Originally Posted by
katara
If we're really getting into specifics here, the original explosion is also bullshit. Shockwaves don't work like that in space. It'd be a sphere, not a disc.
A Death Star is nowhere near the mass of our moon. That said, the damage would still be significant.
Our moon is about 3475 km in diameter. If that hits us, you're probably looking at a total extinction event.
Chicxulub was somewhere between 11-81 km across, and that really fucked us up. That caused massive atmospheric change, practically global environmental chaos, enough to wipe out many major species.
Death Star 2 is 160 km across, so if a large chunk of that fell onto a planet (speed of object not withstanding), I think we can safely say it'd be similar to Chicxulub.
Gravity is also necessary to make bombs drop. This franchise isn't particularly great when it comes to the 'science' part of 'science fiction'.