The Shape of Earth's Orbit

KilljoyKlown

KilljoyKlown

Whatever
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I came across this topic and was wondering, exactly where in this 100,000 year cycle are we at this time? And how might this be affecting our current weather?



The most important orbital change studied by Milankovich is the change in the shape of the Earth's orbit from nearly circular to slightly elongate and back again. The time it takes to go through a complete cycle from circular to elongate and back to circular is about 100,000 years.

Please note that the change in orbital shape shown in the animation is much, much, much larger than the actual change in the Earth's orbit. If the animation showed the actual change in shape, you would not be able to detect it with your eye. The effect has been greatly exaggerated so that you can easily see it.

During the portion of the shape change cycle when the orbit is nearly circular, the Earth-Sun distance is nearly the same for all parts of the orbit, making the Earth's average temperature the same all year round. As the orbit becomes more elongate, the Earth orbits slightly farther from the Sun at aphelion and slightly closer at perihelion, making the average temperature slightly lower at aphelion and slightly higher six months later at perihelion. Also, since the Earth moves more slowly near aphelion, when the orbit is elongated, the time during which the temperatures are lower lasts slightly longer.

http://www.cotf.edu/ete/modules/msese/dinosaurflr/shape.html
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http://en.wikipedia.org/wiki/Milankovitch_cycles

The Earth's orbit is an ellipse. The eccentricity is a measure of the departure of this ellipse from circularity. The shape of the Earth's orbit varies in time between nearly circular (low eccentricity of 0.005) and mildly elliptical (high eccentricity of 0.058) with the mean eccentricity of 0.028. The major component of these variations occurs on a period of 413,000 years (eccentricity variation of ±0.012). A number of other terms vary between components 95,000 and 125,000 years (with a beat period 400,000 years), and loosely combine into a 100,000-year cycle (variation of −0.03 to +0.02). The present eccentricity is 0.017.
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If the relationship between eccentricity of the orbit and time of said cycle is linear, than:
e @ 0.005 corresponds at beginning of cycle or 0th year, e @ 0.028 corresponds to end of cycle or 100,000th year.
0.028-0.005=0.023 variation. 0.017/(0.23/100)=7.39130434783 % of time has passed since zeroth year. 0.0739*100,000=7391th year, from zeroth year. So basically we are just in beginning of the cycle.

And beginning of said cycle was 2013 A.D - 7391 years = 5378 B.C, otherwise the birth of civilization, Mesopotamia as well as early rise of Norte-Chico civilization.
 
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youreyes said:
http://en.wikipedia.org/wiki/Milankovitch_cycles

If the relationship between eccentricity of the orbit and time of said cycle is linear, than:
e @ 0.005 corresponds at beginning of cycle or 0th year, e @ 0.028 corresponds to end of cycle or 100,000th year.
0.028-0.005=0.023 variation. 0.017/(0.23/100)=7.39130434783 % of time has passed since zeroth year. 0.0739*100,000=7391th year, from zeroth year. So basically we are just in beginning of the cycle.

And beginning of said cycle was 2013 A.D - 7391 years = 5378 B.C, otherwise the birth of civilization, Mesopotamia as well as early rise of Norte-Chico civilization.
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Okay so far so good. I'm assuming that year 0 is when the orbit is closest to an actual circle and that year 50,000 is the most elliptical that it gets. Please correct me if that's wrong. Now I'm also interested in the other orbital/planetary cycles Milankovitch worked on. It boggles my mind when I try picture three different length cycles that all have their own input into our weather. I assume they have both best and worst case scenarios depending on how those cycles are interacting with eachother. But I haven't found it yet and would be interested to know how bad or good our current situation is when human made global warming is factored in to the equation?

The Tilt of Earth's Axis

The second orbital change Milankovich studied is the tilt of Earth's axis relative to its orbit around the Sun. The tilt of Earth's axis is the main cause of the seasons. If Earth had no tilt, then the length of daylight and the intensity of solar heating seen by a person standing at a single place on the surface would be the same all year round. The area near Earth's equator would still be hotter than the area around the poles, but there would be no seasonal changes in temperature: the Equator would always be hot, the poles would always be cold, and the US would always be blah!

Image showing the Earth at two different times in one year. The first, the Northern hemisphere is pointed more directly towards the Sun. The second, six months later, it is pointed more away from the Sun. Please have someone assist you with this.

But Earth does have a tilt, so on one side of the orbit, the Northern hemisphere is pointed more directly towards the Sun (as seen on the left side of the picture above). On the other side of the orbit, six months later, it is pointed more away from the Sun (as seen on the right side of the picture above). When the Northern hemisphere is pointed towards the Sun, the days are longer, solar heating is more intense, and temperatures are higher - it is summertime! When the Northern hemisphere is pointed away from the sun, the days are shorter, solar heating less intense, and the temperatures are lower - it is winter! (Notice that when the Northern hemisphere is pointed toward the Sun, the Southern hemisphere is pointed away, and vice versa. So when it is summer in the north, it is winter in the south and vice versa.)

Milankovich found that Earth's tilt is not constant, but varies slightly over a cycle that lasts about 41,000 years. The change is small, but when the tilt is less, less snow melts in the polar regions because of the shorter days and reduced sunlight, allowing glaciers to form and spread. When the tilt is greater, more snow melts during the resulting long summers in the polar regions and glaciers tend to shrink.
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and

The Wobble of Earth's Axis

The third orbital change that Milankovich studied is called precession, the cyclical wobble of Earth's axis in a circle. The motion is like a spinning top when it is about to fall over. One complete cycle for Earth takes about 26,000 years.

