Seifert Surface has built a tesseract in Second Life.

He built his model of the 4-dimensional cube as a Victorian home. Here’s what you’ll see if you visit the home in SL:

Not exactly astonishing. You appear to just loop around and wind up back where you started. But stay with me here.

A tesseract is the extension of a cube into 4-dimensional space, and it’s very difficult (if it’s even possible) for humans to conceptualize it. Try to think of it geometrically, not realistically. As the square is to a line, and a cube to a square, so is the tesseract to the cube.

Another way to understand it is to imagine the vertices. In a square, each vertex extends in two directions. In a cube, each vertex extends in three directions. What happens when you add another dimension and extend the cube’s vertices in four directions? That’s a tesseract.

Hard to conceptualize, right? Take another look at someone walking through Surface’s tesseract house, this time with the camera zoomed far out:

Is it making more sense? Of course, this isn’t really what a tesseract looks like, but it’s an effective illustration. As in a cube, where each side of its component squares adjoin another side, each face of the tesseract’s component cubes adjoin another face. To represent a 4-dimensional object in 3-dimensional space,* the cubes move so their faces can adjoin.

Meg and Charles Wallace Murray never had it so good.

If you really want your mind blown, here’s a functional tesseract version of Rubik’s Cube.

SL users can portal to Surface’s “Crooked House” here.

More info here.

Still too pedestrian for you? A 5-dimensional Rubik’s Cube here.

*Technically, this is representing a 4D object in a 2D representation of 3D. But lets keep it simple.