Dispersion Measure
A measure of how much a radio signal's lower frequencies lag behind higher ones as they travel through space, revealing the amount of ionized gas encountered.
A quantity that describes the delay between radio waves of different frequencies as they propagate through ionized gas in space. Lower frequencies arrive later than higher frequencies due to interactions with free electrons. Dispersion measure is commonly used in radio astronomy to estimate the distance to pulsars and fast radio bursts, and is expressed in units of parsecs per cubic centimeter.
What this means in real life
When a radio signal from a distant pulsar reaches Earth, its low-frequency component arrives slightly later than its high-frequency component—like runners of different speeds finishing a race at different times. Measuring this delay tells astronomers how much ionized gas the signal passed through.
What it isn’t
It is not a measure of how strong or bright a radio signal is. Dispersion measure describes only the timing delay between frequencies, not the signal's intensity or power.
Commonly misused online
Social media sometimes conflates dispersion measure with signal strength or quality, suggesting a high dispersion measure means a 'stronger' detection. In reality, it only indicates distance or gas density along the signal's path.
Based on 1 reference source, including Wikipedia. Last verified July 16, 2026.