The Map of Physics

Summary

This video script offers an insightful overview of the vast field of physics, dividing it into three main branches: Classical Physics, Quantum Physics, and Relativity. It starts with Isaac Newton's laws and contributions to optics and calculus, then delves into electromagnetism, mechanics, and thermodynamics. The script highlights the shift from classical to modern physics, marked by Einstein's theories of relativity and the quantum revolution. It also touches on current mysteries like dark matter and energy, and the quest for a unified theory of quantum gravity, ending with the philosophical implications of physics.

Takeaways

• 🌌 Physics encompasses a vast array of topics, from cosmic scales to the subatomic world.
• 📚 The script introduces physics as divided into Classical Physics, Quantum Physics, and Relativity.
• 🔍 Isaac Newton's laws of motion and universal gravitation are foundational to classical physics.
• 📐 Newton's development of calculus is essential for the mathematical derivations in physics.
• 🌈 Optics, the study of light, is a significant branch of physics with practical applications in telescopes and cameras.
• 🌊 Fluid mechanics, the study of liquids and gases, is intricate and crucial for understanding aerodynamics.
• 🔥 Thermodynamics deals with energy transformations and the concept of entropy, indicating energy's usefulness.
• 🌐 Einstein's theories of special and general relativity revolutionized our understanding of space, time, and gravity.
• 🧬 Quantum physics delves into the behavior of atoms and subatomic particles, leading to technologies like computers and lasers.
• 🌑 The mysteries of dark energy and dark matter, which constitute most of the universe, remain unsolved in physics.
• 🤔 Philosophy underlies physics, prompting questions about the nature of reality and the universe's existence.

Q & A

What are the three main branches of physics?

The three main branches of physics are Classical Physics, Quantum Physics, and Relativity.

Who was Isaac Newton, and why is he significant in physics?

Isaac Newton was a physicist who developed the laws of motion and the law of universal gravitation. He also invented calculus, a powerful mathematical tool used in physics.

How is mathematics connected to physics?

Mathematics is the language of physics and can be thought of as the bedrock upon which physics is built. It provides the tools and framework to derive and describe physical laws.

What is electromagnetism, and who discovered it?

Electromagnetism is the study of electric and magnetic fields and their interactions. James Clerk Maxwell discovered that electricity and magnetism are two aspects of the same phenomenon and formulated the laws of electromagnetism.

What is chaos theory?

Chaos theory deals with large complex systems and explains how small differences in initial conditions can lead to significantly different outcomes.

How does relativity differ from classical physics?

Relativity, developed by Albert Einstein, describes the behavior of objects at very high speeds and the nature of spacetime, while classical physics focuses on objects moving at much lower speeds and doesn’t account for the effects of very fast motion or gravity's influence on spacetime.

What is quantum physics?

Quantum physics studies the behavior of matter and energy at the smallest scales, such as atoms and subatomic particles. It includes atomic theory, particle physics, and quantum field theory.

What is the Standard Model in particle physics?

The Standard Model describes the fundamental subatomic particles and how they interact. It is the best framework we have for understanding the universe at the smallest scales.

Why is quantum gravity considered a major unsolved problem in physics?

Quantum gravity is a challenge because physicists have not yet figured out how to combine quantum physics and general relativity into one theory that can describe the entire universe.

What are dark matter and dark energy?

Dark matter and dark energy are mysterious substances that seem to make up about 95% of the universe. They are not yet fully understood, and current physics only describes the remaining 5% of the universe.

Outlines

00:00

🪐 Overview of Physics

Physics encompasses a vast range of topics, from the cosmic scale of galaxies to the microscopic world of subatomic particles. This map of physics highlights its three main branches: Classical Physics, Quantum Physics, and Relativity. Classical Physics begins with Isaac Newton, whose laws of motion and universal gravitation provided a foundation for understanding movement and gravity. Newton also developed calculus, a vital tool for physicists. Optics, a subfield of classical physics, explores light and how it interacts with materials, leading to technologies like telescopes and microscopes. The behavior of waves, including light, follows certain principles, such as reflection and diffraction, which connect to electromagnetism, a field unified by James Clerk Maxwell. Electromagnetism explains phenomena like light and electricity. Classical mechanics also covers the motion of solid objects, while fluid mechanics studies the flow of liquids and gases. The complexity of fluid behavior leads to chaos theory, which examines how small changes can lead to significant outcomes. Thermodynamics deals with energy transformation and entropy, illustrating that energy underpins all of physics. By 1900, classical physics provided a 'clockwork' view of the universe, though anomalies like Mercury's orbit and unexplained electron behavior hinted at deeper mysteries.

