The Huge Bang is usually described because the explosive beginning of the universe—a singular second when house, time, and matter sprang into existence. However what if this was not the start in any respect? What if our universe emerged from one thing else—one thing extra acquainted and radical on the similar time?
In a brand new paper, published in Physical Review D (full preprint here), my colleagues and I suggest a putting different. Our calculations counsel the Huge Bang was not the beginning of all the things, however relatively the end result of a gravitational crunch or collapse that shaped a really large black gap—adopted by a bounce inside it.
This concept, which we name the black gap universe, gives a radically completely different view of cosmic origins, but it’s grounded fully in identified physics and observations.
In the present day’s standard cosmological model, primarily based on the Huge Bang and cosmic inflation (the concept the early universe quickly blew up in dimension), has been remarkably profitable in explaining the construction and evolution of the universe. But it surely comes at a value: It leaves a few of the most basic questions unanswered.
For one, the Huge Bang mannequin begins with a singularity—a degree of infinite density where the laws of physics break down. This isn’t only a technical glitch; it’s a deep theoretical drawback that means we don’t actually perceive the start in any respect.
To clarify the universe’s large-scale construction, physicists launched a quick part of speedy growth into the early universe referred to as cosmic inflation, powered by an unknown area with unusual properties. Later, to clarify the accelerating growth noticed right now, they added one other “mysterious” part: dark energy.
Briefly, the usual mannequin of cosmology works effectively—however solely by introducing new ingredients we’ve got by no means noticed instantly. In the meantime, probably the most primary questions stay open: Where did everything come from? Why did it start this manner? And why is the universe so flat, easy, and huge?
New Mannequin
Our new mannequin tackles these questions from a unique angle—by wanting inward as an alternative of outward. As a substitute of beginning with an increasing universe and attempting to hint again the way it started, we contemplate what occurs when an excessively dense assortment of matter collapses beneath gravity.
It is a acquainted course of: Stars collapse into black holes, that are among the many most well-understood objects in physics. However what occurs inside a black gap, past the occasion horizon from which nothing can escape, stays a thriller.
In 1965, the British physicist Roger Penrose proved that beneath very common circumstances, gravitational collapse must lead to a singularity. This consequence, extended by the late British physicist Stephen Hawking and others, underpins the concept singularities—just like the one on the Huge Bang—are unavoidable.
The thought helped win Penrose a share of the 2020 Nobel prize in physics and impressed Hawking’s world bestseller A Brief History of Time: From the Big Bang to Black Holes. However there’s a caveat. These “singularity theorems” depend on “classical physics” which describes strange macroscopic objects. If we embody the results of quantum mechanics, which guidelines the tiny microcosmos of atoms and particles, as we should at excessive densities, the story could change.
In our new paper, we present that gravitational collapse doesn’t have to finish in a singularity. We discover a precise analytical resolution—a mathematical consequence with no approximations. Our math reveals that as we method the potential singularity, the dimensions of the universe modifications as a (hyperbolic) operate of cosmic time.
This easy mathematical resolution describes how a collapsing cloud of matter can attain a high-density state after which bounce, rebounding outward into a brand new increasing part.
However why do Penrose’s theorems forbid such outcomes? It’s all right down to a rule referred to as the quantum exclusion principle, which states that no two similar particles often called fermions can occupy the identical quantum state (comparable to angular momentum, or “spin”).
And we present that this rule prevents the particles within the collapsing matter from being squeezed indefinitely. Consequently, the collapse halts and reverses. The bounce just isn’t solely doable—it’s inevitable beneath the suitable circumstances.
Crucially, this bounce happens fully inside the framework of common relativity, which applies on giant scales comparable to stars and galaxies, mixed with the fundamental rules of quantum mechanics—no unique fields, additional dimensions, or speculative physics required.
What emerges on the opposite aspect of the bounce is a universe remarkably like our personal. Much more surprisingly, the rebound naturally produces the 2 separate phases of accelerated growth—inflation and darkish vitality—pushed not by hypothetical fields however by the physics of the bounce itself.
Testable Predictions
One of many strengths of this mannequin is that it makes testable predictions. It predicts a small however non-zero quantity of optimistic spatial curvature—which means the universe is not exactly flat, however barely curved, just like the floor of the Earth.
That is merely a relic of the preliminary small over-density that triggered the collapse. If future observations, comparable to the continuing Euclid mission, verify a small optimistic curvature, it might be a robust trace that our universe did certainly emerge from such a bounce. It additionally makes predictions in regards to the present universe’s price of growth, one thing that has already been verified.
The SpaceX Falcon 9 rocket carrying ESA’s Euclid mission on the launch pad in 2023. Picture Credit score: ESA, CC BY-SA
This mannequin does greater than repair technical problems with standard cosmology. It might additionally shed new mild on different deep mysteries in our understanding of the early universe—such because the origin of supermassive black holes, the character of darkish matter, or the hierarchical formation and evolution of galaxies.
These questions will probably be explored by future house missions comparable to Arrakihs, which can research diffuse options comparable to stellar halos (a spherical construction of stars and globular clusters surrounding galaxies) and satellite tv for pc galaxies (smaller galaxies that orbit bigger ones) which can be troublesome to detect with conventional telescopes from Earth and can assist us perceive darkish matter and galaxy evolution.
These phenomena may also be linked to relic compact objects—comparable to black holes—that shaped throughout the collapsing part and survived the bounce.
The black gap universe additionally gives a brand new perspective on our place within the cosmos. On this framework, our whole observable universe lies inside the inside of a black gap shaped in some bigger “mother or father” universe.
We aren’t particular, not more than Earth was within the geocentric worldview that led Galileo (the astronomer who prompt the Earth revolves across the solar within the sixteenth and seventeenth centuries) to be positioned beneath home arrest.
We aren’t witnessing the beginning of all the things from nothing, however relatively the continuation of a cosmic cycle—one formed by gravity, quantum mechanics, and the deep interconnections between them.
This text is republished from The Conversation beneath a Inventive Commons license. Learn the original article.
