The Map of Physics
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The Map of Physics

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.


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