Our Universe May Exist in a Multiverse, Cosmic Inflation Discovery Suggests
By by Miriam Kramer, Staff Writer
6 hours ago
Our universe may be one of many, physicists say. In fact, that's the most likely scenario.
The first direct
evidence of cosmic inflation — a period of rapid expansion that occurred
a fraction of a second after the Big Bang — also supports the idea that
our universe is just one of many out there, some researchers say.
On Monday (March 17), scientists announced new findings that mark the first-ever direct evidence of primordial gravitational waves
— ripples in space-time created just after the universe began. If the
results are confirmed, they would provide smoking-gun evidence that
space-time expanded at many times the speed of light just after the Big
Bang 13.8 billion years ago.
The new research also lends credence
to the idea of a multiverse. This theory posits that, when the universe
grew exponentially in the first tiny fraction of a second after the Big
Bang, some parts of space-time expanded more quickly than others. This
could have created "bubbles" of space-time that then developed into
other universes. The known universe has its own laws of physics, while
other universes could have different laws, according to the multiverse
concept. [Cosmic Inflation and Gravitational Waves: Complete Coverage]
"It's hard to build models of inflation that don't lead to a
multiverse," Alan Guth, an MIT theoretical physicist unaffiliated with
the new study, said during a news conference Monday. "It's not
impossible, so I think there's still certainly research that needs to be
done. But most models of inflation do lead to a multiverse, and
evidence for inflation will be pushing us in the direction of taking
[the idea of a] multiverse seriously."
Other researchers agreed on the link between inflation and the multiverse.
"In most of the models of inflation, if inflation is there, then the multiverse
is there," Stanford University theoretical physicist Andrei Linde, who
wasn't involved in the new study, said at the same news conference.
"It's possible to invent models of inflation that do not allow [a]
multiverse, but it's difficult. Every experiment that brings better
credence to inflationary theory brings us much closer to hints that the
multiverse is real."
When
Guth and his colleagues thought up cosmic inflation more than 30 years
ago, scientists thought it was untestable. Today, however, researchers
are able to study light left over from the Big Bang called cosmic microwave background radiation (CMB).
In the new study, a team led by John Kovac of the Harvard-Smithsonian
Center for Astrophysics found telltale signs of inflation in the
microwave background. The researchers discovered a distinct curl in the
polarization pattern of the CMB, a sign of gravitational waves created by the rapid expansion of space-time just after the Big Bang.
Linde, one of the main contributers to inflation theory, says that if
the known universe is just one bubble, there must be many other bubbles
in the cosmic fabric.
"Think
about some unstable state," Linde explained. "You are standing on a
hill, and you can fall in this direction, you can fall in that
direction, and if you're drunk, eventually you must fall. Inflation is
instability of our space with respect to its expansion.
"You have something growing exponentially," he added. "If you just let
it go … it will continue exponentially growing, so this [the known
universe] is one possibility of something going wrong with this
instability, which is very, very right for us because it has created all
of our space. Now, we know that if anything can go wrong, it will go
wrong once and a second time and a third time and into infinity as long
as it can go."
Follow Miriam Kramer @mirikramer and Google+. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.
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