Physicists have put forward a bold hypothesis that our universe has a mirror twin, which can manifest itself as clusters of invisible but matter-attracting neutrinos - what we call dark matter.
A new unusual idea suggests that at the moment of the Big Bang, a “mirror” Universe appeared along with ours, rushing along the time axis in the opposite direction.
Although in principle, it is impossible to get into this anti-Universe, its existence should manifest itself in the Universe in the form of a yet undiscovered variety of neutrinos. Clusters of such neutrinos can create the very dark matter whose particles cannot be found, despite all the efforts of physicists.
The theory of a mirror or anti-universe
The hypothesis of the existence of a “mirror” universe was put forward a few years ago by a team of scientists led by the famous South African astrophysicist Neil Turok, who now works at the University of Manchester (UK). Their new paper has been accepted for publication in the Annals of Physics and made available in the open online preprint library arXiv.org. It considers some of the implications of this unusual idea, including dark matter.
The most fundamental symmetry in physics – CPT invariance – speaks of the invariance of physical laws with simultaneous inversion of charges (C), coordinates (P), and time (T). Science knows various exceptions – violations of P- and C-symmetries, as well as their various combinations.
For example, violation of CP invariance can lead to the dominance of particles and the almost complete absence of antiparticles in the Universe. However, no simultaneous violation of the CPT symmetry has yet been discovered: if the charges, coordinates, and time are reversed in the system, in principle, nothing will change for it.
Neil Turok and his co-authors have applied CPT invariance to the universe itself. In such a hypothetical picture, our world turns out to be only half of a binary system. Its CPT reverse twin travels through time in the opposite direction, with opposite charges and mirrored coordinates.
Calculations have shown that the existence of an anti-universe in a “double” Universe makes it possible to quite simply explain the existence of dark matter. This mysterious substance is not visible to any scientific instrument, since it is able to interact with ordinary matter only through gravity.
Dark matter can only be seen by the attraction of ordinary matter: for example, along the trajectories of stars around an invisible gravitating cluster. This makes it possible to map clumps of dark matter on the scale of entire galaxies but does not make it possible to capture and study the particles that make it up.
Hypothetical ideas about new particles
Until now, there are only hypothetical ideas about these particles. And if we start from the fact that we live only in half of the integral “double” CPT-invariant Universe, then one hypothesis becomes more. Neil Turok and his colleagues showed that in this case, new types of neutrinos should appear.
Today there are six of them (electron, muon, and tau neutrinos plus their antiparticles with opposite charges), they all have a positive spin, although the rest of the fundamental particles are both positive and negative. But with the existence of a second anti-universe, neutrinos with reverse spin must also exist.
They practically do not interact with ordinary matter in any way and can only appear in very massive clusters, due to their gravity – just like a hypothetical dark matter. According to the calculations of Neil Turok and his colleagues, the number of such neutrinos should be enough to observe all the necessary effects of dark matter.
The unusual hypothesis allows us to draw several testable conclusions about the fundamental properties of neutrinos. In particular, it predicts that at least one type of these particles must be massless. So far, this question remains open: the experiments allowed us to establish only the upper limit of neutrino masses. Perhaps new work will help to clarify them completely – and we will receive the first evidence in favor of the existence of a twin anti-Universe of our own.
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• Al-Sibai, N. (2022, March 17). Scientists say there may be a mirror universe in which time runs backwards. Futurism.
• Boyle, L., Finn, K., & Turok, N. (2022, January 22). The big bang, CPT, and Neutrino Dark matter. arXiv.org.
• Sutter, P. (2022, March 16). Our Universe may have a twin that runs backward in time. LiveScience.
• Young, C. (2022, March 17). There might be an “anti-universe” going backwards in time before the big bang. Interesting Engineering.