Comment by mystified5016

Consider a bubble rising to the surface of a pond. As the bubble breaches the surface, it extends beyond the surface and expands as the pressure reduces.

If you consider the surface of the water as a 2D plane, the bubble expands into a third dimension perpendicular to the others. The bubble's surface is made of the same water as the surface of the pond, and there is no hard boundary between them. The bubble pushes part of the 2D plane into the third dimension, which results in the water having more surface area than the total possible area of the 2D plane.

Area (space) has been created without creating matter or energy. The surface is simply extended into an extra spatial dimension.

The way I like to interpret the big bang is as a higher dimensional structure folding or knotting itself such that a bubble is forced into a 3D space. The bubble expands and thus creates more volume than is possible in the lower-dimensional surface the bubble was formed on. This is my ill-informed interpenetration of M-theory.

Dunno why, but much of mathematics and the universe in general makes much more sense to me when viewed in terms of dimensionality. Our universe is 'just' a 4D slice of a higher dimensional structure, and I find a certain kind of beauty in that. In another life, I'd have been a string theorist