The concept of the "edge" of the observable universe can be a bit misleading. It's important to understand that the observable universe is the portion of the universe that we can potentially see and gather information from. It is determined by the finite speed of light and the age of the universe.
The universe is estimated to be about 13.8 billion years old, which means that the observable universe extends to a distance of roughly 13.8 billion light-years in all directions from our vantage point. Beyond that distance, the light from objects hasn't had enough time to reach us yet.
However, it's crucial to note that the universe is likely much larger than the observable universe. The unknown, in this context, refers to the regions of the universe that are beyond our observational reach. There could be a vast expanse of space beyond the observable universe that we simply cannot detect due to the limitations of light speed and the age of the universe.
Speculating about what lies beyond the observable universe is challenging because we don't have direct observational evidence. Some cosmological theories propose the existence of a "cosmic horizon" or a boundary between the observable and unobservable regions. However, without observational data from beyond the observable universe, it remains an area of great uncertainty.
It's worth mentioning that the concept of the universe itself can be a subject of debate and exploration in physics. Some theories propose the existence of a multiverse, where our universe is just one of many universes with different physical properties. If the multiverse hypothesis or other similar ideas turn out to be correct, then our understanding of the unknown would expand significantly.
In summary, the unknown refers to the regions of the universe beyond our observational reach, and the concept of an "edge" is more accurately described as the boundary of the observable universe. The limitations imposed by the finite speed of light and the age of the universe restrict our current understanding of what lies beyond that boundary.