A physicist from the University of Campinas in Brazil isn't a big fan of the idea that time started with a so-called Big Bang. So Instead, Juliano César Silva Neves imagines a collapse followed by a sudden expansion, one that could even still carry the scars of a previous timeline.

The idea itself isn't new,
but Neves has used a fifty-year-old mathematical trick describing black holes
to show how our Universe needn't have had such a compact start to existence. At
first glance, our Universe doesn't seem to have a lot in common with black
holes. One is expanding space full of clumpy bits; the other is mass pulling at
space so hard that even light has no hope of escape. But at the heart of both
lies a concept known as a singularity – a volume of energy so infinitely dense,
we can't even begin to explain what's going on inside it.

"There are two kinds of
singularity in the Universe," says Neves. “One is the alleged cosmological
singularity, or Big Bang. The other hides behind the event horizon of a black
hole."

Taken a step further, some
propose the Universe itself formed from a black hole in some other bubble of
space-time. No matter which kind we're talking about, singularities are zones
where Einstein's general relativity goes blind and quantum mechanics struggles
to take over. Sci-fi writers might love them, but the impossible nature of
singularities makes them a frustrating point of contention among physicists.

The problem is, if we
rewind the expanding Universe, we get to a point where all of that mass and energy
was concentrated in an infinitely dense point.

And if we crunch the numbers
on collapsing massive objects, we get the same kind of thing. Singularities
might break physics, but so far we haven't been able to rule them out. On the
other hand, some physicists think there's some wiggle room. Theoretically
speaking, not all models of a black hole need a singularity to exist.

"There are no
singularities in so-called regular black holes," says Neves.

In 1968, a physicist by the name
of James Bardeen came up with a solution to the singularity problem. He devised
a way of mathematically describing black holes that did away with the need for
a singularity somewhere beyond its event horizon, calling them 'regular black
holes'.

The history and reasoning
behind Bardeen's model is, well, super dense; but for a tl;dr version – he
assumed that the mass at the heart of a black hole needn't be constant, but
could be described using a function that depended on how far from its centre
you were. That means we can dust our hands of any stupid singularities, as mass
still behaves as if it has volume. Even as it is still squeezed into a tight
space.

Neves suggests we take
Bardeen's work even further and apply it to that other annoying singularity –
the cosmological variety that preceded the Big Bang.

By assuming the rate of the
Universe's expansion depended not just on time, but its scale as well, he
showed there was no need for a quantum leap out of a singularity into a dense,
voluminous space 13.82 billion years ago. So what happened instead?

"Eliminating the
singularity or Big Bang brings back the bouncing Universe on to the theoretical
stage of cosmology," says Neves.

This 'bouncing Universe' is
actually a century-old idea that the expanding Universe as we experience it
today is space bouncing back outwards after a previous contraction. Though it's
currently somewhat of a fringe concept in cosmology, Neves supports the view
that traces of the pre-collapse Universe might have survived the Big Crunch. If
so, finding those scars might help validate the hypothesis.

"This image of an
eternal succession of universes with alternating expansion and contraction
phases was called the cyclical Universe, which derives from bouncing
cosmologies," says Neves.

Until we have solid
observations, the bouncing Universe model will no doubt stay in the 'nice idea'
basket. Still, anything that solves the singularity problem deserves
investigating. Neves's work is just one of a number of possible solutions that
swaps around assumptions to eliminate the need for physics-breaking
impossibilities.

It's a sticking point we'll
need to solve sooner or later.

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