Does the multiverse exist? Scientists present first evidence

Between 1912 and 1922, astronomer Hubble measured the spectra of many galaxies and found that their spectra were all redshifted, meaning they were moving away from Earth. In 1929, Hubble compiled the observational data and published his results that the farther away galaxies are from us, the faster they are receding, which means that the universe is expanding. Later, many scientists reversed Hubble's law and discovered that there is a starting point for the universe, that is, the Big Bang.

For the first few hundred thousand years after the Big Bang, the universe was filled with a hot plasma soup of atomic nuclei, electrons, and light. As the universe expanded, by about 380,000 years, the temperature of the universe dropped below 3,000 Kelvin, at which point electrons were captured by atomic nuclei to form atoms, and light was finally released to illuminate the universe. Today, this light is cooled to 2.7 Kelvin by the expanding universe and becomes the cosmic background radiation.

In 1964, Penzias and Wilson built a microwave receiver for radio astronomy observations. But when they used the instrument, they found a lot of radio background noise. These noises seem to be coming from all directions, and there is no way to get rid of them by any means. It was later confirmed that these noises were the cosmic microwave background radiation.

The discovery gave support to the Big Bang theory, and Penzias and Wilson were awarded the Nobel Prize in 1978.

Later, the European Space Agency launched the "Planck" satellite to map the cosmic microwave background radiation in more detail. Scientists have found that the cosmic background radiation temperature is not uniform, which is caused by tiny quantum density fluctuations after the big bang, which also supports the inflation theory from the side.

We can see from the picture that those blue spots are 0.00015 degrees lower than their surroundings, which scientists call cold spots. However, researchers from the Centre for Extragalactic Astronomy at Durham University in the UK believe that these cold spots are evidence of an outer universe. A collision of our bubble universe with another bubble universe in the multiverse would imprint the background radiation, leaving a cold spot.

Quantum mechanics uses wave functions to describe the positions and properties of particles. There are many possible forms of this particle, but we need a way to realize one possibility and eliminate the others. According to the Copenhagen interpretation of quantum mechanics, observation can collapse the wave function, forcing the particle into a definite state. The most famous example of this is "Schrödinger's cat," which is both alive and dead at the same time.

There are many other theories that have tried to replace the Copenhagen interpretation, Everett's theory of the multiverse is one of them, and has become the favorite theory of many science fiction works. Everett believed that the wave function is real and it does not collapse. Every result of a quantum measurement exists in some universe, in which case there must be a very large number of universes.

The final paper by renowned physicist Stephen Hawking also dealt with the multiverse. Hawking pointed out that cosmic inflation after the Big Bang could have happened repeatedly, creating many universes. Hawking's idea is an extension of the cosmic inflation theory, and the evidence support for the inflation theory is the uneven temperature of the background radiation, so scientists can believe that the cold spot of the background radiation is used as evidence for the multiverse.

Through inflationary theory we can also predict that the universe is like an infinite fractal consisting of different pocket universes separated by inflation. The laws of physics may vary from one universe to another, and together they make up a multiverse.