Scientists Have Pinpointed the Number That Explains the Universe

Caroline Delbert
·3-min read

From Popular Mechanics

With new research, scientists have the most accurate measurement ever of one of the fundamental constants of the universe.

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The fine-structure constant, which helps us balance the energy difference between coarse and fine atomic models, is in the same family as constants like the speed of light. Now, its numerical value—close to the ratio 1/137—has increased from eight significant figures to a newly realized 11.

But this time, the good news has a downside of sorts, too: it effectively rules out a gray area where scientists were guessing a hidden force of nature might exist. Quanta explains:

“[Saïda Guellati-Khélifa at the Kastler Brossel Laboratory in Paris] gauges the fine-structure constant by measuring how strongly rubidium atoms recoil when they absorb a photon. The recoil velocity reveals how heavy rubidium atoms are—the hardest factor to gauge in a simple formula for the fine-structure constant.”

The previous best measurement, from a rival group based at the University of California, Berkeley, also came from an experimental assembly that has room to improve. Using rubidium instead of her rival group’s cesium is just one way Guellati-Khélifa's setup is different. Quanta says the Berkeley team has a new laser and the Paris team has a new vacuum tube, meaning we’ll likely see an exchange of new values in the very near future.

There are 26 fundamental constants in total, and these are “dimensionless,” meaning they’re abstract number values that aren’t linked with any specific kind of unit. The fine-structure constant is minuscule, because it’s measuring the discrepancy between a slightly less tiny measurement of an atom and a slightly more tiny one. The new model, researchers say, is accurate down to 81 parts per trillion:

“Because discrepancies between standard-model predictions and experimental observations may provide evidence of new physics, an accurate evaluation of these predictions requires highly precise values of the fundamental physical constants. Among them, the fine-structure constant α is of particular importance because it sets the strength of the electromagnetic interaction between light and charged elementary particles, such as the electron and the muon.”

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So until we know all of what explains the entire tiny missing space, researchers can continue to fill it with any number of ideas. That’s how a lot of advancement in physics is made to begin with, and having more parameters helps researchers narrow down their candidate field.

Think of it like a game of Carmen Sandiego: As you travel the world, you learn more about what your culprit isn’t like, until just one option is left.

The size of the discrepancy between the two values is also of interest to researchers. Instead of only changing the finest decimal points at the very end, a value further forward has also changed.

That means at least one team has made some kind of error, Quanta explains. And it’s not a sure thing that the newer value is automatically the one without the error—they could both have one, or the newer setup could be at fault. It’s key that both groups continue research so that we always have more than one value to compare.

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