Solve this in 10 seconds.

... of course it's only a 2-dimensional image of a 3-dimensional net, so it's kinda hard to work your mind around it...

That actually gave me a headache.

What is 4D, anyway?

1-dimension is a line, right?

You can get a square (2 dimensions) by taking 2 lines and connecting them.

You can get a cube (3 dimensions) by taking 2 squares and connecting them.

Theoretically, if we had a 4th spatial dimension, taking 2 cubes and connecting them would give you a tesseract, a "4-D cube," which we can only see represented as a 3-dimensional net, much as you'd draw a 2-dimensional net of a cube.

The people on youtube who keep saying "u nubs 4 dimention is time wtf is this" annoy me to no end. Yes, your science teachers have told you the 4th dimension is time, it runs perpendicular to the other 3. This is a THEORETICAL fourth SPATIAL dimension, repeat SPATIAL, just like left-right, front-back, and up-down. The fancy undulating 3-D images you're seeing are just virtual representations of a 4-dimensional object. Yeesh.

Yay Tesser!

Wait, what?

oh.... god....
I don't even understand the possibility of this... I mean, I know it's theoretically impossible, but... I can't figure it out visually. And if I can't figure out a visual representation in my head, I just can't comprehend it...

My brain hurts now.

That is beyond my comprehension.

You wanna make your brain hurt even more? Look up penteract, hexeract, hepteract, etc...

Meh, once you get past tesseract it's the same idea; they're all in extra spatial dimensions we can't percieve, and they just get more and more complicated.

*attempts to wrap her visual mind around 5D, aka Tesseract connected to another Tesseract*

*mind implodes*