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PBS Digital Studios is one of the best things on YouTube.

I particularly like SpaceTime, Eons, and Crash Course. There are many others, too.

They have a lot of great history shows as well. I catch myself watching Rocky Mountain PBS and Wyoming PBS as late night TV on occasion.

They're more dry than the ones you mentioned, but pleasant to nod off to.

And IdeaChannel, before they stopped making new episodes.