Proof of Big Bang Seen by Space Probe, Scientists Say

Davide Castelvecchi
for National Geographic News
March 17, 2006

New NASA space-probe observations of the oldest light in the cosmos are the most direct evidence yet that the universe expanded extremely quickly immediately after the big bang, physicists say.

Charles Bennett of Johns Hopkins University in Baltimore, Maryland, led the team overseeing NASA's Wilkinson Microwave Anisotropy Probe (WMAP). He and colleagues announced the new results Thursday in a teleconference.

Previous experiments—including WMAP results released in 2003—had provided strong evidence for the rapid-expansion theory, called inflation, that was first proposed by physicist Alan Guth in 1980.

In the trillion-trillionth of a second after the big bang, the universe expanded from the size of a gumball to astronomical proportions, according to the inflation theory. The universe then settled into a more leisurely pace of expansion over the past 13.7 billion years or so.

Smoking Gun

WMAP now has the most convincing evidence yet for inflation: a reading of the light released just after the big bang. This cosmic afterglow, known as microwave background, is made of a similar type of radiation to that which carries signals to a TV antenna.

The afterglow is as valuable to a cosmologist as the earliest fossils are to a paleontologist. It is the oldest radiation ever detected, still traveling almost 14 billion years after it was emitted.

The microwaves bathe the entire universe in a perpetual buzz, reaching Earth from all directions. The buzz is virtually uniform, but not quite.

Tiny variations at different points in space allow scientists to draw maps of the early universe, as the WMAP team has done with unprecedented detail.

These cosmic baby pictures show us a time when the universe was a smooth, fiery broth, when stars and galaxies had yet to form under the pull of gravity (photo: another view of the early universe).

Finer Points

The team said cosmologists will now be able to delve into the finer details of how inflation happened.

Continued on Next Page >>


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