So some theoretical physicists are seriously considering the theory of the multiverse, according to which our world is just one of many. Moreover, applying quantum theory to the universe, we are forced to admit that it exists simultaneously in many states.
In other words, by allowing the application of quantum fluctuations to the Universe, we are practically forced to admit the existence of parallel worlds. It is also interesting that the combination of string theory and the "eternal" version of inflationary cosmology (talking about the inflationary model of the Universe) provides a natural basis for the so-called "landscape multiverse".
Multiverse Theory: Inflation
To begin with, the concept of the multiverse emerges in several areas of physics (and philosophy) at once, but the most striking example is the theory of inflation, which describes a hypothetical event that happened when our universe was very young - less than a second old. According to NASA, in an incredibly short period of time, the Universe has gone through a period of rapid expansion, "swelling", becoming larger and larger.
Thus, while inflation ended in our universe, there could be other, much more distant regions where inflation continued - and continues right now. Moreover, individual universes, according to LiveScience, can "pinch off" larger swelling, expanding universes, creating an endless sea of eternal inflation, filled with numerous individual universes.
This may explain why our universe has properties that it possesses, and especially those that are difficult to explain using concepts such as dark matter or the cosmological constant. "If there was a multiverse, then we would have random cosmological constants in different universes, and it's just a coincidence that the one that we have in our universe, takes on the value that we observe," said Dan Heling, a cosmologist at the University Arizona and expert in multiverse theory.
Multiverse Theory: Observations and Evidence
Interestingly, another evidence of the existence of the cartoon is observations - in our Universe so many things had to happen that the existence of life seems incredible. And if there was only one Universe, most likely, there would be no life in it. But in the multiverse, the likelihood of life is much higher. But this theory can hardly be called convincing, which is why most scientists remain skeptical about the idea of a multiverse.
And yet, many have tried to find more physical, convincing evidence of its existence. For example, if a neighboring universe happened to be near ours a long time ago, it may have collided with it, leaving a noticeable imprint.
This imprint could be in the form of distortions of the cosmic microwave background radiation or relic radiation (light left over from when the universe was a million times smaller than it is today) or in the strange properties of galaxies in the direction of the collision, according to a paper published by researchers at University College London. ...
Some astrophysicists have gone even further, looking for special kinds of black holes that might be artifacts from parts of our universe that split off into their own universe through a process called quantum tunneling.
"The potential discovery of these black holes could then indicate the existence of a multiverse," the theoretical physicists say. However, all these types of searches have not yet led to anything, so today the Multiverse remains hypothetical.
Multiverse Theory: Background Radiation
In 1964, physicists Arno Penzias and Robert Wilson worked at Bell Laboratories in Holmdel, New Jersey, creating ultra-sensitive microwave receivers for radio astronomy observations. But whatever they did, they did not succeed in ridding the receivers of the background radio noise, which, oddly enough, seemed to be coming from all directions at the same time.
Penzias contacted Princeton University physicist Robert Dicke, who suggested that radio noise could be cosmic microwave background radiation (CMB), which is the primary microwave radiation that fills the universe.
This is the story of the discovery of the CMB, simple and elegant. For their discovery, Penzias and Wilson received the Nobel Prize in Physics in 1978, and with good reason. Their work ushered in a new era of cosmology, allowing scientists to study and understand the universe like never before.
Interestingly, the work of physicists also led to one of the most amazing discoveries in recent history: the unique features of the relic radiation may be the first direct evidence that an infinite number of worlds outside the known universe really exist. However, in order to correctly understand this unusual statement, it is necessary to make a journey to the beginning of time.
Multiverse Theory: The Big Bang
According to the generally accepted theory of the origin of the universe, during the first several hundred thousand years after the Big Bang, our universe was filled with an incredibly hot plasma, consisting of nuclei, electrons and photons, which scattered light.
By about 380,000 years, the continued expansion of our universe had cooled it to temperatures below 3,000 Kelvin, which allowed electrons to fuse with nuclei to form neutral atoms, and the absorption of free electrons allowed light to illuminate darkness.
Proof of this - in the form of the previously mentioned CMB - is what Penzias and Wilson found. Their discovery ultimately helped establish the Big Bang theory.
For many eons, the ongoing expansion has cooled our universe to a temperature of only about 2.7K, but this temperature is uneven. Differences in temperature arise due to the fact that matter is unevenly distributed throughout the universe. This is believed to be caused by tiny fluctuations in quantum density that occurred just after the Big Bang.
In 2017, researchers from the University of Durham in the UK published a paper suggesting that CMB prints (called cold spots) may be evidence of other worlds. The authors hypothesized that the spots in the microwave background radiation appeared as a result of a collision between our universe and another.
Multiverse Theory: Dark Matter
New, extremely interesting research adds another proof to the treasury of the theory of the Multiverse. Its results, Vice writes, suggest that black holes formed from collapsed universes generate dark matter, and our own universe may look like a black hole to outsiders.
Note that dark matter is an invisible substance that accounts for most of the mass of the Universe - although it does not emit detectable light, it still exists, since it has a gravitational effect on clusters of galaxies and other emitting objects in space.
A dizzying array of hypotheses have been proposed to explain dark matter, but now scientists have suggested that primordial black holes, hypothetical objects dating back to the early days of the universe, "are a viable candidate for dark matter." This conclusion was reached by an international team of researchers from the United States, Japan and Taiwan, in a paper published in the scientific journal Physical Review Letters in January this year.
And yet, at the moment, all of these concepts are speculative, although physicists expect new ways of observing with sophisticated telescopes in the coming years to help answer many questions.
Multiverse Theory: Inflation Again
Famed British theoretical physicist Stephen Hawking died on March 14, 2018 after spending decades confined to a wheelchair and dependent on a speech synthesizer due to the suffering caused by amyotrophic lateral sclerosis. The last research work of the scientist, published just 10 days before his death, was written together with the professor of theoretical physics Thomas Hertog and concerned the multiverse.
Who knows which of the countless worlds we live in?
Their work is essentially an extension of the Theory of Inflation, which suggests that before the Big Bang, the universe was filled with energy that was part of space itself, and this energy caused space to expand at an exponential rate. It was this energy that gave rise to the Big Bang, and this is what we talked about earlier.
However, since inflation, like everything else, is quantum in nature, this means that there must be regions of space in the universe where inflation ends and the Big Bang begins. However, these areas can never collide with each other, since they are separated by areas of inflating space.
Multiverse Theory: Criticism and Conclusions
In conclusion, it should be said that when someone talks about the theory of the multiverse, it can sound both cocky and humble at the same time. But many physicists have a completely different reaction: in their opinion, the idea of a multiverse is unscientific and perhaps even "dangerous" in that it can lead to misdirected scientific efforts.
One way or another, despite the criticism of the theory of the plurality of worlds, the data of scientific research (some of which are described in this article) make it possible to put forward even such seemingly insane theories. After all, returning to the anthill analogy, what do we know about the world we live in?