Five hundred years ago this month, the German monk Martin Luther challenged the practices of the Roman Catholic church, sparking the Protestant Reformation and shaping how Christians think and worship.Bishop Denis Madden, of the Catholic Archdiocese of Baltimore, and Rev. Mark Hanson, of the Evangelical Lutheran Church in America, describe the dialogue aimed at reuniting their denominations.And we speak to Yu Na Han, who curated an exhibit at the Walters Art Museum about Luther’s life as father, friend, and husband.