05:03

🔬 The Quantum Revolution and Relativity

As the 20th century dawned, new discoveries in physics revealed the limitations of the classical view. Albert Einstein introduced the theories of special and general relativity. Special relativity showed that the speed of light is constant and that time slows at high velocities. General relativity proposed that gravity results from the bending of spacetime. While Einstein tackled the very large, quantum physics emerged to explain the very small. Atomic theory evolved to describe atoms in increasing detail, from basic structures to complex behaviors involving energy levels and wave-like electron distributions. Condensed matter physics applies quantum principles to solids and liquids, giving rise to technologies like computers and lasers. Nuclear physics explores the atomic nucleus and powers technologies like nuclear fission and fusion. Particle physics goes deeper into the fundamental particles of the universe, encapsulated in the Standard Model. Quantum field theory merges quantum mechanics with relativity but leaves out gravity, leaving physicists searching for a unified theory, such as quantum gravity. Furthermore, the puzzles of dark matter and dark energy highlight that our understanding of the universe is far from complete, covering only about 5% of what is out there. The remaining 95% remains a mystery.

Keywords

💡Classical Physics

Classical physics refers to the physics theories developed before the 20th century, primarily focusing on macroscopic systems like motion, gravity, and light. In the video, it is described as the foundation of physics, covering Newton’s laws of motion, universal gravitation, and classical mechanics. These principles formed the understanding of a 'clockwork universe' around 1900, before newer developments like quantum physics emerged.

💡Quantum Physics

Quantum physics studies the behavior of matter and energy on the smallest scales, such as atoms and subatomic particles. The video discusses how this branch of physics emerged after experiments revealed inconsistencies in classical theories, leading to a new understanding of the microscopic world. It includes atomic theory, particle physics, and quantum field theory.

💡Relativity

Relativity, specifically Einstein’s theories of special and general relativity, revolutionized the understanding of space, time, and gravity. The video explains how special relativity introduced the idea that the speed of light is constant, and general relativity describes how objects bend spacetime, creating gravitational effects. Relativity deals with the 'very big'—the scale of planets and galaxies.

💡Isaac Newton

Isaac Newton is a central figure in classical physics, known for his laws of motion and universal gravitation. In the video, Newton’s work is highlighted as the basis for classical mechanics, and his invention of calculus is noted as a critical tool for deriving new physics. His contributions bridged the gap between Earthly physics and celestial mechanics.

💡Electromagnetism

Electromagnetism is the study of electric and magnetic fields and their interactions. The video explains how James Clerk Maxwell unified electricity and magnetism into a single framework and showed that light is an electromagnetic wave. Electromagnetism is key to understanding not just electrical phenomena but also optics and wave theory.

💡Thermodynamics

Thermodynamics studies energy transfer and the laws governing heat and work. The video describes it as the science of energy and entropy, which measures the disorder in a system. It explains how thermodynamics helps us understand processes from heat engines to the arrow of time, playing a critical role in classical physics.

💡Quantum Field Theory

Quantum field theory combines quantum mechanics with special relativity to describe the behavior of subatomic particles through fields. The video points to quantum field theory as the most accurate description of the universe at the quantum level, but it lacks a working theory of gravity, leaving an unsolved gap in modern physics.

💡Chaos Theory

Chaos theory deals with systems that are highly sensitive to initial conditions, where small changes can lead to vastly different outcomes. The video refers to this concept in explaining how fluid mechanics and large, complex systems behave unpredictably over time, making it challenging to model or predict their behavior.

