SWhat changed
Ewen and Purcell observed radio emission from neutral hydrogen in the Milky Way near the 21-centimetre wavelength. Their 1951 report describes a signal concentrated near the Galactic plane, with a measurable frequency shift consistent with relative motion. The result gave radio astronomers a way to study hydrogen beyond regions visible in ordinary light.
Scientific scope
Ewen and Purcell observed radio emission from neutral hydrogen in the Milky Way near the 21-centimetre wavelength. Their 1951 report describes a signal concentrated near the Galactic plane, with a measurable frequency shift consistent with relative motion. The result gave radio astronomers a way to study hydrogen beyond regions visible in ordinary light. The result concerns the reported fixed-beam observations and their frequency calibration. Dutch and Australian observations were separate follow-up reports. Inferring Galactic structure from the line requires additional observations and a model of gas motion.
Evidence
The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. The result concerns the reported fixed-beam observations and their frequency calibration. Dutch and Australian observations were separate follow-up reports. Inferring Galactic structure from the line requires additional observations and a model of gas motion.
Contributors
- The named authors in the research record · SCIENCE: These are the listed authors of the cited contribution sources. Paper authorship does not quantify individual effort. An incomplete list is explicitly marked; same names are not automatically merged.
Provisional WRS assessment, edition 2026-10-28.1. Independent expert calibration is pending. This grade does not certify correctness or assign ownership.
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