Q: Can a human being survive in the fourth dimension?

Physicist: Nopers.  But to understand why, it’s important to know what a dimension is.

When someone says “we live in the third dimension” what they should really say (to be overly-precise) is “the universe we inhabit has three spacial dimensions”.  There are a few ways that you can tell that you live in a three dimensional world.  The easiest is to try to come up with as many mutually-perpendicular directions as you can; you’ll find three without too much trouble, but you’ll never find a fourth.

These three directions are mutually perpendicular and and no new direction can be perpendicular to all three.

If you’re feeling terribly clever, you’ll find lots of other examples that demonstrate the three (and not two or four) dimensionality of our universe.  For example, if you can tie a simple knot then you definitely live in three or more dimensions (no knots in 2-D) and if you can make a Klein bottle then you definitely live in four or more dimensions.

In 2-D you can’t tie a knot without the rope passing through itself, and in 3-D you can’t build a Klein bottle without the same problem.

A dimension is a direction.  Living in more dimensions means having more directions you can move in.  There are many weird physical consequences to living in more dimensions, but the one you’d notice first (if you were somehow to suddenly to appear in a 4-D universe) is immediate death.

An actual 2-D creature would collapse in 3-D.  What it considers to be its insides just looks like more surface to we 3-D folk.

If a paper doll (two-dimensional being) were suddenly brought into three dimensional space all of its innards would become outtards.  Similarly, there is nothing whatsoever supporting your body in a fourth direction, so if you were to find yourself with a few extra dimensions your insides would follow the path of least (zero) resistance and fall out.  It would be super gross, but would make no more of a mess than an infinitely thin oil slick.  Any local 4-D critters probably wouldn’t even notice.