There are several reasons why we cannot see everything with our telescopes. The limitations of telescopic observations are primarily due to factors such as distance, the size of objects, the sensitivity of our instruments, and the presence of intervening objects or phenomena. Here are some key points to consider:
Distance: The universe is vast, and objects located at extremely large distances from Earth are challenging to observe. The farther an object is from us, the dimmer its light becomes due to factors such as the inverse square law of light propagation. This limits our ability to detect and observe very distant objects, especially those outside our own galaxy, the Milky Way.
Size of objects: Some objects in space, such as small asteroids or distant moons, may be too small or faint for telescopes to resolve or detect. Even with powerful telescopes, there are limits to the smallest objects we can observe, especially when they are located at significant distances.
Sensitivity of instruments: The sensitivity of telescopes determines their ability to detect faint signals or light from distant objects. While modern telescopes are highly sensitive, there are still limits to the faintest signals they can detect. Fainter objects may require longer exposure times or more advanced techniques, such as stacking multiple images, to enhance their visibility.
Intervening objects or phenomena: Sometimes, objects we would like to observe are obscured by other objects or phenomena. For example, interstellar dust clouds can block or scatter light, making it difficult to observe objects behind them. Additionally, atmospheric conditions, such as turbulence and light pollution, can affect the clarity and quality of observations made from the Earth's surface.
Regarding the distance of objects that we can't see, it depends on the specific object and its characteristics. The observable universe has a finite size due to the limited speed at which light travels, which sets a limit on the distance we can see. The most distant objects we have observed are galaxies billions of light-years away. However, there are certainly objects and regions in the universe beyond our current observational reach, as their light has not reached us yet or is too faint for our current instruments to detect.
Scientists and astronomers continually strive to develop more powerful telescopes and innovative observation techniques to push the boundaries of what we can observe and understand about the universe. Technologies like space-based telescopes and advancements in instrumentation continue to expand our view and improve our ability to explore the cosmos.