After the Big Bang, there was another Dark Bang…

This is a picture of the galaxy cluster Cl0024+1654 taken by the Hubble Space Telescope, with dark matter shown in blue.

Introduction: The mystery of dark matter has always puzzled scientists. Recently, some physicists have proposed that dark matter was formed in another cosmic "Big Bang". If this theory is confirmed, it may change our view of the early universe.

Today, astronomers generally agree that the universe began with a Big Bang: About 13.7 billion years ago, an extremely hot, dense point of radiation suddenly exploded, giving rise to the universe as we know it today.

However, is this Big Bang the only event that created the universe? Some physicists have proposed a bold idea that there may be another "Dark Big Bang" after the Big Bang, which can explain the mysterious source of dark matter in the universe.

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Invisible dark matter

Dark matter is a substance that we cannot directly observe. It neither emits nor reflects light. However, by observing and analyzing the gravitational effects on other substances, scientists believe that dark matter exists in the universe and its quantity is huge, accounting for about 85% of all matter in the universe.

Dark matter has an important influence on the formation and movement of galaxies, and is also a key clue for astronomers to study the structure and evolution of the universe. However, the nature and origin of dark matter has always been a mystery.

Schematic diagram of the Big Bang

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Is there a dark bang after the Big Bang?

In the paper "Dark Matter and Gravitational Waves from the Dark Big Bang" submitted in February last year, American scientist Katherine Freese and Swedish scientist Martin Wolfgang Winkler proposed the theory of "Dark Big Bang".

The two scientists are from the University of Michigan and Stockholm University in Switzerland. Catherine Freeze is a world-leading expert in dark matter research. According to their theory, the "dark big bang" may be the source of dark matter and dark radiation.

The two scientists' "dark big bang" theory holds that the dark big bang occurred sometime after the initial Big Bang. They also believe that the "dark big bang" occurred in a so-called "dark sector" composed of dark matter and dark energy. At some point, this dark sector may have undergone a phase transition, converting the dark vacuum energy into a high-temperature dark particle plasma.

According to their paper, dark matter could be produced in a variety of ways during the dark big bang. One possibility is so-called "dark matter cannibalism," where dark matter particles devour each other. Another possibility is that dark matter particles annihilate in pairs and then go through a cooling phase called "thermal freeze."

The researchers also found that the dark matter explosion must follow certain restrictions; if it happened too early, there would be too much dark matter now; if it happened too late, there would be too little dark matter now. But if the dark explosion occurred when the universe was less than a month old, it would be consistent with all known observations.

Schematic diagram of using pulsars to detect gravitational waves

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It's not easy to verify the new theory

Although it is confirmed that dark matter produced by the dark big bang event is difficult to detect directly or indirectly, Freeze and Winkler still believe that the dark big bang may produce a unique gravitational wave signal. Gravitational waves are ripples in space-time that are still rippling in the universe. This means that the dark big bang theory may be tested with the help of gravitational waves in the future.

However, the two authors of the paper also admitted that the sensitivity of current gravitational wave detectors is not enough to detect the gravitational wave signal of the dark big bang. But another gravitational wave detector that uses distant pulsars, the so-called "pulsar timing array" experiment, may be able to do this.

Reference Information:

https://thedebrief.org/dark-big-bang-theory-argues-a-second-cosmological-origin-event-could-help-resolve-dark-matter-mystery/

https://www.livescience.com/a-dark-big-bang-may-have-flooded-the-universe-with-invisible-matter-new-study-proposes

Planning: Zhang Chao, Li Peiyuan, Yang Liu

Reviewed by: Li Xin, Research Librarian of Beijing Planetarium