In ancient religious texts, the Bible mentions that Jesus could see the entire Earth from a high location (Matthew 4:8), suggesting a flat Earth view. Under this assumption, everyone on Earth would be able to see the full moon at the same time. However, this view is scientifically incorrect, as today we know the Earth is spherical and the full moon is only visible from the night side of Earth. For a full moon to occur, the Sun, Earth, and Moon must align, with the Earth positioned between the Sun and the Moon. However, only those on the night side of Earth can see the full moon, while those on the daytime side cannot, as the Sun's light overshadows the moon. Therefore, the full moon is visible only at night, and people on opposite sides of Earth will experience the full moon at different times due to Earth's rotation.

The full moon occurs at the exact moment when the Sun and Moon are aligned on opposite sides of Earth. If you observe the full moon during the day in your location, it means you're observing the specific alignment at that time, but since Earth is spherical, only those on the nighttime side of Earth can view it. This is why the full moon appears from sunset to sunrise, but not during the day. In very rare cases, both the Sun and the full moon may be visible briefly at opposite ends of the horizon during sunrise or sunset, but the full moon is primarily visible only during the night. This is a concept only recently fully understood, as it depends on Earth's rotation and spherical shape.

Interestingly, the Quran describes the visibility of the full moon in a way that aligns with our current understanding of astronomy, even though this was not known at the time of its revelation. Quran 84:16-18 states:

This passage describes how the full moon can only be seen from twilight and throughout the night, aligning perfectly with the scientific fact that the full moon is not visible during the day due to Earth's spherical nature. Thus, the Quran's description of the full moon's visibility during twilight and night further supports the modern understanding of the moon's phases and the spherical shape of Earth. This is consistent with the fact that a full moon cannot be observed simultaneously by all people on Earth, as would be the case if Earth were flat.