Science

Cats purr when content, but also when frightened, hurt, or sick, which suggests purring helps them self-soothe. The sound comes from the larynx at about 25 to 30 vibrations per second.

Yes. Perch belong to the class Actinopterygii, the ray-finned fishes, in the order Perciformes and family Percidae. Their fins are supported by bony spines and rays, not fleshy lobes.

Bristol, England, recorded the highest ketamine level of any European city in the latest Europe-wide wastewater study. Its 2025 sampling week averaged 338.95 milligrams of ketamine per 1,000 people per day, more than double the next European city, Amsterdam (149.33 mg), followed by Berlin (132.23 mg). Bristol’s highest single day was a Saturday, at 551.57 … Read more

ARO-MAPT is an experimental RNA interference (RNAi) drug from Arrowhead Pharmaceuticals, given as an injection under the skin, that is designed to silence the MAPT gene in the brain and so reduce production of tau, a protein that clumps into tangles in Alzheimer’s disease and related disorders called tauopathies. In interim Phase 1/2a results announced … Read more

DNA is made of nucleotides, each with a phosphate group, a deoxyribose sugar and one of four bases (A, T, G, C); two sugar-phosphate strands twist into a double helix joined by A-T and C-G base pairs.

A Northwestern University study in mice, published in Nature Communications in October 2026, points to a small group of somatostatin neurons in the central amygdala, a brain region that processes fear and stress. Mice given a synthetic cannabinoid (a lab drug that acts like THC) froze more often and avoided a fox-urine predator scent, and … Read more

Solid moon rocks are often denser than many common Earth rocks of the same type, especially iron-rich mare basalts, but porous highland rocks and impact breccias can be lighter. Laboratory measurements on Apollo samples and lunar meteorites find mare basalt grain densities around 3.3–3.5 g/cm³ (bulk densities often near 3.0–3.3 g/cm³ after porosity), while feldspathic … Read more

NASA named astronaut and engineer Christina Koch as the agency’s acting deputy chief engineer, effective Sunday, November 1, 2026. She succeeds Katherine Van Hooser, who is retiring on October 21 after more than 35 years at NASA. In the new role, Koch will help lead NASA’s engineering community on technical oversight, mission readiness, and engineering … Read more

Yes, at least in one long-running U.S. population study. Researchers tracking the Greater Cincinnati and Northern Kentucky region found that the rate of first-ever strokes among adults ages 20 to 54 rose from 33.9 cases per 100,000 person-years in 1993–1994 to 62.2 in 2020, nearly doubling, while stroke rates in older adults declined. The increase … Read more

Yes — orcas (Orcinus orca, killer whales) are marine mammals in the dolphin family: warm-blooded, air-breathing, live-bearing, and milk-nursing, not fish.