Earth's radio waves have traveled vast distances since the advent of radio communication. The extent of their reach depends on the power of the transmitter, the frequency used, and various other factors. Here are a few examples:
Radio and Television Broadcasts: Powerful radio and television broadcasts have traveled far beyond Earth's surface. They have been detected by radio telescopes and spacecraft throughout the solar system. For instance, the Arecibo Observatory in Puerto Rico has received radio signals from space objects, including pulsars and other galaxies.
Interstellar Communication: A few intentional attempts have been made to send radio signals beyond our solar system to potentially communicate with extraterrestrial civilizations. The most famous example is the Arecibo message sent in 1974 from the Arecibo radio telescope. It was aimed at the globular star cluster Messier 13, which is about 25,000 light-years away.
Voyager Spacecraft: The Voyager 1 and Voyager 2 spacecraft, launched in 1977, carry a Golden Record that includes various sounds and images representing Earth. These spacecraft have now ventured beyond our solar system into interstellar space. While the Voyager signals are not in the radio frequency range anymore, they represent humanity's farthest intentional radio transmissions.
Leakage Radiation: Earth's radio waves have also unintentionally leaked into space due to everyday radio and television broadcasts, radar systems, and other human-made signals. These signals continue to propagate into the universe, but they become progressively weaker and harder to detect as they travel vast distances.
It's important to note that the farther radio waves travel, the more they disperse and weaken due to factors like inverse square law and interstellar medium. Consequently, the detectability and strength of these signals decrease significantly over long distances.