The concept of multiple universes dates back to the 6th century, when the pre-Socratic Greek philosopher Anaximander first proposed the idea of infinite worlds.
However, the ideas of the multiverse only gained scientific weight in the 1980s, along with the theory of inflation, which not only explained why the universe was so flat and smooth, but also predicted the endless creation of new “bubble” species of universes.
And now it seems that scientists are finally closer than ever to finding evidence that could prove the existence of a multiverse.
One hundred years after Edwin Hubble proved that there are other galaxies, we may soon find proof of the existence of the multiverse
Image credit: ESA Hubble
Image credit: ESA
Image credit: ESA Hubble
The most advanced multiverse model known to date is cosmological inflation. The theory was first proposed by physicist Alan Guth in the 1980s, who proposed that after the Big Bang, about 13.8 billion years ago, the universe expanded exponentially at a fraction of a second. This process could be compared to a huge microscope that magnified the temporal random change in the amount of energy at a point in space, corresponding to a scale of less than 10-28cm, to cosmological distances by leaving marks in the cosmic microwave background and in the distribution of galaxies.
Inflation is also part of the current known model of the universe, called Lambda Cold Dark Matter (LCDM), in which the shape of the trajectory of the universe resembles a funnel that grows larger and wider over time.
At the heart of this cosmological inflation is the idea of ”bubbles”—infinite, unique universes that were created when some parts of spacetime expanded faster than others.
The Russian-American theoretical physicist Andrei Dmitrievich Linde later noticed that the exponentially rapid expansion of the universe could occur not only in a false vacuum, but also during a slow transition from a false vacuum. Therefore, in 1983, he proposed another version of inflation theory – chaotic inflation. In his study, the physicist explained inflation as a natural (and may even be inevitable) consequence of the chaotic initial conditions in the early universe.
Yet in 2013, when the European Space Agency announced a map of the cosmic microwave background (CMB) created from data collected by a satellite called Planck, the inflationary theory faced some serious problems.
While multiverse ideas gained scientific weight in the 1980s with the inflation proposal, scientists are currently looking for alternative ideas.
Image credit: ESA
Image credit: NASA
Image credit: NASA
Therefore, many cosmologists in recent years have been looking for alternatives that could finally reveal the story of the history of our universe. One such could be the cyclic universe theory, which states that the universe is formed over and over again in cycles.
“What I didn’t like about inflation is that there are very few real predictions – you don’t get much more than you put in. I just thought there had to be a better explanation,” said Neil Turok, a physicist at the University of Edinburgh, UK.
Scientists who proposed the cycle model suggest that the Big Bang was not the beginning of time. They believe that this led to another phase that has several cycles of contraction and expansion that repeat endlessly.
“It allows us to go beyond the Big Bang, but without any magical philosophical problems, because time has always existed in the past,” said Stephon Alexander, a professor of physics at Brown University and co-inventor of inflation. a model of the universe based on string theory.
As another concept that doesn’t invoke cosmic inflation, in 2018 physicist Neil Turok proposed a mirror universe—one that stretches back in time since the Big Bang.
While the inflationary theory states that the early universe expanded into an infinite number of different universes, known as the inflationary multiverse, the mirror universe theory is much more economical and predictable.
“It’s an approach that was born out of a certain sense of frustration with previous approaches. In my opinion, they have all become quite complicated and contrived, including my own approaches,” explained Turok.
“I think we could theoretically be on the verge of the next big revolution. It will be inspired by data, by the failure of traditional paradigms. It will change our view of the universe,” he added.
Turok and his team predict that our universe could have a twin in which time moves backwards.
Image credits: Physics
“We know that the early universe was dominated by hot radiation. This means that if you turn the clock back from there, the size of the universe will shrink to zero in a very simple way. Mathematically, you can trace a straight line that cuts through the Big Bang. This allows us to extrapolate back to another ‘mirror image’ copy of our universe on the other side of the big bang,” the physicist shared the revolutionary idea.
“The two sides of the universe have grown continuously in opposite directions since the big bang, following the known laws of gravity and particle physics.” The extreme simplicity of the vast universe, which is very smooth and flat, is a direct result of the simplicity of these laws,” he added.
Turok’s mirror universe theory not only proposes a simpler explanation for the history of the universe, but also aims to get some answers about dark matter.
“We realized that our idea could solve the puzzle of dark matter, the mysterious substance that holds galaxies together, in the form of particles that we haven’t seen directly but for which we already have strong evidence,” said Turok.
“They’re called right-handed neutrinos. They have been used since the 1970s to explain the tiny masses of left-handed neutrinos that have been observed. While every other dark matter model postulates an entirely new particle, we don’t have to. That was a huge surprise,” he added.
While the mirror universe theory goes further in explaining things that inflation cannot, all scientific predictions will be tested in large-scale galaxy surveys like the Vera C. Rubin Observatory.
The largest LSST camera ever built for astrophysics, with a resolution of 3,200 megapixels, will soon help unravel the mysteries of the universe by capturing detailed images of the Southern Hemisphere sky over a period of 10 years, creating the most comprehensive time-lapse view of our universe ever seen.
“Getting the camera to the top was the last big piece of the puzzle. With all the components of Rubin physically in place, we are on the path to transformative science with LSST,” enthused Victor Krabbendam, who is the project manager of the Rubin Observatory.
Rubin Observatory, with its 3,200-megapixel LSST camera, the largest ever built, is on its way to finding evidence of the existence of the multiverse.
Image credits: VERA C. RUBIN Observatory
Image credits: VERA C. RUBIN Observatory
Image credit: ESA Hubble
Modern physics, including quantum theory and cosmology, proposes several theories about how our universe could be just one of many. Until today, everyone still lacked some kind of evidence or proof, yet it seems that the situation will change very soon.
Thanks to the Vera C. Rubin Observatory and their largest digital camera ever constructed, we may discover that we live in an entire ocean of other universes.
People on the internet have been inundated with news of the possibility of a multiverse
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