depths of space right down to subatomic particles.

And if you don’t already know physics its sometimes difficult to see how all these 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.

Mathematics 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, and 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 a 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 into 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 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 a 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 else.

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 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 relativity and general

relativity.

Special relativity is 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 orbit, to energy levels 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 a 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 called 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 physics only really describes 5% of what we know about and everything else, at the

moment, is a mystery.

And there are many other mysteries out there like the big bang, and no doubt there’s

other things that we don’t even know we don’t know.

a 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 we are actually finding out the truth.

And just why is all of physics like this?

Well those are rather big questions, ones which we 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.

Ummm.

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

few different things and I kind of like this animation style so let me know 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 you.