As our sphere orbits Sun,
So Sun orbits Black Hole
At the center of our galaxy,
As eternity unfolds.
In a quarter billion earthly years
Our solar system circles round,
Weaves thru the mid galactic plane
Where other stars are densely found.
Fifteen times since life began
We have circum-rotated,
And ten times in each orbit grand
The planet’s devastated.
Our Sun’s own cloud of comets
On the solar system’s edge
Are jostled from their sedate paths,
Fall inward from their ledge.
With corresponding timing
Ancient craters have been found.
It seems Earth’s plagued with comet storms
As the cosmic year spins round.
Bombardments are not good for life.
Half a dozen times
Mass extinctions cleared our world
As doomsday peals chimed.
Things have been quiet for some time
Since dinosaurs disappeared.
The Sun careens past cosmic dust,
Dark matter, stars, and fears.
Such grand cosmic motion can only be estimated, and the number of Earth’s mass-extinctions depends on your definition, but our movement through the galaxy makes me feel very small and oblivious.
space.com on extinctions and comet strikes
Wikipedia on Galactic year