Any Geophysicist Out There?

“How manyu Irishmen does it take to change a lightbulb?

One to hold the bulb and another four or five to drink until the room begins to spin.

Slánte!”

“When the spinning gets real bad I sleep near the side of the bed with one foot on the floor. I think it helps or maybe it just makes it faster to get out of bed to puke.”

“If you're outside, it's a good idea to grab a nearby treetrunk, or lacking that, sink your fingers into the ground and grip the turf so that you aren't slung off into space during the night.”

“Anybody ever get the end-over-end bedspins? Those are the worst...”

“"how different planets behave... spinning backwards, sideways, etc."
Tilt

I'm still looking for directions.
Backwards?
sideways?
up?”

“DANGER! DANGER, nowslimmer.”

“Soooo...

Does our axial tilt vary over time? I don't see why it wouldn't. Nothing else in the Universe appears to be static. I'm thinking that either the timescale would tremendously long... or the cause would be have to be cataclysmic. As in "When Worlds Collide," for the Sci-Fi example, <G>

It's well known that the earth slowly 'wobbles' like a spinning top.... the 'Precession of the Equinoxes'. The planet completes one of these 'wobbles' every 26,000 years. The North Pole points towards Polaris at the present time, and will again... in another 26,000 years.

But I don't remember seeing a changing axial tilt being discussed... and a web search isn't turning up anything.


As for the possible implications of such a change, seasons could become less pronounced... or more pronounced. With less axial tilt, seasonal variations would be less. With more of a tilt... parts of the planet could become unrecognizable in extreme cases: glaciers could appear where there were once jungles and vice versa.

Bathing suit and snowshoe weather, <G>”

“proofreading? what proofreading?”

“I think I remember reading how North Africa was transformed from a forest into the worlds largest desert by a 1 degree shift in the earths axis. I saw something once about how the moon plays a crucial role in keeping the earths rotation from fluctuating to wildly, but the moon is getting farther and farther away from earth every year and in the distant future will leave earths orbit possibly causing the earths axis to fluctuate by as much as 90 degrees.”

“this is why i wanted ti email - cause as much fun as some of the responses were - i really just want the questions answered by someone who's really in the know....

okay - that sounded really snotty :) not meant to!

okay - so I've read most of the stuff you guys dug up - Tilt - thanks for your answers

Okay - link between shift in the degree of earth's axis and the ice ages...any thoughts?”

“I think the many of the ice ages were caused by volcanic eruptions or meter strikes. Both through dust high in to the atmosphere, blocking the Sun's ray, causing temperatures to drop.”

“theories they are...

Hey Tilt - is it possible to track the earth's degree of tilt on its axis for the past? If so, how? Can you send some links my way while I continue to do my own research?”

“What Causes the Ice Ages?
Scientists have done extensive studies of glaciers and their movement, both past and present. This includes features created by glaciers, both erosional and depositional. However, a widely accepted theory for the causes of the ice ages has not yet been established. They do agree that there are some very good possibilities, including:

Changing of continental positions (plate techtonics);
Uplift of continental blocks;
Reduction of CO2 in the atmosphere; and
Changes in the earth's orbit.
For more on these possibilities click here

Because the moving of plates is extremely gradual, it cannot explain the glacial and non-glacial climates that took place during the Pleistocene epoch.

Today, scientists think that the changes in climate during the Pleistocene may have been caused by variations in the earth's orbit. This idea or hypothesis was first developed by a Yugoslavian scientist, Milutin Milankovitch. He believed that the amount of solar radiation is the most important factor in controlling the earth's climate. The amount of solar radiation would vary based on the following:

Variations in the shape of the earth's orbit around the sun (referred to as eccentricity)
Changes in the angle that the axis makes with the plane of the earth's orbit (referred to as obliquity)
The wobbling of the earth's axis (called precession)
Milankovitch used these factors to figure the amount of solar energy in connection with the earth's surface temperature to correlate changes in the climate during the Pleistocene epoch.

It is worth noting that these variables cause little or no change in the amount of solar energy hitting the earth. The impact is caused by the degree of contrast between the seasons. For instance, a milder winter in the middle to high latitudes means greater snowfall, while cooler summers would mean a reduction in the snowmelt. Although Milankovitch did his studies in 1938, modern scientists currently back up his theories. The studies were very detailed and mathematically complex, but the conclusions were in agreement with the theory. They found that the changes in the earth's climate over the last several hundred thousand years are directly related to changes in the geometry of the earth's orbit. Specifically, they stated "It is concluded that changes in the earth's orbital geometry are the fundamental causes of the succession of the Quaternary ice ages."”

“well hot damn - guess I'm not such a dummy after all - it's good to see that some of my kernals of ideas aren't too far out in left field! wooowhooo!

now - how is the position ofthe earth's axis measured in prehistoric times?”

“must hike - can you post the source of the bit of info? is there a link?

ta”

“Ice Ages, eh?

a-Ha! Milankovitch cycle...

hmmmmm... obliquity cycle....



Oh, Here's the disclaimer I had at the beginning of the blather I almost posted at 2 AM.... I'm sure it's still applicable, LOL

~~~~~~~~~~
I've been thinking about all this spinning we have going on in the solar system, and how it began (speaking purely as computer programmer who really doesn't know #&%!$ but can sometimes fake it).

Well, Hell -- I'll take a shot at it (keeping in mind that these explanations are worth exactly what you paid for them, LOL). And if I screw up, I'm sure someone here will be kind enough to set me straight.
~~~~~~~~~~”

“http://aa.usno.navy.mil/faq/docs/seasons_orbit.html

"There is another important cycle that has the potential to affect the Earth's climate; it is a 41,000-year variation in obliquity, the tilt of the Earth's axis with respect to a direction perpendicular to its orbital plane. This variation is different from precession - the two motions are at right angles to each other - and astronomically is a much smaller effect. The obliquity varies by only a few degrees back and forth, and the current value of 23.4° is near the middle of the range. However, climatologically, the obliquity variation has the potential to have a fairly direct effect on seasonal extremes. After all, it is the obliquity that causes our seasons in the first place - if the Earth's axis were perpendicular to its orbital plane, there would be no seasons at all."”

“uh oh, It's starting to get a bit thick....


CLIMATE, ASTRONOMICAL FORCING, AND CHAOS

Fundamental to what we feel are some of the potential breakthroughs that may be realized by a Pangean coring transect is the record of Milankovitch cyclostratigraphy preserved in the Triassic-Jurassic basins. Because the underlying celestial mechanics is relatively arcane, but necessary for the understanding of the science issues, and the geological record has potential to help constrain celestial mechanical issues, a short review of the relevant concepts is presented here. More in-depth treatments, from which this is derived, can be found in Laskar (1990, 1999), Laskar et. al. (1993), Berger et. al. (1992), Berger and Loutre (1990, 1994) and Hinnov (2000).




They do mention possible evidence in the geologic record....”

“And may the Force be with you.”

“The tilt of our Earth's axis has varied throughout geologic time. As you know, the earth spins on that axis, and as stated above, that axis has a wobble. Well, that wobble has a slight wobble, and even that slight wobble has a slight wobble. Milankovich's ideas were far ahead of his time, kind of like the concept of plate tectonics, and have been proven to be valid mechanisms since.

On a brighter note, the spin of our Earth around that axis is slowing down ever so gradually. Why? Ocean currents, atmospheric conditions, etc., and even the convection currents in our upper mantle/asthenosphere. Back in the Paleozoic, there were more than 360 days to a year because of the faster spin. Who knows how much harsher the weather was like back then, and how less it may be far in the future?”