Several of the key people involved in the search for intelligent life way, way out there believe that it would communicate with us in English. They base such a belief on the almost certainty that such life would be at very least half a million years more advanced than us or quite possibly a billion years more advanced than us. Thus their artificial intelligence could scan our worldwide mass communications and quickly understand all our languages.

There is also a case for Mandarin, French and Spanish. Presumably they could concurrently send the same message to various parts of Earth in the appropriate local language. Though perhaps messages would be to one specific receiving point at either end, scrambled. We would not want some evil blighter on Earth to send an unpleasant message.

What do you reckon?