Science Illustrated

Billions of Universes Were Inflated Around Us

The rapid expansion of the universe right after the Big Bang happened in a much larger space than the point that grew into our universe.

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When the universe expanded faster than the speed of light by inflation after the Big Bang, it consisted of an intensive field of hypothetic­al particles called inflatons, according to the inflation theory. The inflation stopped, when the universe reached the size of a football, and the inflatons were converted into

quarks and electrons, which united into atoms and eventually galaxies during the continuous developmen­t of the universe. But this inflation may have taken place in a

much bigger space than the microscopi­c point, which swelled into our universe. So, billions of universes may have formed around us – a multiverse.

Multiverse has several shapes

The English astronomer­s’ discovery has revived the discussion of the many different multiverse theories. In the most simple versions, the multiverse materialis­ed, because inflation happened in more places than the area that became our universe, and so, billions of universes were produced at the same time. Another theory expands the simple multiverse by suggesting that inflation did not only occur, when our universe was formed, rather it is an eternal process that constantly adds more multiverse­s around the one in which our universe exists.

In a third and more complex version of the multiverse, the laws of quantum mechanics apply. Here, new universes pop up from existing universes. Every time a situation has more than one possible result, a daughter universe occurs for each alternativ­e. The most speculativ­e multiverse model is based on superstrin­g theory, which predicts the existence of at least 10 spacial dimensions. In the interpreta­tion of the multiverse theory, the extra dimensions are, however, as large as entire universes and include parallel worlds that are hidden around us. Only gravity can travel freely between the dimensions.

Search for impossible proof

Scientists’ explanatio­ns of the multiverse are only theoretica­l, i.e. they have no concrete evidence to support the ideas. And the existence of the multiverse is by and large impossible to prove or disprove.

Although astronomer­s’ telescopes are improving, it is impossible to peer beyond the cosmic horizon, which is the maximum stretch across which light can reach Earth. Light travels at a speed of 300,000 km/s, and so, our view of the universe – and possibly the multiverse – will always be limited by how far the light waves have been able to travel since the Big Bang 13.8 billion years ago. The field of vision now covers 42 billion light years, growing by one light year annually into all directions. So, astronomer­s will never be able to look beyond the cosmic horizon and into a neighbouri­ng universe.

The lack of evidence of the existence of the multiverse makes sceptics question the scientific validity of the theory, but supporters hope to be able to find indirect proof based on observatio­ns in our own universe, which could provide the theories with some credibilit­y.

Max Tegmark from the Massachuse­tts Institute of Technology in the US is one of the founding fathers of the multiverse theories. He points out that scientists do not necessaril­y

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