First Contact with an extraterrestrial civilization comes down to one huge paradigm shift for humanity: becoming aware. Any type of First Contact will lift a veil of ignorance and allow us to view the universe in a new way. Humanity will change. Depending on how dramatic the type of First Contact, that change could be profound.
First, let me offer my apologies to Thomas Kuhn, who would probably not appreciate the use of the term paradigm shift in this way. Kuhn, most notably in the Structure of Scientific Revolutions,applied the term only to science and to concrete facts that change in a scientific revolution. Kuhn would probably not agree that the description of a change in human thought could be considered a paradigm shift, because the idea of a change in perception is far too nebulous and could have many different explanations. Still, the worldview concerning intelligent life would be altered forever.
Many researchers agree that the type of First Contact will decide how dramatic the change is for humanity. If SETI researchers intercept a message from a far off star system it will take years of study to try and make sense of the message. If we decide to send them a message that would most likely take dozens of years. If they send us a message, especially if it is designed to be easier for us to understand, the change would be more immediate and have more impact. Direct First contact, an Earth landing by an extraterrestrial civilization, would create the greatest turbulence for society.
Direct First Contact could fundamentally change human civilization to the point that historians would come to describe things in terms of Before First Contact and After First Contact. Much of the impact would come in the changes to our base of knowledge. Just knowing that we are not alone is profound. However, new evidence based revolutions in science and technology would provide the biggest challenge, and perhaps create the most trouble. More on that next week.