Why don't solar eclipses occur every month?

Why don't solar eclipses occur every month?

• A. A Solar eclipse happens when the Moon blocks the Sun; they don’t occur monthly because the Moon's orbital plane is tilted about 5 degrees to Earth’s orbit.
• B. They occur every new Moon.
• C. They happen only when the Sun is at its highest point in the sky.
• D. They only happen during lunar eclipses.

Answer: (A)

The key idea is that eclipses require a very precise alignment of the Sun, the Moon, and the Earth. The Moon does its orbit around us about once a month, so new Moons happen monthly. But the Moon’s orbital plane is tilted about 5 degrees relative to Earth’s orbit around the Sun. Because of this tilt, during most new Moons the Moon sits a little above or below the Sun in the sky, so its shadow misses Earth. Only when the new Moon happens to occur near one of the two points where the Moon’s orbit crosses the Sun–Earth line (the nodes) can the Sun, Moon, and Earth line up closely enough for the Moon to cast a shadow on Earth, producing a solar eclipse. That alignment is rare and the shadow path is narrow, so solar eclipses don’t happen every month even though a new Moon does.

The key idea is that eclipses require a very precise alignment of the Sun, the Moon, and the Earth. The Moon does its orbit around us about once a month, so new Moons happen monthly. But the Moon’s orbital plane is tilted about 5 degrees relative to Earth’s orbit around the Sun. Because of this tilt, during most new Moons the Moon sits a little above or below the Sun in the sky, so its shadow misses Earth. Only when the new Moon happens to occur near one of the two points where the Moon’s orbit crosses the Sun–Earth line (the nodes) can the Sun, Moon, and Earth line up closely enough for the Moon to cast a shadow on Earth, producing a solar eclipse. That alignment is rare and the shadow path is narrow, so solar eclipses don’t happen every month even though a new Moon does.