evolution by collision?

[fantastical]

who agrees with the theory that since the earth is oscillating back and forth across an arm of the Milky Way galaxy (every 26 million years or so, proven by gravitational calculations), and it inevitably must collide with interstellar debris in the cluttered centerline of the arm (since gravitational force causes the center to be most occupied), that our planet could likely "gain" new, never-before-seen material as a consequence of these collisions with certain "space agents?"

In another word, could evolution occur from our planet picking up new material from these collisions, thus forming new life? what other facts could support/refute this theory?

[stoo_pid]

The hypothesis you refer to is known as Panspermia.  One of the best known supporters of panspermia was British astronomer Fred Hoyle.  If I remember correctly Francis Crick (as in Watson & Crick) is also a great believer.  Carl Sagan wrote quite a bit on it as well.

Nowhere near enough space here to discuss the theories but bung that term in google & you'll have plenty to read through.

[magicdice]

"and it inevitably must collide with"

ha, yeah. think about this: the chances of 2 galaxies colliding is very similar to the chance of 2 wasps flying around the albert hall crashing in to each other. not that likely

once these 2 wasps have flown in to each other, it's still bloody unlikely that any of the planets within these wasps will collide. so the net probability of 2 planets/stars colliding with each other is about equivalent to 2 wasps flying around europe flying in to each other.

europe's pretty big. wasps can fly fairly high. enough said

[fantastical]

3 points: first Interstellar debris consists more of just plantets. It can be asteroids, meteors, and whatever else. Second, there is a gravitational attraction that pulls these things into each other. Third, we are living (earth, that is) at a very fortunate time. The earth is situated at the very edge of the galaxy's arm right now (proven) that a collision doesn't pose much of a threat (since it is very sparse at the edge compared to the center)

Completely dismissing this theory is like dismissing some of the fundemental laws of nature; gravitational force being one of them. True, it is not "likely" that we would collide with anything...right now. Start talking about statistics with time being millions of years, and its probabilities, all of a sudden Europe becomes very VERY cluttered with bees.

[fantastical]

Another thought: it's been argued that Earth, in its days before its accretion into a planet, collided with an asteroid of some sort with a lot of frozen water on it. Touching down on Earth's fetus, it deposited this huge amount of water overwhelming earth with this new element. The entire earth was covered by water, before a land mass began to emerge, and all the other fundemental elements (where'd they come from, eg nitrogen, carbon etc.)

Check out this site for some more insight to these things: http://mb-soft.com/

[Dagman]

It's been said somewhere the Earth may have passed through the tail of a comet and been showered with enough dust to set off a chemical reaction that created life. Might have been Carl Sagan that suggested it. I think he referred to it as a life creating soup! 

[BillyBB]

As I understand there can be slow change through breeding and also faster change through mutation, either genetic anomalies or through outside influence such as environmental change.

[BillyBB]

Hmm, there is a more pertinent question elsewhere for this answer which makes no real sense here.

Sorry, it's late.