# Why don't we see solar and lunar eclipses often? [duplicate]

Since we see the new moon at least once in a month when the Moon gets in between of the Sun and the Moon at the night and as far as I know if this happens during the day, you'll get to see a solar eclipse. Why don't we get to see this often or in the day?

Does it mean that in some part of world there's a solar eclipse when we are seeing a new moon? I'm looking for a diagram or interactive way to understand this if possible as I'm not a native English speaker, but I'll try my best to do so.

• – Qmechanic May 13 '12 at 21:02

## 1 Answer

If the Moon's orbit around the Earth were in exactly the same plane as the Earth's orbit around the Sun, we'd have a total solar eclipse every month (but 100% totality would be seen only from the tropics).

But in fact they're not in the same plane. The Earth's spin axis is tilted by about 23 degrees relative to the Earth's orbit around the Sun, and the Moon's orbit is closely aligned with the Earth's spin. As a result, the Sun and the Moon do not follow the same path in the sky.

We get a solar eclipse only when (a) there's a new Moon, so the Sun and Moon are in the same position east-to-west, and (b) the new Moon happens when the Sun and Moon happen to be closely aligned north-to-south.

Since the Sun and Moon are both about half a degree wide (as we see them in the sky), the 23-degree offset of their paths makes solar eclipses relatively rare events.

Lunar eclipses, which occur during the full Moon when Moon passes into the Earth's shadow, are more common because the Earth is bigger than the Moon, and so has a much wider shadow.

• When talking about frequency of eclipses, it's important to distinguish between actual occurrence or someone observing the eclipse. Eclipses aren't as rare as, say, presidential elections and much of the "rarity" is due to the media. For solar eclipses, the rarity is because of the tiny fraction of Earth's surface area, usually over water, the event covers. This page has a nice summary. – user11266 Dec 20 '12 at 16:23
• No problem. Your remark about solar eclipses only being visible from the tropics if Moon's orbit coincided with the ecliptic had not occurred to me before. – user11266 Dec 21 '12 at 13:18