Why isn't the full moon considered the first phase?

Who decided the order of the moon phases, and why do we begin the phases with a phase we can not see? Doesnt it make more sense to start with the moon is fully illuminated. 

5 Answers

  • 4 weeks ago
    Favorite Answer

    Some cultures begin the lunar month at Full Moon. Others begin with the first sighting of the evening Crescent Moon (the "first day of the Moon"). The Chinese lunar month begins at New Moon.

    Most people (non-astronomers) first notice the Moon in the early evening sky and see it grow (waxing) from Crescent to Full.  By that time, the Moon rises at sunset and sets at sunrise. As the Moon gets smaller (waning), it rises later and later, so that most (non-astronomer) people rarely see it after Last Quarter.

    Therefore, it makes sense to begin the lunar month just as most people begin to see the Moon rather than two weeks after everybody has seen it.

  • Fred
    Lv 5
    4 weeks ago

    In western culture  your are referring to two entirely different and separated events. 

    A 'full moon' is when our Moon when viewed from Earth is illuminated by more than 98% of it's surface, this can happen over a three day period.  

    The phases of our Moon in western culture are referred to as 'primary phases' and 'transitional phases'.  The 'primary phases' lasting only momentarily, the 'transitional phases' lasting from moment of primary phase to moment of next primary phase.  

    A 'new moon' is when our Moon falls behind a line passing from our Sun to the center of the Earth.  In a solar eclipse if you were in a place where the eclipse last the longest you would notice the moment of the passing of 'old moon' passes into 'new moon'. If you had a plump bob hanging from a stable point, the plump bob would cast a shadow West  before eclipse and East after eclipse!

    A 'new moon' passed into an 'old moon' when our Moon passes threw a line  drawn from our Sun threw the center of Earth to our in our Moons orbit behind our Erath.  When a Lunar eclipse occurs that moment of transition from new into old happens between the times of full illumination.  The new before the darkness of eclipse  the  'old moon' appearing illuminated by the sun after eclipse.  

  • Mike
    Lv 7
    4 weeks ago

    It has been the custom to begin when the moon is just visible as a very thin crescent at sunset.  That is the basically the day after new moon, so its really the start of the next cycle.

  • JJ
    Lv 7
    4 weeks ago

    Maybe they were a software programmer, because computers usually start with 0 as the first number.

    Source(s): I used Binary Logic to figure this out.
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  • 4 weeks ago

    For the same reason you count up starting at zero.

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