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Has the Earth had it's wobble that causes the seasonal variation in solar energy in the northern and southern hemispheres for it's entire history? Is this variation evident in the geologic record or is it an open question? Could a meteor impact like that which killed the dinosaurs 66 million years ago have altered or created the wobble? Are there any factors dampening or increasing the seasonal wobble over time?

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  • $\begingroup$ Old question I realize but the axial tilt is what causes the seasons. The Wobble or precession has very little to do with the seasons, though it can play a role in ice age formation, over a much longer period of time. $\endgroup$ – userLTK Apr 26 '18 at 5:08
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Has the Earth had it's wobble that causes the seasonal variation in solar energy in the northern and southern hemispheres for it's entire history?

First it depends on how you define the "entire history" of the earth. There was a pre-earth that was hit by a Mars sized body. The collision fragments ultimately collapsed into the present earth and moon. Exactly how massive the pre-earth was and its orbital parameters are "unknown", meaning we know the parameters with much less precision than we know the parameters today.

Second there are two factors here. The seasonal (yearly variation) is caused mostly by the earth's axial tilt even though the distance between the earth and sun varies a bit since the earth's orbit is an ellipse rather than a circle. However the wobble of the earth is better better described as the precession of the earth's axis and it currently has a period of about 26,000 years.

Is this variation evident in the geologic record or is it an open question?

There is evidence in geological record for season and precession changes for the present earth.

Isotopic composition of glacial ice and ocean sediments reflect yearly temperature variations. The yearly temperature changes also cause seasonal changes in the distribution of the earth's weight which effect the precession and tilt.

Lava cools leaving imprints of the instantaneous magnetic field of the earth over geological time. The interaction of the magnetic field drift and reversal, the precession of the earth, the axial tilt of the earth, and the plate movement of the earth is not well understood. It is basically governed by chaotic system interactions. For example plate movement can cause earthquakes which are as of yet unpredictable.

Again what the precession and tilt were like for the "pre-earth" is mostly a mystery.

Could a meteor impact like that which killed the dinosaurs 66 million years ago have altered or created the wobble?

The impact that created the moon was with a Mars sized body and definitely effect the earth's precession and tilt.

Are there any factors dampening or increasing the seasonal wobble over time?

Moon damps the tilt over geologic time. The instantaneous flow of the liquid magma inside the earth may increase or decrease the precession and/or tilt, but as the earth cools the overall effect is to decrease both.

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  • $\begingroup$ I would up-vote if you clarified the difference between precession (wobble) and axial tilt and their influence on seasons. $\endgroup$ – farrenthorpe Jan 22 '17 at 5:40
  • $\begingroup$ @farrenthorpe - absolutely correct. I glossed over that very significant point. $\endgroup$ – MaxW Jan 22 '17 at 6:02
  • $\begingroup$ @MaxW: Did you consider that OP maybe thought of the nutation as wobble, and not the precession? The precession after all has no influence on the existence of the seasons, only when they appear in Earth's orbit. $\endgroup$ – AtmosphericPrisonEscape Jan 22 '17 at 16:43
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Has the Earth had it's wobble that causes the seasonal variation in solar energy in the northern and southern hemispheres for it's entire history?

The Earth wobble this is because it follows precession of equinox cycle and what you mean by wobble is that nutation happens. This is the torque T produce by angular velocity ò multiply by angular momentum L.

T = ò x L

One complete cycle takes 26,000 years on average and Earth was already there for 4 billion years in approximate base on carbon dating of rocks.

4,000,000/26,000 = 153,800 Precession Cycles

One cycle is enough to change different variation of season such as a month of Decemeber could face summer, winter, autumn and spring for the whole duration of precession. But what really impacts a total climate change is base on Milankovitch cycle which he deduce a statement that obliquity in axial precession from 22.1 to 24.5 degrees change so much climate as to compare to our present 23.5 degrees tilting that could happen for every 100,000 years.

100,000/26,000 = 3.8 or 4 Precession Cycles

153,800/4 = 38,450 Precession Seasonal Milankovitch Changes Aprox.

That's a lot of time to conclude that Earth had undergone seasonal variation for a very very long time. This already answer the question 2. Is this variation evident in the geologic record or is it an open question?

Could a meteor impact like that which killed the dinosaurs 66 million years ago have altered or created the wobble?

There are theories that linked the extinction of dinosaurs or meteor impact million years ago such as India-Eurasia Collision which created the modern Himalayan which causes flattening the pole and elongating the surface that changes orientation on axial tilting. Meteor impact theory might not be enough to killed the dinosaurs 66 million years ago. Climate should be seen as a major factor that makes extinction for a certain species. Yet smaller biodiversity are more likely to be adaptive to harsh climate condition enable them to survive and evolve later years.

Are there any factors dampening or increasing the seasonal wobble over time?

Wobble might increase or decrease over time when plate tectonics shifts postion. This is because the distribution of plates varies to the degree of rotation of the Earth. Such as in our generation 2000 AD, looking on geodetic Earth and bathymetric structure leads you to observe flattening of the pole and elongation at equator. The contribution of Himalayan mountain and subduction of the Pacific trench affects the speed rotation thus altering different cycles calculated such as precession and obliquity of the true pole.

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  • $\begingroup$ Earth's "Wobble" or precession has little to do with plate tectonics. It's a gravitational interaction between the Sun, Moon, Earth and to a lesser degree, the planets. $\endgroup$ – userLTK Apr 26 '18 at 5:03
  • $\begingroup$ It is actually unclear what causes the wobble but we cannot also assume plate tectonics has little to do with that. see reference en.wikipedia.org/wiki/Chandler_wobble $\endgroup$ – Kristian Factora Apr 27 '18 at 0:49
  • $\begingroup$ I'm sorry, but it's not unclear at all. It's the gravitational interaction between the rotational bulge and near by massive objects' gravitational pull. en.wikipedia.org/wiki/… astro.wsu.edu/worthey/astro/html/lec-precession.html plate tectonics simply don't have the energy to shift Earth's orbit, and they wouldn't explain the neat and tidy cycle as plate tectonics are more hit and miss, less cyclical. Mars has no plate tectonics and Mars experiences gravitational precession. $\endgroup$ – userLTK Apr 27 '18 at 5:23
  • $\begingroup$ Your link on the Chandler wobble is very interesting, but not relevant. Earth's precession is a large wobble (the entire axis or 22-24 degrees, or about 5,000 km), over 26,000 years. Chandler wobble is a small wobble, 30 feet over a period of 433 days. The Himalayas, for example, are irrelevant compared to Earth's equatorial bulge in terms of mass and gravitational influence. That's not to say they have no effect, but they're not the cause. $\endgroup$ – userLTK Apr 27 '18 at 5:28

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