Reference Terms
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Speed of sound
The speed of sound is a term used to describe the speed of sound waves passing through an elastic medium. The speed varies with the medium employed (for example, sound waves move faster through water than through air), as well as with the properties of the medium, especially temperature. The term is commonly used to refer specifically to the speed of sound in air. At sea level, at a temperature of 21 degrees Celsius (70 degrees Fahrenheit) and under normal atmospheric conditions, the speed of sound is 344 m/s (1238 km/h or 770 mph). The speed varies depending on atmospheric conditions; the most important factor is the temperature. Humidity has little effect on the speed of sound, nor does air pressure by itself. Air pressure has no effect at all in an ideal gas approximation. This is because pressure and density both contribute to sound velocity equally, and in an ideal gas the two effects cancel out, leaving only the effect of temperature. Sound usually travels more slowly with greater altitude, due to reduced temperature.
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Matter & Energy News
October 29, 2025
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Oct. 25, 2025 — A UCLA-led team has achieved the sharpest-ever view of a distant star’s disk using a groundbreaking photonic lantern device on a single telescope—no multi-telescope array required. This technology splits incoming starlight into multiple ...
Oct. 25, 2025 — Researchers propose that hydrogen gas from the early Universe emitted detectable radio waves influenced by dark matter. Studying these signals, especially from the Moon’s radio-quiet environment, could reveal how dark matter clumped together ...
Oct. 24, 2025 — A team of researchers has designed a theoretical model for a topological quantum battery capable of long-distance energy transfer and immunity to dissipation. By exploiting topological properties in photonic waveguides, they showed that energy loss ...
Oct. 23, 2025 — Scientists have developed a chromium-molybdenum-silicon alloy that withstands extreme heat while remaining ductile and oxidation-resistant. It could replace nickel-based superalloys, which are limited to about 1,100°C. The new material might make ...
Oct. 21, 2025 — Researchers have found that 2D materials can self-form microscopic cavities that trap light and electrons, altering their quantum behavior. With a miniaturized terahertz spectroscope, the team observed standing light-matter waves without needing ...
Oct. 20, 2025 — A new light-driven cancer therapy uses LEDs and tin nanoflakes to kill tumors safely and affordably. Developed by teams in Texas and Portugal, it eliminates up to 92% of skin cancer cells without ...
Oct. 19, 2025 — Researchers from NTNU and EPFL have unveiled a compact, low-cost laser that outperforms current models in speed, control, and precision. Built using microchip technology, it can be mass-produced for use in everything from Lidar navigation to gas ...
Oct. 18, 2025 — A collaboration between the University of Michigan and AFRL has resulted in 3D-printed metamaterials that can block vibrations using complex geometries. Inspired by nature and theoretical physics, these “kagome tubes” demonstrate how geometry ...
Oct. 17, 2025 — Researchers discovered how to stabilize a high-performance sodium compound, giving sodium-based solid-state batteries the power and stability they’ve long lacked. The new material conducts ions far ...
Oct. 11, 2025 — A team of engineers at North Carolina State University has designed a polymer “Chinese lantern” that can rapidly snap into multiple stable 3D shapes—including a lantern, a spinning top, and more—by compression or twisting. By adding a ...
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Latest Headlines
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Oct. 29, 2025 — A University of Tokyo team has turned organic molecules into nanodiamonds using electron beams, overturning decades of assumptions about beam damage. Their discovery could transform materials science ...
Oct. 29, 2025 — Rice University researchers have captured the temperature profile of quark-gluon plasma, the ultra-hot state of matter from the dawn of the universe. ...
Oct. 26, 2025 — MIT researchers have devised a new molecular technique that lets electrons probe inside atomic nuclei, replacing massive particle accelerators with a tabletop setup. By studying radium monofluoride, ...
Oct. 24, 2025 — Researchers in Konstanz discovered a way to manipulate materials with light by exciting magnon pairs, reshaping their magnetic “fingerprint.” This allows non-thermal control of magnetic states ...
Oct. 23, 2025 — Chalmers researchers have developed a simple, light-based platform to study the mysterious “invisible glue” that binds materials at the nanoscale. Gold flakes floating in salt water reveal how ...
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Oct. 21, 2025 — Physicists have uncovered the fascinating world of “rotating crystals” — solids made of spinning particles that behave in strange, almost ...
Oct. 18, 2025 — Researchers have unveiled a new model for the universe’s birth that replaces cosmic inflation with gravitational waves as the driving force behind creation. Their simulations show that gravity and ...
Oct. 16, 2025 — Auburn scientists have designed new materials that manipulate free electrons to unlock groundbreaking applications. These “Surface Immobilized Electrides” could power future quantum computers or ...