Experimental tracking (VIDEO) Optica This video is under embargo. Please login to access this video. To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video Caption The researchers used their new method to track a metal sphere with a central hole while it moved down a curved spiral wire under gravity. Credit Zihan Geng, Tsinghua University Usage Restrictions None License Original 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.