DISCLAIMER: This article is being kept online for historical purposes. Though accurate at last review, it is no longer being updated. The page may contain broken links or outdated information.
Deslattes, Richard D. Atomic Physics Division, National Institute of Standards and Technology, Gaithersburg, Maryland.
- Unit of mass
- Alternatives to the artifact kilogram
- Related Primary Literature
- Additional Reading
Physical measurements depend on an evolving structure of base units, algorithms for their realization, and recommended procedures that constitute the International System of Units (SI). Until the second half of the twentieth century, most such base units were defined in terms of specific physical artifacts. These units entered the measurement process by means of replicas of the primary artifacts. Much work has been done to replace these artifact standards by invariant alternatives, such as atomic transition frequencies and fundamental physical constants. Only the base unit of mass remains defined by an artifact. Efforts involving atom counting and electromagnetic force generation may provide an invariant replacement.
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information