Human beings communicate with each other in two ways. The first is the same used by other animals: the emission of sound waves. However, these are slow and do not spread more than a few tens of meters due to the attenuation introduced by the air. That is why we have searched since ancient times for alternatives for communication over long distances. Smoke signals, flags and mirrors were some solutions, although inefficient in terms of the amount of information they could transmit. The cards allowed much more data to be transmitted, but they were very slow.
The great leap occurred with the progressive dominance of electromagnetic waves. In 1791 Claude Chappe invented the optical telegraph , a system with which a symbol could be transmitted every two minutes between Paris and Lille, separated by 230 km. However, this was dependent on weather conditions and did not work at night.
In 1837 the electric telegraph was implemented, the work of William F. Cooke and Charles Wheatstone . In a few years, the United States was able to communicate from east to west and, later, it was possible to transmit across the ocean by means of submarine cables.
In 1901, Guglielmo Marconi developed wireless telegraphy experiments across the entire Atlantic Ocean.
The birth of the information society
Already in the 20th and 21st centuries the application of fiber optics and modern wireless technology have led to the creation of the information society, where we can communicate with each other in real time. All this is possible because electromagnetic waves are transmitted much faster than sound waves. The sound, even in optimal conditions through diamond , reaches a speed 10,000 times lower than with electromagnetic waves transmitted by air or fiber optics. A parameter that allows evaluating the quality of communications is the round -trip time ( RTT). That is, the time that elapses from the time a sender transmits a message to a recipient until the response arrives back. This can be approximated to 2 times the separation between the interlocutors divided by the speed of propagation of the signal. Engineers and scientists define RTT values of around 200 milliseconds as a quality threshold for real-time communication. If we take into account that the speed of sound through the air is 340 m/s, and that the RTT should not exceed 200 ms, we can deduce that the distance for a conversation between two people should not exceed 34 meters. A logical value if we take into account that sound communications are designed to talk between people who are nearby. As for electromagnetic signals, today they can be propagated through guided and wireless media with values around 2×10⁸ m/s, similar to the speed of light (in the case of fiber optics, light is that is transmitted). For this speed, if we want not to exceed the RTT of 200 ms, the separation between two interlocutors must not exceed 20,000 km. Just the greatest distance between any two points on the earth’s surface. In other words, the propagation speed of electromagnetic waves is adequate to communicate in real time between all the inhabitants of the Earth.
We would have to wait 8.4 years to receive a response from a hypothetical interlocutor on a planet that orbits the closest star to Earth, Proxima Centauri- ESA / Hubble / NASA
