PBS SpaceTime has been running for quite some time already. Beyond the obvious space/time and physics aspect, it's also a good example of a fact-based show that shows scientific method and critical thinking in action, without unnecessary drama or exaggerated sensationalist style; it strikes a perfect balance between science and narrative, serious and not-so-serious, in-depth and manageable chunk size. The graphics help to understand some of the material for us non-physicists or math geniuses, and Matt O'Dowd calm voice and wit create an environment suitable both for deep learning and deep relaxation, occasionally battling insomnia.
This is one of the gems of Youtube for sure.