What is the cause of Saros cycles ?

http://www.orbitsimulator.com/gravity/saros.GIF?

Edited January 10, 201510 yr by Bjarne

A Saros cycle is purely a human counting method of eclipses. To get a roughly similar eclipse you need the moon earth sun to be aligned in the same way as last ime you noticed the eclipse. For this to be the case you need the moon to be

1. in the same phase of the moon

2. at the same eccentricity of its orbit

3. crossing the ecliptic (the plane on which the earth/sun rotate)

and

4. it needs to be in the right place

 

These events all happen with periods between 27-29 days - but for a lunar eclipse that repeats a historical eclipse you need them all to be the same (roughly) - so yu have a cycle that is when the 4 factors above return to the same point

draconic 27.212 days x 242.0006247 = 6585.32
anomalistic 27.5455 days x 239.0706649 = 6585.32
synodic 29.53059 days x 222.9999807 = 6585.32
orbital 27.322 days x 241.0263158 = 6585.32

So every 6585 days you are back to a very similar geometry of the sun, moon, and earth - and thus you can predict / understand lunar eclipses because if you had a penumbral eclipse at so-so at such a time 6585.32 days ago you will have another one now

The basic cause is that the orbit of the earth and of the moon are at a slight angle to each other.

The basic cause is that the orbit of the earth and of the moon are at a slight angle to each other.

So the Moon pulls itself up (or down), due to the different angular relation to the Earth / Sun.(?) This is also what I thought

But then the Earth orbit also not happens in a “straight line”

The Earth too must then for example pull itself upwards (or downwards) on its path before and after new moon, in these cases where the moon is "above" (or "below") the Earth, - right?

So this too must also result in some kind of anomaly similar to the Moon? – If not I simple don’t understand why the motion of the Earth shpuld be a exception .

 

I belive this phenomena is caused due to both the orbits of the Moon as well as the orbit of the Earth is affected - but maybe mostly the moon ?

 

Edited January 10, 201510 yr by Bjarne

So the Moon pulls itself up (or down), due to the different angular relation to the Earth / Sun.(?) This is also what I thought

But then the Earth orbit also not happens in a “straight line”

The Earth too must then for example pull itself upwards (or downwards) on its path before and after new moon, in these cases where the moon is "above" (or "below") the Earth, - right?

So this too must also result in some kind of anomaly similar to the Moon? – If not I simple don’t understand why the motion of the Earth shpuld be a exception .

 

I belive this phenomena is caused due to both the orbits of the Moon as well as the orbit of the Earth is affected - but maybe mostly the moon ?

 

I think gravitational center of Earth&Moon should be on green arch.

So the Moon pulls itself up (or down), due to the different angular relation to the Earth / Sun.(?) This is also what I thought

But then the Earth orbit also not happens in a “straight line”

The Earth too must then for example pull itself upwards (or downwards) on its path before and after new moon, in these cases where the moon is "above" (or "below") the Earth, - right?

So this too must also result in some kind of anomaly similar to the Moon? – If not I simple don’t understand why the motion of the Earth shpuld be a exception .

 

I belive this phenomena is caused due to both the orbits of the Moon as well as the orbit of the Earth is affected - but maybe mostly the moon ?

 

 

 

Why the new moon? The earth and moon feel a force toward each other (neither one pulls themselves up or down). If the moon is above the ecliptic, there will be a small component of the force that's up on the earth and down on the moon, as measured from the ecliptic. The center of mass of the earth wobbles in its motion; the earth and moon both orbit the barycenter, which is at some point inside the earth.

 

Why the new moon? The earth and moon feel a force toward each other (neither one pulls themselves up or down). If the moon is above the ecliptic, there will be a small component of the force that's up on the earth and down on the moon, as measured from the ecliptic. The center of mass of the earth wobbles in its motion; the earth and moon both orbit the barycenter, which is at some point inside the earth.

Oh yes of course, thanks