Our universe may have an anti-universe twin on the other side of the Big Bang, say physicists

Physicists propose a mirror-image antimatter universe extending backward in time before the Big Bang.

Key Takeaways:

1. Scientists suggest our universe has a mirror-image “antiuniverse” that existed before the Big Bang.
2. This antiuniverse, filled with antimatter, obeys a fundamental physics rule called CPT symmetry.
3. The theory offers a natural explanation for dark matter, linking it to massive “sterile” neutrinos.
4. The model aligns with unusual radio signals detected by Antarctica’s ANITA experiment.
5. More work is needed to refine the theory, but it could challenge existing cosmological models.

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A radical new theory suggests that our universe may have a mirror-image counterpart—a vast antimatter universe that stretches backward in time before the Big Bang. This idea, proposed by physicists Neil Turok and Latham Boyle from Canada’s Perimeter Institute for Theoretical Physics, relies on a fundamental symmetry of nature known as CPT symmetry. Their model, published in Physical Review Letters, challenges conventional cosmology and may provide an explanation for dark matter.

An Antimatter Universe Beyond the Big Bang

Standard cosmology describes the universe as expanding from a singularity about 14 billion years ago. However, Turok argues that current models rely too much on unproven assumptions, such as cosmic inflation. Instead of inventing new physics, he and Boyle sought a natural extension of the universe that adheres to known physical laws.

Their answer lies in CPT symmetry—a principle stating that physics remains unchanged if time is reversed, space is flipped, and matter is swapped with antimatter. Our visible universe does not obey this symmetry on its own, but a paired universe–antiuniverse system would. In this model, a mirror universe dominated by antimatter existed before the Big Bang, expanding backward in time while our universe expanded forward.

This concept is analogous to the creation of electron-positron pairs in a vacuum. The antiuniverse would be an inverted version of our cosmos, obeying the same fundamental laws but evolving in reverse.

A New Explanation for Dark Matter?

Turok and his colleagues believe this model could naturally explain dark matter—one of cosmology’s biggest mysteries. They propose that dark matter consists of a type of neutrino known as a “sterile” neutrino, which interacts only through gravity. Their calculations predict a sterile neutrino mass of about 500 million times the proton’s mass (5×10⁸ GeV)—consistent with anomalous signals detected by the Antarctic Impulsive Transient Antenna (ANITA).

ANITA has recorded unexplained high-energy particles seemingly traveling up through the Earth, which some researchers suspect may be decaying sterile neutrinos. However, a challenge remains: the CPT model requires these neutrinos to be completely stable. Turok acknowledges this issue but suggests minor adjustments could resolve it.

While this theory is still a work in progress, it provides a fresh perspective on the origins of the universe and the nature of dark matter. If proven, it could revolutionize our understanding of cosmology and challenge long-standing ideas about the Big Bang.