IN ANOTHER victory for big bang theory, astrophysicists have found hints of waves rippling through the sea of ghostly neutrino particles that fill the universe.
According to the theory, about a second after the big bang the universe became 鈥渢ransparent鈥� to the neutrinos that had already been churned out in copious quantities. These neutrinos then streamed freely through space, forming a so-called neutrino background. Variations in density across the universe, caused by the lumpy matter in the fireball of the big bang, would have created ripples in this background.
Roberto Trotta of the University of Oxford and Alessandro Melchiorri of the University of Rome in Italy have found indirect hints of these ripples. They simulated the effect the ripples would have on the microwave background radiation left over from about 300,000 years after the big bang, and on the distribution of galaxies today. Their results agreed well with the actual microwave background measured by NASA鈥檚 WMAP satellite and the distribution of galaxies mapped by the Sloan Digital Sky Survey. The work will appear in Physical Review Letters.
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鈥淲e were very surprised that present-day data allow us to single out very subtle effects like this,鈥� says Trotta. 鈥淚t鈥檚 wonderful that cosmology provides us with a universe-sized laboratory.鈥� But he stresses that better observations of the microwave background are needed to confirm the result. That might have to await the launch of the European Space Agency鈥檚 Planck satellite in 2007.