💡Dark Matter and Dark Energy

Dark matter and dark energy are mysterious substances that make up about 95% of the universe, yet their nature remains unknown. In the video, they are discussed as one of the largest open questions in physics, with our current models only explaining a small fraction of the universe’s actual composition.

💡Philosophy of Physics

The philosophy of physics addresses the fundamental questions about reality, existence, and the nature of the universe. The video highlights how philosophy underpins the motivations behind many of the big questions in physics, such as the nature of reality and whether the universe follows deterministic or probabilistic rules.

Highlights

Physics is a broad subject covering topics from galaxies in space to subatomic particles.

Classical physics can be broken down into three main parts: Classical Physics, Quantum Physics, and Relativity.

Isaac Newton's laws of motion describe how matter moves and his law of universal gravitation ties planetary motion with falling objects on Earth.

Newton invented calculus, a crucial mathematical tool in physics.

Optics is the physics of light, explaining phenomena like refraction and reflection, and is essential in devices like telescopes and cameras.

Electromagnetism, unified by James Clerk Maxwell, explains electric and magnetic fields and describes light as an electromagnetic wave.

Classical mechanics deals with the motion of solid objects, while fluid mechanics explains the flow of liquids and gases.

Chaos theory shows how small differences in conditions can lead to drastically different outcomes in large systems.

Thermodynamics describes energy transfer and entropy, explaining how useful different types of energy are.

Relativity, developed by Albert Einstein, predicts strange effects like time slowing down at high speeds and explains gravity through spacetime curvature.

Quantum physics explores atomic and subatomic scales, leading to technologies like computers and lasers.

Particle physics studies the fundamental particles of matter, described by the standard model, while quantum field theory combines quantum physics and relativity.

Physicists are still working on unifying quantum physics and general relativity, seeking a theory of quantum gravity.

Dark energy and dark matter make up 95% of the universe, but are still largely unexplained.

Big philosophical questions, such as the nature of reality and the existence of free will, continue to motivate physics research.

Transcripts

So physics is a huge subject that covers many different topics

going from galaxies in the depths of space right down to subatomic particles.

And if you don’t already know physics its difficult sometimes to see

how all these different subjects are related to each other.

So this is my attempt to show that in a map, so this is the map of physics.

I hope you enjoy it.

Physics can be broadly broken down in to three main parts:

Classical Physics, Quantum Physics, and Relativity.

We’ll start with classical physics and a good person to start with is Issac Newton.

His laws of motion describe how everything made of matter moves about,

and his law of universal gravitation tied together the motion of planets in the sky

with the falling of objects on Earth into one elegant and general description.

He also invented calculus, a supremely powerful mathematical tool

which has been used over the centuries to derive new physics.

Calculus is really part of mathematics but physics and mathematics are inseparable.

Math is the language of physics, you can imagine it like the bedrock

that the world of physics is built from.

Newton also made strides in the field of optics which is the physics of light

and how it travels through different materials.

It explains, refraction seen in prisms and lenses

which are used to focus light in telescopes, microscopes, and cameras.

Telescopes enabled us to peer into the depths of space and observe the wild array of objects

there and develop astrophysics and cosmology.

Optics is closely related to the theory of waves, which is basically how energy can travel

through disturbances of a medium, like ripples on the surface of a pond or sound through the air.

Light doesn’t need a medium to travel through, it can travel through the vacuum of space,

but it still follows the same principles as all waves namely reflection, refraction and diffraction.

This leads us to electromagnetism: the description of magnets, electricity,

or more generally, electric and magnetic fields.

It was a Physicist called James Clerk Maxwell who discovered that these are two aspects

of the same thing and derived the wonderfully elegant rules of electromagnetism

and theorized that light was an electromagnetic wave.

Electromagnetism also explains all of electricity.

Jumping back a little bit, classical mechanics is related to Newton’s laws and covers

the properties and motion of solid objects, how they move when forces hit them,

what happens when they are joined together, like in gears or buildings, or bridges.

Fluid mechanics is the description of the flow of liquids and gasses.

Using fluid mechanics you can work out how much lift is generated from an aeroplane’s wing,

or how aerodynamic a car is.

