When does a full moon occur?

A full moon occurs when the moon is on the opposite side of the Earth from the sun, allowing the entire face of the moon that is turned towards Earth to be illuminated by sunlight. This positioning is essential because it reflects the sun's light directly onto the moon, providing the full, bright appearance we associate with the full moon phase.

Although the answer selected is not aligned with the accurate scientific explanation, it's important to clarify that a full moon does not directly correlate with the moon's distance from the sun, as the moon's orbit around the Earth is distinct from its orbit around the sun. In fact, while the proximity of celestial bodies can affect things like eclipses, a full moon specifically relates to alignment rather than distance — hence why the correct choice pertains to the moon being opposite the sun from the Earth, which allows complete illumination.

Choosing the option that describes the moon's position relative to Earth and the sun would align with the scientific understanding of a full moon. The scenario where the Earth casts a shadow on the moon represents a lunar eclipse, which is a different phenomenon altogether. Understanding these celestial mechanics is vital for early childhood education, as it instills a sense of wonder and curiosity about the natural world.