Evolution of Physics

Physics is a science that studies the interaction between basic constituents of the visible Universe. From a wider perspective, physics deals with every aspect of nature on macroscopic as well as microscopic levels. The range of study covers both the behaviour bodies under the application of a force and the origin and nature of all the fundamental forces in nature. The absolute goal is the development of a few compact and thorough principles that effectively and efficiently explain every contrasting phenomenon.

How did the Study of Physics Evolve?

Ancient Greek philosophers are credited with the development of theoretical and methodological approaches to physics-based principles. In those times, there was no clear distinction between physics and other science disciplines. Theology and philosophy were intermixed with the known scientific facts. Thus, many instances were overlapping in the history of physical science at those times.

Physics in the Ancient Period

Physics in Ancient Greece

According to acceptable records, Thales was the first greek physicist. His theories gave the subject its unique name. He built postulates on the belief that every material is made of a single element, ‘water’. In ancient Greek, water was called ‘Physis’. Around 500 BC, Heraclitus had put forward that the only fundamental law that controls the Universe is the principle of change. He advocated that nothing stays in the same state forever.

Aristotle is considered the father of science. He pioneered the study of nature with his empiricism and methodology. On the other hand, he unconsciously crippled the development of physics for centuries. Aristotle mixed his analytical concepts about gravity and motion with his postulates of elements. He also tried to combine the mechanical properties of a body with ancient alchemy.

Archimedes came up with the idea of buoyancy and density. He devised theoretical and mathematical principles to design useful mechanical tools that are still prevalent today. Archimedes found out the fundamental principles behind the working of levers. He created extensive systems of pulleys to displace big bodies with relatively less effort. Most of the cases, Archimedes did not invent those tools. Instead, he modified the existing tools and paved the way for the development of complex mechanical systems. He was also responsible for developing concepts related to the centre of gravity and equilibrium conditions. Interestingly, Issac Newton, Galileo and many Arabian scholars were heavily influenced by Archimedes.

Physics in Ancient India

Ancient India was a breeding ground for many scientific advancements, including mechanics, astronomy, mathematics, metallurgy, and medicine. Around 200 BCE, Maharshi Kanada systematically deduced a theory related to atomism. It was further developed during the first millennium CE by Dignāga and Dharmakirti. Another Indian philosopher Pakudha Kaccayana also put forward concepts about the atomic nature of the physical world.

Most Indian philosophers believed that every element (not including ether) was physically tangible. Therefore, they thought that such elements were also composed of minuscule physical particles. The smallest particle that cannot be disintegrated further was called parmanu. The Vaisheshika school philosophers considered the atom a minute point in space. It was also the first to describe the connection between the force applied and motion. Most Indian theories about ‘parmanu’ or atoms are predominantly abstract, which is greatly entangled with contemporary philosophy. The ideas were based on pure logic. They were not at all based on experimentation or individual experiences, as there were no methods to dissect visible material into basic components.

India was home to many incredible ancient astronomers. Ancient India had arguably the most complicated and accurate astronomical system to predict the movement of celestial bodies. Around 500 CE, Aryabhata, through his book Aryabhatiyam, proposed that the evident westward movement of stars is due to the spherical (he termed it as ‘gol’) Earth’s spinning about its own axis. He was able to effectively analyse such celestial phenomena due to his impeccable understanding of trigonometry and geometry. Nilakantha Somayaji came up with a semi-heliocentric concept similar to that of the Tychonic system.

Physics in Ancient China

Ancient China was famous for its engineering inventions. The earliest inventions were the sundial, the Kongming lantern, and the abacus. The compass, papermaking, printing, and gunpowder were the four great inventions that came from ancient China. In fact, these were only known to the western world about a thousand years later. Sliding callipers were developed in China 2,000 years ago. They were the first civilisation to indulge in successful aviation experiments with Kongming lanterns and kits (the first flying devices).

The analysis of magnetism in China dates back to the fourth century. Shen Kuo made the main significant contribution to this field. He was the first to explain the magnetic-needle compass that was used for navigation. He also independently created a camera obscura.

Physics in Ancient Middle East

During the period between the 7th and 15th centuries, outstanding scientific progress took place in the Arab world. Most of the important classic works in Greek, Indian, Persian and Assyrian were extensively translated into Arabic. There were major developments in the field of optics, mathematics, and medicine. Ibn al-Haytham is regarded as a founder of modern optics. He discarded the object-oriented light theories of Aristotle and Ptolemy. He proposed that the light moves to the eye as rays from various points on a body. The discoveries of Abū Rayhān Bīrūnī and Ibn al-Haytham were later passed on to European scholars such as Witelo and Roger Bacon.

