How close would the Moon have to be to Earth for there to be a solar eclipse every month?

Answer 1

I agree that orbital inclination is the thing, not distance. If the Moon remained at its current distance but changed its orbital plane to coincide exactly with the orbital plane of the Earth around the Sun (the ecliptic), then there would be a solar eclipse every month.

However, to make the Moon's shadow hit Earth even if the 5 degree orbital tilt remains, trigonometry tells me that the Moon would have to be about 5 times closer than it is now. The Moon is now 30 Earth diameters away and the tangent of 5 degrees times 30 is 2.6, which means the Moons shadow is 2.6 Earth diameters above center or 5.2 Earth radii above center. You need the shadow less than one Earth radius off center to hit Earth. 6 times the tangent of 5 degrees is 0.52. That would make the center of the shadow miss by 0.02 Earth radii, but since the shadow would be bigger, part of the edge would still hit Earth. So 6 instead of 30 Earth diameters away is 5 times closer, or 48,000 miles. And at such a close distance the eclipses would be totally different in character, with the Moon appearing 5 times larger than the Sun in the sky we would not see the Sun just barely covered with the corona visible all around. We would see most of the corona covered too, as seen from the center of the umbra.

Answer 2

It wouldn't make much difference. The tilt of the Earth's axis away from and toward the Sun and the orbit of the Earth and Moom around the Sun would often prevent the necessary alignment of the Sun, Moon and Earth for the eclipse to occur. Each object would need the same perpendicular polar alignment and a perfectly synchronous orbit befoe it could happen each month.

Answer 3

Distance from Earth is not an issue, the Moon's orbital plane would have to be inclined 0 degrees relative to Earth's orbit, currently the inclination of the Moon's orbit is 5 degrees.

Answer 4

500 miles away