Physicists Calculate Upper Limit For Speed Of Sound In The Universe

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  • 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


ExoTerra to develop upper stage for Virgin Orbit LauncherOne

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SAN FRANCISCO – Colorado startup ExoTerra Resources announced a NASA Small Business Innovative Research contract Oct. 5 to develop a solar electric upper stage to boost small satellites traveling on Virgin Orbit’s LauncherOne beyond low Earth orbit.

With ExoTerra’s Solar Electric Propulsion Upper Stage, LauncherOne customers could reach destinations including geostationary orbit, trans-lunar injection orbit, Earth-Moon Lagrange points and low lunar orbit, according to the ExoTerra news release.

“This win allows ExoTerra to begin development of an upper stage that will deliver up to 150 kilograms of payload to the moon,” according to the news release. The upper stage also could transport 180-kilogram payloads to geostationary orbit, the release added.

Virgin Orbit announced plans in 2019 to send small satellites to Mars in 2022 for Polish satellite manufacturer SatRevolution.

“That announcement definitely has attracted the interest of many others in the growing aerospace community,” a Virgin Orbit spokesman said by email.

Virgin Orbit sees “robust demand from customers” eager to travel on LauncherOne to destinations including highly elliptical orbit, geostationary orbit “and even to the moon, Mars, Venus and the asteroid belt,” the Virgin Orbit spokesman said. “Thanks to the ingenuity of the small satellite community, many groups have found ways to do really meaningful missions at each of those destinations using the amount of mass that we can confidently deliver using a stock LauncherOne complemented by a third stage.”

The new upper stage will be propelled by Halo XL, an ExoTerra Hall-effect thruster. The thruster draws on technology ExoTerra licensed from a NASA Jet Propulsion Laboratory program called Ascendant Sub-kW Transcelestial Electric Propulsion System or ASTRAEUS.

“This contract win is an important milestone for ExoTerra and aligns with our goal of developing high efficiency propulsion systems to support lunar and interplanetary missions,” Michael VanWoerkom, ExoTerra president and CEO, said