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Astronomy, Science, Physics…


The Big Bang May Have Created A ‘Mirror Universe’, Where Time Runs Backwards


In November 2018, three scientists from the famous Perimeter Institute for Theoretical Physics in Waterloo, Canada, suggested an astounding theory: the Big Bang spawned not just the known universe, but also a universe that is “its reflection in the mirror.”

A universe in which everything occurs backward and time extends in reverse. From our perspective, the universe “on the other side of the Big Bang” progresses… into the past.


In an article published in Physical Review Letters, the physicists Latham Boyle, Keran Finn, and Neil Turok argued that the universe in which we live is only a small portion of the actual universe, and that if this were true, two of the greatest problems facing physicists (dark matter and inflation) would lose all meaning.


In actuality, dark matter, the unobservable material that makes up over a third of the mass of the universe and that scientists are unable to detect, would be nothing more than a new sort of neutrino (not yet observed). And the phase of inflation, which exponentially enlarged the size of the universe right after the Big Bang and whose cause remains unexplained, would no longer be required.

Now, in a newly published study in the’Journal of Physics,’ the same researchers extend their work and investigate what this ‘anti-Universe’ might be like in which everything moves in reverse. Moreover, their conclusions are really intriguing. As Paul Sutter, an astronomer, says in Live Science, future tests to seek for gravitational waves or to determine the neutrino’s mass might reveal in the coming years whether or not this mirror universe is genuine.

CPT symmetry

There is a set of basic symmetries from which none of the natural forces can escape in our universe. In fact, all equations that best explain reality, from Newton’s Universal Gravitation to Maxwell’s Electrodynamics, Einstein’s Relativity or Quantum Mechanics, fit these fundamental symmetries with rare exceptions. We suppose that the Universe “functions” as effectively whether time goes forward or backward.

The most essential of these symmetries are Charge, Parity, and Time. If we alter the charge of all particles involved in an interaction to their opposite charge, the interaction will remain the same (if we look at an interaction backward in time, it will work exactly the same). The combination of these three symmetries is termed CPT symmetry, based on its initials (‘C’ for Charge, ‘P’ for Parity, and ‘T’ for Time).

It is true that violations occasionally occur, but no one has ever witnessed a simultaneous violation of all three symmetries. Boyle, Finn, and Turok propose in their new study to extend this coupled symmetry beyond the natural forces and throughout the entire universe. Instead of applying this symmetry merely to the “actors” of the Universe (forces and fields), the concept applies it to the “stage” itself, the entire physical object of the Universe.

A basic observation of the cosmos demonstrates that the Universe is not symmetrical. And despite the fact that changing the three parameters in the equations (Charge, Parity, and Time) does not affect the results of any particular interaction, the truth is that in our universe, time moves in only one direction, space expands and never contracts, and there is significantly more matter than antimatter. As if the ‘other half’ were absent.


Therefore, the authors of the paper say, if the cosmos follows CPT symmetry, there must be a mirror-image universe that balances our own. This universe would have the opposite charges to ours, it would be a mirror image of ours, and from our perspective, it would go backward in time. Then, the universe in which we exist would be one of two “twins.” Moreover, the two worlds as a whole would adhere to the CPT symmetry.

What would the cosmos look like if it were inverted?

But what would be the repercussions of such a universe? According to the study’s authors, a universe that follows the CPT symmetry would expand and fill with particles organically, without the requirement for an initial (theoretical) period of extraordinarily fast expansion and inflation, the mechanics of which remain unclear.

Sutter argues in Live Science that a symmetrical universe would add neutrinos to the mix: “There are three known neutrino flavors: the electron neutrino, the muon neutrino, and the tau neutrino. Strangely, all three of these neutrino ‘flavors’ are ‘left-handed’ (referring to the direction of their spin relative to their motion). All other known particles in physics come in left- and right-handed variants, therefore scientists have long pondered the existence of “right-handed” neutrinos.

A universe that adheres to CPT symmetry necessitates the presence of at least one “right-handed” neutrino type. One that would be almost undetectable to scientific instruments and would solely exert gravitational impact on the rest of the universe. Does that sound familiar? Dark matter is defined as an unseen particle that pervades the universe and only interacts through gravity…

Never will we see it

Unfortunately, we will never have access to the other universe since, if it exists, it must exist “after” the Big Bang and hence “before” our own universe. Therefore, we shall have to settle with theoretical investigations. Or maybe not?

In their article, Boyle, Finn, and Turok provide hints that might lead to observations that confirm the existence of this mirror universe. For instance, one of the expectations for this CPT Universe is that at least one sort of neutrinos should be massless. Physicists have only been able to place upper bounds on the masses of neutrinos, at least up to this point. If scientists were able to conclusively quantify these masses and one of them turned out to have no mass at all, this would be a tremendous boost for the CPT symmetric universe theory.

As previously stated, the model concludes that an inflation event never happened. However, scientists who believe in inflation assert that when it occurred, space must have been violently shook and filled with gravitational waves. Numerous scholars hunt for these ‘primordial waves,’ yet they should not exist in a universe with CPT symmetry. Consequently, if no one discovers them in the end, it would be another evidence that the CPT mirror universe idea is accurate.

Reference(s): Research Paper, Livescience