Precisely how long is a day on Earth?
Your answer is B. 23 hours 56 minutes. I did find several sources saying it is 23.93 hours, but you don’t have that as a choice so I assumed you meant 23 hours 56 minutes. “Even the answer “23 hours 56 minutes 4.091 seconds” is just a starting point. That number is an average, and every day is a slightly different length by a few microseconds.” “A day of exactly 86,400 SI seconds is the fundamental unit of time in astronomy. For a given planet, there are two types of day defined in astronomy: 1 apparent sidereal day – a single rotation of a planet with respect to the distant stars (for Earth it is 23.934 hours); 1 solar day – a single rotation of a planet with respect to its star. In astronomy, the sidereal day is also used; it is about 3 minutes 56 seconds shorter than the solar day, and close to the actual rotation period of the Earth, as opposed to the Sun’s apparent motion.
