Collisions between the cosmos and other universes may have left all the "bruises" on a map of ancient cosmic radiation. Our universe is believed to have spread rapidly in a process called inflation in the first moments after the Big Bang. Some physicists suspect inflation is occurring, the implementation in some regions while other stops as part of the universe we live in this picture, called eternal inflation, new universes are constantly popping into existence like bubbles in a vast, vast sea of \u200b\u200bspace-time.
Many of these universes should be taken to each other as soon as they are. But universes born together could crash if they are expanding faster than the space between them.
If our universe was beaten by another bubble universe, the impact statement would be colossal explosions of energy. If this happened before inflation ended in our review of the universe, could leave a mark that still might be detectable. Now Stephen Feeney, of University College London and colleagues say they may have discovered traces of its kind in the cosmic microwave background (CMB), the all-sky glow that comes from photons emitted when the universe was less than 400,000 years age.
Hot and Cold
A collision could alter the duration of inflation continued in the area of \u200b\u200bimpact. If the expansion continues for longer than it should, the density of matter in the impact zone would be lower than the surrounding regions. These show the CMB cold spot. By contrast, a shorter period of inflation could create a warm place in the CMB.
The team calculated the probable temperature profiles for this purpose and have searched the CMB data from NASA's Wilkinson Microwave Anisotropy Probe.
The search turned up four circular patches, each covering an area of \u200b\u200bsky equivalent to at least eight full moons (arxiv.org/abs/1012.1995 and arxiv.org/abs/1012.3667). One is a cold place that had been cited as evidence of another universe that interact with ours.
"There is no obvious explanation of the features dull," says team member Matthew Johnson of the Perimeter Institute for Theoretical Physics in Waterloo, Canada.
Calling Cards
If collisions with other universes, in fact, creating these patches, which should have left other calling cards in the CMB, as characteristics that distinguish them in orientation, or polarization of the CMB photons. The satellite of ESA Planck, which was released in 2009, should be able to detect these signs. His first full-sky map is expected in 2012.
Even if only one of these points proves to be a clash of bubbles, which would be "a discovery of the first magnitude," says Thomas Levi, University of British Columbia in Vancouver, Canada. The findings reinforce the theories - such as string theory - which require a large number of universes with different properties.
"It is encouraging that there are some of the candidates," says Alexander Vilenkin of Tufts University in Medford, Massachusetts. But he adds that even if there bubble universes, could not be at a pace that guarantees would have clashed with our universe.
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