A smoke ring is a visible vortex ring formed by smoke in a clear atmosphere.
Smokers may blow smoke rings from the mouth, intentionally or accidentally. Smoke rings may also be formed by sudden bursts of fire (such as lighting and immediately putting out a cigarette lighter), by shaking a smoke source (such as an incense stick) up and down, by firing certain types of artillery, or by the use of special devices, such as vortex ring toys. The head of a mushroom cloud is a large smoke ring.
A smoke ring is commonly formed when a puff of smoke is suddenly injected into clear air, especially through a narrow opening. The outer parts of the puff are slowed down by the still air (or by edges of the opening) relative to the central part, imparting it the characteristic poloidal flow pattern.
The smoke makes the ring visible, but does not significantly affect the flow. The same phenomenon occurs with any fluid, creating vortex rings which are invisible but otherwise entirely similar to smoke rings.
When blown in still air, a smoke ring usually travels roughly straight from the opening over a surprisingly large distance, maintaining its shape, until dispersed by turbulence or other interference.
Read more about Smoke Ring: Smoking and Breathing, Volcanoes
Famous quotes containing the words smoke and/or ring:
“Smoking ... is downright dangerous. Most people who smoke will eventually contract a fatal disease and die. But they don’t brag about it, do they? Most people who ski, play professional football or drive race cars, will not die—at least not in the act—and yet they are the ones with the glamorous images, the expensive equipment and the mythic proportions. Why this should be I cannot say, unless it is simply that the average American does not know a daredevil when he sees one.”
—Fran Lebowitz (b. 1950)
“Close friends contribute to our personal growth. They also contribute to our personal pleasure, making the music sound sweeter, the wine taste richer, the laughter ring louder because they are there.”
—Judith Viorst (20th century)