Multiverse Theory

Drop a bath bomb into a tub, and you will see countless foam bubbles popping up across the surface. Some cosmologists suggest that the birth of our universe might have looked very similar to this bubbly bath.

Right after the Big Bang, our young universe underwent cosmic inflation, expanding faster than light in the blink of an eye. But according to some models, this rapid stretching did not stop everywhere at once. In some pockets, inflation slowed down and cooled into stars and galaxies, while elsewhere the expansion raged on.

As a result, countless independent bubble universes formed across an ever-expanding cosmic space. Our universe is simply one tiny bubble floating in this boundless sea. Under some theoretical frameworks, such as string theory, the fundamental physical constants in other bubbles—like the mass of particles or the strength of gravity—could be entirely different from our own.

On the morning of an important exam, you might agonize over taking the bus or the subway before finally choosing the bus. But what if another version of you took the subway in a different reality?

In quantum physics, microscopic particles can exist in multiple states at once until they are measured. According to the many-worlds interpretation, making an observation does not magically erase the unchosen possibilities. Instead, every possible outcome is realized in its own branching universe.

In everyday terms, you could imagine a reality where you took the bus and another where you took the subway, both coexisting in parallel. However, what splits reality in this interpretation is not human decision-making, but countless microscopic quantum events happening constantly. With every such event, new parallel universes branch out like limbs on an ever-growing tree.

The multiverse is not a fantasy story where you can hop through dimensional portals to meet an alternate version of yourself.

In most multiverse models, other bubble universes or branched worlds are completely isolated from ours by physics. There is no known way for us to visit them or even send a signal. Physicists once looked for imprints left by collisions with neighboring bubbles in the cosmic microwave background, but no convincing evidence has been found. This leads to a fierce debate among scientists: if something cannot be tested or observed, is it still science?

Strictly speaking, the multiverse is not a proven scientific law. It is a mathematical hypothesis built to logically explain how our early universe expanded and why the quantum world behaves so strangely.