The edit at 0:21 in this clip from "2001: A Space Odyssey" is often regarded as the best piece of film editing in cinema history.
It's a type of editing known as a "match cut" in which two objects are visually mated to establish metaphorical or chronological continuity between scenes.
Here we see the our ancestor's weapon morph into a Soviet satellite carrying MIRVs: Multiple Independently-targetable Reentry Vehicles, i.e. some sort of futuristic space-delivered nuclear weapon. The second and/or third satellites that come into view are competing American missile-delivery platforms.
None of this is in any way explicit in the movie, because the director Stanley Kubrick decided to delete titles explaining what in the heck was going on.