Fluid mechanics is notoriously difficult, mostly because motions of tiny things

like molecules get really complicated really fast.

Which leads us to Chaos theory.

Chaos theory is the description of large complex systems

and how small differences in initial conditions can lead to very different final outcomes.

Thermodynamics is the description of energy and how it passes from one form to another.

It also includes entropy which is a measure of order and disorder, and basically

tells you how useful different kinds of energy are.

Energy is fundamental property to physics and although I have written energy here,

I should have written it everywhere on this map because everything has energy.

So that is all of classical physics, the picture of the Universe we had around the year 1900.

It told us we lived in the Universe where everything ran sort of like clockwork, if you could measure

everything accurately enough the future was kind of predetermined.

However, not everything was solved, there were just a few of holes in experiments

that hinted at something more.

The orbit of Mercury was slightly too fast and some strange things happened

on the smallest scales with electrons and light which were all unexplained.

Physicists at the time thought that they would solve and explain these problems soon enough

but poking at them they unraveled the new domains of relativity and quantum physics

and turned our understanding of the Universe completely on its head.

Albert Einstein was the genius who developed the theories of special and general relativity.

Special relativity predicts that the speed of light is constant for all observers

which means that when you travel really fast weird stuff starts happening like time slowing down.

It also states that energy and matter are different aspects of the same thing

through the famous formula E=mc2.

General relativity says that space and time are part of the same fabric called spacetime,

and that the force of gravity comes from objects bending spacetime,

making other objects fall in towards them.

While relativity describes the very big, other physicists were busy at work on the very small

in the world of Quantum Physics.

Atomic theory probed the nature of the atom, and more and more detailed descriptions

of the atom were developed.

From a tiny sphere, to electron orbits, to energy levels

and then to the electrons being wave-like charge distributions.

Condensed matter physics describes the quantum physics

of many atoms together in solids and liquids, and is where many great technologies have come from

like computers, lasers, and quantum information science.

Nuclear physics describes how the nucleus of atoms behave, and explains radiation,

nuclear fission, the splitting of the atom used in our nuclear power plants, and nuclear fusion

which takes place in the Sun and will hopefully soon be harnessed here on Earth.

Particle physics probes even deeper to find the fundamental subatomic particles that everything

is made of and are described in the standard model of particle physics.

Quantum field theory captures all of quantum physics and combines it with the special theory

of relativity and is the best description of the Universe we have.

Unfortunately Quantum field theory doesn’t include gravity

and so physicists don’t know how to join together quantum physics

and the general theory of relativity leading to the giant chasm of ignorance.

One day in the future we hope to close this chasm and come up with a theory of all

of physics we call it quantum gravity, and there are many attempts to do this some examples

are string theory or loop quantum gravity and there is many more.

But quantum gravity isn’t the only thing we observe but don’t understand,

there are also the major puzzles of dark energy and dark matter

which seem to make up 95% of the Universe.

So all of our physics only really describes 5% of what we know about and everything else,

at the moment, is a mystery.

There are many other mysteries out there like the Big Bang,

and no doubt there’s things beyond that that we don’t even know that we don’t know.

Which gets to the lofty cloud which floats over all of physics: philosophy.

Although many physicists make fun of philosophy, it is the big philosophical questions

that motivate a lot of physics, like, "What is the fundamental nature of reality?"

"How come the Universe even exists?"

"Do we have free will if we are just made of physics?"

or "How do we know that the way that we do physics and science actually gets

to the fundamental truth of the Universe?"

And, just, why is all of physics like the way it is?

Well those are the big questions, ones which we may or may never answer,

but that is no reason to give up trying, after all, physicists are not quitters.

And that was the map of physics.

So that’s the end, thanks for watching the video I hope you enjoyed it.

Um.

I’m still kind of working on the format of this channel and playing around

with a few different things and I kind of like this animation style.

So let me know in the comments if you enjoy this kind of stuff and if you want me to do more

and if there are any specific subjects you want me to cover, I’m totally open to ideas,

I’ve got a whole bunch of videos that are coming down the pipe so keep your eyes peeled for those.

So until next time. See ya.