If you have a basic understanding of physics, you’ll know that there are many quantities defined as constants. But just how constant are these values? Modern science has only been around for 400 years, so to test if these constants change we need to find ways to measure them billions of light-years away.
And researchers from Swinburne University, Australia and the University of Cambridge, UK, have now confirmed that the fine-structure constant, which characterizes the strength of the electromagnetic force, has not changed during the last 8 billion years.
The results, published in the Monthly Notices of the Royal Astronomical Society, was possible thanks to the observations of a faraway quasar, a supermassive black hole emitting an incredible amount of light. The different colors of light were absorbed by the many atoms and molecules on its long journey towards our planet, and that’s what the team needed for the measurements.
"The pattern of colors tells us how strong electromagnetism is in this galaxy, and because the quasar is one of the brightest ones known, we were able to make the most precise measurement so far," said lead author of the study, Swinburne PhD candidate Srđan Kotuš, in a statement.
"We found electromagnetism in this galaxy was the same as here on Earth within just one part per million – about the width of a human hair compared to the size of a sports stadium."
Previous studies had reported a change in the fine-structure constant over the ages of the universe, but this latest one claims to be the most accurate measurement of the strength of the electromagnetic interaction.
"For me, finding that electromagnetism is constant over more than half the universe's age just deepens the mystery – why is it that way? We still don't know," co-author Professor Michael Murphy of Swinburne added.
"It's remarkable that distant galaxies provide such a precise probe of such a fundamental question. With even larger telescopes now being built, we'll be able to test it even better in the near future."
Since its introduction in 1916, the fine-structure constant has fascinated and puzzled physicists. It is roughly 1/137, but we don’t have a solid explanation why or where this particular number arises from. No theory we currently have predicts its value.
And yet it is crucial for us and the universe. If the value was larger, it would stop stars from fusing hydrogen. Just a 4 percent variation would result in stars that couldn’t form the carbon we are made of. The fine-structure constant is responsible for how chemicals interact in our bodies, and even why toast always falls on the buttered side.