Captcha in Critical System (IMAGE) Max-Planck-Gesellschaft Caption Indecipherable for computers: the Captcha with the password is very grainy, as it is generated in a physical system close to a critical change of state (left). In a chaotic process, it is made completely unreadable. The process can be reversed with an easily remembered password, however. Credit Sergej Flach / MPI for the Physics of Complex Systems Usage Restrictions None 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.