What if the universe were not outside, but inside? A hypothesis suggests that we could live inside a black hole
Upon gazing at the sky, — every galaxy, every atom, every thought — could be contained within something else. But a group of cosmologists has been contemplating a possibility for years that completely changes that idea:
The hypothesis, although sounding like a science fiction experiment, is supported by an unsettling parallelism. Share the same characteristics: a singularity and an event horizon. A beginning and a limit.
### When equations reflect
According to Einstein’s general theory of relativity, both are curvatures of spacetime generated by mass and energy. In both cases, the cosmic fabric deforms to the extreme: in a black hole inward, in the universe outward.
In the seventies, physicist Raj Kumar Pathria and mathematician I. J. Good proposed something that seemed like a simple mathematical curiosity: , maybe it’s not a coincidence. Perhaps the universe is that black hole.
Decades later, theoretical physicist Lee Smolin went further. He suggested that each could give rise to a new universe inside it, with slight variations in the laws of physics. We would be, in that view, . A genealogy of black holes engendering offspring universes.
### Opposing singularities
The resemblance between both scenarios is undeniable:
– Both stem from a singularity, a point where the physical laws no longer apply.
– Both are surrounded by a horizon beyond which nothing can return.
– And both imply such enormous density that time and space lose their usual meaning.
The difference, however, is the direction of the arrow. While black holes collapse inwards, the universe expands outwards. One destroys space; the other creates it. Physicist Ghazal Geshnizjani, from the Perimeter Institute for Theoretical Physics, summarizes it as follows: “Mathematically, they are closely related. They are like the opposite of each other.”
In some way, the universe could be the inverted image of a : a cosmic reflection that expands instead of collapses but obeys the same geometric logic.
### How would we know if it’s true
If the universe were really the inside of a black hole, there should be signs. One of them would be the existence of a privileged direction, a natural orientation of the cosmos. In theory, an invisible axis marking the “center” of our black hole.
But so far, there is no evidence of it. without a special direction. This uniformity contradicts the idea that we inhabit a structure with defined center and edge.
Still, physicists like Niayesh Afshordi, also from the, believe that the hypothesis remains fascinating. “It’s not crazy,” he says. “We just have to make the details work.”
### The limit of knowledge
Resolving the question requires uniting two worlds that still resist fitting together: general relativity, which describes gravity, and quantum mechanics, which explains the behavior of the universe on tiny scales. Both theories work, but together they break right where we need them most:
Until physics achieves a theory of quantum gravity, scientists will continue to be unable to describe what happens inside a black hole… or what exactly happened before the
### A mirror of the abyss
. It is a metaphor for our position in the cosmos. From within, everything seems to expand, move away, cool down. But if the universe were really the inside of a , perhaps we would only be seeing the other side of a cosmic mirror.
We may never verify it, but thinking about it confronts us with an uncomfortable truth: understanding the universe is trying to understand ourselves from within the darkness.
