In astronomy, what is meant by the term Syzygy when referring to the relative positions of the Sun, the Earth and the Moon along a straight line?

Introduction / Context:
The term Syzygy is used in astronomy and celestial mechanics to describe a special alignment of three or more celestial bodies. This concept is important for understanding phenomena such as eclipses and certain tidal effects. In the context of the Earth Moon Sun system, Syzygy refers to a particular geometrical arrangement. This question asks you to identify the correct description of Syzygy among several closely related positional statements.

Given Data / Assumptions:

• The term is being used in connection with the Sun, the Earth and the Moon.
• We are interested in their relative alignment along a straight or nearly straight line.
• Some options describe special cases like eclipses or quadrature, while one describes the general alignment.
• The focus is on the general meaning of Syzygy, not only on one particular type of eclipse.

Concept / Approach:
Syzygy occurs when three celestial bodies lie in a straight or nearly straight line, with respect to the central body or an observer. In the Earth Moon Sun system, Syzygy happens during new moon and full moon phases, when the Sun, the Moon and the Earth are aligned. During new moon, the Moon is between the Earth and the Sun; during full moon, the Earth is between the Sun and the Moon. In both cases, the three bodies are aligned, which is the essence of Syzygy. Right angle positions, such as first and last quarter phases, are not Syzygies. Thus, the correct definition mentions all three bodies in a straight line, not only one of the possible arrangements.

Step-by-Step Solution:
Step 1: Recall that Syzygy refers to an alignment of three celestial bodies in a straight or nearly straight line. Step 2: Apply this to the Sun, the Earth and the Moon, where alignment occurs at new moon and full moon. Step 3: Examine option a, which describes the Sun, the Earth and the Moon lying in a straight line, matching the general definition. Step 4: Observe that option b is a special case where the Earth is between the Sun and the Moon, corresponding to full moon, but it does not cover the new moon alignment where the Moon lies between the Earth and the Sun. Step 5: Recognise that option c covers another specific arrangement but again is not the general definition, and option d describes a right angle configuration, which is not Syzygy.

Verification / Alternative check:
Astronomy references describe Syzygy as any celestial configuration in which three bodies are aligned. In the case of the Earth Moon Sun system, Syzygy is mentioned during both solar and lunar eclipses because the alignment is very close to perfect. During first and last quarter phases, the angle between the Earth Moon line and the Earth Sun line is about ninety degrees, and this configuration is called quadrature, not Syzygy. This supports the interpretation that the term applies to general straight line alignment of the three bodies as described in option a.

Why Other Options Are Wrong:
Option b refers only to the situation where the Earth lies between the Sun and the Moon, which is a full moon Syzygy, but does not mention the new moon alignment where the Moon is between the Sun and the Earth.

Option c focuses on the Sun and Moon being on one side of the Earth, which again covers only part of the cases and does not explicitly state the alignment of all three bodies.

Option d describes the Moon in a right angle position relative to the Sun and the Earth, which corresponds to quadrature, not to Syzygy.

Common Pitfalls:
Students sometimes narrow the meaning of Syzygy to one particular type of eclipse or to only one alignment configuration, missing the broader idea that any three body straight line arrangement qualifies. Another pitfall is confusing Syzygy with quadrature because both involve specific geometrical relationships. Remembering that Syzygy implies approximate collinearity of the three bodies helps avoid mixing it up with right angle situations.

Final Answer:
Syzygy is the condition when the Sun, the Earth and the Moon lie nearly in a straight line.