2007-03-20 20:25:23 · 13 answers · asked by krunal 3 in Science & Mathematics ➔ Astronomy & Space
Lunar phase refers to the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases vary cyclically as the Moon orbits the Earth, according to the changing geometry of the Earth, Moon, and Sun. One half of the lunar surface is always illuminated by the Sun, and is hence bright, but the portion of the illuminated hemisphere that is visible to an observer can vary from 100% (full moon) to 0% (new moon). The boundary between the illuminated and unilluminated hemispheres is called the terminator.
The phases of the Moon have been given the following names, which are listed in sequential order:
Dark Moon - Not visible
New Moon - Not visible, or traditionally, the first visible crescent of the Moon
Waxing Crescent Moon - Right 1-49% visible
First Quarter Moon - Right 50% visible
Waxing gibbous Moon - Right 51-99% visible
Full Moon - Fully visible
Waning gibbous Moon - Left 51-99% visible
Third Quarter Moon - Left 50% visible
Waning Crescent Moon - Left 1-49% visible
New Moon - Not visible
The Moon makes a complete orbit about the Earth approximately once every 27.3 days. With a mean orbital speed of 1.023 km/sec, the Moon moves relative to the stars each hour by an amount roughly equal to its angular diameter, or by about 0.5°. The Moon differs from most satellites of other planets in that its orbit is close to the plane of the ecliptic, and not to the Earth's equatorial plane. The lunar orbit plane is inclined to the ecliptic by 5.1°, whereas the Moon's spin axis is inclined by only 1.5°. The Earth and Moon orbit about their common center of mass, which lies about 4,700 kilometres from Earth's center (about three quarters of the Earth's radius). On average, the Moon is at a distance of about 384,399 km from the center of the Earth, which corresponds to about 60 Earth radii.
2007-03-20 20:38:57 · answer #1 · answered by ponkeyrumu 2 · 2⤊ 1⤋
I have cut and paste a section from a bbc website on reading which u'll get the answer for ur question.
One must be aware that only one half (and the same half)of the moon is visible from our Earth.
This is because the time the Moon takes to spin on its axis is exactly the same as the time it takes to orbit the Earth.
Coming to your question...
when the moon appears to increase in size it is called waxing and when the moon appears to decrease in size it is called waning.
This is so because, only half of the moon is illuminated by the Sun and this is not always the same half that is visible from the Earth.
2007-03-23 02:17:41 · answer #2 · answered by Anonymous · 0⤊ 0⤋
The Earth increases by around 30 to 60 tons per day as it gathers interstellar dust, debris and small meteorites. Allowing for the smaller size of the Moon, it should be increasing by 2 to 4 tons per day by the same process.
2007-03-21 08:13:38 · answer #3 · answered by bh8153 7 · 0⤊ 0⤋
What the moon does is impossible for a planetary body. It's orbit and period of rotation are exactly the same, causing the exact same side to always face the earth. By exact I mean no difference in time duration at all between one and the other. This can not stay this way without some action on the moon to keep this perfect relationship in harmony. The moon must trim it's rotation to keep this perfect balance. Find out how! Make a name for yourself.
2007-03-21 03:39:26 · answer #4 · answered by Anonymous · 0⤊ 1⤋
It is due to the movement of the sun, earth and moon. When earth come in between the both, then due to the Shadow of the earth we can not see the full moon.
It is really pity on you, if you don't know all this as a student of engineering.
2007-03-23 06:57:45 · answer #5 · answered by KILOIA 2 · 0⤊ 0⤋
It is never too late to find out the answer- but I have to say that it is kind of weird that you don't know the answer to this. Maybe astronomy has never been part of the curriculum of your elementary school. The phases occur as the moon revolves around the earth. It endlessly goes through these phases- from a crescent to full and back.
2007-03-21 03:41:04 · answer #6 · answered by justmemimi 6 · 0⤊ 1⤋
if ur in 2nd year den what u have read it till now if u donmt know how the moon is increase or decrease day by day what have u learn up till now
2007-03-21 03:34:42 · answer #7 · answered by luv2yas 4 · 0⤊ 1⤋
Second year engineering student and you don't understand the phases of the moon? That's incredible. I won't be hiring you.
2007-03-21 03:39:19 · answer #8 · answered by Anonymous · 0⤊ 1⤋
The "phases" occur as the moon is forshadowed my the earth, which lies between it and the sun.
Please don't design any elevators.
2007-03-21 04:40:12 · answer #9 · answered by LELAND 4 · 0⤊ 1⤋
I think he wanted to ask why at the horizont is bigger than when it's up high. It's an optical illusion because of the atmosphere.
2007-03-21 05:02:23 · answer #10 · answered by Asiminei G 1 · 0⤊ 1⤋