CV is doing a tutorial on gravitational waves

Straight-up General Relativity is so refreshing after getting lost in the Escherian landscape of Quantum Mechanics. CV is doing a lovely tutorial on Gravitational Waves, which, for extra credit, includes a readable example of a gauge artifact:

The difficult childhood of gravitational waves | Cosmic Variance:

...It might sounds strange that, given an equation describing their existence, gravitational-waves could nonetheless be questioned by large numbers of physicists. However, general relativity can be tricky, and it’s not always straightforward to understand what it’s trying to tell us. In this particular case, the question was whether or not gravitational waves were a gauge artifact. It can sometimes get confusing as to whether an effect is truly physical, or is just a byproduct of the coordinate system one has chosen. For example, look at the latitute/longitude coordinate system on the Earth. This system gets weird at the poles, where suddenly the longitude is no longer well defined (there are an infinite number of valid longitudinal coordinates for the same point). The North and South poles are somehow special, and if all you had were the coordinates, you might be afraid to take a walk there. Who knows what lurks at the singularities?! Needless to say, the problem is with the coordinates, and not with the poles themselves...

I'm looking forward with bated breath to the next installment ...