hubble deep field
Hubble eXtreme Deep Field "XDF" (2012) view — except for a few stars, every speck of light is an entire galaxy — some as old as 13.2 billion years. NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team

Are the laws of nature constant throughout the universe, or do they change depending on where one is?

As far as we can tell, the fundamental laws that govern our understanding of reality, including the four fundamental forces — the strong and weak nuclear force, the gravitational force, and the electromagnetic force — are unchanging, and a new study based on light spectra of a distant quasar has now provided further confirmation.

Quasar — a quasi-stellar radio source — is a compact region surrounding a galaxy’s supermassive black hole, heated to such an extent that it emits massive amounts of energy and can even outshine the galaxy in which it resides.

As light from quasars travels to us, some of it gets absorbed by the gas and dust in the galaxies that lie on the way. However, only very particular wavelengths of light are absorbed, depending on how photons interact with the atoms in the medium. Since this interaction is electromagnetic in nature, studying the spectrum of the light as it reaches Earth can tell us what the strength of this fundamental force was in distant corners of the cosmos.

For this particular study, published in the Monthly Notices of the Royal Astronomical Society, scientists observed light from a quasar 8.5 billion years after it passed through distant galaxies.

“The pattern of colours 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,” study lead author Srđan Kotuš from the Swinburne University of Technology in Australia, said 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.”

However, while the study confirms that electromagnetism in distant galaxies has the same strength as here on Earth with the highest precision yet, it also highlights a lingering question — why?

“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 Michael Murphy, also from Swinburne University, said in the statement. “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.”