The Huge Bang is commonly described because the explosive delivery of the universe—a singular second when area, 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, printed in Bodily Evaluation D (full preprint right here), my colleagues and I suggest a placing different. Our calculations recommend the Huge Bang was not the beginning of every thing, however somewhat the end result of a gravitational crunch or collapse that shaped a really huge black gap—adopted by a bounce inside it.
This concept, which we name the black gap universe, presents a radically totally different view of cosmic origins, but it’s grounded fully in identified physics and observations.
Right now’s normal cosmological mannequin, based mostly on the Huge Bang and cosmic inflation (the concept that the early universe quickly blew up in dimension), has been remarkably profitable in explaining the construction and evolution of the universe. Nevertheless it comes at a worth: It leaves a few of the most elementary questions unanswered.
For one, the Huge Bang mannequin begins with a singularity—a degree of infinite density the place the legal guidelines of physics break down. This isn’t only a technical glitch; it’s a deep theoretical downside that means we don’t actually perceive the start in any respect.
To elucidate the universe’s large-scale construction, physicists launched a short part of speedy enlargement into the early universe referred to as cosmic inflation, powered by an unknown subject with unusual properties. Later, to elucidate the accelerating enlargement noticed at the moment, they added one other “mysterious” part: darkish vitality.
In brief, the usual mannequin of cosmology works effectively—however solely by introducing new components we’ve by no means noticed immediately. In the meantime, probably the most primary questions stay open: The place did every thing come from? Why did it start this fashion? And why is the universe so flat, easy, and enormous?
New Mannequin
Our new mannequin tackles these questions from a unique angle—by wanting inward as a substitute of outward. As a substitute of beginning with an increasing universe and making an attempt to hint again the way it started, we take into account what occurs when a very dense assortment of matter collapses beneath gravity.
This can be 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 normal circumstances, gravitational collapse should result in a singularity. This end result, prolonged by the late British physicist Stephen Hawking and others, underpins the concept that singularities—just like the one on the Huge Bang—are unavoidable.
The concept helped win Penrose a share of the 2020 Nobel prize in physics and impressed Hawking’s international bestseller A Temporary Historical past of Time: From the Huge Bang to Black Holes. However there’s a caveat. These “singularity theorems” depend on “classical physics” which describes extraordinary 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 answer—a mathematical end result with no approximations. Our math reveals that as we method the potential singularity, the dimensions of the universe adjustments as a (hyperbolic) perform of cosmic time.
This easy mathematical answer 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 precept, which states that no two an identical particles referred to as 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. In consequence, the collapse halts and reverses. The bounce will not be solely potential—it’s inevitable beneath the appropriate circumstances.
Crucially, this bounce happens fully inside the framework of normal relativity, which applies on giant scales comparable to stars and galaxies, mixed with the essential rules of quantum mechanics—no unique fields, further dimensions, or speculative physics required.
What emerges on the opposite facet of the bounce is a universe remarkably like our personal. Much more surprisingly, the rebound naturally produces the 2 separate phases of accelerated enlargement—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 will not be precisely 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 continued Euclid mission, affirm a small optimistic curvature, it might be a powerful trace that our universe did certainly emerge from such a bounce. It additionally makes predictions in regards to the present universe’s charge of enlargement, 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 issues with normal cosmology. It might additionally shed new gentle 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 shall be explored by future area missions comparable to Arrakihs, which is able to examine 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 might 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 presents 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 “mum or dad” universe.
We’re not particular, not more than Earth was within the geocentric worldview that led Galileo (the astronomer who advised the Earth revolves across the solar within the sixteenth and seventeenth centuries) to be positioned beneath home arrest.
We’re not witnessing the delivery of every thing from nothing, however somewhat the continuation of a cosmic cycle—one formed by gravity, quantum mechanics, and the deep interconnections between them.
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