Gravity’s Great Mystery Deepens: New Measurement of Universal Constant Contradicts Previous Results
"Every measurement is an opportunity to learn."
– Lead researcher Stephan Schlamminger, on the dispiriting process of measuring Big G.
Scientists at the National Institute of Standards and Technology (NIST) have published a new measurement of the gravitational constant (Big G) that defies both its own target and the accepted scientific standard. The value obtained does not match the result of the experiment it sought to replicate, adding another layer of intrigue to one of physics' most stubborn puzzles.
Measurement Details
The team meticulously measured Big G at 6.67387 × 10^-11 cubic meters per kilogram per second squared.
- This value is 0.0235% lower than the result of the specific experiment they were attempting to replicate.
- It also differs from the current CODATA recommended value.
The "Life-Sucking" Challenge
For over 225 years, scientists have wrestled with measuring the gravitational constant. Unlike the speed of light or Planck’s constant, which can be measured with astonishing precision, Big G remains stubbornly imprecise.
- The CODATA recommended value for Big G still carries an uncertainty of 22 parts per million.
- Lead researcher Stephan Schlamminger described the work as “life-sucking” and at times dispiriting, comparing the process to a "random number generator."
"The honest truth is, this work is incredibly difficult. But we reframed it. Every measurement is an opportunity to learn."
Physicist Christian Rothleitner noted that measurements of Big G are "all very scattered" and inconsistent across the globe.
Avoiding Bias: A Secret in an Envelope
In a novel approach to ensure objectivity, the team employed a blinded experimental design to ward off personal bias. A secret offset number was kept in an envelope, unknown to the researchers, until the study's conclusion—ensuring their results were not subconsciously skewed.
What Does This Mean?
While the discrepancy is significant, researchers not involved in the study caution that it is most likely due to unknown systematic errors rather than new physics.
Despite the challenges, Schlamminger expressed hope that young researchers will not be discouraged from pursuing measurements of Big G, calling it a fundamental puzzle worth solving.
The research was published in the journal Metrologia on April 16.