The respective speeds of sound and light are oft-discussed and researched, and we seem to have a pretty good idea of what speeds each can reach.
The speed of light is 299,792,458 meters per second (983,571,056.43 feet per second), the absolute speed limit of the universe. And it maintains that speed no matter what medium it’s traveling through.
Sound, on the other hand, operates differently; traveling faster through greater densities. On Earth, sound moves at 1,500 meters (5,000 feet) per second in water, and in air around 340 meters (1,115 feet) per second.
In solids, sound moves much faster, though the speed is dependent on the solid itself.
Scientists may have identified the maximum speed of sound, discovering that sound would be fastest if it were to propagate through solid hydrogen.
Though solid hydrogen only occurs at astonishingly high pressures like those found inside gas giants like Jupiter, they calculated that sound would move along at 36 kilometers per second (22 miles per second) in it. That likely represents the highest speeds reached by sound in or out of our universe.
But it’s not just the speed of sight and sound that have scientists intrigued, leading to the investigation of the speed of smell.
Yes, smell.
Smell occurs when odors – volatilized chemical compounds – bind to receptors in your nasal cavity. Some compounds are more volatile than others, meaning that they evaporate more easily in normal Earth conditions, which is what you end up smelling.
Since it is the volatile chemical compound that you are detecting, rather than a wave traveling through a medium, smell is a lot slower than sound. It depends upon the medium through which the smell is traveling.
Like sound, pressure and temperature affect how fast smell can propagate.
Smell certainly moves the slowest of the three things discussed here; since human noses detect the chemical compound, rather than a wave, the speed is significantly slower. How slow, or fast, depends upon the medium through which the smell is traveling. Like sound, pressure and temperature affect how fast smell can propagate.
Smell will diffuse in all possible directions until equilibrium is reached, thanks to the second law of thermodynamics.
Smells are subject to air flows in the environment that one finds themselves, as it will diffuse at a pace commiserate with the size of the environment it is in.
While the speed of a smell is heavily dependent on the factors of pressure, temperature, and air flow, there are ways of estimating it.
Graham’s Law tells us that the effusion rate – or the speed at which gases flow through a hole without collisions between molecules – of a gas is inversely proportional to the square root of the mass of its individual particles, which is also known as the molar mass.
Still not sure what all that means?
Check out the video below, from The Action Lab, on YouTube, for a visual demonstration that might clear things up.
Use your new-found knowledge how you need next time you’re in a crowded elevator.
You know what I’m talking about, right?
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