  We propose a new model for the extended Ly alpha blobs found recently at high
redshift z ~ 3. The observational properties of these blobs are; 1) the
observed Ly alpha luminosities are ~ 10^{43} h^{-2} ergs s^{-1}, 2) they appear
elongated morphologically, 3) their sizes amount to ~ 100 kpc, 4) the observed
line widths amount to ~ 1000 km s^{-1}, and 5) they are not associated with
strong radio-continuum sources. All these observational properties seem to be
explained in terms of galactic winds driven by successive supernova explosions
shortly after the initial burst of massive star formation in the galactic
centers. The observed number density of Ly alpha blobs (~ 3.4 x 10^{-5} h^3
Mpc^{-3}) may be explained if their present-day counterparts are elliptical
galaxies with a luminosity above ~ 1 L^*.
