Planet Jupiter not only affects our tides, it captures asteroids that could destroy all life on Earth. (But it missed one). If it wasn't for the asteroid that killed off the dinosaurs, there wouldn't be a "Rise of The Mammals".
Given that asteroids and comets are discovered passing "unseen", and too close for comfort, efforts of scientists should be directed towards early discovery of these missiles. I'd even approve of government subsidies!
==8-O
I wholeheartedly agree -- national defense presupposes no planet-wide extinction event.