Scientists have done the equivalent of measuring triangles drawn in our three-dimensional universe by looking at a picture of the early universe (remember the cosmic microwave background from chapter 3?) and studying the spatial relationship between different points on that picture. And what they found was that the triangles they measured correspond to those of flat space. The other way in which we know that space is basically flat is by looking at the thing that causes space to curve in the first place: the energy in the universe. According to general relativity, there is a specific amount of
...more
