The Tachyonic Antitelephone
Stimulating critical thinking - a loose series on paradoxes
Gödel's is a newsletter about interweaving ideas and making decisions under uncertain conditions. I discuss knowledge management, mental models, and supporting Tools for Thought.
Tachyons were first proposed in the 1960s as part of quantum field theory. They have an imaginary mass and move exclusively at faster-than-light speed. However, their existence has not yet been confirmed experimentally, and most physical theories assume a world in which nothing can move faster than light in a vacuum.
The paradox arises when one considers the possibility that such particles could be used to transmit information, which could lead to a causality violation - that is, the effect could occur before the cause.
Let's imagine a straightforward but illustrative situation to understand the tachyonic antitelephone paradox: Two scientists, Zara and Dex, are in galaxies so far apart that it would take years for a light signal to travel from one to the other. However, the two have access to a hypothetical technology that uses tachyons for communication, allowing messages to be transmitted instantaneously, faster than light.
One day, Zara sends Dex a message using the tachyonic antitelephone, which he receives immediately. Dex, astonished by the message, decides to reply immediately via the tachyonic antitelephone. By utilizing the faster-than-light speed of tachyons and certain principles of relativity, Dex could theoretically create a situation where his reply reaches Zara before she has sent her original message.
This leads to a causal paradox, as the answer (effect) arrives before the question (cause). This raises serious questions in a universe where cause and effect have a linear relationship. How can Dex reply to a message before Zara has even sent it? Would this mean that events can be undone? Could this lead to a loop where events cause themselves?
Albert Einstein's special theory of relativity, published in 1905, revolutionized physics by showing that the laws of physics are the same for all observers in uniform motion and that the speed of light in a vacuum is constant for all observers, regardless of their motion and helps solving this paradox.
A central aspect of the special theory of relativity is the insight that nothing can travel faster than light. This is based on the assumption that the mass of an object would increase infinitely as it approaches the speed of light, which would require an infinite amount of energy to reach that speed.
Einstein discussed the probability of a paradox of causality based on faster-than-light signals already in a thought experiment with Arnold Sommerfeld in 1910. This laid the base for the tachyonic antitelephone paradox.
