The Massive Bang is usually described because the explosive start 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 identical time?
In a brand new paper, printed in Bodily Evaluation D (full preprint right here), my colleagues and I suggest a placing various. Our calculations recommend the Massive Bang was not the beginning of the whole lot, however quite 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, affords a radically totally different view of cosmic origins, but it’s grounded solely in identified physics and observations.
Immediately’s customary cosmological mannequin, based mostly on the Massive 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. However it comes at a worth: It leaves among the most elementary questions unanswered.
For one, the Massive Bang mannequin begins with a singularity—some extent 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 implies we don’t actually perceive the start in any respect.
To elucidate the universe’s large-scale construction, physicists launched a quick section of speedy growth into the early universe known as cosmic inflation, powered by an unknown subject with unusual properties. Later, to clarify the accelerating growth noticed right now, they added one other “mysterious” element: darkish vitality.
Briefly, the usual mannequin of cosmology works effectively—however solely by introducing new elements now we have by no means noticed straight. In the meantime, essentially the most primary questions stay open: The place did the whole lot come from? Why did it start this fashion? And why is the universe so flat, easy, and huge?
New Mannequin
Our new mannequin tackles these questions from a distinct angle—by trying inward as a substitute of outward. As an alternative of beginning with an increasing universe and making an attempt to hint again the way it started, we contemplate what occurs when an excessively dense assortment of matter collapses below 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 below very normal situations, gravitational collapse should result in a singularity. This consequence, prolonged by the late British physicist Stephen Hawking and others, underpins the concept that singularities—just like the one on the Massive Bang—are unavoidable.
The thought helped win Penrose a share of the 2020 Nobel prize in physics and impressed Hawking’s world bestseller A Transient Historical past of Time: From the Massive Bang to Black Holes. However there’s a caveat. These “singularity theorems” depend on “classical physics” which describes peculiar macroscopic objects. If we embrace the consequences 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 an actual analytical resolution—a mathematical consequence with no approximations. Our math reveals that as we method the potential singularity, the scale of the universe adjustments as a (hyperbolic) operate of cosmic time.
This straightforward 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 section.
However why do Penrose’s theorems forbid such outcomes? It’s all all the way down to a rule known as the quantum exclusion precept, which states that no two equivalent particles often known as fermions can occupy the identical quantum state (similar 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 will not be solely potential—it’s inevitable below the best situations.
Crucially, this bounce happens solely inside the framework of normal relativity, which applies on massive scales similar to stars and galaxies, mixed with the essential 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 constructive spatial curvature—that 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, similar to the continuing Euclid mission, verify a small constructive curvature, it will be a robust trace that our universe did certainly emerge from such a bounce. It additionally makes predictions concerning the present universe’s charge 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 issues with customary 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 house missions similar to Arrakihs, which is able to research diffuse options similar 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 are tough 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—similar to black holes—that shaped through the collapsing section and survived the bounce.
The black gap universe additionally affords 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’re not 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 below home arrest.
We’re not witnessing the start of the whole lot from nothing, however quite the continuation of a cosmic cycle—one formed by gravity, quantum mechanics, and the deep interconnections between them.
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