Judah Levine with NIST Time Scale (image) National Institute of Standards and Technology (NIST) Share Print E-Mail Caption NIST physicist Judah Levine with the NIST time scale, an array of hydrogen masers (microwave versions of lasers) that maintains official US civilian time. NIST atomic clocks are used to calibrate the time scale. Credit Burrus/NIST Usage Restrictions please use proper image credit Share Print E-Mail 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.