Distance: The vast distances between stars mean that any signals sent by humans or detected by ETs would have to be extremely powerful or efficiently targeted to be noticeable from a significant distance.
Type of signals: The type of signals humans produce - such as radio waves and light from cities or satellites - might not be something that ETs would recognize or be interested in.
Signal strength: The strength of human-generated signals gradually weakens as they travel through space, making them harder to detect the further an alien civilization might be.
ET technology: The level of technological advancement and sensitivity of ET instruments would play a role in their ability to detect and interpret human signals.
Search direction: If ETs were actively searching for signals, they might not be looking in the direction of Earth or at the specific frequencies used by humans.
Interstellar communication: The complexity of interstellar communication protocols and the need for civilizations to agree on standards for communication could pose a challenge.
Considering the vastness of the universe and the potential for complex technological civilizations, the possibility that ETs might be able to detect signs of human activity cannot be ruled out entirely. However, the probability and feasibility of such detection remain highly uncertain and debated among scientists and researchers.
