  We present full sky microwave maps in five bands (23 to 94 GHz) from the WMAP
first year sky survey. Calibration errors are <0.5% and the low systematic
error level is well specified. The 2<l<900 anisotropy power spectrum is cosmic
variance limited for l<354 with a signal-to-noise ratio >1 per mode to l=658.
The temperature-polarization cross-power spectrum reveals both acoustic
features and a large angle correlation from reionization. The optical depth of
reionization is 0.17 +/- 0.04, which implies a reionization epoch of 180+220-80
Myr (95% CL) after the Big Bang at a redshift of 20+10-9 (95% CL) for a range
of ionization scenarios. This early reionization is incompatible with the
presence of a significant warm dark matter density. The age of the best-fit
universe is 13.7 +/- 0.2 Gyr old. Decoupling was 379+8-7 kyr after the Big Bang
at a redshift of 1089 +/- 1. The thickness of the decoupling surface was dz=195
+/- 2. The matter density is Omega_m h^2 = 0.135 +0.008 -0.009, the baryon
density is Omega_b h^2 = 0.0224 +/- 0.0009, and the total mass-energy of the
universe is Omega_tot = 1.02 +/- 0.02. The spectral index of scalar
fluctuations is fit as n_s = 0.93 +/- 0.03 at wavenumber k_0 = 0.05 Mpc^-1,
with a running index slope of dn_s/d ln k = -0.031 +0.016 -0.018 in the
best-fit model. This flat universe model is composed of 4.4% baryons, 22% dark
matter and 73% dark energy. The dark energy equation of state is limited to
w<-0.78 (95% CL). Inflation theory is supported with n_s~1, Omega_tot~1,
Gaussian random phases of the CMB anisotropy, and superhorizon fluctuations. An
admixture of isocurvature modes does not improve the fit. The tensor-to-scalar
ratio is r(k_0=0.002 Mpc^-1)<0.90 (95% CL).
