There may be a second universe out there, and it could be why anything exists at all

Scientists have been trying to understand why the universe exists at all. When the universe was very young, they believe it created two types of particles. One is matter, which makes up everything we see around us, and another is antimatter, which is basically matter’s opposite. They should have been created in equal amounts.

So, if the universe really had equal amounts of both, they should have completely canceled each other out and left behind energy. But this didn’t happen. Somehow, matter was left behind and formed stars, planets, galaxies, and everything we see around us. Now, they think it might be connected to a hidden universe. Here’s how.

In physics, there is a principle called CPT symmetry that involves charge, parity, and time. It’s expected to hold true everywhere and at all times. If scientists were to find that it can be broken, it could point to something beyond our current understanding of particle physics. 

A new study in The European Physical Journal C argues that's basically what happened, just briefly, right after the Big Bang. As the authors put it, "The combined CPT symmetry is widely regarded as exact, and its violation would necessarily indicate physics beyond the Standard Model (SM) of particle physics."

But what if the laws of physics aren’t actually being broken? The researchers suggest that our universe could have a mirror-like twin, with the opposite orientation and time running backward compared with ours. On its own, each universe might look unbalanced. When put together, though, the overall symmetry could still work out perfectly.

“We propose that the Big Bang generated […] a pair of universes with opposite orientations, and that CPT symmetry may have been locally violated during the earliest stages of cosmic evolution,” the authors added.

The researchers point to something called the inflaton field, a theoretical force believed to have driven the universe's explosive growth right after the Big Bang. They suggest a tiny mismatch here is what tipped the scales. 

“A mass difference between the inflaton and its corresponding anti-inflaton field can lead to unequal particle–antiparticle production rates during reheating,” the authors wrote. “The paired-universe model preserves the geometric integrity of spacetime symmetries while providing a natural setting in which CPT symmetry may be globally conserved but locally broken.”

On this topic, quantum physicist Maria Violaris shared her idea in a paper posted to arXiv. Under the many-worlds interpretation, every quantum outcome is supposed to spin off its own separate reality, and those realities can never talk to each other. 

She points out that her own proposal doesn’t really leave much room for those kinds of fantasies. As she explains, “Everything is mediated by the super observer.” The local observers, as Violaris puts it, “don't control message transport,” while the controlling figure “doesn't know the message contents.” In other words, the power and knowledge are unevenly distributed, and this makes it much less likely that information could simply be collected from the other universe.