Portal 2: Get Schrodinger’s Catch Achievement Easily
Start Chapter 6: The Fall, proceed through this level until you access a room called 1958 28. This room has a cube inside which is enclosed in a glass box. Blue Gel is streaming out from a pipe in a corner. Save your game as you enter the room – you might need to reset this puzzle if you fail later.
You have to create a portal beneath the gel and get over the crate so you can cover the cube with goo. The cube then begins to bounce around till it shatters the glass. Catch this cube before it hits the floor. To easily get the cube instead of rushing to catch it, wait for it to smash the glass then pour water over it. Remove all gel right before it jumps out of the box. Get into the box and retrieve it. If the cube doesn’t pop out of the box before you get a hold of it, it never touched the ground and your Schrodinger’s Catch Achievement / Trophy is unlocked.