Altering the Milankovitch Cycles

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In summary, Milutin Milankovitch suggested that the Pleistocene ice ages were determined by three factors: eccentricity, obliquity, and precession. The alternate Earth discussed has the same eccentricity as our Earth but has a different range of axial tilt and a different pole star, Sirius. With a lower tilt and different pole star, the climate on this alternate Earth would likely be dramatically different and the extent of ice ages would also be affected. Polaris will continue to be the North Star for a few more cycles before it moves too far from the polar locus, while Sirius will become the southern pole star in 67000 and 152000.
  • #1
JohnWDailey
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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?
 
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  • #2
Polaris will not be the pole star for 26,000 years. It becomes the pole star for a few hundred years every 26,000 years. It has been doing this, and will continue doing this until its proper motion takes it significantly far from its current location
 
  • #4
Polaris is currently the pole star. In a few hundred years, it will not be as close to the pole. In 26,000 years it will return to the pole position. During every 26,000 year period, several stars take turn being the Pole star, including Vega.

Sirius can never be the north star as it is in the southern sky.
With a tilt of 20-25 degrees, it can't ever be the southern star either. It is too close to the celestial equator.
 
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  • #5
tony873004 said:
Sirius can never be the north star as it is in the southern sky.
With a tilt of 20-25 degrees, it can't ever be the southern star either. It is too close to the celestial equator.
I am from Nebraska, and I see Sirius on Orion's Belt.
 
  • #6
JohnWDailey said:
I am from Nebraska, and I see Sirius on Orion's Belt.
"Sirius can be seen from almost everywhere on the Earth's surface, with only observers north of 73 degrees latitude unable to see it, and it does not rise very high when viewed from some northern cities, reaching only 13° above the horizon from Saint Petersburg." (Wiki)
Valentine is 42°N , rest is south of Valentine.
 
  • #7
fresh_42 said:
Valentine is 42°N , rest is south of Valentine.
The point being?
 
  • #8
JohnWDailey said:
The point being?
You can see Sirius, as well as me, for both of us live south of 73°N, you live south of or near Valentine (42°N) as you've said, me on 50°N. However, although we can see Sirius, it's far from being near the sky's north pole. It's more south in the sky for even people in Australia can see Sirius.
 
  • #9
tony873004 said:
...With a tilt of 20-25 degrees, it can't ever be the southern star either. It is too close to the celestial equator.
I take this back. Sirius has a high proper motion, and it is traveling almost due south in our skies. It WILL become the southern pole star in 67000 AD, and again in 152000 AD.

Polaris has a slow proper motion. It has been, and will continue to be the north star for a few more cycles before it moves too far from the polar locus .

To illustrate, here are 2 simulations. On the left of each screen is a Play button [>] to begin the simulation. Next to the play button is [->]. This let's you run time into the past.

This simulation shows how the northern pole stars change over time in 26,000 year cycles. Notice that Polaris doesn't move much in 26,000 years and once again becomes the pole star in the future. If you run it backwards in time, Polaris was the pole star 26,000 years ago as well. Notice how Vega becomes the pole star in 13000 AD, and Thuban becomes the pole star in 23000 AD
http://orbitsimulator.com/gravitySi...1,4,465,1,4,530,0,4,660,1,260,30,1,260,200,40

This simulation shows the southern sky. Notice that Sirius travels very fast across the sky as it is very close to Earth. It becomes the southern polar star in 67000 and 152000.
http://orbitsimulator.com/gravitySi...1,4,465,1,4,530,1,4,660,1,260,30,1,260,200,39
 
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1. What are Milankovitch cycles?

Milankovitch cycles refer to the long-term changes in the Earth's orbit and axial tilt that occur over thousands of years. They are named after Serbian scientist Milutin Milankovitch, who first proposed the theory in the 1920s.

2. How do Milankovitch cycles affect climate?

Changes in the Earth's orbit and axial tilt can impact the amount of solar radiation the Earth receives, which can affect global temperatures and climate patterns. For example, when the Earth's tilt increases, summers become warmer and winters become colder, leading to glacial periods.

3. Can we alter Milankovitch cycles?

No, we cannot directly alter Milankovitch cycles. These changes are natural and occur over thousands of years. However, human activities such as greenhouse gas emissions can contribute to climate change and can indirectly affect the Earth's climate system.

4. What would happen if we could alter Milankovitch cycles?

If we were able to artificially alter Milankovitch cycles, it could have significant impacts on the Earth's climate and ecosystems. For example, artificially changing the Earth's tilt or orbit could disrupt the delicate balance of the Earth's climate and lead to extreme weather events and disruptions in the natural environment.

5. Can we predict future changes in Milankovitch cycles?

Scientists use mathematical models to study past and present Milankovitch cycles and make predictions about future changes. However, these predictions are not exact and can be affected by other factors, such as human-caused climate change. Therefore, it is important to continue studying and monitoring Milankovitch cycles to better understand their impacts on the Earth's climate.

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