In mathematics, four-dimensional space (“4D”) is a geometric space with four dimensions. It typically is more specifically four-dimensional Euclidean space, generalizing the rules of three-dimensional Euclidean space. It has been studied by mathematicians and philosophers for over two centuries, both for its own interest and for the insights it offered into mathematics and related fields.
Algebraically, it is generated by applying the rules of vectors and coordinate geometry to a space with four dimensions. In particular, a vector with four components (a 4D vector or 4-tuple) can be used to represent a position in four-dimensional space. The space is a Euclidean space, so has a metric and norm, and so all directions are treated as the same: the additional dimension is indistinguishable from the other three.
when we put on those 3-D glasses, we see a world that has shape, a world that we could walk in. We can imagine existing in such a world because we live in one. The things in our daily life have height, width and length.
In his theory of special relativity, Einstein called the fourth dimension time, but noted that time is inseparable from space.
Einstein described gravity as a bend in space-time. Today, some physicists describe the fourth dimension as any space that’s perpendicular to a cube — the problem being that most of us can’t visualize something that is perpendicular to a cube
Researchers have used Einstein’s ideas to determine whether we can travel through time. While we can move in any direction in our 3-D world, we can only move forward in time. Thus, traveling to the past has been deemed near-impossible, though some researchers still hold out hope for finding wormholes that connect to different sections of space-time