Obligatory "I'm not a physycist, but...". String theories require extra spatial dimensions (to total of 10, 11 or 26), but those dimension are so small and/or

Obligatory "I'm not a physycist, but...". String theories require extra spatial dimensions (to total of 10, 11 or 26), but those dimension are so small and/or looping so that we cannot detect them. Other approach is to treat our 3D space as slice of higher dimensional space. https://en.wikipedia.org/wiki/String_theory#Extra_dimensions https://en.wikipedia.org/wiki/String_theory#Extra_dimensions String theories have a lot of problems (biggest ones is that they are currently unverifiable using experiments and they do not give any meaningful predictions about our 3D view of universe), but many theoretical physicists are working on them.