Figure 1: (Top) A sky map of the universe $13.7$ billion years ago. The different colors correspond to temperature fluctuations ($+/-200$ milliKelvin) in the cosmic microwave background. (Bottom) A convenient way to analyze this data is to take an angular spherical harmonic transform. The resulting temperature power spectrum is plotted against the order of the spherical harmonic. (The legend indicates the different collaborations that contributed to the data.)