A mean sun is used as the reference for...

Question 1 / 2707066636ee928f7522a1c519bcc

Question 1 of 2707066636ee928f7522a1c519bcc

A mean sun is used as the reference for solar time for three reasons. Which reason is NOT a cause for use of a mean sun?

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Question 1 of 27070

A mean sun is used as the reference for solar time for three reasons. Which reason is NOT a cause for use of a mean sun?

🔍 Key Concepts

• Apparent sun vs. mean sun and why a fictitious "mean" sun is defined • Causes of variation in the apparent solar day: Earth's elliptical orbit and axial tilt • Why time is defined relative to the celestial equator instead of the ecliptic when constructing mean solar time

💭 Think About

• Ask yourself: Which option is not a reason we need to invent a mean sun, but rather describes how we measure time or where the sun appears to move? • Think about which choices are related to changes in the length of the solar day versus choices that just describe geometry or reference planes in the sky. • Identify which items cause the apparent sun to move unevenly along the observer’s hour angle, and which item would remain true even if the apparent motion were perfectly uniform.

✅ Before You Answer

• For each choice, decide: Does this directly cause the apparent solar day to vary in length from one day to the next? • Remember that the mean sun is an imaginary body that moves uniformly along the celestial equator, not the ecliptic—check which statement reflects this. • Verify which option describes a property of our timekeeping system (how we define or measure time) rather than a physical cause of the apparent sun’s irregular motion.

Question 1 of 27070

A mean sun is used as the reference for solar time for three reasons. Which reason is NOT a cause for use of a mean sun?

There are variations in the Earth's rotational speed.

Measurement of time is along the celestial equator.

The speed of the Earth's revolution is not constant.

The motion of the apparent sun is along the ecliptic.

Question 1 / 2707066636ee928f7522a1c519bcc

Question 1 of 2707066636ee928f7522a1c519bcc

A mean sun is used as the reference for solar time for three reasons. Which reason is NOT a cause for use of a mean sun?

Back

Question 1 of 27070

A mean sun is used as the reference for solar time for three reasons. Which reason is NOT a cause for use of a mean sun?