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Physicists Calculate Upper Limit For Speed Of Sound In The Universe

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KEY POINTS

  • Physicists tested sound as it travels through different materials
  • Sound can almost reach its upper limit when traveling in solid atomic hydrogen
  • The finding is vital in different fields of studies like materials science and condensed matter physics

Sound waves can travel to up to 36 kilometers or more than 22 miles per second when traveling through solids or liquids, a new study by a team of physicists revealed. The physicists said that their calculation could be the first known variables representing the threshold of sound waves.    

Before this new finding, the speed of sound was measured based on Albert Einstein’s theory of special relativity that identified sound waves threshold similar to that of the speed of light (300,000 kilometers or over 186,000 miles per second).

In a study, published in the journal Science Advances, the physicists said to calculate for the threshold of the speed of sound, they factored in the two dimensionless fundamental constants. These constants are the fine structure constant and the proton-to-electron mass ratio. 

The physicists explained that these two fundamental constants have already been used in calculations needed to understand the Universe. For instance, the dimensionless fundamental constants are also the basis for calculations of nuclear reactions, proton decay, and nucleosynthesis in stars. The balance between the fundamental constants could also point to the habitable zone where possible life forms could start outside Earth. 

With identifying the upper limit of sound, their finding also became significant in other fields of studies. Setting a known upper threshold of sound is particularly crucial to studies that test the limits of matter such as materials science and condensed matter physics.      

“We believe the findings of this study could have further scientific applications by helping us to find and understand limits of different properties such as viscosity

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Possibility of Dark Bosons Entices Physicists

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Physicists are on the hunt for dark forces. These forces are not as ominous as they sound: “dark” simply refers to the fact that no one has observed them before. In this case, they would act between neutrons and electrons.

One path to investigating dark forces involves using lasers to make precision measurements of isotopes (atoms of an element possessing different numbers of neutrons). If there is a dark force working behind the scenes, it could affect an isotope’s energy levels—discrete regions around the atom’s nucleus where its electrons exist.

Now two teams have independently performed the most precise measurements of this type. Their findings, reported this month in Physical Review Letters, are mixed: One group, led by researchers at Aarhus University in Denmark, analyzed calcium isotopes and saw no deviation from predictions. But the other team, led by scientists at the Massachusetts Institute of Technology, used ytterbium isotopes and found a deviation in the electron energy levels with “three sigma” significance—that is, assuming no dark forces or other factors, the result would happen once every 370 times because of random chance.

If there is a dark force at work here, physicists believe it would be carried by a force-carrying particle: a boson. “‘Dark boson’ is not well-defined,” says Elina Fuchs, a physicist at the University of Chicago and a member of the Aarhus-led team. “It’s just a very feebly interacting particle that can be connected to matter.” These efforts are searches for a dark force, not dark matter—the mysterious stuff that composes 85 percent of the matter in the universe. Such a dark boson could be an important component of dark matter, or it could simply be part of a larger “dark sector” of particles.

The Aarhus-led study’s results do not rule out dark forces, but the M.I.T.-led team’s

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MIT physicists inch closer to zero-emissions power source

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Sept. 29 (UPI) — For the last few years, scientists at MIT have been working on a fusion research experiment called SPARC and, according to a series of papers — published Tuesday in the Journal of Plasma Physics — the research is going quite smoothly.

The research effort, a collaboration between MIT and startup company Commonwealth Fusion Systems, is intended to pave the way for an emissions-free power plant — a fusion reactor.

According to the latest updates, scientists have yet to encounter any unexpected hurdles. What’s more, researchers characterized the remaining challenges as manageable.

Over the last 2 1/2 years, researchers on the project have focused on working out the physical principles underlying their planned fusion reactor. So far, the work has confirmed the validity of the plasma physics behind their SPARC plans.

“These studies put SPARC on a firm scientific basis,” Martin Greenwald, researcher at the MIT Plasma Science and Fusion Center, said in a news release.

“When we build and operate the machine as described in these papers, we fully expect to meet our target for fusion gain and produce a wealth of new and important information on burning plasmas,” said Greenwald, who served as guest editor for the special edition of Journal of Plasma Physics.

Engineers expect their SPARC reactor, or tokamak, to be much more powerful than previous experimental reactors. The reactor will take advantage of advances in superconducting magnets, which will produce a more powerful magnetic field, capable of confining SPARC’s hot plasma.

In the new papers, scientists outlined the calculations and simulation tools that were used to confirm SPARC’s underlying physics.

The primary goal for the SPARC experiment is to achieve a Q factor — a measure of fusion plasma efficiency — of at least 2, an ability to generate double the energy