Physics is everywhere. From falling apples to the motion of planets in our solar system, we all know that Physics plays a very important role in making sure the world around us behaves as it does. 

But who are the people responsible for building our understanding of how the Universe works? And how have they impacted the knowledge of Physics we have today?  

Well, over the past 500 or so years, there have been tremendous contributions to the understanding of Physics, with hundreds of budding scientists adding valuable theories to the discussion.

And out of these, there are a few who have gone on to earn worldwide recognition for making pioneering discoveries, and thus, revolutionising the world as we know it today. 

If you’re wondering, “who is the most famous physicist?” Then you’ve come to the right place - with our list of 4 famous physicists and the theories that made them leading thinkers within this field of science. 

Ready to get inspired? Let’s dive in. 

1. Sir Isaac Newton (1642 - 1727)

Sir Isaac Newton: British-born mathematician, physicist, astronomer, theologian and author - and, widely recognised as one of the most influential physicists of all time.

His pioneering 1687 book, Mathematical Principles of Natural Philosophy, was one of the first in the world to establish classical mechanics, laws of motion and universal gravitation - the dominant scientific principles on gravity (up until Einstein’s theory of relativity came along).

But beyond science, Newton was also a key figure in the philosophic revolution, known as the Enlightenment - an intellectual movement that dominated much of the world of ideas in Europe in the 18th Century. 

In fact, Sir Isaac Newton’s theoretical beliefs had such an influence over popular culture that when he  was knighted by Queen Anne at Trinity College, Cambridge on April 16, 1705, he was honoured for his work in politics and philosophy, and not for his mathematical or scientific accomplishments.

Sir Isaac Newton’s Laws of Motion

Despite his prominence in philosophy and politics, Sir Isaac Newton made significant contributions to the field of Physics. 

You may already be familiar with Newton and the story of the apple falling on his head leading to his discovery of gravity, but it's his famous Laws of Motion which have earned him international recognition as one of the most forward-thinking physicists of the time.

Newton’s laws of motion first appeared in his breakthrough masterpiece, Philosophiae Naturalis Principia Mathematica (1687), which was compiled of three separate books and all written in Latin.

Inspired by his desire to understand the connection between nature and theory,  the book explores Newton’s understanding of gravity, namely, how the Universe is fixed, with Earth and other heavenly bodies moving harmoniously in accordance with mathematical laws.

These mathematical laws - or, written laws of motion - are three statements describing the relationship between the forces acting on an object and the motion of the object. Let’s take a look at them below.

Newton’s First Law: the Law of Inertia

Newton’s first law of motion states that if an object is stationary or moving at a constant speed in a straight line, it will either stay stationary or keep moving in a straight line at constant speed unless a force acts upon it. 

Newton’s Second Law: F = ma

In his second (and most scientifically important) law of motion, Newton offers a quantitative explanation of the changes that a force can have on the motion of an object. 

It states that: “the time it takes to change the momentum of an object is equal in both magnitude and direction to the force imposed on it.” (source)

As the momentum of an object is equal to the product of its mass and velocity combined, momentum, like velocity,  is a vector quantity. That means, when a force is applied, it has the ability to change the momentum or direction of an object - or even both at the same time if the forces allow.

For an object whose mass (m) is constant, it can be represented in the form F = ma, where F (force) and a (acceleration) are both vector quantities. If an object has a force acting on it, it will accelerate in accordance with the equation. Likewise, if an object has no force acting on it, there will be no movement from the object.

Newton’s Third Law: the Law of Action and Reaction

Finally, Newton’s third law of motion - also known as the law of action and reaction - states that when two objects interact, they apply forces to one another that are equal in magnitude, but opposite in direction. 

Newton’s third law is important for analysing problems in ‘static equilibrium,’ where all forces are balanced, but can be either stationary or moving.

For example, when you place a mug down on a table, the mug applies a downward force which is equal to its weight on the table. When we apply Newton’s third law, the table also applies an equal and opposite force to the mug, keeping it still. This force occurs because the weight of the mug slightly deforms the table, with the table pushing back - just like a coiled spring would. 

If an object has a net force acting on it, then it begins to move in accordance with the second law. If there is no net force - either because there are no forces at all, or all forces are balanced - the object does not move and will be in a state of ‘equilibrium.’

