The bold theory of an “anti-universe” where time runs backwards and how it solves various enigmas of the cosmos

The most common image we have of the Big Bang is that from a point a universe emerged that has been expanding.

But what if this universe is just the twin from another universe that formed at the same time at that point and has been expanding in the opposite direction?

That’s the bold proposal recently published by a group of cosmologists at the Perimeter Institute for Theoretical Physics in Canada.

And they go further.

In that anti-universe that they propose, as it moves in the opposite direction to ours, time also runs in the opposite direction.

This hypothesis, as complex as it may seem, is an attempt by its authors to explain more simply and “economic“, several mysteries of the cosmos, among them the enigmatic dark matter.

Perimeter Institute
That graphic illustrates the model of the universe and its mirror image that arises from the Big Bang.

On the other side of the mirror

There are two key concepts to understand the idea of ​​an anti-universe.

The first has to do with the Standard Model of particle physicsthe theory that describes the fundamental particles of which the universe is made and the forces that make them interact with each other.

According to the Standard Model, whenever a particle of matter arises, so does its antimatter counterpartan identical particle but with a different charge.

That means that during the Big Bang the same amount of matter and antimatter was produced.

And the second concept is symmetry.

In cosmology, this principle indicates that any physical process remains the same even if time runs backwards, if space is reversed or if particles are replaced by antiparticles.



Based on those two principles, the analogy that could be made is that just as a universe exists, one could expect a universe to exist. symmetric antiuniverse whom we know.


In a recent study from the Perimeter Institute for Theoretical Physics, the authors analyzed a type of symmetry called CPT, the initials of charge, parity, and time.

This symmetry indicates that if they are inverted loads, image and time of a particle interaction, that interaction will behave in the same way.

So, this symmetry that applies to particles, according to the authors of the study, could also be applied to the universe as a whole, which opens the possibility of a symmetrical universe.

“The universe as a whole is symmetric CPT”the authors write in their research.

Under this premise, the Big Bang is a starting point in which the universe originates and its mirror image.

“We suggest that the universe before the Big Bang is the ‘antiverse’ of the universe after the Big Bang,” say the authors.



How is that anti-universe?

Latham Boyle, one of the study’s co-authors, cautions that he has no certainties on the hypothesis of the antiuniverse and that its proposals must be verified experimentally.

But he thinks his calculations give him some clues.

“So far, we believe that the antiverse is a genuine mirror image reflected in time, with exchanged particles and antiparticlesBoyle says in conversation with BBC Mundo.

According to that vision, that antiverse it is not an independent universebut a mere reflection of our universe.

“We have an ‘anti-self’ in the other universe, but it’s not independent,” says Boyle.

“If you choose to have eggs for breakfast, your antiverse version cannot choose to have bacon for breakfast.”

“If you have eggs for breakfast, he will have to have breakfast. anti-eggs“.


Do we live in the universe or in the antiverse?

And what about time in the antiverse?

As proposed by Boyle and his colleagues, the Big Bang is like a mirror that not only inverts the image but also the time direction.

On both sides of the universe time moves on moving away from the big bangonly that on one side the arrow of time goes to the right, and on the other it goes to the left.

“Every side of the universe thinks it’s perfectly normal,” says Boyle. “Both believe their time is moving forward.”

“From our perspective, in the antiverse time moves backwardsbut for them we are the ones going the other way around”.

That idea of ​​Boyle’s holds another mind-boggling possibility: maybe we are the ones in the anti-universe and we don’t know.

And another question that you may be asking yourself: is it possible to travel to that anti-universe?

“We can’t cross over to the other side of the looking glass,” says Boyle. “For that it would have to be possible travel to the past“.

That is, you would have to travel through space-time, cross the Big Bang singularity and come out the other side.



minimalist solutions

But beyond these science-fiction-like ideas, the work of Boyle and his colleagues also proposes solutions to more practical problems of physics and cosmology.

His proposal offers challenging insights into three fundamental concepts of cosmology: dark matter, inflation after the Big Bang ands gravitational waves

dark matter is a mystery ingredient that makes up 25% of the universe, but until now no one has been able to observe what it is or what it is made of.

Dark matter, however, can be noticed by the gravitational influence that it exerts on the cosmos.

For years, scientists have proposed various theories to explain what dark matter is, but still nobody has a convincing answer.

Some of the possible answers hold that dark matter is made of a particle we don’t know yet, that is, it is outside the Standard Model.

Boyle’s study, however, offers a “cheaper” answer to the dark matter puzzle.

Standard Model

The Standard Model describes the fundamental particles that make up the universe.

His proposal is that to explain dark matter it is not necessary to imagine new particles.

Instead, Boyle thinks the answer may be that dark matter is made of “right-handed neutrinos”a variety of neutrinos, which are not part of the Standard Model.

It has not yet been proven that there are “right-handed neutrinos“, but according to Boyle, many scientists agree that it may be part of the Standard Model.

In this way, Boyle saves himself the effort of speculating with new particles and finds the answer in the laws of physics that we already know.

So far, the known neutrinos are “left-handed,” referring to the direction in which they spin.

But in a symmetrical universe, a right-handed neutrino would also be expected to exist, that is, a antineutrinoaccording to astrophysicist Paul Sutter, in an article on the portal livescience in which he reviews Boyle’s study.

These right-handed neutrinos would be mostly invisible and their presence could only be detected through gravity.

Dark matter

Dark matter makes up much of the universe, but no one knows what it is made of.

“An invisible particle that pervades the universe and only interacts through gravity It looks a lot like dark matter.”Sutter explains.

Joseph Formaggio, a physicist who investigates the role of neutrinos in cosmology, says that he finds Boyle’s proposal to explain dark matter interesting.

I like your model minimalist“, Tells BBC Mundo Formaggio, who was not involved in the investigation.

“Usually in particle physics many phenomena can be explained by introducing new particles, interactions and fields, with which it’s easy to get lost“.

“But this research has another approach, they do not add anything beyond what we have already observed,” concludes Formaggio, who directs the Division of Experimental Nuclear and Particle Physics at the Massachusetts Institute of Technology.

Formaggio refers to the idea of ​​right-handed neutrinos It’s very commonalthough it is not known if they exist.

“They’re a new particle, but they’re really not,” he says with a laugh.

gravitational waves

Gravitational waves travel through space-time like ripples in a lake.

Neither inflation nor gravitational waves

Finally, the study questions the existence of cosmological inflation and primordial gravitational waves.

Boyle’s model questions whether after the Big Bang there was a period in which the universe expanded rapidlya concept known as inflation.

That inflation, in turn, may have created primordial gravitational waveswhich are ripples that travel in the fabric of space-time, like the ripples generated by a stone thrown into a lake.

Boyle’s proposal holds that instead of inflation, the matter in the universe expanded less forcibly, without the need for a “inflammatory time”.

So, according to this model, if there was no inflation, there were also no primordial gravitational waves.

In 2015 gravitational waves were detected for the first time, Boyle, however, warns that these correspond to events much later than the Big Bang, therefore they are not primordial gravitational waves.

Now you can receive notifications from BBC World. Download the new version of our app and activate it so you don’t miss out on our best content.