When viewed from Earth, Venus subtends an angle of about 1 arcminute (1/60°) when it is at the closest point to Earth in its orbit. If we are watching Venus set in the west over a clear horizon (e.g., ocean), how long would Venus take from the time it first reached the horizon to completely disappear below the horizon?
A) almost instantaneous (much less than 1 second)
B) 1 second
C) about 4 minutes
D) about 4 seconds

Question

Quizplus · Accepted Answer

Given Venus's angular size of about 1 arcminute and the typical angular speed of celestial objects due to Earth's rotation (about 15 arcminutes per minute), it would take Venus approximately 4 seconds to fully set (1 arcminute / (15 arcminutes per minute) = 1/15 minute = 4 seconds).

When Viewed from Earth, Venus Subtends an Angle of About