Scientists are examining competing theories about what may have existed before the big bang, challenging conventional assumptions about the beginning of space, time, and the universe itself.
Instead, the earliest phase of spacetime could be structured in a way that makes the concept of a moment before the big bang meaningless.
A third theory, explored by physicist Latham Boyle, proposes a mirror universe extending in the opposite direction of time from the big bang.
The model suggests that the two sides could exhibit reversed physical properties, including the relationship between matter and antimatter.
Understanding whether the big bang marked the beginning of everything, or a transition from an earlier cosmic state, remains one of the deepest unresolved questions in physics.
Scientists are examining competing theories about what may have existed before the big bang, challenging conventional assumptions about the beginning of space, time, and the universe itself.
The standard cosmological model describes the universe expanding from an extremely hot, dense early state approximately 13.8 billion years ago. However, it does not definitively establish whether time began at that moment or whether an earlier cosmic history existed.
A Scientific American examination of the subject highlights three theoretical approaches that could offer answers.
One is the no-boundary proposal developed by physicists Stephen Hawking and James Hartle. Their model suggests that the universe may have no conventional starting boundary. Instead, the earliest phase of spacetime could be structured in a way that makes the concept of a moment before the big bang meaningless.
Another possibility is a cyclic universe, advocated by Princeton University physicist Paul Steinhardt. This model proposes that the cosmos experiences successive periods of expansion and contraction, with a transition between them resembling a cosmic bounce rather than an absolute beginning.
A third theory, explored by physicist Latham Boyle, proposes a mirror universe extending in the opposite direction of time from the big bang. The model suggests that the two sides could exhibit reversed physical properties, including the relationship between matter and antimatter.
Researchers hope that observations involving gravitational waves, neutrinos, and changes in cosmic expansion could help distinguish between such competing explanations.
Nevertheless, none of these theories has been conclusively demonstrated.
The problem remains particularly challenging because scientists cannot directly observe events beyond the limits of the early universe's measurable history.
Understanding whether the big bang marked the beginning of everything, or a transition from an earlier cosmic state, remains one of the deepest unresolved questions in physics.
