Though its actual vastness is substantially more grandiassed, the observable cosmos spans 13.7 billion years into the past. Cosmic expansion defines the limit of our "Hubble Volume" by guiding the farthest light we observe from galaxies now 42 billion light-years away. But this begs a terrible question: beyond this horizon?
First theory: an infinite cosmic ocean
The Big Bang theory holds that space itself might be limitless. If such is true, beyond our Hubble Volume is more of the same—countless galaxies, stars, and planets, repeating eternally. This " Type 1 Multiverse" suggests:
same rules of physics applied everywhere.
endless copies: Your exact doppelganger is reading this paper somewhere.
Philosophically, every conceivable event happens infinitely, always.
The universe's fast expansion means that light from these locations hasn't had time to reach us—never will.
Second Theory: Bubble Universes inside Cosmic Foam
A more extreme theory suggests a "Type 2 Multiverse," in which our planet is one of innumerable vacuum bubbles in an always expanding universe. Every bubble contains:
Different physical laws: atoms never form or gravity might not exist.
Not interacting with other bubbles; holes of unstable spacetime divide them.
If this idea is true, outside our planet is a foreign terrain shaped by laws without our comprehension.
A View Beyond: The Dark Flow Mystery
Astronomers observed galaxies moving in a consistent direction in 2008, as though pulled by gravity from somewhere else than the visible cosmos. Dubbed the "dark flow," this phenomena might suggest:
Grand constructions far beyond our cosmic horizon.
Proof in favor of a multiverse.
Though debatable, future studies of this motion could provide hints about what—or who—lives in the invisible world.
These concepts are still only theoretical for now. The expansion of the universe guarantees areas beyond 42 billion light-years are always hidden. Still, ideas like the multiverse force us to consider not just where we are but also what reality itself might demand.
"The universe isn't just stranger than we imagine," scientist Brian Greene famously remarked, "it's stranger than we can imagine."