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Raven390
2010-Jan-19, 05:37 PM
Astronomers sometimes refer to lunar phases in terms of the age of the Moon. This is the time that has elapsed since new moon phase. Thus, the age of a full moon is half of a 29 1/2 day synodic period, or approximately 15 days.

what is the approximate age of the following?
(a) a waxing gibbous moon

(b) a waning cresent moon

(c) a waxing crescent moon

Thanks

grant hutchison
2010-Jan-19, 05:53 PM
Homework?

You need to work out the sequence of phases. Where do the half moons occur within the cycle? The crescent and gibbous phases will then lie between the new, full and half phases.

Grant Hutchison

NEOWatcher
2010-Jan-19, 06:02 PM
Homework?
Sounds like it to me... but...

Astronomers sometimes refer to lunar phases in terms of the age of the Moon.
Is that true? I've never heard that before.

NorthernBoy
2010-Jan-19, 06:14 PM
The examples asked for are not something with a unique age, as a full moon (pretty much*) is. The moon is waxing crescent at the moment, and will be doing so all the way from New Moon to half moon, from which it will be waxing Gibbous all the way to full moon.

*Although not considering the question before, and although the point of "full moon" may be standardised to be one point in time, I'd assume that the actual full moon can last for at the very least a good few hours.

01101001
2010-Jan-19, 06:47 PM
Play with Lunar Phase Simulator (http://astro.unl.edu/naap/lps/animations/lps.html).

grant hutchison
2010-Jan-19, 07:41 PM
Is that true? I've never heard that before.I've certainly encountered it often enough that it didn't make me pause: the "age of the moon" is the elapsed time from the most recent new moon, where the "new moon" is taken to be the moment at which the moon makes its closest angular approach to the sun.
The succession of phases isn't entirely regular, because of the shape and evolution of the moon's orbit, but it's common enough to see the age of the moon divided into eight equal sectors corresponding to the eight customary phases: new and full, first quarter and last quarter, and the waxing and waning crescent and gibbous phases.

The OP's homework is asking for approximate ages in the centre of the stipulated phases. I'm guessing a quarter-day would be considered acceptable and appropriate accuracy, given how the full-moon age has been rounded.

Grant Hutchison

Centaur
2010-Jan-19, 08:18 PM
Astronomers sometimes refer to lunar phases in terms of the age of the Moon. This is the time that has elapsed since new moon phase. Thus, the age of a full moon is half of a 29 1/2 day synodic period, or approximately 15 days.

what is the approximate age of the following?
(a) a waxing gibbous moon

(b) a waning cresent moon

(c) a waxing crescent moon

Thanks

Your homework assignment can be completed by reading your textbook and applying a little thought. Teachers assign such problems as exercises in research and logic rather than rote memorization of the current subject. Asking for answers from others defeats the purpose. I hope you come again for more general participation in the forum. Unfortunately, most students who come hoping for an easy way to answer homework questions are never heard from again.

BTW, astronomers do indeed refer to the “age of the Moon” since its conjunction with the Sun as an indication of its phase or amount of its apparent disc that is illuminated.