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Scientists are finally figuring out how much dark matter – the almost imperceptible material that shoots everything, but doesn’t emit light – really weighs.
The new estimate helps determine the weight of its particles – with implications for what the mysterious substance actually is.
Research drastically reduces the potential mass of dark matter particles, from about 10 ^ minus 24 electronvolts (eV) to 10 ^ 19 Gigabitron volts (GeV), to between 10 ^ minus 3 eV and 10 ^ 7eV – a possible mass range several billion billion times smaller than before.
The results could help dark matter hunters focus their efforts on the indicated range of particle masses – or they could reveal that a previously unknown force is at work in the universe, said Xavier Calmet, professor of physics. and Astronomy at the University of Sussex in the UK.
Related: The 11 Biggest Unanswered Questions About Dark Matter
Calmet, along with doctoral student Folkert Kuipers, also from the University of Sussex, described their efforts in a new study to be published in the March issue of Physical letters B.
What is dark matter?
By some estimates, dark matter makes up about 83% of all matter in the universe. It is believed to only interact with light and ordinary matter by gravity, which means it can only be seen by the way it bends light rays.
Astronomers found the first clues of dark matter by looking at a galactic cluster in the 1930s, and theories that galaxies are threaded and lined with vast halos of dark matter became common after the 1970s, when astronomers realized that galaxies were spinning faster than they should otherwise. , given the amount of visible matter they contained.
Related: The 12 Weirdest Objects In The Universe
Possible candidates for dark matter particles include tiny ghostly particles known as neutrinos, theoretical dark and cold particles called axions, and proposed weakly interacting massive particles, or WIMPs.
The new mass limits could help eliminate some of these candidates, depending on the details of the specific dark matter model, Calmet said.
Quantum gravity
What scientists do know is that dark matter seems to interact with light and normal matter only through gravity, not through any of the other fundamental forces; and so the researchers used gravitational theories to arrive at their estimated range for dark matter particle masses.
Importantly, they used concepts from quantum gravity theories, which resulted in a much narrower range than previous estimates, which only used Einstein’s general theory of relativity.
“Our idea was very simple,” Calmet told Live Science in an email. “It’s amazing that people haven’t thought of this before.”
Einstein’s general theory of relativity is based on classical physics; it perfectly predicts how gravity works most of the time, but it breaks down under extreme circumstances where the effects of quantum mechanics become significant, such as at the center of a black hole.
Quantum gravity theories, on the other hand, attempt to explain gravity through quantum mechanics, which can already describe the other three known fundamental forces – the electromagnetic force, the strong force that holds most matter together, and the weak force that causes radioactive decay.
None of the quantum gravity theories, however, yet have strong evidence to support them.
Calmet and Kuipers estimated the lower limit of the mass of a dark matter particle using general relativity values and estimated the upper limit from dark matter particle lifetimes predicted by theories of quantum gravity.
The nature of the values in general relativity also defined the nature of the upper limit, so they were able to derive a prediction that was independent of any particular model of quantum gravity, Calmet said.
The study found that while quantum gravitational effects were generally almost insignificant, they became important when a hypothetical dark matter particle took an extremely long time to decay and the universe was about as old as it was. is now (about 13.8 billion years ago), he said. .
Physicists previously estimated that dark matter particles must be lighter than the “Planck mass” – about 1.2 x 10 ^ 19 GeV, at least 1000 times heavier than the largest known particles – but heavier than 10 ^ minus 24 eV to accommodate observations of the smallest galaxies known to contain dark matter, he said.
But so far, few studies have attempted to narrow the scope, even though great strides have been made in understanding quantum gravity over the past 30 years, he said. “People just hadn’t looked at the effects of quantum gravity on dark matter before.
Unknown force
Calmet said the new limits for dark matter particle masses could also be used to test whether gravity alone interacts with dark matter, which is widely assumed, or whether dark matter is influenced by an unknown force from the nature.
“If we had found a dark matter particle with a mass outside the range discussed in our article, we would not only have discovered dark matter, but also very strong evidence that… there is a new force beyond. gravity acting on dark matter, ”he said.
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This article was originally published by Live Science. Read the original article here.
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