It has long been thought that the universe is spatially symmetric with respect to its fundamental physical properties. Cosmologists relying on data from different regions of the sky (collected from different hemispheres or during different seasons) have always arrived at similar conclusions about the general features of the universe. But new research indicates the universe might not be so symmetric after all.
A group of astrophysicists from the University of New South Wales, Swinburne University of Technology, and the University of Cambridge has compared around 300 results taken from both the Keck Observatory and Very Large Telescope and found a significant difference of 1 in 100,000 in the value for the fine structure constant, . Interestingly, that difference seems to depend on which direction the telescopes are pointed.
The fine structure constant is a unit-less number that characterizes the strength of the electromagnetic field. It is usually defined in terms of other fundamental constants, such as the unit-charge, the speed of light and the permittivity of empty space:
Previously, differences in the measured value of were thought to be explained by variation in time. Since light collected from a nearby galaxy is much younger than light from a distant one, it is difficult to tell whether a difference between the light samples is due to when or where it was produced. These new results analyze light from different regions of the universe, but produced at the same time. If correct, these results would show that the variation must be in space, not time.
According to University of South Wales Professor John Webb, “The implications for our current understanding of science are profound. If the laws of physics turn out to be merely ‘local by-laws’, it might be that whilst our observable part of the universe favours the existence of life and human beings, other far more distant regions may exist where different laws preclude the formation of life, at least as we know it. If our results are correct, clearly we shall need new physical theories to satisfactorily describe them.”
As Webb suggests, there are interesting implications for fine-tuning arguments. If the values of the fundamental constants are not constant and precisely tuned for life, but rather vary throughout the universe with many values that are not conducive to life, the same arguments used to argue our universe is unlikely can be used to argue our universe is likely after all.
Many philosophers have wondered whether the fundamental laws of nature can vary in time (see Marc Lange’s “Could the Laws of Nature Change”) but most accounts assume that the laws cannot vary over space. For instance, Tim Maudlin argues the laws hold at every spacetime point, and according to both and David Lewis and David Armstrong, the laws are true of the entire universe (everywhere and everywhen). Philosophers will have their work cut out for them if it turns out that the laws of nature can vary over distance, especially if that variation is fundamental.