Thursday, July 18, 2013

A Universe Without Expansion

What if the universe were static rather than expanding? What if, in fact, it could even be shrinking? And what if there never was a Big Bang cosmological singularity? These are the possibilities proposed by C. Wetterich from the University of Heidelberg in a new paper published this month with the title A Universe Without Expansion. 

Einstein, among others, believed in a static universe. But after Hubble’s discovery that all objects in the universe have a red shift, which means they are traveling away from us, the conclusion was reached that the universe is expanding and all attempts at finding static solutions were abandoned. But, as Wetterich explains, there was always a “loophole in the argument.”  The assumption was that the masses of electrons and protons are constant throughout the evolution of the universe. But what if that were not the case? An atom with a higher mass would emit photons with higher energy than one with lesser mass. Since higher energies correspond to higher frequencies, the light from heavier atoms would be blue shifted, while those from lighter ones would be in the red part of the spectrum.

What if the masses of the electrons and protons were smaller at an earlier time in history? Since we observe the universe as it was millions or billions of years ago—the time it takes their light to reach us—if their masses were smaller than they are today their “frequencies of characteristic atomic lines” would produce the same red shift that we see today, without their moving at all. And the degree of red shifting would correspond to the distance from us. In this line of thinking, the Planck mass and the particle masses increase simultaneously with time, while distances remain constant or even shrink.

The model delineates a “variable gravity universe” with an increasing Planck mass or associated gravitational constant. “Since particle masses grow proportional to the Planck mass all observed bounds on the time variation of fundamental constants and apparent violations of the equivalence principle are obeyed.”

The model leads to a view of cosmology as having four phases: a period of early rapid inflation, followed by the shrinking of the Universe during the next two periods, first one of radiation domination followed by matter domination, and finally a period of dark energy domination in which the Universe remains constant. The Big Bang is pictured as extending backward to an infinite negative time without a singularity.

One big problem for this model is that it is hard to test, since one cannot measure the mass of an object except in relation to another object. If all objects have been increasing in mass, a measurement of an object in the past seems impossible (Nature News). Nevertheless, seemingly untestable theories have been put forth before (string theory?) with the expectation that further indirect measurements would someday prove them correct. Even though this paper has not yet been peer-reviewed, it has been received with great interest from the physics community. Einstein, the old rascal, may have been right yet again.