Why does the moon have a crescent shape at times and a convex shape at other times, other than full?

Answer 1

The shining arc of the moon (crescent or convex) is the part of the moon where the Sun light hits the Moon from behind the earth while the rest of the Moon is still covered by the earth shadow. The lighted and shadowed parts of the moon gradually change with time because of the changing relative positions of the Sun and Moon with respect to the earth (& wrt each other). So when the portion of the moon that appears to us as the bottom of the Moon is lighted, we see it as Crescent'; and when the portion that appears to us as the top of the Moon is lighted then we see it as convex. The Moon monthly cycle is completed in approximately 28 days (so the Moon year or lunar calendar (of 354 days) has approximately 11 days less than the solar calendar (365 days), and take approximately 33 years for the same lunar month to start at the same time in seasonal (or Gregarian) calendar. The interesting point in Lunar Calendar is that if a festival or function is based on lunar calendar, then it will advance by 11 days each year so in 33 years it will pass through all the seasons of the year thus providng equal opportunity for all point on earth and all nations to celebrate that festival in all seasons once in 33 years. That is the way it was intended to be, so Northern and Southern hemisphere will have equal opportunity in having Christmass in all seasons of the year once in 33 years; and also no nations will be stuck with fasting in the month of Ramadan in June or July and some other parts will have it easy for fasting in December only which is not the case since Ramadan is based on Lunar Calendar. Lunar calendar equally distribute the ease and hardship and everything else like a white Christmas. The Christian Calendar was linked to Solar Calendar around the time of Pope Gregory so Australia and the others in the Southren hemisphere will always have a summer Christmas!

Answer 2

The shape of the moon is determined by how much of the side facing us is being lit by the sun. You can try it by shining a light on any round object and walking around it; the visible portion of the lit side will depend on where you are and will change just like the shape of the moon does. The moon is always circular, but the unlit part looks black to us and is invisible against the sky.

Answer 3

This best way to picture this is:

Hold a tennis ball, or some other small ball at arms length in a dark room with only one bare light. Slowly rotate in a circle, holding the ball straight off to your left. Pretend you are the earth, and the ball is the moon. As you rotate, you are simulating the moon going around the earth. Notice the light pattern on the ball. It will do just as you said in your question...

Hope this helps!

Answer 4

That is just how sunlight falls on a ball. Take a baseball or golf ball or some kind of light colored, opaque, solid ball ball outside and look at it in the sunlight from different angles to see for yourself. Try looking at it with the Sun behind you and also with the Sun nearly behind the ball, and some places in between to simulate the phases of the Moon.