Hollywood likes to slow down the process so you can appreciate all the tiny pieces in motion. In reality, you'd see a flash, and then nothingness. Debris moves at least 17,000 miles per hour, since that's the speed necessary to maintain a low Earth orbit, and that's 10 times faster than a bullet. According to The Aerospace Corporation, one of the few organizations that tracks space debris, an on-orbit collision would look "more like an explosion of each object, as if they passed through each other and exploded on the other side." Orbiting objects are moving faster than shockwaves can go, so when two of them collide they essentially shoot through each other and then feel the impact from the shockwaves. That means after the collision happens, you'd see each piece explode seemingly on its own as the shockwave hits it. But all of that would occur so fast that you wouldn't even know what had happened. Whatever object you were seeing before would almost seem to disappear.