Mean Solar Time is based on a fictitious sun moving at a constant rate. Which angular rate is used in this definition?

• A. 15 degrees per hour
• B. 360 degrees per day
• C. 1 degree per hour
• D. 24 hours per day

Answer: (A)

Mean Solar Time uses a fictitious Sun moving at a constant angular speed across the sky. It completes a 360-degree circle in 24 hours, so the angular rate is 360 degrees per 24 hours, i.e., 15 degrees per hour (one degree every four minutes). The rate per day is the same idea expressed as 360 degrees per day, but the question asks the rate in degrees per hour, making 15 degrees per hour the best answer.