not even light can escape from within its grasp.

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However, in spite of its wildly mysterious behavior, the black hole obeys certain simple rules. One of those rules, first proposed in 1971 by English physicist Stephen Hawking, has been proven correct by the help of gravitational waves.

The area law, derived from Einstein's general relativity, states that it is impossible for a black hole to decrease in size, at least in the short term. Mathematically:

Recently, a team led by astrophysicist Maximiliano Isi from Massachusetts Institute of Technology studied the gravitational wave data released by the merger of two black holes.

Their calculations show that the total surface area of the resulting black hole is greater than the combined areas of the two smaller black holes. Therefore, Stephen Hawking was right.

However, while black holes cannot shrink according to Einstein's general relativity, they can do so as per the quantum mechanics.

Hawking worked that out too in 1974 – a concept known as Hawking radiation, which is predicted to emit because of strange quantum effects near the black hole's event horizon.

In his 1988 book A Brief History of Time, Hawking thus wrote: Black holes ain't so black. The release of these radiations would cause the black hole to shrink over longer time period and evaporate eventually.

Hence, theoretically speaking, both general relativity and quantum mechanics hold true. Maximiliano Isi said: "I am obsessed with these objects because of how paradoxical they are."

Now that the area law has been established for short to medium time frames, the researchers' next step would be to detect Hawking radiation by observing older black holes; no substantial evidence has been recorded so far.

Isi concludes: Black holes are those phenomena where gravity meets quantum mechanics, which makes them the perfect playgrounds for our understanding of reality.

Who discovered that we are made from star stuff?

Astronomer Carl Sagan popularized the phrase "We are made of star stuff" when he said: Nitrogen in our DNA, calcium in our teeth, iron in our blood and carbon in our food; were made in the interiors of collapsing stars.

However, most people wouldn't know the name of that scientist who actually found it out. It was German American physicist Hans Bethe (1906-2005) who wrote it in a paper titled "Energy Production in Stars" as early as in 1939.

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In 1930s, at the time when European scientists were debating quantum mechanics, Bethe migrated to United States and contemplated the stars. He thus became the first person to figure out that conversion of hydrogen into helium was the primary source of energy in a star.

The process is called nuclear fusion in which many nuclei combine together to make a larger one. It so happens that the resultant nucleus is smaller in mass than the sum of the ones that made it. So, by virtue of Einstein's equation E=mc², the mass is converted to energy.

When a star would eventually run out of hydrogen (its primary fuel) it would start converting helium into carbon, nitrogen, oxygen and so on, in order to keep itself hot.

However, those reactions themselves will halt at some point and the star would no longer be able to support itself against its own gravity and it will die in an explosion.

Therefore, it was proposed that most of the material that we're made from, came out of the dead stars which spewed out those chemical elements into the universe for further use. Hence, we are made of star stuff.

Bethe's groundbreaking paper not only helped in understanding the inner workings of the stars but also solved the age-old questions like: 'How do stars shine?' 'Where did the chemical elements come from?'

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He won the 1967 Nobel Prize in physics for this theory of stellar nucleosynthesis. Bethe would continue to do research on supernovae, neutron stars, black holes and other problems of astrophysics well into his late nineties.

Carl Sagan and Hans Bethe share the stage at Cornell

Now, Carl Sagan, who was earlier at Harvard University, joined Cornell in 1976 and became immediate colleagues with Hans Bethe who had been at Cornell since coming to America in 1935. While Bethe was a professor of physics, Sagan was a professor of Astronomy.

It was unfortunate that the general public still did not know about stellar nucleosynthesis despite Bethe discovering it some 40 years ago and winning the highest prize for it a decade ago. Carl Sagan changed this.

Their common interests in science and politics brought them even closer. Bethe was also a fan of Sagan's 1980 show Cosmos: A personal voyage. In one of the episodes, when Sagan said "We are made of star stuff", he immortalized Bethe's work in television history.

10 Discoveries By Newton That Changed The World

Isaac Newton is one of the few names that will forever be enshrined in physics history and that too with a lot of glamour associated. Contributions of none other physicist match his, well, probably Einstein's, or not even his!? The following are Newton's ten most well-known works that changed the world later on.

