CO2 then goes to the lungs and exhaled out. Fresh Oxygen from air gets in. This is ‘external respiration’ and the lungs acted as an organ of gas exchange.
We can’t really see any air coming out of our nose or mouth; this is because the optical density of exhaled or inhaled air is somewhat similar to the surrounding air. Wouldn’t it be nice if we could actually see them? The way ‘air’ came out, the 'aerodynamics' part; and the way it smoothly mingled with the surrounding air, the 'diffusion' part?
Well, tobacco smoke could be suitable for this rather crude experiment. There is NO DOUBT that tobacco in any of its forms is injurious to health, and I am in no way advocating its use for any purpose, not even here. But there are guys who do smoke. If you look at the expired ‘air’, you can ‘see’ how the thick dense smoke that exits from the mouth gets thinner, as it expands, as the ‘air’ goes further away from the smoker. In a sense, we are 'watching' how exhaled air would actually come out from us, its trajectories and its aerodynamics!
Over a certain period of time, we can see that the density of the smoke diminishes and we can no longer see that wisp of smoke separate from the ambient air. This is due to diffusion of smoke particles down the concentration gradient; surrounding air may be assumed to have zero concentration of smoke, for all practical purposes.
However, one thing that is still ‘smoky’ to me is how the smoke rings, that 'artistic smokers' can produce, behave.
As shown in the picture, one such smoker is seen making circular rings of smoke. Both the outside and the inside of the rings are 'not visible' and we may assume them to be consisting of air rather than smoke. Now as the ring move further away, both the internal and external diameter of the exhaled smoke-ring increase. Provided that the procedure is carried out in a room where there is hardly any air flowing, and stray electrostatic charges are absent; extraneous artifacts can then be minimized and faithful aerodynamics may be expected. If one plots the trajectory of the smoke-ring over time, he will get the result as shown in the picture.
If we now joined the outer peripheries of consequetive rings, we would get a cone. Quite expectedly, the narrower end of this ‘outer cone’ will correspond to the inner margin of the artistic-smoker’s lips. Problem occurs when we construct the inner cone, by joining the internal circumferential points of those rings. Where does the narrower end correspond to now? Honestly, I’m not sure. Clearly, it is somewhere within the mouth (oral cavity). I have asked a few such ‘annular performers’ about how they achieved this feat. Gathering and analyzing data from these hallowed ‘Lords of the rings’ have suggested that the actual ‘point of origin' corresponded to somewhere in the middle of the oral cavity. They used the bases of their tongues to maneuver the smoke by apposing it to the hard palate, and then gently pushed the smoke out. The pharynx and the larynx were automatically shut off in the process.
What is your opinion? Quite some feat anyway!
Statutory Warning: Smoking is injurious to health
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