Quantum Physics

How are we addressing the problems with the multiverse theory?

The possibility of a multiverse comprising of “equal universes” is a well-known sci-fi saying, as of late investigated in the Oscar-winning film “Everything, Wherever, at the Same Time.” Nevertheless, it is scientifically conceivable.

It is essential to state from the beginning that the multiverse’s existence (or lack thereof) is the result of our current comprehension of the fundamental laws of physics; it did not originate in the minds of whimsical physicists who devoured an excessive amount of science fiction.

The multiverse comes in many different flavors. Quantum mechanics, which governs the world of atoms and particles, is the source of the first and perhaps most widely used version. It suggests that a particle can be in multiple states at once—until the system is measured and selects one. As per one translation, all quantum prospects that we didn’t quantify are acknowledged in different universes.

Everlasting expansion
The subsequent rendition, the cosmological multiverse, emerges as a result of vast expansion. In 1981, physicist Alan Guth proposed that the early universe underwent a period of accelerated expansion in order to explain why the universe of today looks roughly the same everywhere. Space was stretched out during this time of inflation, and the distance between any two points grew faster than the speed of light.

Additionally, the existence of the primordial seeds that eventually developed into cosmological structures like galaxies and stars was predicted by inflation theory. By observing minute temperature changes in the cosmic microwave background—the remnants of the Big Bang’s light—in 2003, this was successfully discovered. The space experiments WMAP and Planck then measured it with incredible precision.

The majority of cosmologists now consider cosmic inflation to be the de facto theory of the early universe because of its remarkable success.

However, cosmic inflation had a (potentially unintended) effect. Space is stretched and smoothed on very large scales during inflation, typically much larger than the observable universe. However, in order for our universe to evolve into what it is today, cosmic inflation must come to an end at some point.

However, physicists quickly realized that even if inflation were to cease in all of space-time, some regions would continue to expand. It is possible to consider the regions that continue to expand as a distinct expanding universe. Inflating universes produce even more inflating universes, resulting in a multiverse of universes, and this process continues indefinitely.

“Eternal inflation” is the term given to this phenomenon. After being first described in 1983 by physicists Paul Steinhardt and Alex Vilenkin, eternal inflation remained a curious result of cosmic inflation until the beginning of the 21st century, when it was combined with a concept from string theory to provide a controversial but compelling explanation for the nature of our physical laws.

Although it hasn’t been proven, string theory is currently our best hope for a theory of everything because it combines gravity and quantum mechanics. However, instead of our usual three spatial dimensions plus time, physically realistic string theories must have at least ten dimensions. As a result, six or more of these dimensions must be “compactified,” or curled up so that we cannot see them, in order to describe our current universe.

This has a known mathematical procedure. The fact that there are at least 10500 ways to perform this compactification is the process’s problem—or perhaps its feature. This mind-bogglingly large collection of possibilities is referred to as the “string landscape.” A different set of physical laws, possibly corresponding to a different universe, will be produced by each compactification. This raises two crucial concerns: Why are we where we are in the string landscape?

The first question is elegantly answered by eternal inflation: As a result of the fact that a distinct point in the string landscape is realized by each expanding universe of the multiverse, it is possible for all possible physical laws to exist in the multiverse. But how is it that our universe is so good at making intelligent life like our own? Since we live in the universe where our physical laws are observed, some universes should statistically behave similarly to ours.

However, this viewpoint is highly contentious—many assert that it is not supported by scientific evidence, and it has prompted extensive research.


The multiverse’s observability presents an obvious obstacle. If it does exist, is it theoretically possible to observe the other universes? The answer is no for the quantum multiverse because different universes do not communicate. In contrast, the response in the inflationary multiverse is “yes, if we are lucky.”

Since all of the universes share the same physical space, neighboring universes could theoretically collide, possibly destroying our observable universe and leaving behind remnants and imprints. Hiranya Peiris of University College London and Matthew Johnson of the Perimeter Institute collaborated on a study to demonstrate that such collisions should, in fact, leave traces that can be found in the cosmic microwave background—light from the Big Bang—but that these signatures have not yet been discovered.

Theoretical difficulties lie ahead. The majority of the universes in the string landscape, according to some theorists, are mathematically impossible to exist in the same way as our own. Instead, they are in a swamp of solutions, and it seems like it’s hard to find string theory solutions that let cosmic inflation happen.

Cosmologists and string theorists disagree a great deal about whether or not string theory can even theoretically describe inflation. This conundrum, which suggests that either of the two ideas is incorrect and will result in a revolution in theoretical physics, is both perplexing and exciting.

Finally, cosmic inflation’s very foundation is being questioned right now. The raison d’être of enormous expansion is that, paying little heed to how the early universe looked, expansion would powerfully drive the universe to the smooth universe we see today. However, there has never been a thorough examination of the possibility that cosmic inflation can begin in the first place.

This is because, analytically, solving the equations that describe the process’s beginning is too difficult. Be that as it may, this question is currently being thoroughly tried by a few examination bunches all over the planet, including my own at Lord’s School London, where the force of present-day superior execution figuring is presented as a powerful influence for tackling these previously immovable conditions. Therefore, stay tuned.

Provided by The Conversation 

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