The Universe we inhabit seems to be four-dimensional: the three dimensions of height, length, and depth, along with time.
Since an event is four-dimensional, the boundary of an event is a three-dimensional manifold.
You must remember we're working in a four-dimensional medium.
Neither has matter nor life any inclination or potency to behave in a four-dimensional manner.
Apparently sleep is unnecessary in the higher—the four-dimensional—body.
Our material universe is merely the intersection of tangled world lines of geodesics in a four-dimensional continuum.
I regret that it has been necessary for me in this lecture to administer such a large dose of four-dimensional geometry.
"Well, as far as we know, we live in a four-dimensional universe," the colonel started.
Thus there are three types of parallelograms in the four-dimensional manifold of event-particles.
Attempts have been made to construct drawings and models showing a four-dimensional body.