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Altering the Milankovitch Cycles

J

Jdailey1991

Sage
As I understand it, the Pleistocene ice ages were dictated by three major factors suggested by the Serbian geophysicist Milutin Milankovitch--eccentricity (orbital shape), obliquity (axial tilt) and precession (direction of rotation in relation to fixed stars).

The one identical factor between our Earth and this alternate Earth is the eccentricity--no lower than 0.000055 and no higher than 0.0679.

Back home, Earth's axial tilt varies between 22.1 and 24.5 degrees in a period of 41,000 years. In this alternate Earth, the tilt varies between 20 and 25 degrees in a period of 61,500 years.

Back home, Polaris will be the North Star for a total length of roughly 26,000 years. In this alternate Earth, Sirius will be the North Star for a total length of 46,800 years.

With these changes, how much dramatic of a difference would Earth's climate be? How would they affect the extents of the ice ages?
 
Heliotrope

Heliotrope

Staff
Article Team
:eek:

Ummm…….. I'm going to nod and smile and pretend I know what you are talking about.

Though I'm pretty sure none of your readers are going to care overly much.
 
Steerpike

Steerpike

Felis amatus
Moderator
If you post this question on a forums for physicists or geophysicists or other relevant group, you'll get a bunch of people who will do calculations and try to come up with an answer for this. That's what I'd do in this situation. When I have physics questions, for example, I pose them to someone I know who has a Ph.D. in physics. Do a google search for physics forums or geophysics forums or something like that and create an account. You'll find a lot of people who love just this sort of speculation and figure out how it would work.
 
CupofJoe

CupofJoe

Myth Weaver
Yeah. I'm not certain I understand all of what is in the OP.
What I can say is that it doesn't matter to the climate [long or short term] which star is the North star.
All I can think of as an effect from an increased axial tilt is more pronounced differences between summer and winter. Longer days in the summer and longer nights in the winter. But not by much. A lesser axial tilt, the lesser the seasonal difference.
And I have to agree with H [and I hope you don't mind me being so familiar], unless it is fundamental and central to your story, I can't see many readers being that bothered.
The Helliconia series of books [by Brian Aldiss] have a highly different binary star orbit for an alt-earth. There it is central to the story. During each long year winter destroys civilisations almost back to the stone age each time, with only a little knowledge and technology surviving and the long hot dry summer are almost as damaging.
 
Russ

Russ

Istar
I can assure you that the length of time polaris will be the north star will have no impact on climate or ice ages.

The other question requires a technical knowledge beyond my capacity, but probably searchable with some diligence.
 
W

WhiteCrow

Acolyte
Russ said:
I can assure you that the length of time polaris will be the north star will have no impact on climate or ice ages.
Click to expand...

It does actually.

The Earth wobbles between Sirius and Vega throughout the millennia, based on the axis rotation of the earth. A tilt this way and the Earth points to Sirius, a tilt that way and it points to Vega. Tilt this way - less water, mild winters. Tilt that way - moister temperatures, cooler winters.

The universe does play a part in how our oceans & the water systems on earth act. We've known that for ions, since our very distant forefathers.


We're in the midst of an axis rotation right now hence why we are getting changes in the weather. Warmer summers, more moister in the air [the ever increase in hurricanes & twisters and "violent" storms], and winters that in some areas have not been seen [such as Egypt] for more than a few hundred years.
 
Miskatonic

Miskatonic

Auror
George RR Martin's ASoIaF has seasons that last far longer than those in our world, yet I don't think he's ever gone into any type of physics based explanation as to why this is.

I don't think you have to go overboard with explaining the physics of your universe, as I would imagine just proposing the idea would provide plenty of fodder for endless nerd debates, which isn't necessarily a bad thing.
 
Russ

Russ

Istar
WhiteCrow said:
It does actually.

The Earth wobbles between Sirius and Vega throughout the millennia, based on the axis rotation of the earth. A tilt this way and the Earth points to Sirius, a tilt that way and it points to Vega. Tilt this way - less water, mild winters. Tilt that way - moister temperatures, cooler winters.

The universe does play a part in how our oceans & the water systems on earth act. We've known that for ions, since our very distant forefathers.


We're in the midst of an axis rotation right now hence why we are getting changes in the weather. Warmer summers, more moister in the air [the ever increase in hurricanes & twisters and "violent" storms], and winters that in some areas have not been seen [such as Egypt] for more than a few hundred years.
Click to expand...

You are mistaking the signs for the terrain.

The fact that earth points at Sirius or any other star is meaningless with respect to ice ages or climate change on earth.

The relationship of the earth to the sun has a significant impact on ice ages and climate.

Think of it this way. Say there is a big fire and close to it there is a sign that says "hot" and farther away (or at a different angle if you prefer) there is a sign that says "cold". If I move closer to the "cold" sign I may well get colder. But it is not the sign that is causing the change, it is the fire.

The "universe" does not play a part in how our oceans and water systems on earth act, rather the sun and the moon do.

In fact I would bet that if Sirius and Vega disappeared completely or tripled their distance from earth overnight, it would make no difference in the climate or the ice ages.
 
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