Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Clock comparison yields clues to 'constant' change

19.02.2007
Years of comparisons among the world's best atomic clocks—based on different atoms—have established the most precise limits ever achieved in the laboratory for detecting possible changes in so-called "constants" of nature. The comparisons at the National Institute of Standards and Technology (NIST) may help scientists test the latest theories in physics and develop a more complete understanding of the history of the universe.

Some astronomical and geological studies suggest there might have been very small changes in the values of fundamental constants over billions of years, although the results have been inconsistent and controversial. If fundamental constants are changing, the present-day rates of change are too small to be measured using conventional methods.

However, a new comparison of NIST's cesium fountain and mercury ion clocks, scheduled to appear in this week's issue of Physical Review Letters,* has narrowed the range in which one of them—the "fine-structure constant"— possibly could be changing by a factor of 20. Widely used in physical theory and experiments, the fine-structure constant, represents the strength of the interaction between electrons and photons.

Astronomers and geologists have attempted to detect changes in natural constants by examining phenomena dating back billions of years. The NIST experiments attained the same level of precision by comparing the relative drifts in the "ticks" of an experimental mercury ion clock, which operates at optical frequencies, and NIST-F1, the national standard cesium clock, which operates at lower microwave frequencies. These data can be plugged into equations to obtain upper limits for possible rates of change of the fine structure constant in recent times.

A second study, based on seven years of comparisons of cesium and hydrogen clocks at NIST and in Europe,** achieved record limits on Local Position Invariance, the principle that two clocks based on natural frequencies of different atoms should undergo proportional frequency shifts when subjected to the same changes in gravitational field. The new experiments lowered the upper limit for a possible violation of LPI, by more than 20 times.

Changes in physical constants such as the fine structure constant or the gravitational constant would violate Albert Einstein's original theory of general relativity. Such violations are predicted in recent theories aimed at unifying gravitation and quantum mechanics. NIST scientists now plan an all-optical-frequency comparison of the mercury ion clock with an aluminum ion atomic clock, which could increase measurement precision further, offering a more stringent test of the theoretically predicted changes. Conducting such tests with many different types of atomic clocks offers the best chance of eliminating extraneous factors to clearly identify which, if any, of the fundamental "constants" are changing over time.

Laura Ost | EurekAlert!
Further information:
http://www.nist.gov

More articles from Physics and Astronomy:

nachricht From rocks in Colorado, evidence of a 'chaotic solar system'
23.02.2017 | University of Wisconsin-Madison

nachricht Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

New pop-up strategy inspired by cuts, not folds

27.02.2017 | Materials Sciences

Sandia uses confined nanoparticles to improve hydrogen storage materials performance

27.02.2017 | Interdisciplinary Research

Decoding the genome's cryptic language

27.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>