In ancient times, people believed that the Earth was the center of the universe and that everything else revolved around us. With the use of modern astronomical tools, we discovered that this was not actually the case. In the cosmological sense, our planet does not enjoy a special vantage point in the universe, which means that there is nothing special about our location.
Understanding the Universe With CMB
Today, we use the Copernican and the cosmological principles to understand our place in the universe. Although the regions of space may differ, the cosmos is considered isotropic and homogeneous when viewed at a large enough scale.
The Copernican principle is the cornerstone of modern astronomy and plays an important role in various statistical tests for the viability of cosmological models. Meanwhile, the stronger assumptions of the Cosmological principle suggest that there are no special parts of the universe and that everything is the same everywhere.
The latter implies that here and now is the same as there and now, and here and then is the same as there and then. However, several teams of scientists found violations of this principle when they began to study the cosmic microwave background (CMB), the cooled remnant of radiation from around 400,000 years after the Big Bang. According to our current understanding of physics, the first light that began its journey should be about the same temperature with only minor fluctuations.
NASA's COBE and WMAP joint missions discovered that the cosmic microwave background temperature was 2.726 Kelvin in almost every region of the universe. Small fluctuations in the temperature by a fraction of a degree represent differences in the densities of structures that existed right after the formation of the universe.
If the CMB is divided into segments, scientists can analyze the distributions of temperatures. When the segments are divided into smaller portions, the temperature distribution in these areas should appear completely random. This means that hot and cold regions in the quadrupole should not correspond to the hot and cold areas in the octupole. In this case, however, they do.
A Curious Coincidence
In a 2005 paper, physicists reported anomalous hot and cold spots stretching out along an axis in the universe known as the "Axis of Evil." What makes it strange is that this axis aligns with our solar plane, with temperatures "above" the Solar System slightly cooler than the temperatures from "below."
The finding is pretty unusual and has led some to look for another possible "preferred axis," assuming that the universe is not homogeneous after all. Another paper points to spiral galaxies, which appear to be more "left-handed" than "right-handed."
Many other directional anomalies have been reported in different observations. These include velocity flow, polarization distribution of the quasars, and the anisotropy of the cosmic acceleration. While the confidence level for each anomaly is not too high, the directional alignment of these anomalies is quite significant, suggesting a common origin of such anomalies.
Read also: Cosmic Microwave Background As Primordial Radiation: Does It Confirm the Big Bang Theory?
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