Simon Martin is a Mayanist scholar and senior research specialist at the University of Pennsylvania Museum of Archaeology and Anthropology, known as the Penn Museum. Martin is co-curator of an exhibit there titled “Maya 2012: Lords of Time,” and he is co-author of Chronicle of the Maya Kings and Queens: Deciphering the Dynasties of the Ancient Maya.

Jonathan Kirsch is the author of A History of the End of the World: How the Most Controversial Book in the Bible Changed the Course of Western Civilization. He says apocalyptic anxiety has never been wholly absent from our culture, but it is at an all-time high now, due to current events and natural disasters.

John R. Hall is a professor of sociology at the University of California, Davis. He is the author of Apocalypse: From Antiquity to the Empire of Modernity (2009) and can discuss the history of apocalyptic movements, prophets and groups.

Crawford Gribben is a director of the Trinity Millennialism Project at Trinity College in Dublin, Ireland.

Joseph Gelfer is an adjunct research associate in the School of Political and Social Inquiry at Monash University in Australia and editor of the anthology 2012: Decoding the Countercultural Apocalypse (2011).

Todd Strandberg is executive director of RaptureReady.com, which publishes the Rapture Index.

David Reagan is founder and director of Lamb & Lion Ministries, a Christian organization that proclaims the imminent return of Jesus. It is based in McKinney, Texas.

Wilfred Hahn is founder of Mulberry Press, publishers of the Eternal Value Review. Part of the company’s mission statement is to proclaim the imminent return of Jesus, which it does by keeping watch on world economic developments.

Harold Camping is president of Family Radio and its attendant ministries. He predicted the Second Coming of Jesus on May 21, 2011, followed by the end of the world on Oct. 21, 2011. Camping previously predicted the end of the world in 1994. He lives in Alameda, Calif.