Need help in visu­al­is­ing four dimen­sions? Étienne Ghys has now cre­ated a series of videos for ‘teach­ing’ oth­ers how to visu­alise objects in the fourth dimen­sion (the spa­tial, not tem­po­ral, fourth dimension).

How on earth can we visu­al­ize such a thing? [The] chal­lenge in visu­al­iz­ing four dimen­sions is very sim­i­lar to the one that would be faced by a per­fectly flat crea­ture who lived in two dimen­sions and tried to visu­al­ize three, like the inhab­i­tants of Edwin Abbott’s Flat­land or the lizards in the page in Escher’s Rep­tiles. A cube or a sphere would be nearly unimag­in­able for the two-dimensional lizards, since they are unable to rise out of the plane.