The distance that radio waves can travel in space depends on several factors, including the power of the transmitter, the frequency of the radio waves, and the sensitivity of the receiver. However, even under ideal conditions, radio waves will eventually become extremely weak and difficult to detect as they propagate through space.
If we consider interstellar distances and the potential for communication with another civilization, the distances involved are vast. The nearest known star system to our solar system is Alpha Centauri, located about 4.37 light-years away. This means that light or radio signals from Earth would take about 4.37 years to reach Alpha Centauri.
Assuming we sent a radio message from Earth towards Alpha Centauri, it would take the same amount of time for the message to reach its destination—approximately 4.37 years. However, this is just the time for the message to travel one way. If we want to have a two-way conversation, where a reply is sent back to Earth, we would need to double that time. So, a round trip communication between Earth and a civilization at Alpha Centauri would take approximately 8.74 years.
It's important to note that this calculation assumes direct line-of-sight communication and does not account for any potential delays or limitations due to signal degradation, interference, or the capability of the receiving civilization to detect and respond to the signal. Furthermore, the vast distances between stars and the challenges of interstellar travel and communication make it highly complex and speculative to predict the feasibility of direct communication with another civilization in space.