2. Albert Einstein (1879 - 1955)

German-born physicist Albert Einstein is regularly cited as the most famous physicist of all, with his achievements in the 20th Century continuing to inspire and help the scientists of today study everything from gravitational waves on Earth to understanding life outside of the solar system. 

Hailed as the father of establishing the two pillars of modern Physics, he is credited with having developed the theories quantum mechanics and relativity. Familiar with the equation E=Mc^2? Even those who aren’t familiar with Einstein’s work have come across his formula for special relativity before. 

And if those achievements on their own weren’t enough, he also became a Nobel Prize winner for Physics in 1921 for his “services to theoretical theory,” especially for his pioneering explanation of the photoelectric effect - a vital step in the development of quantum theory.

Einstein really is a prime example of someone who devoted their life to their work. Even up to the day he died, Einstein was on a fruitless quest to be able to combine gravity and electromagnetism into one single theory - apparently even asking for his notes to be brought to him on his deathbed the day before he passed away.

Albert Einstein’s Main Theories

As a physicist, Einstein was fascinated by the forces of nature. Inspired by predecessor, Newton, he felt very strongly that all of nature needed to be described by a single theory, even saying in his 1923 Nobel lecture; “The intellect seeking after an integrated theory cannot rest content with the assumption that there exist two distinct fields totally independent of each other by their nature.”

Despite becoming famous for several brilliant theories in Physics, including the Brownian theory and special theory of relativity, we are going to focus on two of his most prominent: his Theory of General Relativity and Quantum Theory of Light. 

Einstein’s Theory of General Relativity

Published in 1915, Einstein’s theory of general relativity proposes his understanding of how gravity affects space-time interactions. 

The theory of relativity came ten years after his earlier publication on the theory of special relativity, which argued that space and time are inextricably linked, but, with no reference to how gravity played a role in the process.

In fact, you may remember that theory better summed up through the equation: E=mc^2. That is, that the energy of an object is equal to the mass, multiplied by the speed of light squared. 

In the decade that followed between his two papers, Einstein spent a lot of time determining how large objects affect the fabric of space-time - a distortion that today we recognise as gravity.

Outlined in his theory of relativity, Einstein stated that the laws of Physics are the same for all non-accelerating observers, and the speed of light within a vacuum is the same no matter the speed at which an observer travels. As a result, he theorised that space and time were interwoven into a single continuum, known as space-time. To put it simply, events that occur at the same time for one person could occur at different times for another.

When calculating the equations for his general theory of relativity, Einstein realised that large objects caused a distortion in this space-time continuum, pulling smaller objects closer to them. 

A little confusing? Try this: Imagine you place a bowling ball in the centre of a trampoline. Then, imagine trying to roll a golf ball around the edge of the trampoline. Essentially, the golf ball would spiral inwards towards the heavier object - just in the same way that Einstein believed planets in the solar system interacted with objects, such as how the gravity of a planet pulls rockets into space.

Einstein’s Quantum Theory of Light

In November 1922, while on an extended tour of the Far East with his wife Elsa, Einstein received the news that he had been awarded the 1921 Nobel Prize in Physics. 

Interestingly, although Einstein had become most famous for his theory of relativity, the prize was actually awarded for his work on quantum mechanics. More specifically, for his first paper on theory published in 1905 on the photoelectric effect.

This theory highlighted how light is a composition of small particles of energy which have wave-like properties. These particles are now more familiarly known as photons.

In this theory, Einstein also explained the process of emissions of electrons which emerge  from metals which are struck by lightning, which he called the ‘photoelectric effect.’ Over the years that followed, the theory also later led to the invention of the modern TV, which gave technologists the breakthrough to creating devices with screens.

From 1905 to 1923, Einstein was one of only a few scientists interested in the discovery of photons. However, unlike his contemporaries (mainly, Werner Heisenberg and Erwin Schroedinger), he shared different views on quantum mechanics, and so was the lead opposition to the central theories of the time.

3. Stephen Hawking (1942 - 2018)

Finally, Sir Stephen Hawking closes our list of the 3 most famous physicists of all time. One of the most iconic theorists of our era, his work with black holes and relativity remains his most ground-breaking discovery so far, while his books on the matter have helped make science more accessible to everyone. 

