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According to a straightforward interpretation of general relativity, the Big Bang wasn't the start of 'everything'.

Taking Einstein's famous equations at face value and making as few assumptions as possible, a team of researchers has rewound the clock on our Universe to find it wouldn't lead to a stopping point at all, but would take us through a different kind of beginning into a flipped space.


Around 90 years ago, a Belgian astronomer named Georges Lemaître proposed that observed changes in the shifting of light from distant galaxies implied the Universe is expanding. If it's getting bigger, it stands that it used to be smaller.


"At this time, the Big Bang, all the matter in the universe, would have been on top of itself. The density would have been infinite," Stephen Hawking once explained in his lecture on The Beginning of Time.

There are a number of models physicists use to describe the nothingness of empty space. Einstein's general relativity is one - it describes gravity as it relates to the geometry of the Universe's underlying fabric.

Theorems proposed by Hawking and mathematician Roger Penrose claim that solutions to general relativity's equations on an infinitely constrained scale – like the one inside a singularity – are incomplete.

In everyday terms, it's often said physics breaks down at the singularity, leading to a mix of speculations on what little we can tease out of the physics that still makes sense.

Hawking only recently gave his own take in an interview with Neil deGrasse Tyson, where he likened the space-time dimensions of the Big Bang to the South Pole. "There is nothing south of the South Pole, so there was nothing around before the Big Bang," he said.

But other physicists have argued there's something beyond the Big Bang. Some propose that there is a mirror Universe on the other side, where time moves backwards. Others argue in favor of a rebounding Universe.


What the theorem doesn't imply is how the Universe as we observe it necessarily gets to that point in the first place.

Stepping back from the whole singularity issue, the researchers reinterpreted the existing model of shrinking space by distinguishing the map of space-time itself from the 'stuff' in it.

"All the terms that are problematic turn out to be irrelevant when working out the behavior of quantities that determine how the Universe appears from the inside," said Sloan, a physicist from the University of Oxford.

What this essentially adds up to is a description of the Big Bang where physics remains intact as the stage it acts upon re-orientates.





"We introduce no new principles, and make no modifications to Einstein's theory of general relativity – only of the interpretation that is put upon objects," said Sloan.

No doubt this debate will rage on well into the future. Who knows? Maybe there's a similar argument happening in the mirror Universe sometime on the other side of the Janus Point.

This research was published in Physics Letters B.