Final answer:
The authority of a message is the recognized power or legitimacy backing its communication, often rooted in religion, tradition, or legal-political structures. It is necessary that this authority is accepted by people so that they will follow its commands or advice.
Step-by-step explanation:
The authority of a message refers to the source of power or legitimacy in whose name the message is sent. This concept is vital as it underpins the very nature of communication, particularly in the contexts of leadership and governance. The authority can claim its power from various sources such as religion, tradition, or through conquest and it's crucial for such power to be acknowledged and accepted by people. When authority figures issue commands or information, they do so with the expectation that their directives will be followed because the individuals or institutions possess qualities that command respect and obedience.
For instance, if the President of the United States appoints a commission to advise on interstellar communication, the authority comes from the office of the presidency and is accepted because of the established legal and political structures that support it. This commission would then use its accepted power to make a recommendation, relying on their judgment of what they perceive to be reasonable and beneficial.