rarefaction
Particles spreading apart
Rarefaction is a decrease in density, the opposite of compression.
In physics, it describes regions where particles spread apart—as in a sound wave's low-pressure phase.
The term extends to anything thinned out or made less dense: the rarefaction of the atmosphere at high altitudes.
Rarefied air is literally thin; rarefied tastes or circles are figuratively exclusive or elevated.
Thinly scattered or distributed
- tenuousLacking solid foundation
- thinningReducing density or number
- diminishedMade or became smaller
- attenuatedLessened in force
dispersed · scattered · diffuse · spread out · infrequent · depleted · dilute · ethereal
Measured height above reference
- pressureForce upon contact
- thin airSeeming nothingness
- atmosphereGaseous layer around planets
- densityMass-to-volume ratio
oxygen · high elevation · mountain · stratosphere · barometric · hypoxia · acclimatization · breathing
Increase in scope
- gasFormless, expanding substance
- volumeAmount of space filled
- pressure dropReduction in atmospheric force
- spacingInterval arrangement between objects
molecular · kinetic · thermodynamics · diffusion · vacuum · partial vacuum · ideal gas · Boyle's law
Forcing into smaller space
- wavelengthSpatial repetition interval
- propagationAct of spreading widely
- amplitudeMaximum oscillation displacement
- frequencyRate of recurrence
longitudinal · sound wave · pressure wave · oscillation · vibration · medium · periodic · displacement
sparse
Thinly scattered or distributed
- tenuousLacking solid foundation
- thinningReducing density or number
- diminishedMade or became smaller
attenuated · dispersed · scattered · diffuse · spread out · infrequent · depleted · dilute · ethereal · wispy
altitude
Measured height above reference
- pressureForce upon contact
- thin airSeeming nothingness
- atmosphereGaseous layer around planets
density · oxygen · high elevation · mountain · stratosphere · barometric · hypoxia · acclimatization · breathing · aviation
expansion
Increase in scope
- gasFormless, expanding substance
- volumeAmount of space filled
- pressure dropReduction in atmospheric force
spacing · molecular · kinetic · thermodynamics · diffusion · vacuum · partial vacuum · ideal gas · Boyle's law · low density
compression
Forcing into smaller space
- wavelengthSpatial repetition interval
- propagationAct of spreading widely
- amplitudeMaximum oscillation displacement
frequency · longitudinal · sound wave · pressure wave · oscillation · vibration · medium · periodic · displacement · elastic
- acousticssound waves, sound wave, sound, soundwave, vibration
- sound physicssonic boom, sound barrier, Mach 1, Mach number, supersonic
- ecology metricsspecies diversity, evenness, abundance, dominance, genetic diversity
- rarefied gasKnudsen number, effusion
- soundsound, sound waves, echoes, acoustics, vibrations
- waveswave crest, shock wave, wave front, blast wave, seismic wave
rarefactioncompression
Forcing into smaller space
condensation · compaction · densification · pressurization · concentration
rarefactionadulteration
Corrupting by foreign substances
corruption · contamination · degradation · debasement · pollution
rarefactionconcentration
Sustained single-minded attention
proliferation · abundance · densification · saturation · accumulation