Why real-time communication is not possible outside of Earth


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

And what about interplanetary communication?

For the Moon, which is 384,000 km from Earth, the RTT increases to several seconds. This is an unacceptable value for many of the applications we use in our information society. For planets, the RTT reaches minutes. Not to mention the closest star, Proxima Centauri, located 4.2 light years away. His RTT is 8.4 years. We would have to wait more than two Olympics to receive a response from a hypothetical interlocutor on a planet that rotates around this star.

The speed of light would have to increase dramatically to achieve interplanetary or interstellar communication. On the other hand, if the speed of light were lower, it would not be possible to communicate between two points on Earth without running the risk of the RTT exceeding 200 ms. In other words, real-time terrestrial communication would no longer be possible and the information society would collapse.

For example, if the speed of propagation of light in fiber were 2×10⁷ m/s instead of 2×10⁸ m/s, the RTT between Buenos Aires and Seoul (separated by almost 20,000 km) would increase from 200 ms to 2 seconds. This would mean having to wait every time someone speaks, while more demanding applications such as remote surgery or interactive video games could not cope with this increase in time.

The speed of electromagnetic waves is sufficient for human beings to communicate in real time between any two points on Earth, but insufficient for us to continue doing so as we move away from it. The information society is only possible on planets whose diameter is not greater than the diameter of the Earth and only an animal such as the human being, capable of controlling the propagation of electromagnetic signals, can benefit from this technology.

This paradoxical coincidence points to questions such as the fine tuning of the universe or the anthropic principle , while opening the way to more reflections.

One is why the evolution of the human being has converged with the development of the information society on a planet like Earth. The 200 ms RTT, considered suitable for real-time applications, is valid because our brain, combined with other parts of our body such as the eyes and ears, react to different stimuli with response times that fit this value.

Furthermore, this RTT is the result of many years of evolution, and the diameter of the Earth has also been the result of the expansion of the universe. The third parameter, the speed of light, combines with the RTT and the diameter of the Earth towards the creation of the information society, which basically consists of many human beings interacting with each other in real time on the surface of our planet. .

Another reflection refers to the sense of colonizing planets when it is not possible to communicate with them in real time. Will we be able to exceed the speed of light in the future?

Author Bio: Ignacio Del Villar Fernandez is Professor of Electronic Technology at the Public University of Navarra