Template:Moser spindle visual proof.svg

Proof without words that the chro­ma­tic number of a plane is at least 4:

•	Each edge is of unit length.
•	As vertices of each triangle is connected to one another, they must be coloured differently. The top and bottom vertices of each lozenge can be the same colour.
•	However, the bottom edge connecting the bottom vertices (purple) connects two vertices of the same colour, proving the impossibilty of a 3-colouring.

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