"We need a partner anti-universe whose time flow is oppositely related to our universe."

The Upside Down

The current model scientists use to explain the universe around us is made up of three components: regular matter, cold dark matter (CDM), and the cosmological constant, or lambda, a coefficient first introduced by Albert Einstein in 1917 that's related to dark energy.

This standard model of cosmology has served as a way to explain how dark energy causes our universe to expand at an accelerating rate. But while the model has been around for decades, mysteries remain. For one, we have yet to observe dark matter directly. And the exact nature of dark energy, which is estimated to make up 68 percent of the universe, has also proven controversial, with many scientists coming forward with alternate explanations.

Now, a PhD student at the Indian Institute of Technology, Gandhinagar named Naman Kumar has proposed a "new model" that does away with this uncertainty by throwing out dark energy from the equation altogether — which has a highly unusual implication.

"However, there is a price to pay," he wrote in a statement accompanying a paper he recently published in the journal Gravitation and Cosmology. "We need a partner anti-universe whose time flow is oppositely related to our universe."

Dark Mirror

Kumar isn't the first to suggest our universe has a mirrored twin that flows backwards in time. In February, an international team of researchers similarly suggested that dark matter, the mysterious stuff that makes up around 27 percent of the universe, resides in a mirror universe in which atoms never formed.

Of course, Kumar's finding isn't anything more than a working hypothesis regarding the observed accelerated expansion of the universe, which is in his words "one of the greatest puzzles in our understanding of the cosmos."

But as our methods to observe and study the universe improve, astronomers are ever-so-slowly inching towards a possible explanation for this discrepancy — and sometimes, a solution as elegant as an upside-down world where time flows backwards, is our best bet.

"The beauty of this idea lies in its simplicity and naturalness, setting it apart from existing explanations," Kumar argued.

More on mirror universes: Dark Matter May Be a Deformed Mirror Universe, Scientists Say

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