We spread some iron filings evenly inside a small plastic box (CD container). If we bring a magnet close we notice that the iron filings move and follow the movement of the magnet. If we place a magnet below the box, we notice that the iron filings align themselves according to a characteristic formation (see the drawing). In particular, the filings group around the two poles of the magnet: here the filings spread out in a ray; some filings lie flat on the surface while others stand either perpendicularly or obliquely. Space in the presence of a magnet acquires a new property: it becomes the base of a magnetic field. The disposition and orientation of the iron filings describes this. We obtain a representation of this if we place a sheet of acetate in a box (a flat transparent surface with small supports would be useful). If we change the position or even only the orientation of the box, we obtain the same representation. This is therefore characteristic of the effects of the magnet when considered in the surrounding space.
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