NPR's Ailsa Chang talks with Emily Kwong and Regina Barber of Short Wave about the fluid dynamics of crowds, an early fossil of a modern bird and new data on how people's moods change through the day.

Congress holds the power of the purse. But President Trump and Elon Musk are swiftly using executive actions to dismantle federal programs funded and approved by Congress.

School vouchers are a top priority for Gov. Abbott in Texas, where the legislature is poised to pass a $1 billion plan. Democrats say the money would be better used to strengthen public schools.