Laws of motion

1. An object will remain at rest or move in a straight line unless acted upon by an external force.

2. F=ma.

3. For every action, there is an equal and opposite reaction.

Newton's three laws of motion, along with thermodynamics, stimulated the industrial revolution of the 18th and 19th centuries. Much of the society built today owes to these laws.

Binomial Theorem

Around 1665, Isaac Newton discovered the Binomial Theorem, a method to expand the powers of sum of two terms. He generalized the same in 1676. The binomial theorem is used in probability theory and in the computing sciences.

Inverse square law

By using Kepler's laws of planetary motion, Newton derived the inverse square law of gravity. This means that the force of gravity between two objects is inversely proportional to the square of the distance between their centers. This law is used to launch satellites into space.

Newton's cannon

Newton was a strong supporter of Copernican Heliocentrism. This was a thought experiment by Newton to illustrate orbit or revolution of moon around earth (and hence, earth around the Sun).

He imagined a very tall mountain at the top of Earth on which a cannon is loaded. If too much gunpowder is used, then the cannonball will fly into space. If too little is used, then the ball wouldn't travel far. Just the right amount of powder will make the ball orbit the Earth.

Calculus

Newton invented the differential calculus when he was trying to figure out the problem of accelerating body. Whereas Leibniz is best-known for the creation of integral calculus. The calculus is at the foundation of higher level mathematics. Calculus is used in physics and engineering, such as to improve the architecture of buildings and bridges.

Rainbow

Newton was the first to understand the formation of rainbow. He also figured out that white light was a combination of 7 colors. This he demonstrated by using a disc, which is painted in the colors, fixed on an axis. When rotated, the colors mix, leading to a whitish hue.

Newton's disc

Reflecting Telescope

In 1666, Newton imagined a telescope with mirrors which he finished making two years later in 1668. It has many advantages over refracting telescope such as clearer image, cheap cost, etc.

Law of cooling

His law states that the rate of heat loss in a body is proportional to the difference in the temperatures between the body and its surroundings. The more the difference, the sooner the cup of tea will cool down.

Classification of cubics

Newton found 72 of the 78 "species" of cubic curves and categorized them into four types. In 1717, Scottish mathematician James Stirling proved that every cubic was one of these four types.

some cubic curves (Wiki)

Alchemy

At that time, alchemy was the equivalent of chemistry. Newton was very interested in this field apart from his works in physics. He conducted many experiments in chemistry and made notes on creating a philosopher's stone.

Newton could not succeed in this attempt but he did manage to invent many types of alloys including a purple copper alloy and a fusible alloy (Bi, Pb, Sn). The alloy has medical applications (radiotherapy).

When Pioneer of Thermodynamics Was Rejected

Sometimes an idea is so far ahead of the time that when proposed it is met with suspicion and mockery. This happened with English physicist and mathematician James Prescott Joule (1818–1889) when he tried to publish his concept of heat.

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Joule was an avid reader and grew up interested particularly in the field of electricity. He and his brother experimented by giving electric shocks to each other. However, a long-time association with his father's brewery business drew him closer to studying the nature of heat.

In 1843, Joule identified heat as a form of energy. This idea was rejected by the Royal Society because at that time heat was considered to be a "material fluid" which flowed from hot to cold body.

Joule's concept posited that heat was not a fluid but rather a "vibration" from one molecule to another. But at that time (1840s) the existence of atoms and molecules was a disputed subject among scientists. Therefore, Joule's visualization of heat was deemed mere fantasy.

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Despite initial rejection, Joule tried to demonstrate his idea mechanically in 1845. His experiment involved the use of a falling weight, in which gravity does the mechanical work, to spin a paddle wheel in an insulated barrel of water. The spinning increased the temperature of water.

Thus, the experiment not only showed that work and energy were equivalent but also that potential energy of the falling weight was getting converted into heat, hence the rise in temperature. So, heat must be a form of energy.

Joule was laughed at in the beginning but he kept on trying, until his idea became common-sense and he was elected a fellow of the Royal Society in 1850.

He went on to work with renowned British physicist William Thomson, aka Lord Kelvin. Together, they developed the absolute temperature scale and published the Joule-Thomson effect, in 1852, a process which has applications in cooling appliances such as refrigerator and air conditioner.

Today, the SI unit of work (and energy) has been named Joule in his honor. He is also widely recognized as one of the founders of thermodynamics as his results led to the formation of the first law.

