Is the Full Moon Always Visible Across the Globe?
While the concept of a full moon can be a captivating subject, one might wonder whether the full moon is visible from every corner of the Earth. Let's delve into the complexities!
Understanding the Full Moon as an Astronomical Phenomenon
From an astronomer's point of view, a full moon is an instant in time. This occurs when the Moon is at the point in its orbit where the majority of its sunlit side is visible from Earth. For the full moon of 27 April 2021, the precise moment was at 03:31 UTC. In Eastern Daylight Time (EDT), this was 23:31 on the previous day, 26 April 2021.
It's important to note that since the Moon is constantly moving, it can only be seen from half the Earth's surface at any given moment. Thus, if you needed to precisely capture the moment of maximum fullness, you would have to be in the hemisphere facing the Moon at that instant. However, due to the gradual change in the Moon's phase, there is a day or two around the full moon where the Moon still appears more or less full.
Latitude and Visibility
Despite its apparent fullness, the Moon's visibility can be affected by geographical latitude. Due to the inclination of the Moon's orbit and the tilt of Earth's rotational axis, people living in the far north or south (latitude) may go without seeing the Moon for up to two weeks in a row. This can occur during times when the Moon is continuously below the horizon in those regions.
For instance, the full moon on 24 June 2021 will not rise above the horizon in the far north of the Arctic polar circle. Similarly, the full moon on 19 December 2021 will not be visible above the horizon south of the Antarctic polar circle. However, with clear weather, the Moon will still be visible a few days before and after the peak fullness north of the Arctic polar circle.
Conclusion
The visibility of the full moon is a fascinating topic filled with exceptions and nuances. While the full moon phenomenon is universal, the actual visibility is not. Understanding the impact of celestial mechanics, hemispheres, and geographical location helps clarify why the full moon might not be seen in every part of the globe.