Because the position of the moon, earth, and sun are not in the same exact place every month. This means they are a rare occurrence and only happen when the moon, earth and sun are in exact alignment with the earth.
The moon's orbit and the earth's orbit about the sun are in slightly different planes. If they were all in the exact same plane, every full moon would bring an eclipse. With the orbits in slightly different planes, eclipses happen only at full moons when the sun and moon are at the same angle of elevation.
There are two main types of eclipses: solar and lunar. Lunar eclipses occur every 6 months. Solar eclipses occur 2-5 times per year. Eclipses can be partial or total. Partial eclipse covers only part of the sun or moon, while total covers the full entity.
Because the moon phase is irregular
No, eclipses can occur only at a new or full moon.
Typically, lunar eclipses occur once or twice a year. Because more than half of all lunar eclipses are partial, and because lunar eclipses are visible only from the side of the Earth where the Moon is up, you would generally be able to see a total lunar eclipse every other year or every 3rd year from your location. The rest of the eclipses would be either partial, or not visible from your location. You can check the NASA Eclipse Web Page to see the catalog of all eclipses from 2000 BCE to 3000 AD at the link below.
See the list of coming eclipses at the NASA link:http://eclipse.gsfc.nasa.gov/eclipse.htmlHere is a video explaining why we don't get solar eclipses every month. Interesting!
The moon would have to be on a flat plane instead of being on a tilt.
We do. its not a month though. its every 29.5 days
Every year
Because the moon phase is irregular
There are two main types of eclipses: solar and lunar. Lunar eclipses occur every 6 months. Solar eclipses occur 2-5 times per year. Eclipses can be partial or total. Partial eclipse covers only part of the sun or moon, while total covers the full entity.
The Moon's orbit is at an angle to the orbit of the Earth around the Sun so most often the full/new moon is 'above' or 'below' the line directly from the Sun to the Earth so lunar/solar eclipses do not occur every month.
No, eclipses can occur only at a new or full moon.
The moon phases would change.
Typically, lunar eclipses occur once or twice a year. Because more than half of all lunar eclipses are partial, and because lunar eclipses are visible only from the side of the Earth where the Moon is up, you would generally be able to see a total lunar eclipse every other year or every 3rd year from your location. The rest of the eclipses would be either partial, or not visible from your location. You can check the NASA Eclipse Web Page to see the catalog of all eclipses from 2000 BCE to 3000 AD at the link below.
Every month, dummy!
'C' (the missing one) is the correct choice.
Solar eclipses occur when the shadow of the Moon is projected agains the Earth's surface. They don't occur every month because the plane of the orbit of the Moon around Earth doesn't coincide with the plane of the orbit of Earth around the Sun.