 Condensed matter physics

Condensed matter physics is one of the best examples of emergence. We start with a bunch of small elements which we understand fully at the required level (atoms, electrons, quantum mechanics) but then there are complex properties that show up when we put a bunch of them together.

Includes fun things like:

As of 2020, this is the other "fundamental branch of physics" besides to particle physics/nuclear physics.

Condensed matter is basically chemistry but without reactions: you study a fixed state of matter, not a reaction in which compositions change with time.

Just like in chemistry, you end up getting some very well defined substance properties due to the incredibly large number of atoms.

Just like chemistry, the ultimate goal is to do de-novo computational chemistry to predict those properties.

And just like chemistry, what we can actually is actually very limited in part due to the exponential nature of quantum mechanics.

Also since chemistry involves reactions, chemistry puts a huge focus on liquids and solutions, which is the simplest state of matter to do reactions in.

Condensed matter however can put a lot more emphasis on solids than chemistry, notably because solids are what we generally want in end products, no one likes stuff leaking right?

But it also studies liquids, e.g. notably superfluidity.

One thing condensed matter is particularly obsessed with is the fascinating phenomena of phase transition.