Forty years ago, Margaret Geller and John Huchra, at the Harvard-Smithsonian Centre for Astrophysics, discovered the largest structures ever seen by man: galaxies are not scattered randomly throughout the universe but form a cosmic sponge made up of walls and large voids measuring hundreds of millions of light years. Even today, we are still trying to understand how and why these gigantic structures formed.   Guest: Antonaldo Diaferio, professor at the University of Turin and president of Infini.to. In addition to participating in the meeting, during the event it will be possible to visit the interactive museum and attend a show inside the digital planetarium.   AstroTalk is free with a Museum+Planetarium admission ticket