This artist’s interpretation intends to show small grains of a reference material disappearing or floating away. Also shown are two lasers, red and blue, which represent the two different colored lasers used by our instrument. Also visible are linear molecules of carbon dioxide (collections of three balls), CO2. Credit: Creative and Printing Services

AJ Fleisher, Research Chemist, National Institute of Standards and Technology (NIST)

In an essay titled “ The end of artefacts, “ Nobel laureate and National Institute of Standards and Technology (NIST) fellow William D. Phillips details how scientists came to realize the original vision of the metric system, or the International System of Units (SI) — a system of units “for all times, for all people.” With the redefinition of the kilogram in 2019, the new SI was rightly celebrated as a unifying achievement toward the democratization of science, with NIST and its international partners having collectively led the charge.


Adam Jacoff in the NIST Robot Test Facility. Credit: NIST

Adam Jacoff has been a robotics research engineer at the National Institute of Standards and Technology (NIST) since 1988. His research has focused on developing a variety of new robotic capabilities and designing comprehensive suites of tests to foster innovation throughout the robotics community to help keep emergency responders out of harm’s way. Adam, along with the NIST Emergency Response Robotics team, is a finalist for a Samuel J. Heyman Service to America Medal in the Safety, Security and International Affairs category, which is awarded to federal employees who have made significant accomplishments in fields such as civil rights, cybersecurity…


Ed Sisco analyzing wipe samples of the outside of suspected drug packaging by thermal desorption direct analysis in real-time mass spectrometry (TD-DART-MS). Credit: E. Sisco/NIST

Ed Sisco has been a research chemist within the Surface and Trace Chemical Analysis Group at the National Institute of Standards and Technology (NIST) since 2014. His research has focused on chemical identification systems for forensics, homeland security and other applications. Ed is a finalist for a Samuel J. Heyman Service to America Medal in the Emerging Leaders category, which is awarded to federal employees under the age of 35 who have made important contributions early in their professional careers. The Samuel J. …


Callie Higgins with her hybrid atomic force microscope 3D printer. Credit: C. Higgins/NIST

Callie Higgins is a materials research engineer at the National Institute of Standards and Technology (NIST). She studies a special branch of additive manufacturing called vat photopolymerization, which uses light to solidify a liquid resin layer by layer into a 3D object. Callie is a finalist for a Samuel J. Heyman Service to America Medal in the Emerging Leaders category, which is awarded to federal employees under the age of 35 who have made important contributions early in their professional careers. The Samuel J. …


Judah Levine, Physicist and Fellow of the National Institute of Standards and Technology (NIST) and JILA, a joint institute of NIST and the University of Colorado Boulder

This is part 5 in a series. Read part 1, part 2, part 3 and part 4.

The Leap Second Solution

When atomic clocks were developed in the 1950s, scientists needed to match the time and frequency of these new devices to the long-standing astronomical definitions of these same parameters in order to enable a smooth, continuous transition from astronomical to atomic time.

The transition between astronomical time and atomic time was based on measurements made over…


NOAA daily gap-filled, global chlorophyll analysis from VIIRS SNPP and VIIRS NOAA-20 for 21 April 2021 Credit: NOAA/NESDIS/STAR Ocean Color Science Team

B. Carol Johnson, Physicist, National Institute of Standards and Technology (NIST)

It is February 1994 and I am on the research vessel R/V Moana Wave off the coast of Lanai, Hawaii, with the team of the Marine Optical BuoY (MOBY) project. The water is incredibly blue, and I can’t help but be awestruck by the enormous energy, momentum, power and depth of the ocean as I watch the currents and the wind create what appear to be rising and falling pyramids of solid substance, no longer a liquid but a mighty living thing. It is against this backdrop that we…


The prime meridian in Greenwich, UK. Credit: GMaple Design/shutterstock.com

Judah Levine, Physicist and Fellow of the National Institute of Standards and Technology (NIST) and JILA, a joint institute of NIST and the University of Colorado Boulder

This is part 4 in a series. Read part 1, part 2 and part 3.

Greenwich Mean Time

In the previous essay I introduced mean solar time, which averaged the annual variation in apparent solar time so as to generate a time scale that was more consistent with the time scale generated by clocks that used a mechanical device to realize the reference frequency. The device that generated the reference frequency might produce an event every…


Judah Levine, Physicist and Fellow of the National Institute of Standards and Technology (NIST) and JILA, a joint institute of NIST and the University of Colorado Boulder

This is part 3 in a series. Read part 1 and part 2.

Oscillators and Clocks

In the previous essay, I introduced the ideas that frequency and time interval are closely related concepts, and that the time at any instant is a count of the number of basic time intervals (such as the second) that have elapsed since some origin. …


Pipes on a pipe organ. Credit: 2009fotofriends/shutterstock.com

Judah Levine, Physicist and Fellow of the National Institute of Standards and Technology (NIST) and JILA, a joint institute of NIST and the University of Colorado Boulder

This is part 2 in a series. Read part 1.

A short history of frequency

Frequency was originally considered to be the province of musicians. The pitches or frequencies of the notes in a musical scale are defined by ratios — octaves, for example, where the frequency of the higher note is twice the frequency of the lower one. …


Judah Levine, Physicist and Fellow of the National Institute of Standards and Technology (NIST) and JILA, a joint institute of NIST and the University of Colorado Boulder

As a physicist in the National Institute of Standards and Technology (NIST) Time and Frequency Division, I have worked in the general area of operating atomic clocks and using output signals from them to distribute time and frequency information for more than 40 years. I am also a Fellow at JILA, an institute operated jointly by NIST and the University of Colorado Boulder, and I teach in the physics department of the university.

National Institute of Standards and Technology

NIST promotes U.S. innovation by advancing measurement science, standards and technology in ways that enhance economic security and improve our quality of life.

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