Scientists are finally figuring out how much dark matter – the almost imperceptible material that is said to attract everything, yet radiates light – really weighs.
The new estimate helps determine how heavy its particles can be – with implications for what the mysterious things actually are.
The research sharply reduces the potential mass of dark matter particles, from between about 10 ^ minus 24 electron volts (eV) and 10 ^ 19 Gigaelectronvolts (GeV), to between 10 ^ minus 3 eV and 10 ^ 7eV – a possible range of masses many trillions trillions times smaller than before.
The findings may help dark matter hunters focus their efforts on the indicated particle mass – or it may appear that a previously unknown force in the universe is at work, said Xavier Calmet, a professor of physics and astronomy. the University of Sussex in the United States said. United Kingdom.
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 published in the March issue of Physical letters B.
What is dark matter?
According to some estimates, dark matter makes up about 83 percent of all matter in the universe. It is thought to interact only with light and ordinary matter by gravity, which means that it can only be seen by the way it bends light rays.
Astronomers found the first hints of dark matter when looking at a galactic cluster in the 1930s, and theories that galaxies are wrapped and surrounded by large halos of dark matter became mainstream after the 1970s, when astronomers realized that galaxies were faster turn than they would otherwise have to do. , given how much visible matter it contains.
Related: The 12 Strangest Objects in the Universe
Possible candidates for dark matter particles include ghostly, small particles known as neutrinos, theoretical dark, cold particles known as actions, and proposed solid particles with poor interaction, or WIMPs.
The new mass limits could help eliminate some of these candidates, depending on the details of the specific model for dark matter, Calmet said.
Quantum gravity
What scientists do know is that dark matter seems to interact only with gravity with light and normal matter, and not with any of the other fundamental forces; and therefore the researchers used gravitational theories to arrive at their estimated extent for the masses of dark matter particles.
What is important is that they use concepts from theories of quantum gravity, which have led to a much smaller scope than previous estimates, using only Einstein’s general theory of relativity.
“Our idea was very simple,” Calmet told WordsSideKick in an email. “It’s amazing that people haven’t thought about it yet.”
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 in extreme conditions where quantum mechanical effects become significant, such as in the middle of a black hole.
Theories of quantum gravity, on the other hand, try to explain gravity by means of quantum mechanics, which can describe all three other known fundamental forces – electromagnetic force, the strong force that holds most matter together, and the weak force that causes radioactive decay.
However, none of the theories about quantum gravity yet have strong evidence to support this.
Calmet and Kuipers estimated the lower limit for the mass of a dark matter particle using values from general relativity, and the upper limit estimated from the lifetime of particles of dark matter predicted by quantum gravity theories.
The nature of the values from the general relativity also defined the nature of the upper limit so that they could derive a prediction that was independent of any particular model of quantity, Calmet said.
The study found that although quantum gravitational effects were generally almost insignificant, they became important when a hypothetical dark matter particle took a very long time to decay and when the universe was about as old as it is now (about 13 , 8 billion years), he said.
Physicists have previously estimated that particles of dark matter should be lighter than the “Planck mass” – about 1.2 x 10 ^ 19 GeV, at least 1000 times heavier than the largest particles – but even heavier than 10 ^ minus 24 eV to fit. observations of the smallest galaxies known to contain dark matter, he said.
But so far, few studies have attempted to reduce the range, although great progress has been made over the past 30 years in understanding quantity. “People simply have not looked at the effects of quantum on dark matter before.”
Unknown power
Calmet said that the new boundaries for the masses of particles of dark matter can also be used to test whether gravity interacts only with dark matter, which is widely accepted, and whether dark matter is affected by an unknown force of nature.
“If we had found a dark matter particle with a mass outside the range that our paper discussed, we would not only have discovered dark matter, but also very strong evidence that … there is a new force outside the gravity is what acts on dark matter, “he said.
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This article was originally published by Live Science. Read the original article here.