By itself, the wobble of Earth's axis does not directly cause temperature changes like orbital shape and tilt. But it changes the portion of the orbit at which a given season occurs - that is, it changes when a particular season will occur.

Image showing the Earth's tilt at the present time (now). Please have someone assist you with this.
Earth's Tilt At Present Time (Now)

Image showing the Earth's tilt 13,000 years from now. Please have someone assist you with this.
Earth's Tilt 13,000 years from Now

In the upper part of the diagram above labeled "Now," Earth's axis is tilted so that summer occurs in the northern hemisphere on the left side of the Sun and winter on the right. In the lower part labeled "In 13,000 years," the axis has moved to where summer in the northern hemisphere occurs on the right side of the Sun and winter on the left.

So what! You say. If Earth's orbit is nearly circular, then it makes no real difference. But if Earth's orbit is slightly elongate, and perihelion occurs on the right side of the Sun (as shown), then Earth is slightly farther from the Sun on the left side. In this case, northern summer are slightly cooler and northern winters slightly warmer on the "Now" part of the diagram. But in 13,000 years, the axis will have shifted so that summer in the northern hemisphere will occur on the right side of the Sun where Earth is closer, so summers will be hotter, and winters will be colder (and longer).

This is important because glaciers need land on which to form. Most of the land surface on Earth is now in the northern hemisphere, so when the wobble has moved Earth's axis so that northern winters occur on the cooler part of the orbit, glaciers will tend to grow.
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KilljoyKlown said:
Okay so far so good. I'm assuming that year 0 is when the orbit is closest to an actual circle and that year 50,000 is the most elliptical that it gets. Please correct me if that's wrong. Now I'm also interested in the other orbital/planetary cycles Milankovitch worked on. It boggles my mind when I try picture three different length cycles that all have their own input into our weather. I assume they have both best and worst case scenarios depending on how those cycles are interacting with eachother. But I haven't found it yet and would be interested to know how bad or good our current situation is when human made global warming is factored in to the equation?
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I was under impression that the cycle is 100,000 years long and that the maximum eccentricity occurs at 100,000th year. Correct me if I am wrong...the wiki site mentioned an even bigger cycle there too...

Also whether we completely nuke our planet or slowly increase our rate of green house gases emission into atmosphere, does not affect the actual eccentricity of our planet against the sun, what changes through those 100 millenia are the locations where the summers and winter seasons occur, and also increase in change of the season (shorter fall and spring).

Visualization of Milankovitch cycles:

http://web.mit.edu/unity3d/milankovitch/
 
youreyes said:
I was under impression that the cycle is 100,000 years long and that the maximum eccentricity occurs at 100,000th year. Correct me if I am wrong...the wiki site mentioned an even bigger cycle there too...

Also whether we completely nuke our planet or slowly increase our rate of green house gases emission into atmosphere, does not affect the actual eccentricity of our planet against the sun, what changes through those 100 millennium are the locations where the summers and winter seasons occur, and also increase in change of the season (shorter fall and spring).

Visualization of Milankovitch cycles:

http://web.mit.edu/unity3d/milankovitch/
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The complete cycle is 100,000 years, so at 50,000 years it will start back to getting more circular again. I found another chart which might be closer to the true distances. One of the things the article commented on were that sometimes all cycles can line up in a bad way for the Earth and we have a major ice age. Has anyone started a topic on how all the people on Earth would deal with an ice age? Does anyone believe we could stop an ice age from happening?

 
KilljoyKlown said:
After doing the install that was a very good inter active display. However, I'm not sure those graphs mean much to me without a lot of study on that subject. I was hoping for someone who was already knowledgeable on the subject could comment about it in simple easy to understand terms.:D
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if you scroll the time along the shown variations of eccentricity, notice the temperatures at the lowest eccentricity value and highest eccentricity value...basically no actual change.
 
youreyes said:
if you scroll the time along the shown variations of eccentricity, notice the temperatures at the lowest eccentricity value and highest eccentricity value...basically no actual change.
Click to expand...

The article did say that mostly the different cycles do cancel eachother out. But when you are talking many millions of years it is possible that the cycles could line up in a way that cause big problems. Even our solar system has it's orbital cycles around our galaxy. Who can say for sure what causes our ice ages, but I'm betting the next one is not going to be a very good experience for whatever people are living on the Earth at the time.
 
look up time elapses of the sun and you will find interesting videos that show the true orbit and woble just by looking at the path the sun follows ..its like a cursive lower case L....ed lindiscalnin<coral castle builder>
made a pretty impressive sun dial
 
KilljoyKlown said:
After doing the install that was a very good inter active display. However, I'm not sure those graphs mean much to me without a lot of study on that subject. I was hoping for someone who was already knowledgeable on the subject could comment about it in simple easy to understand terms.:D
Click to expand...
I was thinking it could be like a train going around a corner, well the older ones used to press up against the rails and then slide across and later it repeats the rocking motion till it gets around the corner.
So as the Sun drags the Earth around the galaxy I would say the Earth is trying to go straight till the pressure builds up. So the rhythm starts up.
 
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