The cosmological horizon, also known as the observable universe, refers to the boundary beyond which light has not had enough time to reach us since the beginning of the universe. It represents the maximum distance from which information can reach us within the age of the universe.
There are a few reasons why we cannot see beyond the cosmological horizon:
Limited Age of the Universe: The universe is estimated to be approximately 13.8 billion years old. Since light travels at a finite speed, it takes time for light from distant objects to reach us. Objects located beyond the cosmological horizon are so far away that the light they emit has not had enough time to reach us since the Big Bang.
Expansion of Space: The universe is expanding, and this expansion affects the distance between objects. As space expands, the distance between galaxies and other cosmic structures increases. Beyond the cosmological horizon, the expansion of space is occurring faster than the speed of light, preventing light from reaching us.
Inflationary Epoch: In the early stages of the universe's evolution, there was a period of rapid expansion known as cosmic inflation. This inflationary epoch caused regions of space to move beyond our cosmological horizon, making them currently unreachable and outside the observable universe.
Cosmic Microwave Background Radiation: The cosmic microwave background (CMB) radiation is the remnant radiation from the early universe, which we can observe today. It is the oldest light we can detect. The CMB acts as a sort of "fog" beyond which we cannot see clearly, as the intense radiation from the early universe obscures our view of what lies beyond.
These factors combined result in our inability to see beyond the cosmological horizon and directly observe objects or events that are located outside the observable universe based on our current understanding.