Nelson Mandela memorial: --- Johannesburg (CNN) -- It's a moment for the ages.- Tens of thousands of South Africans, dozens of presidents and prime ministers, celebrities and street sweepers are all heading to the same place: a stadium in Johannesburg, where they'll honor Nelson Mandela at a memorial service on Tuesday. - With 91 heads of state attending, security will be tight. -- Among the speakers at Tuesday's memorial will be President Obama, who like Mandela was his nation's first black president. Obama has cited Mandela as his own inspiration for entering politics. -- In addition to Obama, former Presidents Jimmy Carter, George W. Bush and Bill Clinton will attend. More than two dozen U.S. lawmakers also plan to go. - More, CNN, at: http://www.cnn.com/2013/12/10/world/africa/nelson-mandela-memorial/index.html?hpt=hp_t1