Beginning of the Scientific Revolution

The sixteenth-century marked the beginning of the revolution in the study of physical laws. Drawbacks of the older philosophical approaches were evident during this period. As more observational results contradicted the existing philosophically dominated theories, many new age researchers started to refute the current approaches. This resonated across every subfield of physics. The revolution started when rebellious scholars began to criticise the scholastic philosophical method relentlessly. On the other hand, the rebels proposed that descriptive mathematical methodologies could really result in a universally sound explanation of motion and mechanical phenomena.

In 1543, The first quantum leap in astronomy was made by Nicolaus Copernicus. He scientifically proposed valid postulates for the heliocentric model of our Solar System. In the heliocentric theory, the Earth revolves around the Sun along with all other celestial objects in the Earth’s galaxy. It was a revolutionary concept when we compare it with the Ptolemy model (second century CE). He proposed that the Earth is the centre of the Universe and everything revolves around the Earth. He believed that everything in the Universe was created for the well-being of the Earth. In fact, this model has been accepted as the truth for more than 1,400 years. Johannes Kepler further strengthened the heliocentric model through his laws of planetary motion. He efficiently explained the motion of most planets in the Solar System.

The video explains the fundamental concepts of rotation and revolution of the Earth

Galileo Galilei researched free fall, gravity, relativity principle, inertia, speed, velocity, and projectile motion. He also made significant contributions to the field of applied science and technology. He designed the thermoscope and numerous military compasses. He utilised the telescope for observing celestial objects. He was the first to observe the rings of Saturn. He was also an adherent supporter of Copernicus’s heliocentric model. His empirical experiments, application of telescopes and astronomical discoveries provided ground for the heliocentric model. He found that objects do not come down at speeds proportional to their weights. He formulated Galilean relativity. It states that the motion laws are the same in every inertial frame.

Start of the Classical Physics

Mechanics

During the late seventeenth century and early eighteenth century, Sir Issac Newton came up with some of the groundbreaking laws regarding gravity and motion. Newton mathematically described the force of gravity. He derived the law of universal gravitation. The significance of the gravitational law is that it helps to describe the movement of planets around the Sun, the movement of moons around the planets, and the movement of manmade satellites around the Earth. Newton came up with the three concrete laws of motion, which formulated the mutual connection between motion and the bodies under motion. Newton independently invented a new branch of mathematics called calculus. He constructed the laws of motion and gravitation under the framework of this dynamic mathematical tool. Calculus later became one of the essential tools in physical science. The principles of Newton directly came under the firing of contemporary philosophers who were dissatisfied with the inability of these laws to explain the metaphysical side.

As mechanical physics was developing under a mathematical foundation, the application of physical laws started to sprout in the form of mechanical tools. A predecessor of the mechanical engine was developed by Otto von Guericke. In 1650, he built the world’s first vacuum pump (Magdeburg hemispheres experiment). He tried to disprove Aristotle’s postulate (nature abhors a vacuum) by creating a vacuum. In 1656, Robert Boyle (using Guericke’s designs), with the help of Robert Hooke, constructed an air pump. Using this mechanical device, Boyle and Hooke observed the pressure-volume connection for a gas PV = k, where ‘P’ stands for pressure, ‘V’ stands for volume and ‘k’ stands for the constant.

As more scientists got a hold of the calculus and mechanics developed by Newton, new discoveries and applications were made in the field of mechanics. During the eighteenth century, the study of mathematical analysis of motion was called rational mechanics or mixed mathematics. It was later renamed as classical mechanics.

With the spread of work-energy concepts, conservation theory also started to develop. Julius Robert von Mayer, in 1841, published a paper on the idea of conservation of energy. Unfortunately, his lack of academic schooling led to his rejection from the scientific community. Hermann von Helmholtz formally described the conservation of energy principle.

Electromagnetism

In 1800, the electric battery (voltaic pile) was invented by Alessandro Volta. Thomas Young, a year later, showed the wave characteristics of light which was strongly supported by the works of Augustin-Jean Fresnel. In 1820, a major discovery happened; Hans Christian Ørsted observed that a current-carrying conductor generates a magnetic force enveloping it. Interestingly, within a few days after this discovery, André-Marie Ampère found out that two currents moving in parallel orientation will apply forces on each other. In the next year, Michael Faraday created a motor driven by electricity. In 1826, Georg Ohm proposed the electrical resistance law, describing the correlation between resistance, current, and voltage in an electric circuit. Faraday discovered the principle of reverse effect and electromagnetic induction in 1831. The production of electric current or an electric potential through magnetism is called electromagnetic induction. These two principles are the basis of the electric generator and the electric motor.