At age 21, while studying cosmology at the University of Cambridge, he was diagnosed with amyotrophic lateral sclerosis (ALS), something which is depicted in the 2014 biopic film of his earlier life The Theory of Everything. 

As far as his work in science is concerned, Hawking remains one of the most famous physicists of the 21st Century, leading to breakthroughs in furthering our understanding of relativity theory and quantum mechanics with his theory of exploding black holes.

His genre-defining book, A Brief History of Time, has sold more than 10 million copies since its publication in 1988, and has been translated into more than 35 different languages, while the discoveries he made during his career led to many great accolades and achievements, such as being named a fellow of the Royal Society at the age of 32, and later earning the prestigious Albert Einstein Award and more.

Stephen Hawking’s Main Theories

Sir Stephen Hawking made tremendous contributions to the field of Physics, and, more specifically, cosmology.

His work on the origins of the Universe and the formation of black holes have pioneered the study of space for the future, helping us better understand how our solar systems operate.

Research on the the Start of the Universe 

In the 1960s, Stephen Hawking rose to fame with his scientific research on black holes, demonstrating that they aren’t the information vacuums scientists first thought they were.

Inspired by fellow cosmologist and Oxford mathematician, Roger Penrose, who had previously made ground-breaking discoveries into the fate of stars and the creation of black holes, Hawking launched himself into understanding how the Universe began. And so, the pair set on to expand on Penrose’s earlier work, setting Hawking on a path towards changing the world (and universe) we know it as today.

Together, the paid were able to show that if the Universe did emerge from a “Big Bang,” then it must have started from one infinitely small point - which he referred to as a “singularity.” 

At the time, this was revolutionary in the world of cosmology. The cooling afterglows of the Big Bang’s radiation had only just been detected with early technologies, with scientists baffled at understanding how an entire Universe could emerge out of pretty much nothing.  

Hawking’s Theory on Making Black Holes Disappear

In the 1970s, Stephen Hawking ventured onto his next project: understanding exactly what a black hole is. 

What his discovery found - and hence the inspiration for the paper title - was that black holes are not black in colour at all, but are in fact “white hot.”

Early research by John Wheeler discovered that black holes are such dense pockets of space, that everything within their realm collapses to a single point - another example of singularity.

At the time, it seemed inconceivable that these could have anything to do with quantum Physics, and our understanding of how light and electrons work. But Hawking once again made ripples through the scientific world when he proved that quantum theory has a significant impact on the fate of black holes. 

Referencing Einstein’s famous E=mc^2 equation, Hawking demonstrated that black holes can create and radiate new particles through quantum theory, lose energy, and also, lose mass. 

However, he did make the point that in this way, it would take a very, very, very long time for a black hole to evaporate in this way, but in its last moments, explode in a burst of energy which is equivalent to a “million one megaton hydrogen bombs.” 

Hawking’s Theory on the Explanation of the Universe

From his very granular work on understanding singular black holes, Hawking’s later work turned to understanding the Universe as a whole - the ultimate gravitational container in which we all exist. 

Again, drawing on his knowledge of quantum mechanics, Hawking defied all other scientists, showing how it was possible to encapsulate the entire history of our Universe in a single mathematical expression. This expression was called “The Wavefunction of the Universe.”

Interestingly, the expression is self-contained - meaning that it starts and ends with a singularity. If necessary, it can also have history bounce back and forth between the singularity. 

And so, Hawking stated, that there is no need to even ask about what happened before the Big Bang. Using his expression, an existing Universe would explain itself on its own terms.

Summary

Thanks to school, films, podcasts, books and more, we are all well-familiarised with the term “Physics” and how it affects the movements of the world around us and beyond. But it’s important that we are aware of the very people that formed our understanding of the subject as we know it today. 

In this article, we’ve highlighted just three of the most famous physicists of all time: Sir Isaac Newton, Albert Einstein, and Sir Stephen Hawking. We’ve touched on the very basics of the theories which revolutionised science at the time and pushed them into stardom.

But this is just the beginning.

There are indeed so many important and notable contributors to the field of Physics, who, if you are interested in pursuing the subject at A-Level or even university, you should definitely read up on. 

So what are you waiting for? 

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