Retrograde Motion Was a Major Source of Difficulty in Designing

question 26

Multiple Choice

Retrograde motion was a major source of difficulty in designing a theoretical model of the solar system.What is the explanation for retrograde motion?

• A) The planets actually stop and reverse direction in their orbits.
• B) The planets move not in uniform circular motion about the Sun, but rather in circular orbits (epicycles) about points that themselves move about the Sun in circular orbits.
• C) Retrograde motion is an apparent motion of other planets, which we observe only because we are viewing their motion from Earth, itself in motion around the Sun.
• D) Retrograde motion is an apparent motion caused by the precession of Earth's rotation axis.

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Definitions:

Risk Premium

Higher expected rates of return that compensate investors in risky assets. In equilibrium, differences in the rate of return reflect differences in the riskiness of an investment.

Low Risk Asset

An investment that is generally expected to yield returns with relatively lower volatility or risk of loss.

High Risk Asset

An investment with a high potential for significant loss but also the potential for substantial rewards.

Monopoly

A firm that is the single seller in its market. Monopolies have market power because they produce a product or service without close substitutes, they have no rivals, and barriers to entry prevent other firms from entering the industry.