Skip to main content

Are we special after all?

Among the most fruitful philosophical stances for cosmology is the Mediocrity Principle, which states that there is nothing very special about any given observer. Implicit in this principle is that the laws of nature are the same throughout the universe.

But this may not be true. A recent paper reports a study of quasar spectra using the Keck and VLT Observatories. The study revealed a dipolar variation of the fine structure constant Alpha, pointing toward the tiny southern constellation of Ara with an amplitude of Δα/α ~ 10-6 GLyr-1 (109 light year). The statistical significance of this result is ~4.2σ, so there is less than a 1 percent chance that the result is due to random noise. 

Alpha (α) is one of the fundamental constants of the universe. Related to the strength of electromagnetic interactions, it can be considered a measure of the polarizability of the vacuum. A small change in α alters atomic and nuclear transition rates, in particular disrupting carbon nucleosynthesis. 

What could cause a change in vacuum polarizability? In quantum field theory, a changing fine structure constant is most naturally represented as a dynamical scalar field. When such a scalar field is renormalized, its mass becomes quite large -- likely dominating the observed vacuum energy by orders of magnitude. However, as estimates of vacuum energy are traditionally so poor, perhaps the mass associated with a variable fine structure constant is not the problem it appears.

If we interpret a large-scale dipole structure as a sign that the universe may extend far beyond the observable universe, one might expect that Δα/α ~10-6 GLyr-1 suggests a universe at least 106 GLyr (10,000 times the size of the observable universe) in extent.  Thus, instead of a variable fine structure constant manifesting only in small changes in reaction rates, it may force enormous changes in our view of the universe.