This is What Came Before the Big Bang

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Before there
were humans, dinosaurs walked the Earth. Before there was an Earth, there was
just a big cloud of gas and dust floating out in the universe. Before there was
a universe…well, before that is a point that physicists spill a lot of ink
over. We don’t know what happened before the Big Bang gave birth to the
universe, but the smartest people in science have plenty of fascinating

Time Before

The ideas
differ, sometimes wildly, but they all pretty much agree that the Big Bang at
least happened. The Big Bang theory says that our universe began as a point of
infinite gravity and density called a singularity. Then, in a trillionth of a
trillionth of a trillionth of a second, it exploded outward, doubling and
re-doubling and re-doubling in size at a rate faster than the speed of light in
a phenomenon physicists call inflation. (Ordinarily, nothing can go faster than
the speed of light. This was an expansion of space itself, though, so it’s
allowed to bend the rules.)
So the Big
Bang happened, one thing led to another, and now you’re here. But we’re
concerned with everything that happened before that. What caused that
singularity in the first place? For an explanation to have staying power, it
needs to solve a few problems physicists have been puzzling over. The biggest
one? The universe has surprisingly low entropy, a technical term for disorder.
An ice cube has low entropy, for example, because the water molecules within it
are arranged in an orderly way. Once that ice melts, those molecules aren’t
going to spontaneously re-form themselves into a cube. Everything goes in the
direction of disorder, never the reverse. But if that’s the case, the universe
should be a uniform distribution of disorganized subatomic particles. How did
atoms ever form molecules? How did clouds of gas and dust form stars and
planets and galaxies? The only explanation is that the universe had even lower
entropy at its birth than it does today. But how?

The Theories

Here are a
few of the leading contenders for what happened before the Big Bang.
An earlier
universe collapsed into the singularity that started our own.
This idea, known
as the Big Bounce, was first proposed in the 1960s by Princeton researchers
Robert Dicke and James Peebles. Some proponents of the idea say that our
universe is infinite, going through a never-ending cycle of collapse and
expansion (and that means we’re just waiting for another collapse). Critics say
the principles of entropy don’t allow a universe to collapse into a singularity
and out again, and proponents admit it would require some new physics to make
sense. But, as we’ll see, so do many other pre-Big Bang theories.

The universe
was hibernating until something set it in motion.
This idea says that the
pre-Big Bang universe was a small, flat, high-pressure space that was
“metastable,” or stable until it found an even more stable state —
the way a house of cards might sit perfectly solid forever until a breeze came
through. At some point, that “breeze” did come through. It stopped
being metastable, inflating into the universe we know. This theory doesn’t
break the laws of entropy, but it doesn’t explain entropy’s issues with our
current universe, either.

There was
never a singularity.
Instead, all the energy in the universe was bound in the
fabric of space. Known as the inflation hypothesis, this idea says that
fluctuations in this so-called “inflaton field” (that’s no typo!) led
to a huge swell of energy in one patch of the field, which made it expand
incredibly quickly. That exponential growth spurt would leave evidence behind
in the form of primordial gravitational waves — not the big ones discovered by
LIGO in 2015, but tiny imprints in the cosmic microwave background that other
projects (including the BICEP2 experiment) have been searching for. We may not
have found evidence for this one yet, but most cosmologists think it does the
best job of explaining the universe’s low entropy, along with a few other
cosmic quirks.

We’re just
one universe in the multiverse.
This theory is an offshoot of the inflation
hypothesis, and says that the elements that lead to inflation also lead to the
creation of a bunch of smaller, low-entropy universes. Unfortunately, all of
those universes would be closed off from one another, so we’d never be able to
detect them. That’s unsatisfying to some scientists for obvious reasons.

In the end,
we probably can’t ever know for sure how the universe began. But cosmologists
aren’t grasping at straws, either. There is a lot of work being done to at
least further our understanding of the pre-Bang universe, and the strongest
hypotheses will win out along the way.

Via Curiosity.

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