Small splits present in all levels due to interaction between the electron spin and the nuclear spin if it is present, i.e. the nucleus has an even number of nucleons.

As the name suggests, this energy split is very small, since the influence of the nucleus spin on the electron spin is relatively small compared to other fine structure.

TODO confirm: does it need quantum electrodynamics or is the Dirac equation enough?

The most important examples:

The length of its cycle.

Bibliography:

As a Brazilian, Ciro Santilli used to really love playing soccer (but not watching it), until he hurt his knee.

Playing soccer just feels amazing, because you are constantly running around, but with a more specific goal in mind: to get that ball into that goal!

Playing soccer was specially amazing in the flat wet sand beach of Santos. weekend, the sea, feet touching the sand, the sun going down, and your school mates next to you. Nirvana.

It is also true that under those conditions, the skin of your feet will get ripped off due to running on the slightly wet and flat sand no matter how thick it has become. But it is worth it.

Teams would often be slit between "the team with shirts vs the team without shirts", who would just take off their shirts. The two best players would take turns picking players into their teams, the first one to pick would be decided by odds and evens (par ou ímpar).

A pair of Havaianas, or Havaianas rip-offs, stuck into the sand, or even just some school bags, would do as a goal posts. More organized people, especially adults, would have their own water pipe goal with a proper net and all. But doing so would spoil the fun of endless discussions if a non flat ball had gone in or not into an imaginary rectangle.

That's how soccer was meant to be played.

Ciro became however disillusioned with soccer after his injury. It is a shame.

And so after that, Ciro decided to dedicate himself to sports where you can't hurt your knee.

Ciro hates water, so swimming is out of the question. What could be more boring than going back and forth on a fixed location a million times to gain some milliseconds?

And so Ciro has been left with the gym as the only main option for a while.

Running would have been a consideration, but Ciro Santilli's legs sometimes itch when he runs.

This is until he ended up living in a place with decent roads for cycling in the late 2010's, which led to Ciro Santilli's cycling.

High level DNA studies? :-)

For students (who are paying for the university to start with...), they will not claim tutorials linked to courses. But a tutorial that shows university laboratories, it is unclear: www.ox.ac.uk/students/academic/guidance/intellectual-property (archive) This likely includes graduate students, who are also not paid by the university.

For faculty, the university owns everything it seems, to be confirmed.