Problem set due in class, May 14. Show your work, neatly.

1) At approximatly what time was the Universe the density of water? Was it matter or radiation dominated?

2) Planck's law for blackbody radiation gives an intensity, I, as a function of wavelength and temperature. The Universe expands with scale factor R, the intensity I varys as R^-5 while wavelength goes as R. Show that T goes as R^-1. At what wavelength does the blackbody curve of the Universe reach a maximum for 2.7K?