By suggesting that mass, time, and length can be converted into one another as the universe evolves, a new study has proposed a new class of cosmological models that may fit observations of the universe better than the current big bang model.
Wun-Yi Shu, an associate professor at National Tsing Hua University in Taiwan, explains that the new models emerge from a new perspective of some of the most basic entities: time, space, mass, and length. In his proposal, time and space can be converted into one another, with a varying speed of light as the conversion factor. Mass and length are also interchangeable, with the conversion factor depending on both a varying gravitational “constant” and a varying speed of light (G/c²).
Basically, as the universe expands, time is converted into space, and mass is converted into length. As the universe contracts, the opposite occurs.
The speed of light is simply a conversion factor between time and space in spacetime. It is simply one of the properties of the spacetime geometry. Since the universe is expanding, the conversion factor somehow varies in accordance with the evolution of the universe, hence the speed of light varies with cosmic time.
The newly proposed models have four distinguishing features:
- The speed of light and the gravitational “constant” are not constant, but vary with the evolution of the universe.
- Time has no beginning and no end; i.e., there is neither a big bang nor a big crunch singularity.
- The spatial section of the universe is a 3-sphere [a higher-dimensional analogue of a sphere], ruling out the possibility of a flat or hyperboloid geometry.
- The universe experiences phases of both acceleration and deceleration.
The models were tested against current cosmological observations of Type Ia supernovae that have revealed that the universe appears to be expanding at an accelerating rate. Because acceleration is an inherent part of this model, it fits the redshift data of the observed supernovae quite well. In contrast, the currently accepted big bang model does not fit the data, which has caused scientists to search for other explanations such as dark energy that theoretically makes up 75% of the mass-energy of the universe.
The new models may also account for other problems faced by the standard big bang model. For instance, the flatness problem arises in the big bang model from the observation that a seemingly flat universe such as ours requires finely tuned initial conditions. But because the universe is a 3-sphere in this models, the flatness problem “disappears automatically.”
Similarly, the horizon problem occurs in standard cosmology because it should not be possible for distant places in the universe to share the same physical properties (as they do), since it should require communication faster than the speed of light due to their great distances. However, the models solve this problem due to their lack of big bang origin and intrinsic acceleration.
Essentially, this work is a theory about how the magnitudes of the three basic physical dimensions, mass, time, and length, are converted into each other, or equivalently, a theory about how the geometry of spacetime and the distribution of mass-energy interact.