<P> In Western culture , the four principal lunar phases are new moon , first quarter , full moon , and third quarter ( also known as last quarter ) . These are the instances when the Moon 's apparent geocentric celestial longitude minus the Sun 's apparent geocentric celestial longitude is 0 ° , 90 ° , 180 ° and 270 ° , respectively . Each of these phases occur at slightly different times when viewed from different points on the Earth . During the intervals between principal phases , the Moon appears either crescent - shaped or gibbous . These shapes , and the periods of time when the Moon shows them , are called the intermediate phases . They last , on average , one - quarter of a synodic month , roughly 7.38 days , but their durations vary slightly because the Moon 's orbit is slightly elliptical , and thus its speed in orbit is not constant . The descriptor waxing is used for an intermediate phase when the Moon 's apparent size is increasing , from new moon toward full moon , and waning when the size is decreasing . </P>
<P> In Western culture , the four principal lunar phases are new moon , first quarter , full moon , and third quarter ( also known as last quarter ) . These are the instances when the Moon 's apparent geocentric celestial longitude minus the Sun 's apparent geocentric celestial longitude is 0 ° , 90 ° , 180 ° and 270 ° , respectively . Each of these phases occur at slightly different times when viewed from different points on the Earth . During the intervals between principal phases , the Moon appears either crescent - shaped or gibbous . These shapes , and the periods of time when the Moon shows them , are called the intermediate phases . They last , on average , one - quarter of a synodic month , roughly 7.38 days , but their durations vary slightly because the Moon 's orbit is slightly elliptical , and thus its speed in orbit is not constant . The descriptor waxing is used for an intermediate phase when the Moon 's apparent size is increasing , from new moon toward full moon , and waning when the size is decreasing . </P>
what is the fourth phase of the moon
what is the fourth phase of the moon
third quarter ( also known as last quarter )
third quarter ( also known as last quarter )