Final answer:
Humans have attempted to send signals to extraterrestrial intelligent life (ETI) through the use of electromagnetic waves, particularly radio waves. These efforts are part of the Search for Extraterrestrial Intelligence (SETI), which also includes looking for signals from ETI. No confirmed extraterrestrial signals have been detected, and the complexity of the task is described as the 'cosmic haystack problem'.
Step-by-step explanation:
The search for extraterrestrial intelligence (SETI) involves astronomers who use various strategies to detect possible signs of alien civilizations. These include looking for radio signals, which are a form of electromagnetic waves that scientists believe are best suited for interstellar communication. Although humans have been able to receive or send radio messages across interstellar distances for only a few decades, the effort to detect these forms of communication continues with the aim of finding beacons or leakage signals from potential extraterrestrial societies. Active SETI involves sending signals into space, hoping that intelligent life might respond, and while there have been initiatives like the Arecibo message that have intentionally sent signals out into space, there has been no confirmed response from extraterrestrial intelligence as of my knowledge cutoff in 2023.
The possibility of discovering a signal from an extraterrestrial source presents significant challenges in terms of interpreting the message and deciding on a response. The longevity and frequency of such civilizational signals factor into our chances of detecting them amongst what is described as the 'cosmic haystack problem'. Astronomical techniques such as searching for infrared signatures also contribute to this endeavor, indicating advanced civilizations by the heat they put out. Human advancements in technology might eventually increase our ability to send and receive signals, potentially bridging the communication gap with extraterrestrial intelligence if it exists.