Posted on 06/13/2003 6:10:30 PM PDT by blam
Thanks. (It keeps the Feds guessing)
You mean Mungo Man?
There do seem to be cycles (Maybe celestial cycles?). Some of the cycles are so far apart that we have not noticed them yet.
I did some googling as I posted that piece and the most recent, consistent, numbers I came across indicate that the "wobble" causes us to cross the plane every 35 million years. The full cycle (all the way south of the plane to all the way north and back) is therefore around 70 million years. There's also a cycle where we traverse a particular arm of our galaxy every one hundred million years. Right now we're approaching the middle of the plane of the galaxy, from the south to north, and are in the middle of transiting the Orion arm of our galaxy. Is that the point at which we're in most danger (some suggest higher radiation levels mid plane and mid arm) or are we in most danger when we're out in the thin parts? Identified mass extinctions would indicate that we're approaching maximum risk (give or take a few million years), but what have we missed? What nasty things happen between mass events? Maybe we're in danger of big hits right now, but those are merely punctuation marks on otherwise good times. Maybe the periods between those times where there could be big events are simply general misery all the time, with no big events, good or bad (think snowball Earth)? Who knows.
I love cosmology! It really let's us know how little we know and how much there is yet to understand.
The ugly truth is that we live in a chaotic galaxy.
In our solar system there are a few large bodies (Sun, Jupiter, and the planets), and lots of smaller objects (asteroids, comets, small moons etc.) The small objects are difficult to find, and often go unnoticed.
The same ratio of large to small objects also applies to the galaxy. For every star we can detect, there are thousands of smaller, dimmer objects we can't see. Many of them have been ejected from star systems and are wandering about the galaxy.
As long as we remain earthbound (as a civilization), we are just a target.
Yup. this is the 1159BC event recorded in the tree rings worldwide.
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Blam, I do believe that smaller impacts are responsible for decline of ancient civilization as well as migrations patterns. This is on top of volcanic eruptions, earthquakes, and climate changes.
Nature has shaped the course of civilizations more extensively than political or military events. This is indeed something many scholars refuse to confront because they staked so much of their credibility on the rise and fall of civilization mostly by human events.
Especially in ancient times, what human could do is puny in comparison with what nature could unleash. It is even true today. We can just take care of minor natural events. However, we are still at the mercy of major natural events.
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