Gravitational Waves: The Big Bang's Smoking Gun | Space.com
Direct evidence
In 2014, the Harvard-Smithsonian Center for Astrophysics found a faint signal in the cosmic microwave background
radiation (CMB) that signifies the first direct evidence of
gravitational waves ever discovered. Gravitational waves were the last
untested part of Einstein's general theory of relativity.
The Harvard-Smithsonian study spotted gravitational waves as ripples in
space-time possible left over from the rapid expansion of the universe
(called inflation) right after the Big Bang nearly 13.8 billion years ago.
Scientists working on the study found a distinct curling pattern
in the CMB — the comic fog that fills the universe and represents the
earliest detectable radiation — that further supports the idea that the
universe went through a huge period of inflation a fraction of a second
after the Big Bang.
"This work offers new insights into some of our most basic questions:
Why do we exist? How did the universe begin?," astrophysicist Avi Loeb,
who wasn't a member of the study team said in a statement about the
Harvard-Smithsonian research. "These results are not only a smoking gun
for inflation, they also tell us when inflation took place and how
powerful the process was."
Cosmic inflation
CMB radiation came into existence about 380,000 years after the Big
Bang. Scientists have mapped the CMB across the sky and found that it is
a uniform temperature, evidence that bolsters cosmic inflation theory.
"Why the cosmic microwave background temperature is the same at
different spots in the sky would be a mystery if it was not for
inflation saying, well, our whole sky came from this tiny region," Chuck
Bennett, principal investigator of NASA's Wilkinson Microwave
Anisotropy Probe (WMAP) mission, told Space.com in 2013. "So the idea of
inflation helps answer some of these mysteries, and it explains where
these fluctuations came from." ['Smoking Gun' of Universe's Inflation: Gravitational Waves (Infographic)]
