Crowd (IMAGE) Uppsala University Caption Dense crowds with shoulder-to-shoulder contact act like a solid material, with potentially disastrous outcomes. Credit Photograph by Ulrike Biets; illustration by Arianna Bottinelli, David T. J. Sumpter, and Jesse L. Silverberg Usage Restrictions in articles about this study License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.