If aliens were to send us a message in a way that is subject to Einstein's theory of relativity, it would likely be because the theory accurately describes the fundamental nature of space, time, and the propagation of information. Einstein's theory of relativity is a well-established scientific framework that has successfully explained a wide range of phenomena and has been extensively tested and confirmed through numerous experiments and observations.
If aliens possess an understanding of physics similar to ours, they would likely be aware of the principles of relativity and would utilize them in their communication methods. The theory of relativity describes how information can travel at the maximum speed of light, and any signals or messages they send would also be subject to this limitation. It represents a fundamental constraint on the transmission of information across vast distances in the universe.
Furthermore, the theory of relativity is an integral part of our current understanding of the universe, and any advanced civilization capable of interstellar communication would likely have developed technologies and knowledge based on this theory. By adhering to the principles of relativity, they would ensure that their communication methods are consistent with our scientific framework, making it more likely for us to understand and interpret their messages accurately.
It's important to note that we can only speculate about the motivations and methods of extraterrestrial civilizations, as we have no concrete evidence of their existence or their intentions. However, given the scientific validity and widespread acceptance of Einstein's theory of relativity, it is reasonable to assume that any advanced civilization capable of interstellar communication would take it into account when transmitting messages across vast cosmic distances.