EM Observations Overview: Electromagnetic probes of Black Hole rotation

The age of X-ray Astronomy started in 1962, through the discovery of the first source of X-rays outside of our solar system: Scorpius X-1. Only two years later, the galactic black hole Cygnus X-1 was discovered, back when black holes were mere solutions to Einstein's field equations. Throughout the following 60 years, more than 50 X-ray observatories were launched, all producing the data that led to the exponential evolution of our understanding of those mysterious objects, and their effects on their surroundings. However, the picture explaining the physics of black holes is far from complete, especially regarding their rotation, characterized through the dimensionless spin parameter. In this talk, I will discuss the evolution of X-ray methods for probing black hole rotation based on spectral, timing, and polarization measurements, discuss the current results, views, and limitations of the field, and hint at directions for the future, both from an observational and theoretical perspective.