In astronomy and
observational cosmology, The
BOOMERanG experiment (
Balloon Observations Of Millimetric Extragalactic Radiation ANd Geophysics) was an experiment which measured the
cosmic microwave background radiation of a part of the sky during three sub-orbital (
high altitude)
balloon flights. It was the first experiment to make large, high fidelity images of the CMB temperature anisotropies, and is best known for the discovery in 2000 that the geometry of the universe is close to flat, with similar results from the competing
MAXIMA experiment.