magnetism and Indiana Jones At the beginning of Indiana Jones - Kingdom of Crystal Skull, some Russians (posing as US miliary) force Indy to search a warehouse for a crate. Lacking a compass, he throws a handful of gunpowder into the air, hoping the magnetic contents of the crate will pull the gunpowder toward it, showing him where the crate is in the warehouse. He does this twice with gunpowder, the cloud of gunpowder flies through the air toward the crate, underneath some lights, so its movement is visible. How strong would a magnet need to be to 'pull' a cloud of gunpowder (call the distance something like a football field, the warehouse looks pretty big in the movie)

I don't believe there's a magnet in existence today which could 'pull' a cloud of gunpowder the distance of a football field.

The reason: gunpowder contains no metals, and it is not paramagnetic.

Gunpowder's main ingredients are nitrocellulose and nitroglycerin (single or double based)

When Indy got closer to the crate, he used the buckshot from a rifle if I recall correctly - in that case I would guesstimate the same magnetic force as an MRI machine could do it with ease.