What role do orbits play in Earth's climate change?

[Bobby R]

There is a warming cooling pulse in Earth’s life exemplified by tracks left from ancient glaciers to deserts once flush with flora and fauna. When did all this occur and why? Here’s what I think:
Moon orbits Earth, Earth orbits Sun, Sun orbits Milky Way, Milky Way orbits ?
Each event takes longer to complete. For the Sun to orbit the Milky Way it takes roughly 28 million Earth years. In fact, I don’t believe the Sun has made more than 20 orbits since Earth was created. The problem arises when trying to determine what occurs with other stellar objects in our Galaxy during the Sun’s orbit.
For example, to blame global warming on puny little humans is most likely a fine case of naiveté. I would like to look with geologists at our sedimentary layers at 28 million year intervals to see possible repeat activity. Unfortunately, finding something caused during one of the 20 Sun’s Galaxy orbits among the millions of Earth’s Sun orbits and determining which was which is near impossible. However, to rule out the Sun and it’s travel may remove a signature from the portrait. As our Galaxy nears another, when they pass does ours bounce away? Did the shock start Continental drift? Do all stars in our galaxy orbit in the same direction? Is one star orbiting faster than another? Hubble should be able to answer these questions and help put new light on our Solar System’s future. To set some idea of what vast fluctuation can occur look at Earth’s annual weather. Predict what will happen six months from now! Impossible! However, afterwards we know what happened and why it happened. So when scientists analyze space what questions are they asking. More importantly, what questions are they able to answer.

 

[Jonny_trigonometry]

I wouldn't guess that there are 28 million year repeating cycles based on the sun's revolution around the center of the galaxy. This is because when it goes around once, the place where it was before is not the same. The local neighborhood of the sun is pretty much the same all the time, because the stars close to it are moving at roughly the same speed around the center. The main reason why the galaxy is a spiral is because stars orbit at different speeds at different altitudes from the cetner. The ones close to the center move faster, and ones further away move slower. this is just one scale of viewing the dynamics of the galaxy though, smaller scales give many more possibilities.

Continental drift doesn't have much to do with the orbit of the sun around the center of the galaxy. Geologists think it is caused by the convection currents and so forth in the mantle, and the angular momentum of the land and water via rotation of the earth. Meaning, the mass of the water and land will tend to get a more even distribution worldwide rather than having water on one side and land on the other like with pangea. For example, when you spin a bucket of water, it evenly creeps up the sides of the bucket, it doesn't all bunch up in one spot. The mechinism that caused contenental drift could be related to when the atmosphere was able to condense into liquid water on the surface, thus being displaced by the topology of the land and getting an uneven distrubution of mass, and an uneven distribution of crust cooling which changed around the convection currents in the mantle.

 

[Tide]

I believe it takes the Solar System considerably longer than 28 Million years to "orbit" the galaxy (it's about 250 Million years!).

 

[ek]

I believe it takes the Solar System considerably longer than 28 Million years to "orbit" the galaxy (it's about 250 Million years!).

An order here, an order there...



And galaxies do not "bounce" off each other. They are not solid entities. It is quite probable that all the hundreds of billions of stars in each galaxy will not touch each other at all. Of course, being affected materially and being affected gravitationally are not the same. The two galaxies WILL be ripped apart gravitationally, even without physically touching.

And if the Milky Way had had a recent encounter with another galaxy, we'd know it. We would no longer be a spiral. We would be some gravitiationally warped shell of a spiral. Of course this does not mean that this did not happen billion years ago, perhaps it has been long enough that the spiral arms have regenerated, I'm not sure. My knowledge of spiral arm mechanics is pretty limited.

In any case, this will happen in the (far) future. M31 is headed right for us and our repective beautiful spirals will be disfigured by the "collision".

 

[Andre]

I would like to look with geologists at our sedimentary layers at 28 million year intervals to see possible repeat activity.

Indeed that's what geologists are doing, trying to find patterns, to what's going on. There are many discernible cycles but most without a clear period. laskar has shown that the Earth orbit pertubations are chaotic and show constant changing cyclicity. Tectonics change Earth surface continuously showing random climate changes as the continents change the lattitudes.

There is one distinct statistical significant cycle though lasting 62 million years, the abundance of species and periodical extinctions:

http://news.nationalgeographic.com/news/2005/03/0309_050309_extinctions.html

 

[selfAdjoint]

In the current issue of Science there is a paper on the correlation between water vapor and CO2 during the ice age, and they routinely allow for orbital Milankovitch cycles, which they find to be significantly rpresented in ther statistics. So maybe the chaotic scale is longer than a few million years?