Not-So-Constant Constants?

Physicists have found more evidence that perhaps a couple of significant physical constants may have changed over the history of the universe. If these findings are confirmed, then it will require major revisions in the standard models of our natural laws, which depend heavily upon the consistent value of these constants.

Mu

Research indicates that the fundamental constant mu, which defines the magnitude of the strong nuclear force, may have changed over the last 12 billion years. Mu is the ratio of a proton's mass to that of an electron (i.e. the proton-electron mass ratio), or approximately 1836.

The findings come from research at the Free University in Amsterdam and the European Southern Observatory in Chile (which isn't, ironically, nowhere near Europe). Comparing the spectrum of molecular hydrogen gas on Earth to that in quasars 12 billion light-years away, a spectrum which is dependent upon this proton-electron mass ratio. The data analysis shows a difference of 0.002%, which could mean that when the spectrum left the quasar 12 billion years ago the ratio was different.

Cosmological Constant

The cosmological constant may also be changing, it seems. This constant represents the energy of free space and provides a mathematical explanation for the expansion of the universe. Oddly, though, the measured value of the constant is a googol times smaller than predicted by theory, and such discrepencies are not liked by physicists.

The theory of a changing cosmological constant was introduced in the 1980s, with the notion that it was much bigger at the origin of the universe. This concept was dismissed because calculations indicated it would take larger than the age of the universe for the constant to decay from its proposed higher value to that witnessed today.

String theory, however, proposes that perhaps the Big Bang was not the beginning of time. In fact, it's possible that we live in a "cyclic universe," which has gone through a number of Big Bangs and Big Crunches, allowing for time to exist prior to the Big Bang (a point at which the energies of the universe cause the laws of physics break down, mathematically at least).

Paul Steinhardt of Princeton University & Neil Turok of Cambridge University propose that this would allow for the necessary drop in the cosmological constant. If the cycles last about a trillion years, with the cosmological constant not getting "reset" like other physical properties, it could gradually decay through a series of quantum transitions. At high values, the transitions would happen rapidly, but as it reached lower levels the decay would slow down.

Of historical interest, Einstein set the cosmological constant to zero when he came up with the equation that introduced it, because he assumed free space had zero energy and that the universe wasn't expanding. He later called it the biggest blunder of his life, after Edwin Hubble discovered evidence of an expanding universe.

Changing Constants in General

The idea that physical constants change is intriguing, and several constants have been up for speculation over the years. The gravitational constant was considered to be variable years ago and, in just the last couple of years, a major debate has been considered regarding the fine structure constant (and, because they're related, the speed of light). If it is determined that any of these quantities do change, it would have major ramifications throughout physics. It could, for example, help support the extra dimensions which are at the heart of string theory or it could mean we know even less about the universe than we think we do.

Still, there are other discrepencies and curiosities among the numbers that define our universe which are not resolved by these studies, but scientists continue to research it and perhaps, someday, the picture will become even more complete.