hmmm, i guess it depends on what ur interested in. they have a variety of topics. gravity, apes, evolution, space, etc.
any episode labeled "timecapsule" would be a good starting point, i suppose. those are episodes in which they take the 'best of' moments from the past few episodes and merge them into one. i prefer the other episodes tbh to hear in-depth about 1 topic personally, but those can be good to give u a little sample. "Cosmic Queries" episodes are probable the most popular--i like em too. they usually have a comic and tyson, taking random fans questions from social media.