The fine-structure constant is a measure of electromagnetism — one of the four fundamental forces in nature; the others are gravity, weak nuclear force and strong nuclear force. In a paper published in the journal Science Advances, a team of researchers reported that four new measurements of light emitted from ULAS J1120+0641, a quasar located approximately 12.9 billion light-years away, reaffirm past studies that have measured tiny variations in this constant.
This artist’s impression shows how ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun, may have looked. Image credit: M. Kornmesser / ESO.
“The fine-structure constant is the quantity that physicists use as a measure of the strength of the electromagnetic force,” said Professor John Webb, a researcher at the University of New South Wales Sydney and corresponding author of the paper.
“It’s a dimensionless number and it involves the speed of light, something called Planck’s constant and the electron charge, and it’s a ratio of those things. And it’s the number that physicists use to measure the strength of the electromagnetic force.”
The electromagnetic force keeps electrons whizzing around a nucleus in every atom of the Universe — without it, all matter would fly apart. Up until recently, it was believed to be an unchanging force throughout time and space.
But over the last two decades, Professor Webb and colleagues have noticed anomalies in the fine-structure constant whereby electromagnetic force measured in one particular direction of the Universe seems ever so slightly different.
“We found a hint that that number of the fine-structure constant was different in certain regions of the Universe,” Professor Webb said.
“Not just as a function of time, but actually also in direction in the Universe, which is really quite odd if it’s correct, but that’s what we found.”
In the current study, Professor Webb and co-authors looked at the extremely distant quasar ULAS J1120+0641 that enabled them to probe back to when the Universe was only a billion years old which had never been done before.
The team made four measurements of the fine constant along the one line of sight to this quasar.
Individually, the four measurements didn’t provide any conclusive answer as to whether or not there were perceptible changes in the electromagnetic force.
However, when combined with lots of other measurements between us and distant quasars made by other scientists and unrelated to this study, the differences in the fine-structure constant became evident.
“And it seems to be supporting this idea that there could be a directionality in the Universe, which is very weird indeed,” Professor Webb said.
“So the Universe may not be isotropic in its laws of physics — one that is the same, statistically, in all directions. But in fact, there could be some direction or preferred direction in the Universe where the laws of physics change, but not in the perpendicular direction. In other words, the Universe in some sense, has a dipole structure to it.”
“In one particular direction, we can look back 12 billion light years and measure electromagnetism when the Universe was very young. Putting all the data together, electromagnetism seems to gradually increase the further we look, while towards the opposite direction, it gradually decreases.”
“In other directions in the cosmos, the fine-structure constant remains just that — constant.”
“These new very distant measurements have pushed our observations further than has ever been reached before.”
In other words, in what was thought to be an arbitrarily random spread of galaxies, quasars, black holes, stars, gas clouds and planets — with life flourishing in at least one tiny niche of it — the Universe suddenly appears to have the equivalent of a north and a south.
“While still wanting to see more rigorous testing of ideas that electromagnetism may fluctuate in certain areas of the Universe to give it a form of directionality, if these findings continue to be confirmed, they may help explain why our Universe is the way it is, and why there is life in it at all,” Professor Webb said.
“For a long time, it has been thought that the laws of nature appear perfectly tuned to set the conditions for life to flourish. The strength of the electromagnetic force is one of those quantities.”
“If it were only a few per cent different to the value we measure on Earth, the chemical evolution of the Universe would be completely different and life may never have got going.”
“It raises a tantalizing question: does this ‘Goldilocks’ situation, where fundamental physical quantities like the fine-structure constant are ‘just right’ to favor our existence, apply throughout the entire Universe?”
“If there is a directionality in the Universe and if electromagnetism is shown to be very slightly different in certain regions of the cosmos, the most fundamental concepts underpinning much of modern physics will need revision.”
“Our standard model of cosmology is based on an isotropic Universe, one that is the same, statistically, in all directions.”
“That standard model itself is built upon Einstein’s theory of gravity, which itself explicitly assumes constancy of the laws of Nature. If such fundamental principles turn out to be only good approximations, the doors are open to some very exciting, new ideas in physics.”
“We believe this is the first step towards a far larger study exploring many directions in the Universe, using data coming from new instruments on the world’s largest telescopes,” the researchers said.
“New technologies are now emerging to provide higher quality data, and new artificial intelligence analysis methods will help to automate measurements and carry them out more rapidly and with greater precision.”
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Michael R. Wilczynska et al. 2020. Four direct measurements of the fine-structure constant 13 billion years ago. Science Advances 6 (17): eaay9672; doi: 10.1126/sciadv.aay9672
Source link: https://www.sci.news/astronomy/fine-structure-constant-08375.html