Heisenberg and his views on quantum mechanics

Werner Heisenberg was a German theoretical physicist who was awarded the Nobel Prize in 1932 for the creation of quantum mechanics. He was only 25 years old when he discovered the uncertainty principle. Although at the time Heisenberg did not understand his own work, so he handed it to his immediate supervisor, Max Born, and went on vacation.

Absurdity of nature

Heisenberg was one of the very first people to recognize the ridiculousness of quantum mechanics. It was mind-boggling because it did not agree with the existing physics. His discussions with Niels Bohr went through many hours till very late at night and ended almost in despair.

At the end of their talks, Heisenberg used to go for a walk in the neighboring park and repeated to himself again and again the question: Can nature possibly be so absurd as it seemed in the atomic experiments?

Heisenberg quipped: "The smallest units of matter are not physical objects in the ordinary sense; they are forms, ideas which can be expressed unambiguously only in mathematical language."

He derived inspiration from Greek and Eastern philosophies to arrive at some understanding of his work. "All things are numbers", a sentence attributed to Pythagoras especially attracted his attention. A conversation with Tagore about Indian philosophy also made some sense out of the ideas that seemed to him crazy.

Uncertainty principle

In Feb, 1927, Heisenberg wrote in a paper: The words "position" and "velocity" of an electron seemed perfectly well defined before and in fact they were clearly understood concepts within the mathematical framework of Newtonian mechanics.

But actually they were not well defined, as seen from the relations of uncertainty. The more precise the measurement of position, the more imprecise the measurement of momentum, and vice versa. In other words, there was complementarity between the two.

It's worth pointing out that the uncertainty is not a measurement problem but arises due to the wave nature of all quantum objects. Thus, it actually is a "fundamental property" of quantum objects and not a statement about the observational success of current technology.

The main problem was this: A physicist may be satisfied when there is a mathematical scheme and an interpretation of the experiment. But he also has to speak about his results to non-physicists who will not be satisfied unless some pictorial explanation is given in plain language.

Heisenberg's defence

Heisenberg said: "It is not surprising that our language should be incapable of describing the processes occurring within the atoms, for, it was invented to describe the experiences of daily life, and these consist only of processes involving exceedingly large numbers of atoms.

Furthermore, it is very difficult to modify our language so that it will be able to describe these atomic processes, for words can only describe things of which we can form mental pictures, and this ability, too, is a result of daily experience.

Fortunately, mathematics is not subject to this limitation, and it has been possible to invent a mathematical scheme – the quantum theory – which seems entirely adequate for the treatment of atomic processes; and for visualization."

His biggest opponent was Albert Einstein who did not endorse the uncertainty principle as a fundamental law of nature until his death. He had famously remarked: "God does not play dice with the universe" as a joke. Niels Bohr, an advocate of uncertainty principle, replied: "Don't tell God what he can and cannot do."

This Is How Dirac Predicted Antimatter

For those who don't know anything about English theoretical physicist Paul Dirac: he has often been compared to one of the fathers of physics, Sir Isaac Newton. Both were genius mathematicians; socially awkward; they made their greatest breakthroughs in their twenties; both held the Lucasian chair of Mathematics at Cambridge University.

But some may consider Dirac an even greater scientist due to many reasons. While Newton, in his day, became much involved with pseudosciences such as alchemy; he even attempted to reconcile science with faith through his writings. Paul Dirac, on the other hand, an outspoken agnostic, remained true to scientific path, and went on to make many significant contributions to the theory of everything.

Furthermore, while Newton was considered arrogant, too full of himself, who often made use of his authority to dismiss others' opinions. Dirac, on the other hand, was a lean, meek, shy young fellow, who suffered agonies if forced into any kind of small talk. He coined the term Fermion after Italian physicist Enrico Fermi, despite him having worked on the equation which governed the behavior of Fermions.

So that was a little background information on the man that was Paul Dirac. Unfortunately, he never was popularized enough, in fact, hardly anyone knows anything about who he was or what he did in his scientific career. Even so, his work is of primary importance to electronics, especially how electrons flow in the transistor, devices which form the building blocks of any modern-day computer.

What's more: his biggest discovery, prediction of anti-particle, has inspired numerous science fiction writers to create a mirror world in their stories, the collision of which with the real world, would lead to a whole lot of catastrophic activity in the lives of their characters. This is based upon Dirac's work that when matter and antimatter collide, they annihilate one another.

