Planet cracker

[Not another shrubbery]

Originally Posted by lwcamp

Just for reference, in the thread that you link to the relativistic spacecraft would have a kinetic energy of 3.6E22 J (if I did the math right). From the ever useful Atomic Rocket boom table
http://www.projectrho.com/rocket/rocket3x1.html , about 1/6 of the way down the page
that's about an order of magnitude less energy than the Chicxulub event that ended the dinosaurs. It would cause a lot of consternation to the people living there, but would not really damage an earth-like planet.

Handy little site... Bookmarked, and thanks for the link!