The last day of the 2015 World Science Festival saw entertaining discussions of the purpose of sleep, the nature of time, and the potential ways we might harness quantum mechanics—plus a science takeover of Washington Square Park.

The third day of the World Science Festival invited attendees to consider our human origins, our future in space, and our potential for extreme behavior, and pit smarts against each other in a battle of science knowledge.

In the first of two Pioneers in Science installments at the World Science Festival, NASA chief scientist Ellen Stofan answered questions from high school students from across NYC—as well as from kids in Denmark, Spain, and the Czech Republic, who joined the discussion via a Google Hangout. One student asked about the potential for terraforming Mars into a more habitable world; Stofan said that while it might be possible to generate an atmosphere on Mars over millions of years, the Red Planet’s lack of a protective magnetic field would still leave residents vulnerable to the intense radiation borne by the solar wind.

NASA astrophysicist Amber Straughn, who’s appearing in the 2015 World Science Festival program “Cool Jobs,” is working on the next big thing in space science: the James Webb Space Telescope. Her workday is all about tackling big questions about galaxies, black holes, star formation, and other cosmic conundrums. She was also kind enough to answer some questions from us about life as an astrophysicist.

The 2015 World Science Festival has officially arrived, bringing opportunities to spark interest in science all across the five boroughs of New York City. “We’re taking the top scientists in the world, and bringing them here to interact with people, for people to meet them and to listen to them. And they’re really great at communicating science,” Festival co-founder and CEO Tracy Day told NY1.