In the early twentieth century, Dirac, who had just completed his engineering degree, was unemployed. But this made him choose math as a career and thank goodness he did so! Because, a great quantum revolution was ongoing and Dirac, who had merely remained an observer, was keen on becoming a part of it.

Everybody at that time was talking about a young Austrian physicist named Erwin Schrödinger. He just had formulated wave mechanics, that is, an equation which explained the behavior of electron inside an atom. The wave equation, so it was called, gave the probability of finding the electron at any given point inside the atom.

Dirac realized that Schrödinger's wave equation was inconsistent with special theory of relativity. In other words, even though the equation was enough to describe the electronic motion at low velocity, it was yet unable to do the same at speeds approaching that of light. Dirac took this challenge upon himself to find a solution for it.

Unlike other physicists, those who insisted that revelations in physics be firmly grounded on experimental data, (and rightly so) Dirac relied heavily on mathematical consistency instead. To him, if the equation he found had mathematical beauty, then he just assumed that he was going on the correct path. This just goes on to show that Paul Dirac was more of a mathematician rather than a staunch physicist.

After many years, in 1928, Dirac modified the Schrödinger's equation to make it agreeable with Einstein's special relativity. His groundbreaking equation also defined the concepts of spin and magnetic moment of electron. While developing his equation, Dirac realized that Einstein's famous energy-mass relation, E=mc², was only partially right. The correct formula, he claimed, should be E=±mc², the minus sign because one has to take the square root of E²=m²c^4, which was a subtle correction indeed.

But then, according to an axiom of physics, matter particles always tend to the state of lowest energy - for stability. Therefore, the negative sign in E=mc² would imply that all the electrons tumble down to infinitely large negative energy. That is, an electron in a positive energy state (bound or free) should be able to emit a photon and make a transition to a negative energy state. This process could continue forever giving off an infinite amount of light!

Clearly, that isn't the case in the actual, stable universe; real electrons do not behave in such a way. So it made Dirac think of a solution to the problem: he proposed a theoretical model called the Dirac Sea in which he imagined that all the negative energy states were already occupied, meaning, that an electron in positive state could not tumble down to negative energy (since according to Pauli's exclusion principle, no two electrons could share a single energy state).

If a particle of this negative energy sea is given sufficient energy it is possible for it to rise into a positive energy state. A resulting "hole" would be created in the negative energy sea. This hole should have the same mass as the original electron but behave like a positively-charged particle.


Dirac wrote in 1931, after being suggested by Oppenheimer, that this hole was an anti-electron; a re-combination with electron should annihilate both of them. Because, when the electron comes into contact with the hole it spontaneously fills the hole and consequently must release the excess energy that went in.

In 1932, while examining the composition of cosmic rays, high-energy particles that move through space at nearly the speed of light, American physicist Carl Anderson discovered the positron. He observed that a particular particle in the ray behaved out of the ordinary. The trajectory suggested that it had to be positively charged but at the same time 1/1,836 the mass of a proton, exactly that of an electron.

In his 1933 Nobel Prize lecture, Dirac suggested that particle-antiparticle should be a fundamental symmetry of nature. He interpreted the Dirac equation to mean that for every particle there existed a corresponding antiparticle, exactly matching the particle mass but with opposite charge. In 1955, antiproton was discovered by University of California, Berkeley physicists.

The success of Dirac equation shows that a mathematical result can manifest itself in the real world. Paul Dirac had once said, "If you are receptive and humble, mathematics will lead you by the hand." That is pretty much true; his work has been described fully on par with the works of Newton, Maxwell, and Einstein before him. Dirac was undoubtedly a genius.

Where are fundamental forces of physics in real life?

All the visible interactions in nature can be explained in terms of just four fundamental forces. Most physicists think that these four forces must have separated as the universe expanded but which must have essentially been the same under those hot conditions that existed at the Big Bang.

Which is why they are looking for a theory of everything which will set to unify them and reveal a complete understanding of the universe. The string theory and standard model are two such grand unification theories which aim to do so but haven't yet succeeded.

In this post, we will look at how the four fundamental forces apply in day to day life. Two of those forces namely gravitation and electromagnetism we are all well aware of. That is because they are large scale fundamental forces whereas weak and strong forces, which are small scale, hardly catch out our attention.

