Light from distant sources does indeed reach us, but there are a few factors that can affect its detectability or make it challenging to observe.
Cosmological redshift: As I mentioned earlier, light from distant sources can experience cosmological redshift due to the expansion of the universe. This redshift can cause the wavelength of the light to stretch, shifting it towards longer wavelengths, such as infrared or radio wavelengths. In some cases, the redshift can be so significant that the light is shifted out of the visible spectrum, making it undetectable to our eyes or conventional optical telescopes. However, we can still detect and study these longer-wavelength signals using specialized instruments.
Inverse square law: Light, like any other form of electromagnetic radiation, follows the inverse square law. This law states that the intensity of light diminishes with the square of the distance from the source. As light travels through space, it spreads out, causing its intensity to decrease. The farther the light has to travel, the more it spreads out, and consequently, its intensity decreases. At a certain distance, the intensity of the light becomes too weak to be detected by our instruments.
Absorption and scattering: Interstellar and intergalactic medium can contain dust, gas, and other particles that can absorb or scatter light. These particles can block or alter the path of the light, making it more challenging to observe. In some cases, the light from distant sources may be absorbed or scattered to such an extent that it becomes undetectable or significantly weakened by the time it reaches us.
Despite these challenges, we have been able to observe light from extremely distant sources, such as galaxies billions of light-years away, using advanced telescopes and detectors. Scientists continue to develop new technologies and techniques to push the boundaries of observation and study the universe beyond the limitations imposed by these factors.