Scientists finally realize how much dark matter – the almost imperceptible material that is said to draw everything but does not emit light – really weighs.
The new estimate helps identify how heavy its particles could be – with implications for what is actually the mysterious thing.
Research suddenly narrows the potential mass of dark matter particles, from about 10 ^ minus 24 volts (eV) and 10 ^ 19 Gigaelectron volts (GeV), to between 10 ^ minus 3 eV and 10 ^ 7eV – a possible range of mass many trillions of trillions times smaller than before.
The findings could help dark matter hunters focus their efforts on the indicated range of particle masses – or could reveal that a previously unknown force is working in the universe, said Xavier Calmet, a professor of physics and astronomy at the University of Sussex in the Kingdom. United.
Related: Top 11 unanswered questions about dark matter
Calmet, along with PhD student Folkert Kuipers, also from the University of Sussex, described their efforts in a new study that will be published in the March issue of Physical letters B.
What is dark matter?
According to some estimates, dark matter represents about 83% of all matter in the universe. It is believed to interact with light and ordinary matter by gravity, which means that it can only be seen by the way light rays curve.
Astronomers found the first signs of dark matter when looking at a galactic cluster in the 1930s, and theories that galaxies are wrapped and restrained by vast halos of dark matter became commonplace after the 1970s, when astronomers realized that galaxies were spinning faster. than it should be, given how much visible matter they contained.
Related: The strangest 12 objects in the universe
Potential candidates for dark matter particles include phantom, tiny particles known as neutrinos, theoretical darkness, cold particles known as axons, and proposed weakly interacting massive particles or WIMP.
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 know is that dark matter seems to interact with light and normal matter only by gravity and not by any other fundamental force; and so the researchers used gravitational theories to reach their estimated range for dark particle masses.
Importantly, they used concepts from quantum gravity theories, which led to a much narrower range than previous estimates, which used only Einstein’s theory of general relativity.
“Our idea was a very simple one,” Calmet said in an email to Live Science. “It’s amazing that people haven’t thought about it before.”
Einstein’s theory of general relativity is based on classical physics; perfectly predicts how gravity works most of the time, but decomposes in extreme circumstances where quantum mechanical effects become significant, such as in the center of a black hole.
Quantum gravity theories, on the other hand, try to explain gravity by quantum mechanics, which can already describe the other three known fundamental forces – the electromagnetic force, the strong force that holds the largest matter together, and the weak force that causes radioactive decay.
However, none of the quantitative theories of gravity yet have strong evidence to support them.
Calmet and Kuipers estimated the lower limit of the mass of a dark matter particle using values from general relativity and estimated the upper lifetime limit of dark matter particles predicted by quantum theories of gravity.
The nature of values in general relativity also defined the nature of the upper limit, so they were able to obtain a prediction independent of any particular quantum gravity model, Calmet said.
The study found that although quantum gravitational effects were generally almost insignificant, they became important when a hypothetical dark particle took an extremely long time to decompose and when the universe was about as old as it is now ( about 13.8 billion years), he said. .
Physicists have previously estimated that dark matter particles should be lighter than the “Planck mass” – about 1.2 x 10 ^ 19 GeV, at least 1,000 times heavier than the largest known particles – yet heavier than 10 ^ minus 24 eV to match the observations of the smallest galaxies known to contain dark matter, he said.
But so far, few studies have tried to narrow the range, even though much progress has been made in understanding quantum gravity over the past 30 years, he said. “People just weren’t looking at the effects of quantum gravity on dark matter before.”
Unknown force
Calmet said the new limits for dark particle masses could also be used to test whether gravity interacts with dark matter alone, which is widely assumed, or if dark matter is influenced by an unknown force in nature.
“If we found a particle of dark matter with a mass outside the range, we would have discovered not only dark matter, but also very strong evidence that … there is a new force beyond gravity acting on dark matter,” he said. he said.
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This article was originally published by Live Science. Read the original article here.