Transcript: The most sensitive test of the curvature of space uses the cosmic microwave background radiation. These microwaves were released three hundred thousand years after the big bang. The fluctuations in the microwave background were imprinted with a certain angular size, and depending on the shape of the universe, the fluctuations are either magnified or demagnified as they travel through billions of lightyears of space and billions of years of time to reach us. The universe therefore can act as an enormous lens. Careful observations of the fluctuations with NASA’s WMAP satellite shows that there is no space curvature. There is no magnification or demagnification of the fluctuations traveling through vast amounts of cosmic time. The universe therefore is very close to being flat.