What does bolometer mean?
A bolometer is a precision scientific instrument designed to measure radiant energy — most often heat carried by infrared radiation. It works by allowing incoming radiation to warm a highly temperature-sensitive element, then registering the minute change in the element's electrical resistance; from this, the amount of absorbed energy can be calculated with remarkable accuracy. Invented by American physicist Samuel Pierpont Langley in 1878 for his studies of the sun, the device has since become indispensable across physics and astronomy. Modern variants include cryogenic bolometers, cooled to near absolute zero to detect extremely faint signals, and microbolometers, which are small enough to serve as thermal sensors in infrared cameras. Because it responds to any radiation that deposits heat, regardless of wavelength, the bolometer remains one of the most versatile detectors available. The word derives from the Greek 'bole', meaning a throw or ray, combined with '-meter', meaning a measuring device.
nounA scientific instrument for measuring radiant energy, especially heat, by detecting the tiny change in electrical resistance of a temperature-sensitive element as it absorbs radiation.
- An instrument that measures radiant energy (heat or other electromagnetic radiation) via the change in electrical resistance of an absorbing, temperature-sensitive element.
"The astronomer calibrated the bolometer before measuring the faint infrared emission from the dust cloud."
"The telescope's cryogenic bolometer detected infrared waves too faint for any conventional detector."
"Samuel Pierpont Langley invented the bolometer to study how much solar energy reached different parts of the spectrum."
Regular English plural; arrays of many bolometers are common in modern instruments such as astronomical cameras, where they may be referred to collectively as 'bolometer arrays'.
"The camera's focal plane contains thousands of silicon bolometers arranged in a grid."
Invented in 1878 to measure the heat of the sun's rays, the bolometer is now so sensitive it can detect a match struck from miles away — and today it helps astronomers image distant galaxies.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of bolometer
The word 'bolometer' was coined in the late nineteenth century for Samuel Pierpont Langley's newly invented instrument, combining the Greek root 'bole' ('a throw, ray, stroke') with the suffix '-meter' (from Greek 'metron', 'measure'), following the pattern of established scientific instruments like thermometer and barometer. Its Greek roots make it a cousin of other measuring devices built on '-meter'.
Related word forms
How bolometer is actually used
A technical term used almost exclusively in physics, astronomy, and engineering contexts; not part of everyday vocabulary. Often appears in compounds such as 'cryogenic bolometer' or 'microbolometer' (a miniaturized version used in thermal imaging cameras).
Easily confused with bolometer
A barometer measures atmospheric pressure, whereas a bolometer measures radiant heat or electromagnetic radiation.