The first couple hours of Mark Zuckerberg's Senate testimony Tuesday were, as Time puts it, "tedious." Lawmakers' questions made it clear they don't quite understand all the ins and outs of social media (the Week says Zuck spent a fair amount of time explaining how the internet works), and that made it easy for Zuck to give sometimes evasive answers without much pushback. But when Ted Cruz questioned Zuckerberg, the Facebook founder actually appeared to be "on edge," giving us, in Time's words, "the most explosive part" of the hearing. The exchange had to do with whether Facebook is a neutral public forum, with Cruz rattling off a number of instances in which the social network appeared to show its political bias by leaning left. Cruz specifically asked Zuckerberg about Palmer Luckey, a former Facebook employee who left the company after his conservative political views were revealed; Zuck denied those political views had anything to do with his departure. Time has more on Luckey and the Zuck-Cruz exchange. More coverage coming out of the five-hour hearing: