Our universe appears to be “flat” — like a sheet of paper stretching to infinity. If so, that would mean it’s finely balanced — a sort of “just right.”

Albert Einstein’s theory of gravity, known as General Relativity, allows the universe to assume one of three basic shapes. One shape is “closed” — like a sphere. In such a universe, two lights beamed out parallel to each other eventually would circle all the way around to their starting point.

Another possible shape is “open” — curved like a saddle or a really big Pringles chip. The light beams in such a universe would move away from each other for all time.

Finally, there’s a “flat” universe. Two light beams would remain parallel to each other forever — never spreading apart or coming together.

The actual geometry is dictated by the density of the universe — how much matter is packed into its space. In a closed universe, there’s enough matter for its gravity to cause the universe to collapse. An open universe would expand forever. And a flat universe would be balanced — neither collapsing nor expanding without end.

So far, the evidence supports a flat universe, although the matter isn’t completely settled.

Not surprisingly, it’s all pretty complicated. The flat universe is flat in three dimensions — after all, we see galaxies in every direction. To a cosmologist, it all makes sense — a “flat” universe that’s the same every way we look at it.

Script by Damond Benningfield