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Mirror worlds

Suppose, even as you read this, your doppelganger in another universe ? an exact replica of this world ? is playing cricket? Recent advances in cosmology have renewed interest in the existence of parallel universes.

india Updated: Jun 12, 2006 00:06 IST

Suppose, even as you read this, your doppelganger in another universe — an exact replica of this world — is playing cricket? Recent advances in cosmology have renewed interest in the existence of parallel universes. An idea proposed by quantum theorists, this has fascinated generations of physicists and philosophers, permeating not only science but also popular culture and literature — from Plato’s suggestion that we see “mere shadows of reality” to Lewis Carroll’s concept of a rabbit hole for Alice to slip out of the real world.

Like the universe we inhabit, parallel universes are regions of space and time containing matter, galaxies, stars, planets and living beings. Our ‘doubles’ there are supposedly connected to us through mechanisms that only quantum physics can explain. Some scientists believe that wormholes — ‘tunnels’ in space-time connecting blackholes — make it possible for these universes to exist mere millimeters away. They suggest that neuroscience, through the study of altered states of awareness, indicates the proximity of parallel worlds to this universe, and that gravity is just a weak signal leaking out of them into ours.

Most of us are comfortable with the familiar three-dimensional universe, with its up-down, front-back, and left-right options. A sound wave, for instance, ‘exists’ in these three dimensions and propagates in all directions simultaneously like an expanding balloon. In two dimensions, the wave would look like ripples in a pond, spreading only along the surface — not perpendicular to it, which is the third dimension.

In the early Nineties, physicists Theodor Kaluza and Oskar Klein published theories linking electromagnetism with gravity via ‘extra dimensions’. This led to the ‘multiverse’ theory in the Fifties. The idea was to explain the bizarre findings of quantum physics and general relativity and find the holy grail of physics: a ‘theory of everything’ that would unite all the forces of nature — electromagnetism, gravity, and the strong and weak nuclear forces — into a single cohesive expression.

The superstring theory is the most promising roadmap for this. In it, vibrating strings — not point-like particles — make up the universe’s fundamental constituents, with different resonances of the strings creating the different particles that we see. Each string is unimaginably small, about 100 billion billion times smaller than a proton, and vibrates only in a space-time consisting of ten dimensions.

This made physicists realise that the three spatial dimensions once thought to describe the universe weren’t enough. There could be actually 11 dimensions, with our universe just one among an infinite number of membranous ‘bubbles’ that ripple as they wobble through the 11th dimension. This new physics is taking scientists closer than ever to understanding nature’s unity and higher dimensions.