Advances in determination of fundamental constants to guide redefinition of scientific units to rely on constants of nature instead of physical standards
The fundamental constants that govern the laws of nature are being determined with increasing accuracy, according to a review paper published this week in Journal of Physical and Chemical Reference Data, from AIP Publishing.
NIST's watt balance is a powerful measuring tool that is aiding in the redefinition of the kilogram
The paper outlines the proceedings from this year's Workshop on the Determination of the Fundamental Constants, where an international community of physicists and metrologists convened to share their research into an array of fundamental constants. Ultimately, better definitions of these constants will aid in the effort to redefine several standard scientific units, including the kilogram and the Kelvin, by 2018.
Fundamental constants describe a variety of physical properties in the world around us. Planck's constant, for example, governs the relationship between energy and frequency. The fine-structure constant explains the strength of electromagnetic interaction between charged particles. Fundamental constants such as these underlie the development of much of today's technology, from atomic clocks to GPS systems.
They are also linked to the International System of Units (SI), the standard measurement system used throughout the scientific community and in most countries around the world. By defining units like the meter in terms of fixed fundamental constants such as the speed of light, we ensure that they remain the same over time.
However, some SI units, like the kilogram, still rely on a physical standard -- in this case, a platinum-iridium cylinder housed in France. Now that scientific research is carried out across the globe, relying on a single physical standard is somewhat limiting, as mass standards in other countries must be periodically calibrated against the original. In addition, the standard itself is subject to changes in mass over time.
To make the system more consistent and accessible, the international metrology community plans to redefine all SI units in terms of fundamental constants by 2018. Before we can redefine an entire system of units, though, it is important to be certain that the fundamental constants upon which the definitions depend are as accurate and precise as possible. And since different measurement procedures or data collection techniques can yield slightly different results, pinning down the exact values of these constants can be a surprisingly fussy business.
"The objective of the SI is to provide the best possible standards, and the redefinition will be a step in that direction," said Peter Mohr, a researcher at the National Institute for Standards and Technology (NIST).
Luckily, some of the values for previously-contested constants appear to be converging. For instance, the recent workshop highlighted advances in the determination of the Bolzmann constant k, which explains the relationship between temperature and particle energy. Under the new SI system, the fixed Bolzmann constant will be used to define the Kelvin, the SI unit of temperature.
Planck's constant has also seen marked progress. "The Planck constant was problematic in the past, as there were disagreeing values obtained by different experiments. However, the values seem to be converging to a sufficiently reliable value for the redefinition of the SI to move forward," said Mohr. Planck's constant will eventually be fixed and used to define the kilogram.
"The new definitions will make many of the physical constants that are measured now exact in the future. Others, although not exact, will be more accurate," said Mohr. "This will stabilize the values of the constants and provide accurate measurement standards."
The 2015 workshop provided input to the latest adjustment of the official values for a number of fundamental physical constants, now available online. This adjustment is not the final one before the official SI redefinition in 2018, but it's still an important step forward. Growing consensus on the values of certain fundamental physical constants suggests that we may be almost ready to fix their values and move to a more reliable and streamlined measurement system.
The article, "Advances in determination of fundamental constants," is authored by Savely G. Karshenboim, Peter J. Mohr and David B. Newell. It will appear in the Journal of Physical and Chemical Reference Data on July 14, 2015. After that date, it can be accessed at http://scitation.
ABOUT THE JOURNAL
Journal of Physical and Chemical Reference Data is the authoritative resource for critically evaluated reference data for physical science and engineering disciplines. The journal publishes papers which report the best available measurements for the relevant properties. http://jpcrd.
Jason Socrates Bardi | EurekAlert!
Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)
Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
21.10.2016 | Health and Medicine
21.10.2016 | Information Technology
21.10.2016 | Materials Sciences