"Obviously Not" is a phrase often used to express disbelief or to highlight something that is clearly untrue or illogical. It serves as a rhetorical device to emphasize that the answer to a question or statement is apparent and does not require further explanation. In conversations, people might use "Obviously Not" to dismiss an idea or suggestion that seems unreasonable. For example, if someone asks if the Earth is flat, a response of "Obviously Not" indicates that the answer is well-known and accepted based on scientific evidence.