Talk of the Nation on wmukhd2

Generations of physicists have claimed that time is an illusion. But not all agree. In his book Time Reborn: From the Crisis in Physics to the Future of the Universe, theoretical physicist Lee Smolin argues that time exists--and he says time is key to understanding the evolution of the universe.

Scientists reported this week in the journal Cell that they had used somatic cell nuclear transfer techniques to create a source of embryonic stem cells from the skin cells of a patient. George Daley, director of the stem cell transplantation program at Boston Children's Hospital, and Josephine Johnston of the Hastings Center discuss the research.

A report from the UN Food and Agriculture Organization says insects offer a huge potential for improving the world's food security. Peter Menzel, co-author of Man Eating Bugs, describes some insect-based cuisine and the western aversion to creepy-crawly snacks.

As the death toll in Syria climbs and critics blast the Obama administration for not taking more decisive action, former ambassador Christopher Hill points instead to a failure of diplomacy in an op-ed in the New York Times. Hill talks about what the U.S. faces in facilitating talks between the regime and Syrian rebels.

As the summer travel season approaches, air travel provides a barometer for the health of the U.S. economy — and airlines report they're having a good year. After years of financial troubles, industry representatives hope U.S. travelers are more willing to fly. NPR senior business editor Marilyn Geewax explains what summer travel tells us about the health of the economy.