Why does a solar eclipse occur only on a new moon day?

'New Moon' is when the moon is not visible from earth, and the reason it's not visible is because it is between the earth and the sun. It is there all day in the day sky, and the sun is shining on the 'back' of the Moon. read more

On the new moon, the sun is behind the moon, which is why we don’t see the sun’s light reflecting off of the lunar surface. On any other day of the month, the moon is not between the earth and sun, so a solar eclipse would be impossible. Lunar eclipses only occur on the full moon for the opposite reason. read more

Conversely, an eclipse when the Moon is near its farthest distance from the Earth (i.e., near its apogee) can only be an annular eclipse because the Moon will appear to be slightly smaller than the Sun; the magnitude of an annular eclipse is less than 1. read more

Several things need to occur at once to create a total solar eclipse. First, the moon needs to be exactly the right size to block the sun. Next, the sun, moon, and Earth need to line up in a straight line, or nearly so, with the moon between the sun and Earth. Finally, to see the full eclipse, you need to be standing in the correct spot on Earth. Lucky for us, our moon is the perfect size. read more