1. Earth orbits the Sun in a counterclockwise direction once every 365 days. App
ID: 231114 • Letter: 1
Question
1. Earth orbits the Sun in a counterclockwise direction once every 365 days. Approximately how many degrees does Earth move along its orbit in one day?
2. As Earth orbits the Sun, it also rotates in a counterclockwise direction about its axis as shown in Figure 1. we define 24 hours as the same time from when the Sun is highest in the sky one day to when it is highest in the sky the next day. How many degrees does Earth rotate about its axis in exactly 24 hours: 360°, slightly less than 360°, or slightly more than 360°?
3. How long does it take Earth to rotate exactly 360°: slightly less than 24 hours, 24 hours, or slightly more than 24 hours?
4. Two students are discussing their answers to Questions 2 and 3.
Student 1: Earth rotates about its axis once every 24 hours, and one rotation equals 360°.
Student 2: No. When Earth has gone around 360° it has also moved a small amount counterclockwise around the Sun, which means the Sun is not yet at its highest point. Earth must spin a little bit more for the Sun to reach its highest point.
Do you agree or disagree with either or both of the students? Explain your reasoning.
Explanation / Answer
1. 360 degrees/365.25 Days = .9863 degrees per day = about one Degree per Day
2. In 24 hours, the direction toward the Sun changes by about a Degree. Therefore, the Earth has to spin 361 degrees to make the Sun look like it has traveled 360 degrees around the Sky. Therefore more than 360 degrees.
3. To rotate 3600 earth takes 23 hours, 56 minutes, that is, less than 24 hours. And takes 24 hours to complete 361 degrees, completes rotation around the sun.
4. Both the students are correct.
In astronomy, we are concerned with how long it takes for the Earth to spin, with respect to the fixed stars, not the Sun.
So,removing the complication of Earth's orbit around the Sun and just focussing on how long it takes the Earth to spin 360 degrees with respect to the stars.This rotational period is called a Sidereal Day.
On average, it is 4 minutes shorter than a Solar Day, because of the extra 1 degree the Earth spins in a Solar Day.
For 360 degrees rotation( with respect to fixed stars) it takes 23 hours 6 minutes for earth, but for earth's rotation around the sun it takes 361 degrees and so 24 hours
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