A lunar eclipse happens when the Earth, sun and moon align in space, with Earth in the middle. At such times, Earth’s shadow falls on the full moon, causing a lunar eclipse.
Next total lunar eclipse for North America is December 10, 2011
A solar eclipse happens at the opposite phase of the moon – new moon – when the moon passes between the sun and Earth. Why aren’t there eclipses at every full and new moon?
The moon takes about a month to orbit around the Earth. If the moon orbited in the same plane as Earth’s orbit, we would have two eclipses every month. There’d be an eclipse of the moon at every full moon. And, two weeks later, there’d be an eclipse of the sun at new moon for a total of at least 24 eclipses every year.
But the moon’s orbit is inclined to Earth’s orbit by about 5 degrees. That’s why there’s not an eclipse every month. The video below explains it.
There might be some unfamiliar words in this video, including ecliptic and node. The ecliptic is the plane of Earth’s orbit around the sun. The moon’s oribt is inclined to the plane of the ecliptic. The nodes are the two points every month where the moon’s orbit and the ecliptic intersect.
Even though the moon’s orbit is inclined to that of Earth – and even though there’s not an eclipse with every full and new moon – there are more eclipses than you might think. There are from four to seven eclipses every year. Some are lunar, some are solar, some are total, and some are partial. All are marvelous to behold – a reminder that we live on a planet – a chance to experience falling in line with great worlds in space!
Photo credit: pizzodisevo
I wish I could see a video explaining all this visually.(the eclipses with a Moon orbit exactly as Earth’s, and the actual Moon orbit with its 5-degree inclination). It’s difficult to understand/visualize this with words only, yet I’m sure by seeing it in video it would be very easy to understand!
Bibi, I looked around and couldn’t find the video you are seeking. Yes, it would be cool to have one! If anyone knows of one, please let us know …
- ES
Bibi,
Try http://www.youtube.com/watch?v=xwGs8_otT64
The moon’s orbital plane is inclined to the ecliptic – Earth’s orbital plane – by some five degrees, As the moon circles Earth, it crosses the ecliptic – Earth’s orbital plane – twice every month. These points of intersection are called nodes. If the new moon passes appreciably close to a node, then there is a solar eclipse, and if a full moon sweeps close to a node, then it’s a lunar eclipse.
More often than not, however, the new moon and full moon swing too far above or below the nodes for an eclipse to take place.
”if there is a full moon the people that is in that time will be in trouble”
if it was a full moon some people it will be fun and cool, not really.
There is a corollary of this: There really isn’t such a thing as a fully lit moon. In order to be fully lit, the moon has to be in a direct line from sun to earth to moon, and you get an eclipse. Therefore, the full moon, might more correctly be called the fullest moon.
Hello! I have a question about the “Solar and Lunar Eclipse Animation” segment.
Based upon the four cardinal directions – the Earth rotates West to East (which is shown in the graphic); however the orbital direction of the moon relative to the Earth is depictied in the same direction (counterclockwise). Doesn’t the moon actually orbit in the opposite direction to the Earth’s rotation? This would then explain why it rises in the East and sets in the West.
Thanks!
Paula,
The moon revolves around the Earth in the same direction that Earth rotates on its axis – from west to east, or counter-clockwise as viewed from north of the ecliptic – Earth’s orbital plane. After one day, Earth rotates full circle or 360 degrees eastward, whereas the moon only completes about 13 degrees of its orbit, also going eastward. The moon rises in the east and sets in the west because of the Earth’s rotation. But it’s the moon’s eastward motion in orbit that causes the moon to rise and set an average 50 minutes later every day.
Bruce
Thanks alot Bruce!
By the way, do all the planets in our solar system orbit counterclockwise?
Have a great day!
My pleasure Paula. Yes, all the planets orbit the sun counter-clockwise (as seen from north of the ecliptic). The planets revolve around the sun in the same direction that the sun rotates on its axis. You have a great day too!
Bruce
[...] Why aren’t there eclipses at every full and new moon? [...]
hi,
how does eclipse occur if moon’s orbit is 5degree inclined to earth’s orbit?Or there is two path of moon(year orbit and month orbit)???
anupama
class 8
Anupama,
For one half of the month, the moon in its orbit swings north of the Earth’s orbital plane, and for the other half of the month, swings south of the Earth’s orbital plane. Twice a month, the moon crosses the Earth’s orbit at points called nodes. When the moon is traveling from south to north, it’s an ascending node. When the moon is traveling form north to south, it’s a descending node.
If a new moon or full moon takes place when the moon is at or near one its nodes, then it’s a solar eclipse at new moon or a lunar eclipse at full moon.
Bruce
thanks …for that only eclipse takes place….
now i get it….
thank you again
very good
There should be another movement of the moon, making it that only sometimes (and not always) there are eclipses. I mean, without such a movement there wouldn’t be eclipses at all
Ricardo, it’s not really a “movement” that makes it so there aren’t eclipses at every new and full moon. It’s the inclination of the moon’s orbit with respect to Earth’s orbit around the sun. That tilt of the moon’s orbit (see picture in post above) means that the moon is not always on the same plane as the Earth and sun. Sometimes it passes above or below that plane at new or full moon. At such times … no eclipse.
Thanks Deborah! Then, it’s a movement, as long as the position changes with time. I think you mean that what moves is the moon’ orbit plane. This is the movement I’m asking for. Seems to be an oscillation
I have 2 queries:
a)The Sun rises generally in the East but during winter and summer, it can deviate by as much as as 23.5 d from the true East. Does the moon rise and set exactly in the East and the West?
b)It is mentioned above that the moon rises late by about 50 minutes every day. Is this because it its speed of rotation around the earth is not the same as the earth’s speed of rotation around itself?