[Mark Felton]

Actually a 4-dimensional cube would be just an everyday cube. The 4th dimension being time and orthogonal to the space dimensions.

If it exists for any amount of time then it is 4-dimensional.

[Alamo-Girl]

Thank you for your reply!

There are two worldviews on the subject. One sees three spatial dimensions evolving over time.

The other sees four dimensions, one of which is time - x,y,z and t for time.

The first view allows no additional temporal dimensions, the second does, e.g. Vafa's F-theory and Wesson's 5 Dimensional Relativity, 2 Times.

The second view is also expressed in Max Tegmark's Level IV Parallel Universe:

“A mathematical structure is an abstract, immutable entity existing outside of space and time. If history were a movie, the structure would correspond not to a single frame of it but to the entire videotape. Consider, for example, a world made up of pointlike particles moving around in three-dimensional space. In four-dimensional spacetime — the bird perspective — these particle trajectories resemble a tangle of spaghetti. If the frog sees a particle moving with constant velocity, the bird sees a straight strand of uncooked spaghetti. If the frog sees a pair of orbiting particles, the bird sees two spaghetti strands intertwined like a double helix. To the frog, the world is described by Newton’s laws of motion and gravitation. To the bird, it is described by the geometry of the pasta — a mathematical structure. The frog itself is merely a thick bundle of pasta, whose highly complex intertwining corresponds to a cluster of particles that store and process information. Our universe is far more complicated than this example, and scientists do not yet know to what, if any, mathematical structure it corresponds.

“The Platonic paradigm raises the question of why the universe is the way it is. To an Aristotelian, this is a meaningless question: The universe just is. But a Platonist cannot help but wonder why it could not have been different. If the universe is inherently mathematical, then why was only one of the many mathematical structures singled out to describe a universe? A fundamental asymmetry appears to be built into the very heart of reality.”

Tegmark, Max, “Parallel Universes,” Scientific American, May, 2003