We all know we live in three-dimensional space. But what does it mean when people talk about four dimensions? Is it just a bigger kind of space? Is it "space-time," the popular idea which emerged from ...

Tie a trefoil knot in a piece of string, seal the ends together, and try to wiggle it free without cutting. In three-dimensional space, the knot holds firm. Add a fourth spatial dimension, however, ...

Mathematicians say knots cannot exist in four-dimensional space because the extra dimension allows a rope to move around itself and untangle, revealing surprising insights into geometry and topology.

Zsuzsanna Dancso does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond ...