Multiverse is a hypothetical space or realm consisting of a number of universes, of which our own universe is only one.The concept of parallel universes has been depicted frequently in science fiction, without any real evidence that they actually exist.
In the mid-20th century, the ‘Many Worlds’ theory first speculated that multiple versions of reality branch out from one another as distinct entities existing in discrete locations, without any interaction. This new theory suggests that all of these infinite multiple worlds (Multiverse) overlap and occupy the same region of time and space simultaneously, just like a quantum state.
“All possibilities are therefore realized – in some universes the dinosaur-killing asteroid missed Earth. In others, Australia was colonized by the Portuguese,” Wiseman said in a press release. “But critics question the reality of these other universes, since they do not influence our universe at all. On this score, our “Many Interacting Worlds” approach is completely different, as its name implies.”
Today a debate rages over whether multiple universes exist. In recent decades, advances in cosmology have implied (but not proved) the existence of a multiverse. In particular, a theory called inflation suggests that in the instant after the Big Bang, space inflated rapidly for a brief time and then expanded more slowly, creating the vast bubble of space in which the Earth, sun, Milky Way galaxy and billions of other galaxies reside today. If this inflationary cosmology theory is correct, similar big bangs occurred many times, creating numerous other bubbles of space like our universe.
Properties such as the mass of basic particles and the strength of fundamental forces may differ from bubble to bubble. In that case, the popular goal pursued by many physicists of finding a single theory that prescribes all of nature’s properties may be in vain. Instead, a multiverse may offer various locales, some more hospitable to life than others. Our universe must be a bubble with the right combination of features to create an environment suitable for life, a requirement known as the anthropic principle.
But many scientists object to the idea of the multiverse and the anthropic reasoning it enables. Some even contend that studying the multiverse doesn’t count as science. One physicist who affirms that the multiverse is a proper subject for scientific investigation is John Donoghue of the University of Massachusetts, Amherst.
As Donoghue points out in the 2016 Annual Review of Nuclear and Particle Science, the Standard Model of Particle Physics — the theory describing the behavior of all of nature’s basic particles and forces — does not specify all of the universe’s properties. Many important features of nature, such as the masses of the particles and strengths of the forces, cannot be calculated from the theory’s equations. Instead they must be measured. It’s possible that in other bubbles, or even in distant realms within our bubble but beyond the reach of our telescopes, those properties might be different.
Maybe some future theory will show why nature is the way it is, Donoghue says, but maybe reality does encompass multiple possibilities. The true theory describing nature might permit many stable “ground states,” corresponding to the different cosmic bubbles or distant realms of space with different physical features. A multiverse of realms with different ground states would support the view that the universe’s habitability can be explained by the anthropic principle we live in the realm where conditions are suitable and not by a single theory that specifies the same properties everywhere.
Don’t critics say that neither string theory nor inflationary cosmology has been definitely established ?
That’s true of all theories beyond the Standard Model. None of them are established yet. So we can’t really say with any confidence that there is a multiverse. It’s a physical possibility. It may be wrong. But it still may be right.