Physicists set record by measuring temporal distortion on a single millimeter
Venture close enough to a black hole and you’ll quickly learn how the force of gravity warps the very fabric of reality.
Here on Earth, the time-bending effect of gravity is nowhere near as strong. However, it remains measurable. In addition, physicists set a new record by describing the influence of our planet on the âfabricâ of the Universe – they did so on a millimeter scale.
This is an important step that deserves special attention. Zooming in so close to the smooth curve of the foundations of reality could help us solve one of the most pressing problems in all of physics.
Researchers at JILA, a joint effort of the U.S. National Institute of Standards and Technology and the University of Colorado, used a specially designed atomic clock to measure the timing of light waves separated by 1 millimeter (about 0, 04 inch), which resulted in a difference equal to only 0.76 millionth of a trillionth of a percent.
The difference was the result of something called gravitational redshift – a phenomenon caused by the influence of gravity on the frequency of two identical waves relative to each other.
As incomprehensibly small as that figure may seem, it comes as no surprise to researchers. Einstein’s general theory of relativity predicts this very outcome, after all.
What appear to be two separate constants of space and time is actually a single four-dimensional sheet in which the Universe sits. Every time something with mass sinks into it, the surrounding space-time changes shape.
The result means that the length of a second near an object – be it Earth, a black hole, or even a candy – will not be the same length of a second further.
The math is so precise and so thoroughly tested that we can predict this difference for incredibly small distances, even when the gravitational strain is as slight as that of Earth.
They must also be wrong. At least on a small level.
Quantum mechanics is another area of ââphysics that has been thoroughly tested. One of its less intuitive implications is that when you limit a measure of one kind, other properties become inherently less precise.
As reliable as the two monolithic areas of physics are, they don’t really work well together. Time is not as central in quantum mechanics as in general relativity, on the one hand.
Most importantly, that transparent space-time sheet curving so gracefully to general relativity would be a hazy mess under a quantum microscope because of the problem with less precise properties we mentioned earlier. It would create a nightmare for anyone looking for a way to combine the two ideas.
What we need is an indication that either theory has failed, which could mean finding where our predictions falter at a minuscule level.
Just over a decade ago, researchers were able to measure a difference in the relative frequency of light emitted from atoms separated by a vertical distance of just over 30 centimeters (about a foot).
In this new study, using a new type of cavity to improve the power of the experiment, the researchers succeeded in reducing the atomic density by an order of magnitude, reducing the height from a few centimeters to a handful of millimeters.
Into this chamber, they pushed 100,000 atoms of strontium, which they forced to virtually stop by removing as much heat as possible.
They then measured the light emitted from the top and bottom of the stack of atoms and corrected for effects that were not gravitational in nature.
After 92 hours of observing these tiny clocks, they had an average that more or less resembled the expected result if general relativity was true.
The team has yet to publish the work for peer review, but the results are available on the arXiv preprint server for anyone to view.
The degree of difference between the gravitationally redshifted emissions was so small that it sets a record for the fineness of a difference we can detect, giving us a measure of the phenomenon nearly 100 times more accurate than anything that has been made in the past.
It’s not exactly the result that shatters the theory we aspire to, but it’s a lesson in how we can scale down technology to a scale needed to find loopholes in two of physics’ biggest ideas.