In a Galaxy Far, Far Away . . . But It Might As Well Be Next Door

A staple of science fiction is to change the laws of nature, especially by having interplanetary travelers land on a world where those laws differ from the ones on Earth. It is equally a staple of science fact that the laws here are the same as the laws anywhere. But really, that was more assumption than a firm observation.

Well, I’m sorry to say that those of us who think it’d be cool to get wind of a galaxy where quarks roam free or where the speed of light is variable will have to keep waiting. For at least one of the bedrock constants in physics, the value is the same in a galaxy 6 billion light years away as it is on Earth.

The number is the ratio of the mass of the proton to that of the electron, about 1,836.15. Scientists led by Christian Henkel of the Max Planck Institute for Radio Astronomy in Bonn and Michael Murphy of the Swinburne Centre for Astrophysics and Supercomputing in Melbourne, Australia, examined a distant quasar, called B0218+367. The quasar’s light began its journey toward Earth 7.5 billion years ago, and along the way was partly absorbed by ammonia gas in an intervening galaxy 6 billion light years away.

The colors of light that ammonia absorbs is a function of the proton-to-electron mass ratio. Lo and behold, the colors of the quasar light making it through the ammonia galaxy—and from which astronomers can infer the colors that were absorbed—yielded the answer: the proton-electron mass ratio in the ammonia galaxy is the same as it is on Earth. Oh well.

Call me an optimist, but I see some wiggle room here. Something 6 billion light years away is also 6 billion years ago. Maybe we can hope that even if the laws of physics were the same there as on Earth 6 billion years ago, they have since changed? (The idea that the speed of light and other “constants” of nature are not constant isn’t looking as possible as it did when Joao Magueijo got a boatload of money to write his 2003 book Faster Than the Speed of Light: The Story of a Scientific Speculation, but it hasn't been ruled out completely.) And maybe we can hope that this galaxy now has laws of nature that we wouldn't recognize?

The astronomers, who reported their findings in Science (if you cannot access the paper at Science (which charges for content), try the scientists’ Webpage, which also has cool photos and diagrams), plan to keep testing the laws of nature in as many different places and at as many different times in the universe and its lifetime as they can. They say they “hope to find a window into the extra dimensions of space that many theoretical physicists think may exist.”