Q5: Are the phases of the Moon the same all over the world at the same time?

RELATIVELY, THE PHASES OF THE MOON ARE THE SAME ALL OVER THE WORLD AT THE SAME TIME. =D

The reason why we see different phases of the Moon is because of the relative and ever-changing positions of the Sun, the Moon and the Earth periodically. For instance, if you have seen a full Moon, observers like you all over the world would also have seen a full Moon. This is due to the changes in the lighted portions of the Moon, and is therefore not dependent on the location of the observer.

In the Northern Hemisphere, we can identify the phases of the Moon using the following mnemonic as we face North:

DOC - The crescent preceding the full moon (waxing) is in the shape of a D, then there is the full moon in the shape of an O, followed by a crescent in the shape of a C for the waning moon.

Phases of the Moon. Retrieved from: http://www.exploringnature.org/db/detail.php?dbID=42&detID=2856

Nevertheless, people in different locations see the moon in a slightly different manner, especially if they are in different hemispheres.

In the southern hemisphere, observers would see the moon upside down (relative to the way observers in the Northern Hemisphere see the Moon) so the sunlit side is opposite to that of the Northern Hemisphere. Thus, the mnemonic now run this way:

COD - The crescent preceeding the full moon (waxing) is in the shape of a C, then there, again, is the full moon in the shape of an O, followed by a crescent in the shape of a D for the waning moon.

On the other hand, an important factor, the libration of the Moon, or the apparent rocking/rolling of the Moon, affect exactly what portion of the Moon faces the Earth especially during the first and the last quarter phase. The location of the terminator, or the line which distinguishes between the lighted and the dark portions of the Moon, may differ. Consequently, the portions of the Moon that the observers can see may vary from time to time.

Note: The Libration of the Moon can be explained by Kepler’s Laws – the Moon moves faster when it comes nearer the Earth and moves slower when it orbits farther away (on account of its elliptical orbit). This allows us to see 59% of the Moon’s surface, contrary to the common misconception that we only see half of the Moon’s surface due to its Synchronous rotation with the Earth.

Image Source:
Sheri Amsel. Phases of the Moon. In: Exploring Nature Educational Resource [Internet]. [Cited 2012 August 27]; Available from: http://www.exploringnature.org/db/detail.php?dbID=42&detID=2856

Prepared by: Ericka Jane Angeles