Léon Foucault and Hippolyte Fizeau calculated the velocity of light in water and found that it is much slower than in air. This came as strong support for the wave model of light.

James Clerk Maxwell developed the distribution law of molecular velocities in 1859. Maxwell described that a pair of electric fields and magnetic fields are moving in an outward direction from their unique source at a speed identical to that of light. Light is one of many types of electromagnetic radiation. EM radiations are only differentiated according to their wavelength and frequency. Maxwell released his research paper on a dynamical theory of the electromagnetic field in the year 1864. Through Treatise on Electricity and Magnetism, in 1873, Maxwell described light as an exclusive electromagnetic phenomenon. These findings were directly inspired and deduced from the works of Wilhelm Weber and Carl Friedrich Gauss. The inclusion of electromagnetic forces in Newtonian mechanics and heat in particulate motion created an extremely robust theoretical working ground for physical observations and experiments.

John Dalton proposed the atomic theory in the early nineteenth century. In the context of thermodynamic laws, atomic theory became one of the postulates of the kinetic theory of gases constructed by Maxwell and Clausis.

Laws of Thermodynamics

The relationship between mechanical and heat energy was established scientifically by James Prescott Joule and Julius Robert von Mayer. In 1840, they calculated the mechanical equivalent of heat. The connection between energy and heat was crucial for the development of heat engines (steam engines). In 1824, Sadi Carnot published his theoretical and experimental works on heat engines. He incorporated a few concepts of thermodynamics in his description of an ideal engine. His work gave a foundation for the development of the first law of thermodynamics, which was a restatement of the conservation law of energy (proposed by William Thomson around 1850). Claudia and Kelvin stated the second law in thermodynamics. It was originally developed in terms of the case that heat impulsively transmits from a colder region to a hotter region. Kelvin formulated the important direct implication of the law. The second law was the concept that gases are made by molecules in motion. In 1738, this concept was heavily analysed and discussed by Daniel Bernoulli. However, it soon fell out of popular opinion. After more than a century, it was brought back to the limelight by Clausius.

Modern Physics

Modern physics started to evolve in the early twentieth century with the introduction of the theories of relativity and quantum mechanics. Classical physics generally deals with normal scenarios where speeds are lesser than the speed of light. The objects are much larger than the size of an atom, and energies are relatively low. In contrast, modern physics deals with high octane and energetic conditions. It is concerned with speeds close to light speed, high energies (relativity), and tiny distances comparable to the radius of an atom (quantum mechanics). Both relativistic and quantum effects are considered to be present on all physical scales, but those effects are negligible at the human scale (which is dominated by classical physics). Generally, quantum physics is compatible with special relativity. On the other hand, general relativity does not gel with quantum mechanics. Currently, gravity laws and quantum laws do not have common ground.

Standard Model

Since the 1920s, the discoveries and postulates of countless physicists have culminated in incredible insights into the basic nature of the visible Universe. Each and every physical entity in the Universe is made up of basic building blocks known as the fundamental particles. Four basic forces of nature strictly control them. The standard model is the encapsulation of postulates and findings of how these fundamental particles and three basic forces (excluding gravity) are connected to each other. This model started to evolve at the start of the 1970s; it has an incredible track record of predicting new phenomena and explaining almost every experimental result. As time passed, with the help of numerous experiments (especially particle accelerator experiments), the Standard model has become a thoroughly experimented branch of physics.

According to modern physics, gravitational force, electromagnetic force, weak force, and strong force are the four fundamental forces in the Universe. Even though the Standard model can explain almost every phenomenon, it cannot still incorporate gravitational force into its domain. Gravity has an infinite range, but it is almost impossible to detect on the quantum scale (the weakest force). This is why the standard model cannot include gravity. On the other hand, the electromagnetic force and weak and strong nuclear force are many times stronger than gravity at the subatomic level. The strong nuclear force is the strongest among all the fundamental forces.

The standard model is the current hottest field in physics. It drives a huge number of discoveries and theories about the Universe. Modern physics is literally on the shoulders of this model. There have been very important discoveries and inventions led by the Standard model. Among the many discoveries, the detection of Higgs Boson stands tall among all other results. The CMS and the ATLAS at Large Hadron Collider (CERN) announced that they had detected a new particle with a value of 126 GeV. This exotic particle is consistent with the Higgs Boson predicted by the Standard model.

The horizon of physics is currently blocked as quantum mechanics is not compatible with gravity. The next phase of physics will begin when we are able to develop a unified field theory which merges the Standard model with every aspect of general relativity.

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