Největší srážky ve vesmíru

Elliptical galaxies are the largest objects in the Universe - so, in principle, there can be no bigger collisions. But their colliding is rather strange, mainly because nothing really collides with anything. So how can objects so sparse that typically about 99.9999999999999999999999999% of their volume (there are 25 nines by the way) is empty space "collide"? How can we study such a collision when it takes hundreds of millions of years when our lifetimes are incomparably shorter? We will try to answer these and many other questions with the help of computer simulations, images from the world's largest telescopes, and some practical tools (though not life-size ones, of course).