What is cosmology?

Cosmology is the study of the nature of the universe as a whole, including space-time as a container and celestial bodies and matter and energy as its contents. For example, it aims to provide scientific answers to the questions of the history and future, contents, size, and shape of the universe.

 

Since the beginning of the 20th century, cosmology has made dramatic progress. In particular, the discovery of the "expansion of the universe" by astronomer Hubble and the discovery of the cosmic microwave background by Penzias and Wilson were probably the most important scientific achievements. At first glance, our universe appears to be eternal and unchanging. However, in fact, it was born as a hot universe about 13.8 billion years ago and has been expanding ever since. In other words, it became clear that the universe, like us, was born and has been growing ever since.

 

In the 1980s, another advance was made. Although the expansion of the universe is normally deaccelerated by the gravitational force between matter, it is now thought that there may have been a time in the early universe when the universe expanded at an accelerated rate, as if the accelerator had been stepped on. In order to achieve such an accelerated expansion (inflation), we must assume an "invulnerable" energy that does not change its density even if it is inflated. The origin of this energy is still unknown today.

 

There are two other major mysteries in the universe: The light from distant objects is fainter than expected, and most of the mass in the universe (more than 80%) is not ordinary celestial objects or gases. The former can be "explained" by assuming an unknown energy called dark energy and the latter by assuming an unknown mass called dark matter that does not emit or absorb light. However, we must consider physics beyond the framework of the "Standard Model” of particle physics. Examples include string theory, which considers two-dimensional strings, rather than particles, as the "element" of all things, and supersymmetry theory, which predicts unknown elementary particles called supersymmetric particles. These theories were conceived in the latter half of the 20th century, but as we enter the 21st century, we still do not know the details of which laws are correct. Thus, we can verify micro physics by observing the macroscopic world of the universe.

 

In order to address these issues, the Cosmology Laboratory (Inoue Lab.) of the Department of Physics, Faculty of Science and Technology, Kindai University, is focusing on various structures of the universe and continuing research from both observational and theoretical perspectives.