Electromagnetism

This fundamental force is actually a unification of two forces: electric and magnetic. From pioneering experiments of Michael Faraday, genius mathematician James Clerk Maxwell built a set of equations which combined the two forces into one.

one of the first color photographs taken by Maxwell in 1861

Wherever you look in the modern society, electromagnetic force is apparent. Prominent examples include television, radio and computer. With advances in technology our devices got smaller and began to fit in the palm of our hands. With just a click of a button, we are connected with the world through the internet, which is again, an electromagnetic gift to the whole of humanity.

Also, many electromagnetic waves are used for medical treatment as well. Examples: To generate a picture of brain activity an MRI machine uses radio waves or which bone is broken could be seen with x-rays or ultraviolet rays which treat diseases such as Jaundice or gamma rays which are employed to kill cancerous cells.

Furthermore, what we see with our eyes is the visible light, a small part of the full spectrum, colors from violet to red, such as in the rainbow. This is why electromagnetic force is the one we are most familiar with because it is everywhere to be seen; whether in selfies we click or films we shoot.

Gravitation

The Earth goes around the Sun once in a year because it is pulled in by the gravitational field of the Sun. If there was no gravity to keep the earth spinning, would we get to celebrate the New Year's with our friends and family?

The planets and comets and asteroids and other debris are all held together by the gravity of Sun. This suggests that gravity is quite a long range force. Even so, there is a limit to it such as with increasing distance gravitational force declines considerably in its strength.

Stephen Hawking takes a zero gravity flight

At this moment, there are hundreds of satellites circling the earth out of which 24 are fully dedicated to the GPS technology. Think about this: without gravity keeping them in stable orbit, there would have been no google maps and we would be lost without direction in a strange place!

The universal law of gravitation is a unification of terrestrial and celestial mechanics as it was done by Sir Isaac Newton in the seventeenth century. Today, we can understand the origin of the universe by knowing what causes gravitation. Some physicists also can predict how the universe may end by studying how gravity would respond against other forces of nature.

Weak Force

It was known to common people that inside the earth was warm and molten since there were the occasional volcanoes to testify. Then, scientists discovered that the earth was four billion years old which put them to confusion because how could it remain warm for so long? Also, what kept iron melted in the core and enabled the Earth’s magnetic field?

In the twentieth century, it was found that within the earth were radioactive elements in plenty, such as, Uranium and Thorium, which decayed spontaneously thus keeping the earth warm on the inside. Energy from these reactions was explained by Einstein's famous equation which stated that mass and energy were equivalent.

In the decay, neutrinos are emitted which interact only by means of the weak force. Such high speed particles were first detected in 2005 by scientists in the KamLAND collaboration based in Japan. Thus, the inherent heat and temperature of the Earth's core are explained by the weak interaction.

If this had not been the case there would be no molten iron hence no magnetic field around the earth to protect it from the blazing solar wind. As a result, the ozone layer would disappear and we would all be put to death. Thus, beta decay, which is a manifestation of weak force is fundamental to our existence.

What's more the weak force is also responsible for radioactive decays which help to generate light in the Sun and which help to determine age of a fossil on the Earth.

Strong Force

Since protons are positive charges and since like charges repel one another and since the distance between them within the nucleus is so small, the electric repulsion should be so high that they should fly apart! What is it then that binds them together?

Strong force is the glue that holds the nuclei together; so naturally it should be a very short range force but with an enormous strength advantage over electromagnetic force. And you know what is interesting? Most of the mass of a proton (or neutron) is the result of the strong force field energy. This means that most of our own mass is just a manifestation of that same energy.

Life without strong force would not exist because without it protons would not come together in the first place. But, due to strong force, the protons can bind together to become an unstable Helium. Then which decays under the guidance of the weak force and visible light is made in the process. Using which fruits and vegetables be made on the Earth. Consumed by animals. Like us.

Weak and strong forces are both short range forces so they hardly have any large scale technological applications yet we know for sure that there would be nothing without them and that in itself is beautiful isn't it!?

Summing up

Two forces govern all the macro scale activities in the universe whereas the other two more important forces rule the micro world. As mentioned before, scientists are looking for a theory of everything which would unify all the four forces of nature into one coherent system. But, what if there is a fifth force of nature?