<p>An eclipse (solar or lunar) happens when the Moon, Sun and Earth align in space and when the Moon intersects exactly with Earth's orbital plane around the Sun. However the Moon's orbit is not exactly the same as Earth's orbital plane (ecliptic) but inclined with a couple degrees. </p>

<p>The locations where the Moon intersects the ecliptic, called nodes, change in time. It happens two times every month but only when these nodes coincide with new or full moon an eclipse will happen.</p>

CC BY-SA 3.0
2017-08-22T17:43:21.723Z
2017-08-22T17:43:21.723Z
3TW3
<p>The moon's orbit is at a slight angle from the plane of earth's orbit around the sun, so it doesn't always hit the right spot, as described <a href="https://eclipse2017.nasa.gov/faq" rel="noreferrer">on NASA's Total Solar Eclipse 2017 site</a>:</p>

<blockquote>
  <p>Eclipses only occur if the Moon is located within 0.5 degrees of the
  plane of the ecliptic, on a line that passes through the center of the
  Sun and the Earth. The Moon travels along an orbit that is inclined by
  5 degrees to the ecliptic plane, so there are only two opportunities
  each month when it passes through the plane of the ecliptic. These
  points are called the ascending and descending nodes. Eclipses of the
  Sun only occur if new moon occurs when the Moon is near of one of
  these nodes. A similar argument explains why lunar eclipses do not
  occur every full moon at the node opposite the Sun from the Earth.
  <a href="https://i.sstatic.net/jNQg7.png" rel="noreferrer"><img src="https://i.sstatic.net/jNQg7.png" alt="diagram showing tilt of moon&#39;s orbit"></a></p>
</blockquote>

CC BY-SA 3.0
2017-08-22T17:45:58.803Z
2017-08-22T17:45:58.803Z
jeffronicus
<p>The moon takes about a month to orbit around the Earth. So why we don't have solar eclipse every month?</p>

CC BY-SA 3.0
2017-08-22T17:46:53.957Z
Looked for existing answer here or on Astronomy, didn't find one.
jeffronicus
CC BY-SA 3.0
2017-08-22T17:56:29.800Z
https://www.youtube.com/results?search_query=why+don%27t+we+have+solar+eclipses+every+month+
BarocliniCplusplus
CC BY-SA 3.0
2017-08-22T21:15:40.960Z
[Did you try to answer your question?](http://lmgtfy.com/?q=why+don%27t+we+have+a+solar+eclipse+every+month)
maxathousand
CC BY-SA 3.0
2017-08-22T21:16:04.657Z
There's [an xkcd for that](https://xkcd.com/1878/).
wim
<earth-rotation>
why we don't have solar eclipse every month?
karthikdivi
# why we don't have solar eclipse every month?

(Asked by: username_0 on 2017-08-22)

The moon takes about a month to orbit around the Earth. So why we don't have solar eclipse every month?

**Tags:** earth-rotation

> **Comments:**
> **username_1**: Looked for existing answer here or on Astronomy, didn't find one.  
> **username_2**: https://www.youtube.com/results?search_query=why+don%27t+we+have+solar+eclipses+every+month+  
> **username_3**: [Did you try to answer your question?](http://lmgtfy.com/?q=why+don%27t+we+have+a+solar+eclipse+every+month)  
> **username_4**: There's [an xkcd for that](https://xkcd.com/1878/).  

---

## 2 answers

### Answer by username_1 on 2017-08-22. Score: 9 | Accepted answer

The moon's orbit is at a slight angle from the plane of earth's orbit around the sun, so it doesn't always hit the right spot, as described [on NASA's Total Solar Eclipse 2017 site](https://eclipse2017.nasa.gov/faq):

> Eclipses only occur if the Moon is located within 0.5 degrees of the
> plane of the ecliptic, on a line that passes through the center of the
> Sun and the Earth. The Moon travels along an orbit that is inclined by
> 5 degrees to the ecliptic plane, so there are only two opportunities
> each month when it passes through the plane of the ecliptic. These
> points are called the ascending and descending nodes. Eclipses of the
> Sun only occur if new moon occurs when the Moon is near of one of
> these nodes. A similar argument explains why lunar eclipses do not
> occur every full moon at the node opposite the Sun from the Earth.
> [![diagram showing tilt of moon's orbit](https://i.sstatic.net/jNQg7.png)](https://i.sstatic.net/jNQg7.png)


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### Answer by username_5 on 2017-08-22. Score: 2

An eclipse (solar or lunar) happens when the Moon, Sun and Earth align in space and when the Moon intersects exactly with Earth's orbital plane around the Sun. However the Moon's orbit is not exactly the same as Earth's orbital plane (ecliptic) but inclined with a couple degrees.

The locations where the Moon intersects the ecliptic, called nodes, change in time. It happens two times every month but only when these nodes coincide with new or full moon an eclipse will happen.


---

