The sun bounces up and down as it roams the Milky Way, and such wavering might have hurled showers of comets Earth's way that caused mass extinctions, including the one that killed the dinosaurs, a new study claims.

Such cosmic impacts might also have spread life to alien worlds, scientists speculate.

However, doubts have been raised about these suggestions.

To arrive at the comet showers idea, astronomers calculated the path of our solar system across the Milky Way as it circles the galactic core. As we pass through the densest part of the galactic disk, the gravitational pull of the surrounding gas and dust clouds dislodges comets in the Oort Cloud in the outer solar system, causing these icy goliaths to plunge toward the sun, the researchers said.

Link (http://news.yahoo.com/s/space/20080513/sc_space/earthextinctionsblamedoncosmicspeedbump)

Unkowable is always fun to speculate....only a time probe can tell us what was there 30 million years ago....or is that 60....

Hmmm, the sun's evil twin who's had a vendetta toward us since the beginning - or the speed bump...

I'm with Paul on this one, "As you cross the galactic plane, it's not like you go over a speed bump. The variation in any cratering rate would be very gentle, not in sudden pulses."

I'd bet that the tidal forces from the center of our galaxy against the far reaches of the Oort cloud are more than enough to dislodge members and send them hurtling towards the sun, or jupiter.

This could be a process which can help explain the regularity of mass extinctions.

The great news is were scheduled to cross the galactic plane in 2012!

The great news is were scheduled to cross the galactic plane in 2012!

No.
You have been misinformed.

I think 2012 will be a manmade disaster....on the economic front. The sea level rise engulfing New york will be later. Then we can blame the terrorists too....:D