[Aug 2, 2022: Edwin Cartlidge]
Our universe may be a mirror image of an antimatter universe spreading backwards over time. (credit: Getty Images)
Our universe may be a mirror image of an antimatter universe stretching back in time before the Big Bang. So claim physicists in Canada, who have produced a new cosmological model positing the existence of an “antiuniverse” that, paired with our own, preserves a fundamental law of physics called CPT symmetry. Researchers still need to work out many details of their theory, but they say it naturally explains the existence of dark matter.
The standard cosmological models tell us that the universe – space, time and mass/energy – came into existence about 14 billion years ago and has since expanded and cooled, creating a progressive fusion of subatomic particles, atoms, stars and planets. headed towards formation.
However, Neil Turok of the Perimeter Institute for Theoretical Physics in Ontario believes that these models’ reliance on ad-hoc parameters means that they resemble Ptolemy’s description of the solar system. One such parameter, they say, is the brief period of rapid expansion known as inflation that may account for the mass uniformity of the universe. “This is the limit of the mind that you explain a new phenomenon by inventing a new particle or field,” he says. “I think it may be misleading.”
Instead, Turok and his Perimeter Institute colleague Latham Boyle set out to develop a model of the universe that could explain all observable phenomena based only on known particles and fields. He asked himself if there was a natural way for the universe to expand beyond the Big Bang – a singularity where general relativity breaks down – and then the other way around. “We found that there was,” he says.
The answer was to assume that the universe as a whole obeys the CPT symmetry. This fundamental principle requires that any physical process remain the same if time is reversed, space is reversed, and particles are replaced by antiparticles. Turok says this is not the case for the universe we observe around us, where time moves forward as space expands, and there is more matter than antimatter.
Our universe may be a mirror image of an antimatter universe spreading backwards over time. (credit: creative commons)
Instead, Turok says, the entity respecting symmetry is an in-universe-antiuniverse pair. The Anti-Universe will retreat from the Big Bang over time, as it grows larger, and along with antimatter its spatial properties will be reversed compared to those in our universe – similar to the formation of the electron-positron Position pairs in a vacuum, Turok says.
Turok, who also collaborated with Kieran Finn of the University of Manchester in the UK, acknowledges that the model still needs a lot of work and is likely to have many detractors. In fact, he says he and his colleagues “had a lengthy discussion” with referees reviewing the paper for physicals. Review The paper – where it was eventually published – on temperature fluctuations in the cosmic microwave background. “They said you have to explain the ups and downs and we said it was a work in progress. Eventually they gave up,” he says.
In very broad terms, Turok says, the fluctuations are caused by the quantum-mechanical nature of space-time near the Big Bang singularity. While the distant future of our universe and the distant past of the universe would provide definite (classical) points, all possible quantum-based permutations would exist in the middle. He and his colleagues counted examples of each possible configuration of the CPT pair, and worked out which one was most likely to exist. “It turns out that the universe most likely is the one that looks like ours,” he says.
Turok says that quantum uncertainty means that the universe and the universe are not exact mirror images of each other – which precipitates thorny problems like free will.
But problems aside, Turok says the new model provides a natural candidate for dark matter. This candidate is a super-elusive, very massive particle called a “sterile” neutrino, hypothesized to have a finite (very small) mass of the more common left-handed neutrino. According to Turok, the CPT symmetry can be used to work out the abundance of right-handed neutrinos in our universe from first principles. Taking into account the observed density of dark matter, they say that the volume produces a mass of about 5×108 GeV for a right-handed neutrino—about 500 million times the mass of a proton.
Turok describes that mass as “tantalizingly”, derived from some of the anomalous radio signals observed by the Antarctic Impulsive Transient Antenna (ANITA). The balloon-borne experiment, which flies high over Antarctica, typically observes cosmic rays moving down the atmosphere. However, on two occasions ANITA has detected particles traveling through Earth with masses between 2 and 10×108 GeV. Given that normal neutrinos would almost certainly interact before reaching it, Thomas Weiler of Vanderbilt University and his colleagues recently proposed that the culprits were decaying right-handed neutrinos.
Turok, however, points to a fly in the ointment—that the CPT symmetric model requires these neutrinos to be completely immobile. But he remains a cautious optimist. “It is possible for these particles to decay over the age of the universe, but it takes a little adjustment to our model,” he says. “So we’re still curious but I certainly wouldn’t say we’re confident at this stage.”
Check out our New Discovery section for more science and technology stories the bright side of the news,
Note: Above Contents Edwin Cartridge, Content can be edited for style and length.
Like feel good stories like this? bring The Bright Side of the News’ newsletter,